Summary Judgment for Defendant in Drug Case

A federal court recently granted summary judgment against Illinois plaintiffs who alleged that the blood clotting drug Trasylol caused the husband's kidney failure. See Miller v. Bayer Corp., No. 09-81262 (S.D. Fla., 7/3/13). (One of the remaining cases in the MDL.)

Plaintiff underwent double coronary artery bypass graft and aortic valve replacement surgery. At the time of his surgery, he was a former smoker with a lengthy medical history which included hypertension, hyper-lipidemia, chronic renal insufficiency, and coronary artery disease. The surgeon used Trasylol during the surgery to help control the bleeding. Plaintiff had signed an informed consent which enumerated the potential risks and benefits of cardiac surgery including infection, bleeding, heart damage, stroke, kidney damage, or even death.

After his surgery, Mr. Miller experienced a small acute left hemispheric stroke;  he also experienced a transient rise in his serum creatinine which peaked at 2.4 on postoperative day eight. (Creatinine is a waste product formed by the breakdown of a substance important for converting food into energy; if the kidneys are damaged and cannot function normally, the amount creatinine in the blood can increase.)

Plaintiffs sued for personal injuries allegedly caused by the use of the drug during surgery. Defendant moved for summary judgment as to each of Plaintiffs’ claims, asserting (1) under Illinois law, causation is an element of each of Plaintiff’s claims, and Plaintiffs’ expert’s causation testimony was inadmissible; (2) even if Plaintiffs’ expert’s testimony were admissible, their apparent claims failed because they were seeking damages for Mr. Miller’s stroke, and their
expert was not qualified to render an opinion as to the cause of the stroke. Plaintiffs responded that despite some confusion, ultimately they were not seeking damages due to Mr. Miller’s stroke, but for his “acute renal failure”; that the expert was qualified to testify; and “the temporal connection" between Mr. Miller’s acute renal failure and the injection of Trasylol, together with the alleged absence of renal issues prior to the surgery and the fact that Trasylol is supposedly a nephrotoxic agent, were sufficient to support an opinion that Trasylol was a substantial contributing factor in causing Mr. Miller’s injuries. 

The court noted that expert medical opinion evidence is usually required to show the cause of an injury or disease because the medical effect on the human system of the infliction of injuries is generally not within the sphere of the “common knowledge of the lay person.” See Fuesting v. Zimmer, Inc., 421 F.3d 528, 536 (7th Cir. 2005), rev’d on other grounds by Fuesting v. Zimmer, Inc., 448 F.3d 936 (7th Cir. 2006); Ancho v. Pentek Corp., 157 F.3d 512, 519 (7th Cir. 1998); Goffman v. Gross, 59 F.3d 668, 672 (7th Cir. 1995); Wallace v. McGlothan, 606 F.3d 410, 420 (7th Cir. 2010). Claims for negligence, strict liability, breach of express warranty, breach of implied warranty, fraudulent misrepresentation, fraudulent concealment, violation of consumer protection statutes, wrongful death, and loss of companionship, as well as a survival claim  all will fail where a plaintiff has no evidence of specific causation. See Schrott v. Bristol-Myers Squibb Co., 403 F.3d 940 (7th Cir. 2005). To avoid summary judgment, the Plaintiffs therefore must come forward with evidence that would allow a reasonable jury to find causation. Causation must be established by provable facts; it cannot be based on guess, conjecture, surmise, possibility, speculation, or mere allegation. 

In summary, plaintiffs' expert opined that in all medical certainty causation of Mr. Miller’s
alleged renal failure was likely multifactorial, with significant contributing factors including
cardiopulmonary bypass surgery, associated blood pressure fluctuations, and the use of the medication.  The drug, he said, "in all medical certainty, was a significant contributing factor.”
Additionally  he opined that the physicians caring for Mr. Miller “would not have used” this drug
had they been aware of the association of mortality and acute kidney injury.  Plaintiffs argued the expert had conducted a legally sufficient differential diagnosis which emphasized the  "temporal connection between Mr. Miller’s acute renal failure and the injection of Trasylol, together with the absence of renal disease or issues prior to the surgery.

This court falls in the camp of those who conclude that a differential diagnosis, properly performed, constitutes a reliable methodology for determining medical causation under Daubert. See Guinn v. Astrazeneca Pharms. LP, 602 F.3d 145, 153 (11th Cir. 2010); Ervin v. Johnson & Johnson, Inc., 492 F.3d 901, 904 (7th Cir. 2007).  Readers will recall that we have explained how plaintiffs have mis-used the notion of differential diagnosis, jumping from a medical method to figure out what disease a patient has to a legal method to figure out why the patient has the disease.  In any event, the court noted that an expert does not establish the reliability of his techniques or the validity of his conclusions simply by claiming that he performed a differential diagnosis on a patient.  Instead, a court must examine whether the expert correctly applied the differential diagnosis methodology. 

As applied in several courts, the method requires an expert to rule in all the potential causes of a patient’s ailment and then by systematically ruling out causes that would not apply to the patient, the physician arrives at what is the likely cause of the ailment. Westberry v. Gislaved Gummi AB, 178 F.3d 257, 262 (4th Cir. 1999)).  Plaintiff experts routinely make a couple mistakes:  Expert testimony that rules in a potential cause of a patient’s symptoms that is not so capable is unreliable.  At the rule out step, the expert must at least consider the other causes that could have given rise to Plaintiffs’ injury.  Courts vary on whether the expert must rule out all possible alternative causes, or the most likely ones, or at least consider other factors that could have been the sole cause of the plaintiff's injury.  A differential diagnosis that fails to take serious account of other potential causes may be so lacking that it cannot provide a reliable basis for an opinion on causation.  And an expert must provide a reasonable explanation as to why he or she has concluded that any alternative cause suggested by the defense was not the sole cause of the plaintiff’s injury.

The court then noted that  a temporal connection between exposure to chemicals and an onset of
symptoms, standing alone, is entitled to little weight in determining causation. See McClain v.
Metabolife Int’l, Inc., 401 F.3d 1233, 1254 (11th Cir. 2005); Happel v. Walmart Stores, Inc., 602 F.3d 820 (7th Cir. 2010).  Temporal proximity is especially unreliable where conditions independent of
exposure to the drug could have been the sole cause of the plaintiff’s injury, and the expert fails to
explain the relative contribution of the drug to the injury.  Here, one flaw in the expert's methodology was his failure to account for or appropriately address numerous risk factors at both the rule in and rule out stage., factors which either alone or in combination could explain Mr. Miller’s alleged renal injury. These factors include, but were not limited to: pressure stabilizing medications; extended pre-surgical and post-operative hypertension; and pre-surgical chronic renal failure. Even to those factors which the expert did rule in, he either gave them short shrift at the rule-out stage, or dismissed them without discussion.  In neither his report nor deposition did the expert provide any explanation for why he concluded that Mr. Miller’s various risk factors other than exposure to Trasylol were not the sole cause of his injuries. In fact, during his deposition, he conceded several additional risk factors for Mr. Miller that he had failed to consider in rendering his opinion, and further testified that many of those risk factors, either alone or in concert, could have caused Mr. Miller’s transient creatinine rise. He was forced to admit that Mr. Miller, without Trasylol, “could have had the same postoperative course.”


Thus there was no way to determine that one factor had more of an effect than the others. That led plaintiff to argue that Trasylol somehow tipped the scales causing his renal injury (the so-called straw that broke the camel's back).  But after sorting through these opinions and the Plaintiffs’ response to Defendants’ Motion, the court found that exclusion of the expert was warranted because of the absence of a reliable methodology, the failure to provide a plausible explanation for why he concluded that Mr. Miller’s various risk factors other than exposure to Trasylol were not the sole cause of his renal injury. Under Illinois law, a party cannot create a genuine issue of fact merely by presenting an expert witness who is willing to express an unsupported opinion that favors the party’s position. See Lewis v. CITGO Petroleum Corp, 561 F.3d 698, 705 (7th Cir. 2009).

 

 

 


 

Supreme Court Denies Cert in Case Excluding Treater Opinions

Readers may recall our post about Simmons v. Novartis Pharmaceutical Corp., a case in which the Sixth Circuit affirmed the exclusion of plaintiff's expert testimony seeking to link osteonecrosis of the jaw to plaintiff's use of two cancer medications. The issue was specific causation, and the court helpfully noted that a treating physician’s testimony is subject to Daubert; that an expert's statement that he found “a very close association” between ONJ and the class of drugs is not enough; and that while a treater may be qualified to diagnose a patient, a diagnosis is merely a hypothesis, which does not by itself satisfy Daubert and Rule 702.

The Supreme Court earlier this month denied the plaintiff's cert petition. See Simmons v. Novartis Pharmaceutical Corp., U.S., No. 12-283, cert. denied 11/5/12).

Plaintiff had argued that when a case involves medication that has not been widely studied, and thus published about, a different standard should apply.  She also argued that the opinions would have been admissible under the law of Maryland which, she said, requires only that expert opinions be expressed “to within a reasonable degree of medical/dental probability.”

Novartis has had a number of victories in similar cases, challenging treating physicians who seek to offer expert causation opinions. 

State Supreme Court Affirms Exclusion of Experts' Inferential Opinions

Follow our train of thought: we have posted about the misuse of the differential diagnosis concept, as plaintiff experts morph it from an accepted tool for deciding what is wrong with a patient to a method for explaining why and how the patient suffered his injury/illness.  Now, three computer experts sought to opine that a software flaw prevented a health monitor alarm from sounding, claiming their methodology was just "like a medical differential diagnosis"!  Fortunately, the South Carolina Supreme Court rejected that attempt last week.  See Graves v. CAS Medical Systems Inc., No. 27168 (S.C., 8/29/12).

Their doctor ordered that the plaintiffs use a monitor manufactured by CAS to track their infant child's breathing and heart rates as a precaution. The monitor was designed to sound an alarm, if the subject were to experience an apneic, bradycardia, or tachycardia event. Once the breathing or heart rate returns to normal, the alarm stops. Each machine also keeps a log of any events, which is the term for when the alarm sounds, and records the pertinent data and vital signs. As an additional safety measure, CAS installed not only a back-up alarm, but also a feature that records whether the alarm sounded. This system operates primarily through an independent and separate microphone specifically designed to listen for the alarm. If it hears the alarm, it then makes a notation in the monitor's internal log. If it does not hear the alarm, then it records "Front alarm not heard," and the monitor will sound the backup alarm. A microphone listens for this back-up alarm as well and records whether it was heard. If the back-up alarm fails, all the lights on the front of the monitor flash.

Tragically, the child died from Sudden Infant Death Syndrome (SIDS), which essentially means that no attributable cause of death exists. Plaintiffs claimed the monitor's alarm never sounded that night. Additionally, they testified that all the lights on the front of the monitor were on, although they were solid and not flashing. Another family member who was asleep downstairs also allegedly could not recall hearing the alarm go off.  Plaintiffs further testified the machine was not turned off until the next day, when the monitor was removed for testing.

Plaintiffs filed a strict liability design defect claim against CAS, contending the monitor's software design caused the alarm to fail.  Their claim revolved around what is known as "spaghetti code," which is when computer code is unstructured and can result from the overuse of "goto" or "unconditional branch" statements, which causes a signal working its way through the code to jump around instead of following a linear path.  This in turn caused the signal to be pushed off course and never reach its destination.

To support this theory, the Graves designated three software experts to testify regarding the alarm's alleged failure. In arriving at their conclusions that a software defect caused the alarm to fail, none of the experts did much actual testing of the software. Instead, they used a "reasoning to the best inference" analysis, which was "similar to a differential diagnosis" in the medical field. In this case, three potential causes were identified: hardware error, complaint error, and software error. Complaint error means that the monitor was misused or the alarm did sound and the Graves failed to hear it.  All the experts were able to dismiss hardware error as a cause because the machine was tested and shown to be functioning properly. Thus, the question became whether complaint error or a software error occurred.

The experts excluded complaint error because the machine was hooked up properly, and they did not believe anyone would sleep through the alarm. In other words, because the Graves claimed the alarm did not wake them, that means it must not have gone off. After being confronted with the fact that the monitor listens for the alarm and separately records whether it was sounded, the experts opined that it must be "certain" the internal logs showing the alarm actually did sound were not reliable "in light of the undisputed testimony that the alarm did not function." That left software error as the most likely cause of the alleged failure, they opined.

Defendant moved to have all these experts excluded, arguing none of them met the reliability factors for scientific testimony set forth in State v. Council, 335 S.C. 1, 515 S.E.2d 508 (1999). CAS also moved for summary judgment, contending that without this expert testimony plaintiffs had no evidence of a design defect. The trial court agreed that their opinions were unreliable both as scientific evidence and as nonscientific evidence and thus were inadmissible. Having excluded the opinions of all the Graves' experts, the lower court granted CAS's motion for summary judgment.

The state Supreme Court noted that this was its first opportunity to assess the reliability of an opinion rendered using the "reasoning to the best inference" methodology, so looked for guidance to the analysis of the United States Court of Appeals for the Tenth Circuit, which had already done so. In Bitler v. A.O. Smith Corp., 400 F.3d 1227 (10th Cir. 2004), the court held that "[e]xperts must provide objective reasons for eliminating alternative causes" when engaging in this analysis. Id. at 1237. Furthermore, "an inference to the best explanation for the cause of an accident must eliminate other possible sources as highly improbable, and must demonstrate that the cause identified is highly probable." Id. at 1238. Although the expert need not categorically exclude all alternate causes, that does not relieve the expert of his burden to prove the alternate cause is at least highly improbable based on an objective analysis. See id. at 1237–38 & n.6. The court found this objectivity requirement consistent with the quality control element of State v. Council.

Here, there was evidence that the alarm worked properly and the plaintiffs failed to hear it. In addition to the monitor's recordation of hearing the alarm sound, the family pediatrician testified he believed plaintiffs slept through it, the court noted. The doctor was aware of just how exhausted the parents were. Although the alarm is loud, if one is tired enough, he testified that it is possible to sleep through it. His opinion was bolstered by the fact that the machine seems to have worked just as it was supposed to and recorded the breathing issues perfectly. The log also seems to show the alarm managed to stimulate the baby into breathing normally at times.

This evidence does not mean that is exactly what happened.  But there was enough that an expert needed to take it into account.. Instead, the experts simply assumed the alarm did not sound and provided no reason for discounting the evidence to the contrary other than the assertion of the persons alleging a failure. Thus, they did not objectively discount the evidence of complaint error as required. See Clark v. Takata Corp., 192 F.3d 750, 757 (7th Cir. 1999) ("Simply put, an expert does not assist the trier of fact in determining whether a product failed if he starts his analysis based upon the assumption that the product failed (the very question that he was called upon to resolve), and thus, the court's refusal to accept and give credence to [the expert's] opinion was proper.").

The trial court did not abuse its discretion in excluding the opinions, and summary judgment was warranted. 

Fifth Circuit Affirms Exclusion of Plaintiff Causation Experts in Chemical Case

The Fifth Circuit recently affirmed the dismissal of most of a plaintiff's personal injury claims against a chemical company, based on the conclusion that certain expert witness testimony was inadmissible. See Johnson v. Arkema Inc., No.11-50193 (5th Cir. June, 2012).

Plaintiff Johnson worked as a machine repairman at a glass bottling plant in Waco, Texas from May 1998 to the end of 2008. On two separate occasions, first in early June 2007 and again in July 2007, Johnson claims he was directed to perform work in close proximity to a device known as a C-4 Hood, which was designed, manufactured, and installed by defendant. C-4 Hoods are
utilized to apply a chemical coating to the glass bottles as the bottles are transported along a conveyor belt. According to Johnson, the C-4 Hood he worked near to on those two occasions failed to perform its proper functions, resulting in his alleged exposure to harmful chemicals.

Plaintiff sued. Arkema then filed motions to exclude the opinions of Dr. Richard Schlesinger, Johnson’s expert toxicologist, and Dr. Charles Grodzin, Johnson’s expert pulmonologist, under Federal Rule of Evidence 702 and the Supreme Court’s decision in Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579 (1993). Arkema also filed a motion for summary judgment, contending that absent those experts, Johnson was unable to present scientifically reliable evidence establishing that exposure to the chemicals can cause restrictive lung disease and pulmonary
fibrosis (his alleged injury types). The district court granted the motions, and plaintiff appealed. 

On appeal, plaintiff contended that the district court abused its discretion in excluding Dr. Schlesinger’s expert opinion on general causation.  The district court excluded Dr. Schlesinger’s testimony after determining, inter alia, that: (1) Dr. Schlesinger could not cite to one epidemiological or controlled study of humans indicating that exposure to the relevant chemicals could cause restrictive lung disease and pulmonary fibrosis; (2) the scientific literature was devoid of any data or peer reviewed articles indicating that exposure to the two chemicals will result in chronic lung disease, and such a proposition is not generally accepted in the scientific community.

Plaintiff argued that the two fell into a "class" of chemicals that have been shown to cause these injuries. In forming a reliable opinion regarding the effects of exposure to a particular chemical, an expert may extrapolate data from studies of similar chemicals. BUT to support a conclusion based on such reasoning, the extrapolation or leap from one chemical to another must be reasonable and scientifically valid.  Thus, courts are free to reject a theory based on extrapolation when there is simply too great an analytical gap between the data and the opinion proffered. Here, save for highlighting their shared classifications as "irritants," the expert did not attempt to explain any direct correlation or “fit” between the chemicals at issue and the known scientific data concerning exposure to, for example, chlorine, ammonia, or nitric acid vapor. Accordingly, given the diverse chemical structures and toxicities of irritants, which plaintiff acknowledged, the district court did not abuse its discretion in concluding that Dr. Schlesinger’s “class of chemicals” theory presented “too great an analytical gap between the data and the opinion proffered.

The next issue was reliance on language in an MSDS, which is useful for many of our readers in toxic tort cases.  The district court found the "warning" language in a competitor's MSDS to be irrelevant and unreliable because: it did not clearly state a causation conclusion, and, most importantly, Johnson did not provide any science behind the MSDS, such as the duration or concentration of exposure needed to produce the noted effects, or the scientific literature relied upon by the drafter for the statements contained in the MSDS.  Under such circumstances, the MSDS, standing alone, need not have been accorded any weight. Plaintiff also relied on general hazard language in defendant's own MSDS. But could cite no authority for the proposition that material safety data sheets constitute per se reliable support for an expert’s opinion. To the contrary, in exercising its discretion as a gatekeeper, a court may refrain from treating a MSDS as reliable until it is presented with scientific evidence justifying the relevant statements found within the MSDS.

Finally, Johnson contended that he was exposed to amounts of one of the chemicals (HCl) that were between two and ten times the permissible exposure levels set by OSHA, NIOSH, and the Acute Exposure Guideline Levels set by the National Research Council. Regulatory and advisory bodies such as IARC, OSHA and EPA utilize a “weight of the evidence” method to assess the carcinogenicity or toxicity of various substances in human beings and suggest or make prophylactic rules governing human exposure. This methodology results from the preventive perspective that the agencies adopt in order to reduce potential public exposure to possibly harmful substances. The agencies’ threshold of proof is lower (for policy reasons) than that appropriate in tort law, which traditionally makes more particularized inquiries into cause and effect, and requires a plaintiff to prove that it is more likely than not that another individual has caused him or her harm. See generally Wright v. Willamette Industries, Inc., 91 F.3d 1105, 1107 (8th Cir.1996). Thus, such regulatory chemical guidelines are not necessarily reliable in all toxic tort cases. And a court should confirm the underlying basis for their  proscriptions before an expert’s reliance on them can pass Daubert muster. Here, plaintiff did not provide any scientific data or literature to explain how or why the various exposure limits and guidelines were established for the chemicals. Similarly, he had no evidence that the guidelines and exposure limits existed to protect people from developing severe restrictive lung disease and pulmonary fibrosis, his diseases. Thus, the court concluded that the OSHA, NIOSH, and NRC guidelines and exposure limits, standing alone, were insufficient to demonstrate abuse of discretion on the part of the district court.

As to the other expert, Dr. Grodzin’s research and analysis essentially mirrored Dr. Schlesinger’s save for one key distinction: Dr. Grodzin performed a so-called “differential diagnosis” of Johnson. A reliable differential diagnosis typically, though not invariably, is performed after physical examinations, the taking of medical histories, and the review of clinical tests, including laboratory tests, and generally is accomplished by determining the possible causes for the patient’s symptoms and then eliminating each of these potential causes until reaching one that cannot be ruled out.  Even in jurisdictions that accept this questionable approach to causation, the results of a differential diagnosis are far from reliable per se. For example, before courts can admit an expert’s differential diagnosis, which, by its nature, only addresses the issue of specific causation, the expert must first demonstrate that the chemical at issue is actually capable of harming individuals in the general population, thereby satisfying the general causation standard. In other words, the suspect has to be reasonably and reliably "ruled in."

Here, Dr. Grodzin’s differential diagnosis was based on the presumption that the two chemicals  were actually capable of causing restrictive lung disease and pulmonary fibrosis in the general population. Dr. Grodzin did not present any reliable or relevant scientific evidence to bolster this assumption. Consequently, the fact that Dr. Grodzin claimed he conducted a differential
diagnosis did not save his opinion from the same fate as Dr. Schlesinger’s opinion.

 (Note, the court concluded that plaintiff did not need expert witnesses to demonstrate that his immediate acute injuries after exposure and which allegedly sent him to the emergency room, could have been caused by the chemical.  Thus, this part of the case was remanded.)

 

 

 

State Supreme Court Holds Causation Evidence Insufficient

The Vermont Supreme Court recently held that a plaintiff's evidence that exposure to benzene allegedly caused his cancer was insufficient to get to the jury.  Blanchard v. Goodyear Tire & Rubber Co.,  No. 2010-250 (Vt. 8/5/11).

Plaintiff was diagnosed with non-Hodgkin's lymphoma, and he attributed the onset of the disease to benzene exposure that allegedly occurred between 1968 and 1973 while he was a teenager playing on a ball field on the grounds of the former Goodyear rubber manufacturing plant. That  plant operated in Windsor, Vermont from 1936 to 1986. He sued, alleging that the field itself was polluted and that there was a gully in the outfield that transported foul-smelling and oily stormwater discharge away from the manufacturing plant.

Defendants moved for summary judgment. The lower court concluded that plaintiff was not entitled to present his case to a jury because he had provided insufficient evidence to support an inference that he had been exposed to benzene in any amount, let alone an amount that could have caused his illness, nor sufficient expert testimony sufficient to eliminate other potential causes of his disease. On appeal, plaintiff argued that his circumstantial evidence of causation was sufficient to present his case to the jury.

The state Supreme Court noted that the plaintiff could not survive the motion for summary judgment on his toxic tort claim unless he was able to point to evidence suggesting a probability, rather than a mere possibility, that (1) he was exposed to the specified chemical at a level that could have caused his physical condition (general causation); and (2) the exposure to that chemical did in fact result in the condition (specific causation).  In a toxic tort case, general causation addresses whether a substance is capable of causing a particular injury or condition in a population, while specific causation addresses whether a substance caused a particular individual's alleged injury. E.g., King v. Burlington Northern Santa Fe Ry. Co., 762 N.W.2d 24, 34 (Neb. 2009). General causation is typically shown through epidemiological studies, and plaintiffs in toxic exposure cases in Vermont generally must demonstrate specific causation by submitting evidence concerning the amount, duration, intensity, and frequency of exposure. Citing  Henricksen v. ConocoPhillips Co., 605 F. Supp. 2d 1142, 1157 (E.D. Wash. 2009) (citing several appellate court cases holding that experts testifying as to specific causation must pay careful attention to amount, intensity, and duration of exposure).

The court recognized that in some toxic tort cases it is impossible to quantify exposure with hard proof, such as the presence of the alleged toxic substance in the plaintiff's blood or tissue and the precise amount of the toxic substance to which an individual plaintiff was exposed. Plourde v. Gladstone, 190 F. Supp. 2d 708, 721 (D. Vt. 2002).  Therefore, expert testimony on toxic injuries may be admissible where dosage or exposure levels have been established through sufficient reliable circumstantial evidence. While it is not always necessary for a plaintiff to quantify exposure levels precisely, the courts generally preclude experts from testifying as to specific causation without having any some measurement or reasonable estimate of a  plaintiff's exposure to the allegedly harmful substance. Finally, a defendant's concession that its product contains a carcinogen, say benzene, does not excuse a plaintiff from having to show the benzene contained in defendant's product is capable of causing the illness at issue.

When direct evidence of the precise amount of exposure to a toxic substance is limited, some courts have allowed expert witnesses to use a differential diagnosis process as a method of proving specific causation. We have posted before about the mis-use and mischaracterization of this process.  Differential diagnosis is a scientific analysis entailing the weighing of relevant evidence, listing all likely explanations of the patient's observed symptoms or injury, then eliminating all but one.  Some courts have made the leap from allowing the process designed to arrive at a diagnosis (what disease caused the symptoms) to arrive at a cause (what substance caused the disease). However, said the state court, even the courts that do recognize differential diagnosis are reluctant to admit causation testimony based on a differential diagnosis where the proffered expert possesses only weak circumstantial evidence that some exposure occurred and makes insufficient effort to scientifically evaluate or estimate the degree of exposure or dosage. Also, and significantly, standing alone, the presence of a known risk factor is not a sufficient basis for ruling out idiopathic origin in a particular case, particularly where most cases of the disease have no known cause. In such cases, analysis beyond a differential diagnosis is required.

Here, plaintiff pointed to three bits of circumstantial evidence. First, he offered statements made by himself and boyhood friends concerning their alleged exposure to chemicals from the Goodyear plant when they were teenagers playing ball on a field adjoining the plant.  Second, plaintiff relied on the testimony of the project manager for an environmental firm hired by Goodyear in 2007 to conduct a site investigation in response to a clean-up agreement reached by Goodyear and the State of Vermont. The 2009 report stemming from the investigation listed contaminants of concern, including petroleum products containing benzene, that could have been released into the environment. Third, plaintiff relies upon the testimony of his two experts, who testified that occupational exposure to benzene is generally associated with a risk of non-Hodgkin's lymphoma, and that plaintiff's cancer was not caused by an immunodeficiency disorder, one of the known causes of that form of cancer.

That evidence "falls well short" of what plaintiff would be required to show in order to prevail in a jury trial. Indeed, if a jury were to find in favor of plaintiff on the evidence relied upon by plaintiff, said the court, "we would have to overturn the verdict." In the end, plaintiff's suspicion that his cancer was caused by exposure to benzene on the Goodyear ball field when he was a teenager was purely speculative. There was no way to know whether any benzene-containing product actually contaminated the ball field.  And there was no evidence indicating the amount or concentration of benzene that was present, even assuming some was. Nor was there any evidence indicating plaintiff's level of exposure to any benzene that may have been present on the field. Nor was plaintiff able to point to studies indicating a risk of cancer posed by exposure to limited amounts of benzene from petroleum products in an outside environment.  

Further, plaintiff could not rely upon differential diagnosis to overcome the complete lack of evidence as to the level of any exposure to benzene. A large percentage of cases of plaintiff's type of lymphoma are of unknown origin. Thus plaintiff's experts could not rule out all other causes, an essential part of the differential diagnosis.  E.g., Whiting v. Boston Edison Co., 891 F. Supp. 12, 21 n.41 (D. Mass. 1995) (concluding that differential diagnosis cannot be used to explain disease where 90% of cases of disease are of unknown origin).
 

Appeals Court Upholds Summary Judgment Based on Daubert in Benzene Case

The Sixth Circuit last week upheld the dismissal of a plaintiff''s claim that benzene exposure caused her cancer. Pluck v. BP Oil Pipeline Co., No. 09-4572 (6th Cir.,  5/12/11).  The central issue was the exclusion of plaintiff's causation expert's opinion based on a "differential diagnosis" that failed to reliably rule in benzene exposure as a potential cause of plaintiff's cancer, and to rule out some other potential exposures.

This case arose from benzene contamination allegedly caused by gas-pipeline releases allegedly resulting in the seepage of gasoline into the surrounding soil and groundwater. Benzene, a component of gasoline, is a known carcinogen in sufficient doses under certain exposure circumstances, and is also ubiquitous in the ambient air and is a component or constituent of vehicle exhaust and cigarette smoke, said the court. Plaintiffs purchased a home in the area,  and used well water to drink, wash, shower, and irrigate their yard and garden. In October,  1996, plaintiffs say they noticed a gasoline odor in their home and water, and benzene was first detected in the well on their property in the amount of 3.6 parts per billion (“ppb”).  They began drinking bottled water in lieu of tap water, although they claim to have resumed drinking tap water upon the drilling of a new, deeper well. Between 1997 and May 2002, the new well tested negative for benzene twenty-two times.

Mrs. Pluck was diagnosed with Non-Hodgkins lymphoma (“NHL”) in 2002 at age forty-eight. She filed suit, alleging claims of strict liability for hazardous activity, negligence, and loss of consortium. To support their claims, plaintiff and spouse retained Drs. Joseph Landolph and James Dahlgren as experts on causation to demonstrate that benzene is generally capable of causing NHL and specifically caused Mrs. Pluck’s NHL. Defendant filed motions in limine to exclude the testimony of Dahlgren and Landolph on the grounds that their testimony failed to satisfy the standard for reliability set forth in Daubert. In particular, BP argued that Dr. Dahlgren’s testimony on specific causation was unreliable because he formulated a specific causation opinion without evidence of dose, and subsequently performed an unreliable dose reconstruction in an attempt to support his opinion.  Dahlgren then submitted a supplemental declaration in which he evaluated Mrs. Pluck’s illness under a "differential-diagnosis" methodology. The district court granted the motions, and plaintiff appealed.

In a toxic tort case, as here, the plaintiff must establish both general and specific causation through proof that the toxic substance is capable of causing, and did cause, the plaintiff’s alleged injury.  As to specific causation, the plaintiff must show that she was exposed to the toxic substance and that the level of exposure was sufficient to induce the complained-of medical condition (based on a dose-response relationship). Both causation inquiries involve scientific assessments that must be established through the testimony of a medical expert. Without this testimony, a plaintiff’s toxic tort claim will fail.

The Plucks had to concede that the expert Dr. Dahlgren did not establish dose; they instead argued that Dahlgren used differential diagnosis to determine specific causation. Defendant argued that Dr. Dahlgren did not apply differential diagnosis in either his expert opinion or his deposition, but did so only in an untimely supplemental declaration filed five months after the deadline for expert reports. And in any event, his approach was flawed. The Sixth Circuit has recognized differential diagnosis, properly done, as an appropriate method for making a determination of causation for an individual instance of disease. Differential diagnosis -- originally a standard technique for determining what disease caused a patient's symptoms -- has been adapted in some courts as an acceptable scientific technique for identifying the cause of a medical problem by eliminating the likely causes until the most probable one is isolated. A physician who applies differential diagnosis to determine causation considers all ("rules in") relevant potential causes of the symptoms and then eliminates ("rules out") alternative causes based on a physical examination, clinical tests, and a thorough case history.

Even in courts that accept this adapted method, not every opinion that is reached via a differential-diagnosis method will meet the standard of reliability required by Daubert.  Calling something a “differential diagnosis” or “differential etiology” does not by itself answer the reliability question but prompts at least three more:

(1) Did the expert make an accurate diagnosis of the nature of the disease?

(2) Did the expert reliably rule in the possible causes of it?

(3) Did the expert reliably rule out the rejected causes?

If the court answers “no” to any of these questions, the court must exclude the ultimate conclusion reached.

Here the court agreed that Dahlgren could not reliably “rule in” benzene exposure as the cause of Mrs. Pluck’s NHL. In recognition of the fact that benzene poses a health concern at certain levels of exposure, the EPA has stated that the maximum permissible contaminant level for benzene in
drinking water is 5 ppb. 40 C.F.R. § 141.61(a)(2). Dahlgren, however, did not ascertain Mrs. Pluck’s level of benzene exposure, nor did he determine even whether she was exposed to quantities of benzene exceeding the EPA’s safety regulations. The levels of benzene in the Plucks’ wells never exceeded the maximum permissible contaminant level of 5 ppb designated by the EPA.

Dahlgren’s opinion that Mrs. Pluck’s “low-level exposure” to benzene caused her NHL was thus not grounded in “sufficient facts or data,”  nor did it reflect the “reliable principles and methods” required by Rule 702. It was, instead, pure conjecture.  Although the Plucks argued that the district court required too much specificity regarding Mrs. Pluck’s dose, this argument was also without merit. The mere existence of a toxin in the environment is insufficient to establish causation without proof that the level of exposure incurred could cause the plaintiff’s symptoms. See also McClain v. Metabolife Int’l, Inc., 401 F.3d 1233, 1242 (11th Cir. 2005) (causation “requires not simply proof of exposure to the substance, but proof of enough exposure to cause the plaintiff’s specific illness”).

Finally, even if Dr. Dahlgren had properly “ruled in” benzene exposure as the cause plaintiff's NHL, he failed to “rule out” alternative causes of her illness, as is required under the differential-diagnosis methodology. See also Wills v. Amerada Hess Corp., 379 F.3d 32, 50 (2d Cir. 2004) (expert’s opinion suffered from a “fatal flaw” when he acknowledged that cigarettes and alcohol were risk factors for developing squamous-cell carcinoma but failed to account for these variables in concluding that decedent’s cancer was caused by exposure to toxic chemicals such as benzene and PAHs).  In this case, Dahlgren acknowledged in his deposition that Mrs. Pluck was
exposed to other sources of benzene, from her extensive smoking habit and from other organic solvents.  Yet, Dr. Dahlgren neither identified these other solvents nor determined Mrs. Pluck’s potential level of exposure to these other possible sources of benzene.Thus, Dahlgren failed to “rule out” alternative causes of Mrs. Pluck’s NHL.

The court of appeals determined that the district court did not abuse its discretion in concluding that the expert did not perform a reliable differential diagnosis.  And summary judgment properly followed.

 

MDL Court in Peanut Butter Litigation Grants Multiple Summary Judgments For Defense

The MDL court overseeing the coordinated federal litigation stemming from a 2007 peanut butter recall recently granted summary judgment to the defendant manufacturer ConAgra Foods in multiple cases.  See Southern v. ConAgra Foods Inc., MDL 1845, No. 09-1544  (N.D. Ga. 9/29/10).

Readers may recall that in 2007, ConAgra Foods Inc. recalled jars of Peter Pan and Great Value peanut butter that were made at its Georgia plant, after the CDC and FDA observed a possible association between these products and reports of salmonella poisoning.  As part of the recall, ConAgra instructed consumers to discard the jar but to save the lid, which contained the product code identifying when and where the peanut butter was manufactured.  After the recall, multiple consumers sued ConAgra, alleging they had contracted salmonella after eating either Peter Pan or Great Value peanut butter. The lawsuits were consolidated in an MDL in the Northern District of Georgia.

To prove causation, each plaintiff must show that it is more likely than not that contaminated peanut butter caused his or her illness. The best way to show that peanut butter is contaminated with Salmonella is to test the peanut butter itself, said the court. The fact that the peanut butter was recalled here does not mean that it was contaminated. In fact, most of the recalled peanut butter was completely free of Salmonella contamination. During discovery, accordingly, ConAgra asked the plaintiffs to provide the product code for the peanut butter that allegedly caused their illnesses. It also asked the plaintiffs whether they submitted a blood, urine, or stool sample to a doctor for testing. Because the symptoms of Salmonellosis are similar to those of other common gastrointestinal illnesses, these samples were important in determining causation, said defendant.

Here, the 19 plaintiffs could not establish causation, as a matter of law. First, they could not show that the peanut butter they ate was manufactured by ConAgra at the Sylvester plant during the outbreak.  Plaintiffs did not know the product codes from their peanut butter. Without these numbers, which indicate when the peanut butter was manufactured, it was impossible to know whether the peanut butter was at risk of contamination.

Second, the plaintiffs did not provide enough evidence to show that they contracted Salmonellosis shortly after eating the peanut butter. Symptoms alone are not enough to permit a reliable diagnosis of this disease because the symptoms of Salmonellosis – usually diarrhea, abdominal cramps, and fever – are more commonly associated with viruses, parasites, fungi, other bacteria, toxins, and various chronic diseases. Indeed, the CDC estimates that nearly 300 million cases of diarrhea and related gastrointestinal symptoms occur each year of other causes. A positive blood, urine, or stool sample is the best way to show that Salmonella caused a plaintiff’s illness. A proper differential diagnosis by a physician who examined and treated a plaintiff during his illness may also support a finding of causation in some cases, said the court.  

But none of the plaintiffs here provided evidence of a differential diagnosis or a positive blood, urine, or stool culture. None of the plaintiffs' available medical records indicated that the plaintiffs’ doctors considered and excluded other causes or performed any form of differential diagnosis or diagnostic tests. To the contrary, the records showed that most plaintiffs did not even visit the doctor until several months after eating the allegedly contaminated peanut butter.

Without more, concluded the court, no reasonable jury could find that it was more likely than not that
contaminated peanut butter caused the plaintiffs’ alleged illnesses.

 

 

Court of Appeals Vacates Jury Verdict for Plaintiff in Welding Case

The Sixth Circuit last week vacated one of the rare plaintiff verdicts in the welding rod litigation.  Tamraz  v. Lincoln Electric Co., et al., 2010 WL  3489002 (6th Cir. 9/8/10).  The key issue in the appeal was the trial court's decision to allow a causation expert, Dr. Walter Carlini, to testify on behalf of the plaintiff Jeff Tamraz over defendants' Daubert challenge.

From roughly 1979 to 2004, Jeff Tamraz worked as an independent-contracting welder in California, on bridges and buildings.  Plaintiffs contended that Mr. Tamraz suffers from manganese-induced Parkinsonism as a result of exposure to manganese-containing welding fumes on these jobs.

The case went to trial in 2007, and the jury in the Northern District of Ohio (plaintiffs are from Oregon) returned a plaintiff verdict, awarding $17.5 million to Jeff Tamraz in compensatory damages and $3 million to his wife, Terry Tamraz, for loss of consortium.

Defendants, including Lincoln Electric, Hobart Brothers Co. and ESAB Group Inc., appealed on various grounds, including the trial court's decision to permit the testimony of Dr. Carlini on causation issues despite the Daubert challenge.

The opinion offers a number of useful observations for toxic tort litigation, especially on the almost-always central issue of causation.

It begins with a nice overview of the science on the spectrum of movement disorders often termed "parkinsonism" that have different causes and different but overlapping symptoms.  No one disputed that plaintiff here suffered from parkinsonism; the questions were what kind and from what cause. Apparently, every doctor to examine Tamraz reached a different conclusion about one or both of those issues.  Plaintiff's expert concluded that Tamraz suffers from “manganese-induced parkinsonism,” but not in the sense of a manifestation of the disease "manganism," as that phrase is sometimes used in these welding cases. Rather, he believed that manganese exposure caused something closely akin to traditional Parkinson's Disease in Tamraz.  Dr. Carlini hypothesized that Tamraz might have a genetic predisposition to Parkinson's Disease, and that manganese in lower levels than necessary to cause true manganism might nevertheless “trigger” the symptoms of Parkinson's Disease, like “the straw that broke the camel's back.” He did not believe that Tamraz has Parkinson's Disease in the strict medical sense, but manganese caused a disease that he believed to be otherwise similar to Parkinson's Disease. 

Defendants disputed this conclusion that manganese exposure caused the illness; that is, they challenged Dr. Carlini's etiology (what caused the disorder diagnosed?), not the methodology to arrive at his general spectrum diagnosis (what disorder caused the set of symptoms observed?).  And the Sixth Circuit agreed there were serious issues here. The problem here was that, when Dr. Carlini testified that manganese exposure caused Tamraz's condition, he went beyond the boundaries of allowable testimony under Rule 702.

The opinion was at most a working hypothesis, not admissible scientific “knowledge.” Fed.R.Evid. 702. His theory was a "plausible hypothesis. It may even be right. But it is no more than a hypothesis."  For example, the expert admitted that the literature hypothesizing a link between environmental toxins and latent genetic Parkinson's Disease was “all theoretical.”  He also conceded there were no studies finding a link between manganese and true Parkinson's Disease.  He further he conceded that he was speculating that Tamraz had an underlying predisposition to Parkinson's Disease, even though Tamraz had no family history of Parkinson's Disease. 

And finally, even if manganese could cause Parkinson's Disease in someone like Tamraz, that did not show that manganese did cause Tamraz's Parkinson's Disease. Parkinson's Disease occurs commonly in the general population and usually without any known cause. Any given case of Parkinson's Disease thus might have occurred regardless of the manganese exposure, making it hard to attribute one case to manganese exposure over all of the other possible causes.

Plaintiffs stressed on appeal that Dr. Carlini opined “with a reasonable degree of medical certainty,” but the court of appeals correctly noted that the phrase --the conclusion by itself-- does not make a causation opinion admissible. The “ipse dixit of the expert” alone is not sufficient to permit the admission of an opinion. General Elec. Co. v. Joiner, 522 U.S. 136, 146 (1997). Minus that one phrase, nothing in this testimony took the opinion beyond speculation, theory, hypothesis. 

Plaintiffs, understandably, also tried to bolster the opinion by emphasizing areas of agreement among experts on the general diagnosis of some parkinsonism disorder.  But in conflating “manganese-induced parkinsonism” with manganism, plaintiff conflated diagnosis with etiology, erasing the distinction between Tamraz's disease and what caused it. Diagnosis and etiology, however, both were in play in this case. Because Dr. Carlini diagnosed Tamraz with something akin to Parkinson's Disease, not manganism, and because Parkinson's Disease unlike manganism has no standard etiology and lots of idiopathic cases, Dr. Carlini's etiology opinion had to rise or fall on its own.

Plaintiffs also trotted out the standard "differential diagnosis" argument, the tent that supposedly (and too often does) covers all kinds of unreliable causation opinions from medical experts.  The court here made some very useful observations about this issue. 

1) Most treating physicians have more training in and experience with diagnosis than etiology. See D. Faigman, Judges as “Amateur Scientists”, 86 B . U. L.Rev. 1207, 1221-22 (2006); E. Imwinkelried, The Admissibility and Legal Sufficiency of Testimony About Differential Diagnosis (Etiology), 56 Baylor L.Rev. 391, 405 (2004); M. Henefin, Reference Guide on Medical Testimony, in Reference Manual on Scientific Evidence 439, 471-72 (2d ed.2000). 

2) When physicians think about etiology in a clinical setting, moreover, they may think about it in a different way from the way judges and juries think about it in a courtroom. 

3) Getting the diagnosis right matters greatly to a treating physician, as a bungled diagnosis can lead to unnecessary procedures at best and death at worst. See Bowers v. Norfolk S. Corp., 537 F.Supp.2d 1343, 1361 (M.D.Ga.2007). But with etiology, the same physician may often follow a precautionary principle: If a particular factor might cause a disease, and the factor is readily avoidable, why not advise the patient to avoid it? Such advice  --telling a worker, say, to use a respirator-- can do little harm, think the doctors, and might do some good. See J. Hollingsworth & E. Lasker, The Case Against Differential Diagnosis: Daubert, Medical Causation Testimony, and the Scientific Method, 37 J. Health L. 85, 98 (2004). A lower threshold for making a causation decision serves well in the clinic but not in the courtroom, said the court. 

Of course, some courts permit the physician to testify as to etiology using this methodology, e.g., Hardyman v. Norfolk & W. Ry. Co., 243 F.3d 255, 260-67 (6th Cir.2001), but even these courts must apply the Daubert principles carefully in considering it. The ability to diagnose medical conditions is not remotely the same as the ability to deduce, in a scientifically reliable manner, the causes of those medical conditions. Gass v. Marriott Hotel Servs., Inc., 501 F.Supp.2d 1011, 1019 (W.D.Mich.2007), rev'd on other grounds, 558 F.3d 419 (6th Cir.2009). Doctors thus may testify to both, at least in the Sixth Circuit, but the reliability of one does not guarantee the reliability of the other. 

Thus, whether plaintiffs described Dr. Carlini's causation methodology as “differential etiology” or “differential diagnosis,” that label does not make it reliable. Using the differential diagnosis method is not some "incantation that opens the Daubert gate.”  The issues remain, did the expert make an accurate diagnosis of the nature of the disease? Did the expert reliably rule in the possible causes of it? Did the expert reliably rule out the rejected causes? If the court answers “no” to any of these questions, the court must exclude the ultimate conclusion reached. See Best v. Lowe's Home Ctrs., Inc., 563 F.3d 171, 179 (6th Cir .2009).

Here, Dr. Carlini's opinion failed the last two prongs because his efforts to “rule in” manganese exposure as a possible cause, or to “rule out” other possible causes, turned on speculation and theory and hypothesis, not a valid methodology. 

While expressing sympathy for the plaintiffs, the court observed that ignoring Rule 702 — allowing the law to "get ahead of science" — would be just as unfair. Such an approach eventually would destroy jobs and stifle innovation unnecessarily, because it would impose liability on business based on speculation, not science.

Case remanded for new trial, with different evidence obviously. 

(The dissent would have found the challenge going to the weight, not admissibility of the testimony, and the trial court's decision not an abuse of discretion.)

General Causation Opinion Excluded by Eleventh Circuit in Autism Case

The Eleventh Circuit recently  affirmed a judgment for defendant Evenflo Co. in a suit by a plaintiff who had alleged that the car seat manufacturer was responsible for her son's autism. Hendrix v. Evenflo Co., 2010 WL 2490760 (11th Cir., 6/22/10).

Plaintiff alleged that her son sustained traumatic brain injuries when a child restraint system manufactured by Evenflo allegedly malfunctioned during a minor traffic accident. Hendrix further alleged that those brain injuries caused the son to develop autism spectrum disorder (“ASD”). The district court excluded testimony from two of Hendrix's expert witnesses that the accident caused the ASD, concluding that the methods used by Hendrix's experts were not sufficiently reliable under Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993). See Hendrix v. Evenflo Co., Inc., 255 F.R.D. 568 (N.D.Fla. 2009). The lower court then granted partial summary judgment to Evenflo on Hendrix's ASD claim, determining that without the excluded testimony there was no reliable evidence to support Hendrix's theory that the accident caused the ASD. Hendrix voluntarily dismissed, with prejudice, her remaining damages claims and filed a notice of appeal.

Hendrix's experts relied primarily on the controversial differential etiology method to link the child's traumatic brain injury to his ASD diagnosis. Differential etiology, said the court, is a medical process of elimination whereby the possible causes of a condition are considered and ruled out one-by-one, leaving only one cause remaining. It is a questionable extension of the method by which doctors diagnose a disease into the area of what caused the disease.

The Eleventh Circuit has previously held that, when applied under certain circumstances that it thinks will ensure reliability, the differential etiology method can provide a valid basis for medical causation opinions. The reliability of the method must be judged by considering the reasonableness of applying the differential etiology approach to the facts of this case and the validity of the experts' particular method of analyzing the data and drawing conclusions therefrom. According to the court, a reliable differential etiology analysis is performed in two steps. First, the expert must compile a comprehensive list of hypotheses that might explain the set of salient clinical findings under consideration; the issue at this point in the process is which of the competing causes are generally capable of causing the patient's symptoms. See Clausen v. M/V New Carissa, 339 F.3d 1049, 1057-58 (9th Cir.2003). Second, the expert must eliminate all causes but one.

With regard to the first step, the district court must ensure that, for each possible cause the expert “rules in” at the first stage of the analysis, the expert's opinion on general causation is derived from scientifically valid methodology.  Hollander v. Sandoz Pharm. Corp., 289 F.3d 1193, 1211 (10th Cir.2002); Siharath v. Sandoz Pharms. Corp., 131 F.Supp.2d 1347, 1362-63 (N.D.Ga.2001). This is because a fundamental assumption underlying differential etiology is that the final, suspected cause must actually be capable of causing the injury. Thus, here, the experts' purported use of the differential etiology method will not overcome a fundamental failure to lay the scientific groundwork for the theory that traumatic brain injury can, in general, cause autism.

The Eleventh Circuit has distinguished cases in which the medical community generally recognizes that a certain chemical or product can cause the injury the plaintiff alleges from those in which the medical community has not reached such a consensus. In the second category of cases, the district court must apply the Daubert analysis not only to the expert's methodology for figuring out whether the agent caused the plaintiff's specific injury, but also to the question of whether the drug or chemical or product can, in general, cause the harm plaintiff alleges. Thus, the district court must assess the reliability of the expert's opinion on general, as well as specific, causation.  In this regard, the court (like most) rejects the “post hoc ergo propter hoc fallacy" which assumes causality from temporal sequence; a mere temporal relationship between an event and a patient's disease or symptoms does not allow an expert to place that event on a list of possible causes of the disease or symptoms. Case studies and clinical experience, used alone and not merely to bolster other evidence, are also insufficient to show general causation.

Here, none of the medical textbooks and epidemiological studies submitted by the expert came close to providing useful evidence of a definitive causal link between traumatic head injuries and autistic disorders, and none provided even marginal support for plaintiff's theory of a relationship between abnormal cerebral spinal fluid pressure and problems with cerebellum pressure, leading to autism. For example, the text chapter listing the known etiological factors involved in ASD does not mention acquired trauma in the perinatal brain.

Plaintiff also attempted to sidestep the deficiencies in the medical literature by focusing on the expert's experience and training. Merely demonstrating that an expert has experience, however, does not automatically render every opinion and statement by that expert reliable. The witness must explain how that experience leads to the conclusion reached, why that experience is a sufficient basis for the opinion, and how that experience is reliably applied to the facts. The trial court's gatekeeping function requires more than simply “taking the expert's word for it.”

Judgment for defendant affirmed.

Sixth Circuit Weighs In On Differential Diagnosis

A federal appeals court has reinstated a suit in which a Tennessee plaintiff alleged his exposure to a pool cleaner caused him to lose his sense of smell. The 6th Circuit found that the trial court had improperly excluded his medical expert from testifying. Best v. Lowe's Home Centers Inc., 2009 WL 1010883 (6th Cir.  4/16/09).

Of great interest to readers of MassTortDefense is the court’s treatment of the concept of differential diagnosis. This diagnostic method has long been used by treating physicians to assess what ails a patient, and it involves a logical process of ruling in and ruling out possible diagnoses based on symptoms, test results, and other medical evidence. The process has been hijacked by plaintiff experts to offer an aura of reliability to opinions not only about the diagnosed injury, but the cause of the injury. Plaintiff experts may make no effort to establish why a cause is even on the list to be ruled out (assuming general causation), and may rule out potential alternative causes with far less rigor than doctors would exclude alternative diagnoses in the real world.

Plaintiff in Best claimed to suffer from permanent loss of his sense of smell as a result of a pool chemical spilling onto his face and clothing at a Lowe's Home Center store. Best planned to introduce the expert testimony of Dr. Francisco Moreno, a board-certified otolaryngologist, in order to establish the causal link between the chemical spill and his injuries. The district court excluded Dr. Moreno's testimony, holding that the method employed by the doctor in drawing his conclusions regarding causation was “unscientific speculation.” This resulted in summary judgment.

In summary, because of the temporal relationship between Best's exposure to the chemical and the onset of his symptoms, in conjunction with an effort to eliminate other possible causes of anosmia, Dr. Moreno formed the opinion that the inhalation of the Aqua EZ caused Best to lose his sense of smell. The 6th Circuit stated that Dr. Moreno thus employed a “differential diagnosis” methodology in forming his opinion. Differential diagnosis is, according to the court, the method by which a physician determines what disease process caused a patient's symptoms. The physician considers all relevant potential causes of the symptoms and then eliminates alternative causes based on a physical examination, clinical tests, and a thorough case history. Hardyman v. Norfolk & W. Ry. Co., 243 F.3d 255, 260 (6th Cir.2001). The court was less than precise in its treatment of the slippery slope between causation of symptoms (what disease is causing the symptoms) to causation of disease (what toxic exposure caused the disease that caused the symptoms).

Dr. Moreno formed his opinion regarding Best's alleged loss of his sense of smell by considering a list of the possible causes of such an injury, including virus, accident, tumor, surgery, or exposure to chemicals, as well as Best's use of medications. He noted that the chemical was quite concentrated, and relied on Best's report that the material splashed onto his face and clothing. Dr. Moreno ruled out medications as the cause, based on his knowledge of the side effects.

The 6th Circuit said it recognizes differential diagnosis as an appropriate method for making a determination of causation for an individual instance of disease. Differential diagnosis is considered to be “a standard scientific technique of identifying the cause of a medical problem by eliminating the likely causes until the most probable one is isolated.” Hardyman, 243 F.3d at 260 (quoting Westberry, 178 F.3d at 262).

But the court did note that not every opinion that is reached via a differential-diagnosis method will meet the standard of reliability required by Daubert. To determine which opinions do and do not, the court adopted the reasoning of the Third Circuit in In re Paoli Railroad Yard PCB Litigation, 35 F.3d 717 (3d Cir.1994).  A medical causation opinion in the form of a doctor's differential diagnosis is reliable and admissible where the doctor (1) objectively ascertains, to the extent possible, the nature of the patient's injury, (2) “rules in” one or more causes of the injury using a valid methodology, and (3) engages in standard diagnostic techniques by which doctors normally rule out alternative causes to reach a conclusion as to which cause is most likely. In connection with the third “rules out” prong, if the doctor engages in very few standard diagnostic techniques by which doctors normally rule out alternative causes, the doctor must offer a good explanation as to why his or her conclusion remains reliable. Similarly, the doctor must provide a reasonable explanation as to why he or she has concluded that any alternative cause suggested by the defense was not the sole cause.