Key Takeaways
The GLP-1 MDL order requiring objective diagnostic testing provides another precedent for early resolution of threshold expert and injury requirements in personal injury product liability MDLs.
In the multidistrict litigation ("MDL") involving Ozempic and other glucagon-like peptide-1 receptor agonist medications ("GLP-1 Ras") prescribed for type 2 diabetes and chronic weight management, the court recently issued a threshold ruling requiring plaintiffs that allege gastroparesis (delayed stomach emptying) to support their claims with objective diagnostic testing. In re Glucagon-Like Peptide-1 Receptor Agonists Prods. Liab. Litig., MDL No. 3094, 2025 WL 2396801 (E.D. Pa. Aug. 15, 2025).
The decision followed early expert discovery and motions on the "cross cutting issue" of "whether a physician can reliably diagnose a patient with gastroparesis without performing a gastric emptying study." Id. at *1. The parties' experts agreed that "there must be objective evidence of delayed gastric emptying" to support claims of "all subsets of gastroparesis other than drug-induced gastroparesis." Id. at *3. The court therefore focused on the experts' disagreement as to what objective testing, if any, is needed to reliably diagnosis drug-induced gastroparesis.
Plaintiffs' experts opined that a differential diagnosis based on a plaintiff's clinical presentation alone, without a gastric-emptying study, is sufficient to establish drug-induced gastroparesis. Id. at *9-10. Defendants moved to exclude on the grounds that plaintiffs' experts' proffered approach was "nothing more than a symptoms-based methodology" that was "contrary to clinical guidelines" and unreliable. Id. at *12. The court agreed, citing a comprehensive literature review of peer-reviewed articles and diagnostic guidelines, all of which considered objective testing a diagnostic requirement for all forms of gastroparesis. Id.
The court held that "the mere statement by an expert that he or she applied a differential diagnosis in determining causation does not ipso facto make that application scientifically reliable or admissible." Id. at *10 (citation omitted). When an expert engages in "very few standard diagnostic techniques by which doctors normally rule out alternative causes" and "offers no good explanation as to why his or her conclusions remain[s] reliable," the differential diagnosis fails to satisfy Rule 702. Id.
The court thus excluded the diagnostic opinions of plaintiffs' experts under Rule 702 and held that a plaintiff alleging drug-induced gastroparesis must have undergone a gastric-emptying study at the time of diagnosis. Id. at *36. While acknowledging that this requirement may bar some plaintiffs' claims, the court emphasized that "it would be perhaps more unjust to hold Defendants potentially liable for damages based on an unreliable diagnosis." Id.
The court relied on the Third Circuit's decision in In re Zostavax, discussed previously in Re:Torts, which affirmed the dismissal of over 1,100 shingles cases for failure to comply with an order requiring plaintiffs to provide PCR testing, used to diagnose shingles, as a threshold requirement of causation. See In re: Zostavax (Zoster Vaccine Live) Prods. Liab. Litig.,2024 WL 3423709 (3d Cir. July 16, 2024).
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