Products Liability Law Daily Expert testimony failed to explain how rat studies applied to humans in MRI injury suit
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Monday, August 5, 2019

Expert testimony failed to explain how rat studies applied to humans in MRI injury suit

By Jeffrey H. Brochin, J.D.

Patients were unable to prove that MRI image-enhancing agent was a potential cause of their gadolinium deposition disease.

A federal district court in Arizona has granted motions to exclude expert testimony filed by manufacturers and distributors of gadolinium-based contrast agent (GBCA) in a case involving allegations of severe illness—gadolinium deposition disease (GDD)—in patients who were administered GBCA in the course of MRI imaging examinations. Although GBCAs are proven to cause nephrogenic systemic fibrosis (NSF) in patients who suffer from impaired kidney function, the patients who filed the instant claims were free from kidney disease, and their theory that GDD resulted from the contrast agent could not be proven (Davis v. McKesson Corp., August 2, 2019, Campbell, D.).

NSF versus GDD. Gadolinium is a rare earth metal that exhibits magnetism only in the presence of an externally applied magnetic field. Therefore, it is used in the MRI image-enhancing agent GBCA. Since their initial approval in 1988, GBCAs have been used more than 450 million times worldwide. Although all GBCAs are mostly eliminated from the body through the kidneys, in 2006 a strong association was detected between GBCA use in patients with advanced kidney disease and the development of the medical condition NSF. As a result, the U.S. Food and Drug Administration updated its Public Health Advisory for GBCAs, warning about the risk of NSF in patients with renal failure. That warning, along with policies and procedures adopted by healthcare facilities, led to the virtual elimination of new NSF cases.

The instant patients were not sufferers of renal disease, yet claimed they contracted GDD from GBCAs when the agent was not eliminated from their bodies. The issue before the court, therefore, was whether those patients could prove causation between their GDD and GBCAs.

Overcoming Daubert exclusion hurdle. The court noted that the patients could clear their Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), evidentiary hurdle on general causation if they presented expert opinions that GBCAs are in fact a cause of GDD, and that GBCAs were therefore a potential cause of their alleged illnesses. Stated differently, the issue before the court was whether the patients’ experts could present admissible opinions under Rule 702 that GBCAs are in fact a cause of GDD.

Unproven hypotheses not admissible. As the Supreme Court stated in Daubert, merely generating hypotheses—even reasonable ones—is not enough for admission of expert testimony; rather, in order to qualify as "scientific knowledge," an inference or assertion must be derived by the scientific method, and proposed testimony must be supported by appropriate validation based on what is known. Scientists whose conviction about the ultimate conclusion of their research is so firm that they are willing to aver under oath that it is correct prior to performing the necessary validating tests could be viewed by the court as lacking the objectivity that is the hallmark of the scientific method.

Causation experts’ testimony inadmissible. Based on the foregoing standard, the court examined the testimony of each of the causation experts proffered by the patients. Two of the experts had not conducted any independent research, but only studied the issue specifically in preparation for the instant cases. Their testimonies were excluded accordingly. As to the primary expert, he offered much detail as to the studies he had performed, and described how gadolinium in many free forms is toxic to humans. He noted that although most GBCAs are eliminated from the body by the kidneys, gadolinium is always retained in the body, even with normal renal function.

However, the court found that throughout his discussion, the primary expert mixed studies regarding NSF with case reports, surveys, animal data, and in vitro data. As to neurological effects, he discussed a study involving the direct injection of GBCAs into the brains of rats, and another study showing that intravenous injection of GBCAs could increase seizures in dogs when the permeability of the blood-brain barrier was altered. But he did not explain why the results of those studies could be extrapolated reliably to humans; he did not discuss doses in the studies and how they relate to doses in humans; and he did not explain why direct brain injections in rats and alteration of the blood-brain barrier in the dogs provided reliable information about the effects of GBCAs in humans with healthy kidneys.

The court found that the primary expert’s testimony did not satisfy the standard set forth in Daubert and, therefore, his testimony was ruled inadmissible. The court granted the GBCA manufacturers’ motions as to exclusion of the causation testimony.

The case is No. :2:18-cv-01159-DGC.

Attorneys: C. Brooks Cutter (Cutter Law P.C.) for Hilary Davis. Habib Nasrullah (Wheeler Trigg O'Donnell LLP) for McKesson Corp. and McKesson Medical-Surgical Inc. Alison Rebecca Christian (Christian, Dichter & Sluga, P.C.) for Guerbet LLC.

Companies: McKesson Corp.; McKesson Medical-Surgical Inc.; Guerbet LLC

MainStory: TopStory MedicalDevicesNews ExpertEvidenceNews CausationNews ArizonaNews

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