We can chalk it up to advancing age, but we find that we repeat ourselves more often as we get older and more redundant. This dynamic is surely exacerbated by our insistence on use of the first person plural and the multiple posters here, who lack a Borg-like collective consciousness.  We have already posted twice this year on exclusions of Dr. Blond by Judge Middlebrooks in the Trasylol MDL.  Perhaps the latest decision is not so different than the prior decisions, but we have enjoyed reading decisions out of Trasylol since the memorable evisceration of noted author and serial “prostilocutor,” Suzanne Parisian, in In re Trasylol Products Liability Litigation, 709 F. Supp. 2d 1323 (S.D. Fla. 2010). Besides, decisions rejecting facile calls to “differential diagnosis” as a stamp of a reliable causation opinion have more use than awkward puns in our post titles.  Being punny matters, but kicking out the sort of “significant contributing factor” causation opinions that are often offered in drug cases matters more.

       After a counsel list almost as long as the opinion itself (at least in the standard Lexis format), In re Trasylol, MDL No.  1928, Case No. 09-81262, 2013 U.S. Dist. LEXIS 93552 (S.D. Fla. June 30, 2013), describes a fairly standard summary judgment issue: does the sole causation expert offered by plaintiff provide admissible causation testimony to support any of plaintiff’s claims?  Plaintiff had a double coronary bypass and aortic valve replacement surgery, during which he received the defendant’s anti-bleeding medication.  He subsequently experienced a stroke attributed to a cardiac embolus and also experienced a few days of further elevation of creatinine, a measure of kidney function that was already elevated upon plaintiff’s admission.  While the only injury addressed in Dr. Blond’s testimony was to plaintiff’s kidney, plaintiff’s spouse (also a plaintiff) testified that they were suing over the stroke and she was unaware of any kidney injury. Somewhat curiously, the court proceeded to evaluate the admissibility of Dr. Blond’s opinion on a renal injury.  An “injury” that produces no damages is typically not an injury you can get to trial on and, whereas plaintiff’s stroke was debilitating, his episode with further elevated creatinine went away without dialysis and apparently had no lasting effects.  It also did not equate to renal failure according to plaintiff’s treating physician, who considered “a transient rise in serum creatinine [] a fairly common postoperative (CABG) issue.”  Id. at *28 n.10.  Well, if a plaintiff has no proof of causation for the injury that produced damages and no admissible expert proof of causation for any injury, then he is definitely not supposed to get past summary judgment.  So, maybe spending the extra pages to analyze the admissibility of an opinion on a basically irrelevant injury was not so curious.

            As you would expect from the prior decisions, Dr. Blond’s causation opinion was purportedly derived from a differential diagnosis.  Based on his extensively quoted report, however, his causation opinion was pretty soft:  “causation was likely multifactorial,” with four identified risk factors for kidney injury other than defendant’s drug, which was still “a significant contributing factor.”  Id. at *42.  We are not quite sure why Dr, Blond’s report used the phrase “a significant contributing factor,” but it is not as strong as “the cause,” ‘the most likely cause,” “the most significant cause,” or even “the most significant contributing factor.”  As a matter of substantive law, different states have different standards for causation, regardless of the procedural requirements for admitting expert testimony in federal courts sitting in diversity.  This decision did not discuss the Illinois standards, perhaps because they were not raised by plaintiff to buttress the admissibility of Dr. Blond’s soft causation opinion. From our quick look at the Illinois Pattern Jury Instructions, there is nothing clearly adopting or rejecting the standard of “a significant contributing factor” in either the proximate cause instruction for negligence (“a cause that, in the natural or ordinary course of events, produced the plaintiff’s injury. [It need not be the only cause, nor the last or nearest cause. It is sufficient if it combines with another cause resulting in the injury.]”) or for strict product liability (“[a] [any] cause which, in natural or probable sequence, produced the injury complained of. [It need not be the only cause, nor the last or nearest cause. It is sufficient if it concurs with some other cause acting at the same time, which in combination with it, causes the injury.]”).  Wherever Dr. Blond got his phrase—maybe from the jury instruction on cause from somewhere else—it seemed like an obvious hint that even a veteran testifier for plaintiffs did not have much to implicate the defendant’s drug in this case.

            It turns out what he had was not sufficiently reliable to be offered at all.  Drawing on some fairly good law from the Eleventh and Seventh Circuits on differential diagnosis—as far as such law goes—the court took a hard look at what alternative causes Dr. Blond ruled in and how he ruled them out.  His report failed to account for several possible causes for kidney injury, some of which he acknowledged were possible contributors in plaintiff’s case.  Id. at **52-53. This failure was due in part to missing basic medical records on the plaintiff’s history of chronic renal disease and statements by treating physicians correlating his chronic and acute renal problems with hypertension.  Id. at *59. In whittling down the other risk factors present in plaintiff’s case to implicate the defendant’s drug (such as he did), Dr. Blond “fails to provide a reasonable explanation for why he concluded that [plaintiff’s] various risk factors other than exposure to [defendant’s drug] were not the sole cause of his renal injury.”   Id. at *57.  It is particularly noteworthy that Dr. Blond still failed despite the chance to buttress his methodology with some self-serving affidavit in response to the motion or even prior orders slamming him. The court chalked up Dr. Blond’s decision to implicate defendant’s drug among potential causes as a combination of improper reliance on temporal proximity and shamelessly focusing on the cause that helped plaintiff’s case.  Id.at **56-59.  These are no doubt correct, but we think there is something more fundamental at play.

            While Dr. Blond surely did a sloppy job with his differential diagnosis, we are not sure that you can really arrive at a reliable and legally sufficient specific causation expert opinion through differential diagnosis where all the expert says is that cause was “multifactorial” and the defendant’s product was in the mix.  UnderGuinn v. AstraZeneca Pharms. LP, 602 F.3d 1245, 1253 (11th Cir. 2010), “[a]lthough a reliable differential diagnosis need not rule out all possible alternative causes, it must 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.’“  See2013 U.S. Dist. LEXIS 93552, **49-50.  Guinn and other cases that the court cites focus the analysis on whether the expert can rule out alternative causes as the “sole cause” of plaintiff’s injuries.  This, however, turns the burden of proof of causation on its head.  The plaintiff has to prove the causation required by substantive state law, typically through expert testimony that meets applicable procedural requirements.  The cases requiring experts to have legitimate reasons for excluding alternative causes in arriving at reliable causation opinions are certainly consistent with Rule 702 and Daubert.  The court twice quoted one of our favorite pre-Daubert expert decisions, Viterbo v. Dow Chemical Co., 826 F.2d 420, 423 (5th Cir. 1987), in rejecting where an expert acknowledges the plaintiff’s injury “could have had numerous causes and . . . simply picks the cause that is most advantageous to [a plaintiff’s] claim.”  See 2013 U.S. Dist. LEXIS 93552, ** 52 & 58-59.  Once Dr. Blond acknowledged that “there’s no way [to] determine that one factor had more of an effect than the others,” he was actually acknowledging that he did not do a differential diagnosis at all.  Id. at *57.  He was just saying the use of defendant’s drug was a risk factor, which is not the same as a specific causation opinion.  The result here—exclusion of Dr. Blond’s opinion and summary judgment—is right, but we would like to see courts cut through the claim that a pseudo-specific causation opinion derived from a differential diagnosis and say simply “No, you did not do a differential diagnosis and you are not offering a real causation opinion.”

            In this case, we also saw one of the basic issues with the over-acceptance of differential diagnosis.  Clearly, exposure to the defendant’s product cannot be on the list of potential causes unless there is reliable evidence that it can cause the injury at issue (at relevant exposure levels).  The court cites law to that effect.  However, it started the meat of its analysis of Dr. Blond’s opinions by “assum[ing], without deciding that general causation has been established.”  Id. at **35-36 n.13.  We do not think such an assumption can ever be made, although considering general cause in a case without specific cause (or an injury that produced damages) may be a waste of time.

            Lastly, we have a practice note in anticipation of the dreaded and misleading (because defendants do not have the burden of proof on causation) reverse-Daubert motion by plaintiffs on defendants’ experts.  In determining that Dr. Blond’s causation opinions were not admissible, the court also noted that his reportwas “deficient” in failing to list acknowledged risk factors that plaintiff had as risk factors for plaintiff and failing to consider relevant medical records.  Id. at *59.  Without an extended diatribe on the pros and cons of different approaches to defense expert reports, it should suffice to say that the court’s approach here suggests a potential downside to abbreviating the discussion of potential risk factors.  There can be tendency to use verbiage like “plaintiff had various other risk factors, including but not limited to . . .” or “defendant’s drug cannot be implicated as the cause of plaintiff’s injury because of the presence of risk factors identified previously” and assume that details will be fleshed out in deposition.  Cost-conscious plaintiff lawyers in serial litigation, perhaps having spent a chunk of their budget on retaining an expensive veteran expert, may not depose all the defense experts in each case.  And you could be left with a report that does not give a detailed rejection of the plaintiff’s differential diagnosis opinion for a multifactorial injury that should not fly in the first place.  Or maybe we are just making up issues after defendant wins summary judgment.  It is a sunny Friday afternoon in July and our mind wanders.