Re: Morris-Stiff G, Falk G, Kraynak L, et al.: The Cholecystokinin Provocation HIDA Test: Recreation of Symptoms Is Superior to Ejection Fraction in Predicting Medium-Term Outcomes. J Gastrointest Surg 2010

While it is important from time to time to visit and even revisit the validity and utility of diagnostic examinations, the recent paper “The cholecystokinin Provocation HIDA Test: Recreation of Symptoms Is Superior to Ejection Fraction in Predicting Medium-Term Outcomes” reports extraordinary findings which are not easily reconciled with published literature and clinical experience. First of all, 41 of the 42 patients with right upper quadrant pain and normal ultrasound examinations became persistently pain free following cholecystectomy, suggesting a nearly 100% prevalence of biliary dyskinesia in this population. Either the group studied was highly preselected and skewed to disease, or that the methods and criteria of evaluation (“gold standard”) were overly lax, which exaggerated the prevalence of disease in this cohort. Secondly, even if we accept that all 41 patients had biliary dyskinesia, it is equally remarkable that they all experienced “typical pain” following a 30-min Sincalide injection, reflecting a 100% sensitivity for this maneuver, which is in contradiction to a large body of prior clinical experience where infusion of Sincalide does not usually elicit pain, even in patients with documented disease. One has to wonder whether methodological issues are the cause of these anomalous findings. To wit, the paper is very short on details regarding the subjective measurement of pain. It is unclear when the patients were asked about the pain, as we are only told that they were interviewed in the outpatient clinic following the procedure. Was this done immediately following the procedure, or at the 2-week follow-up? Were any written instruments employed? Was there any attempt to grade the severity of the pain? It would seem that the most accurate assessment of symptoms during infusion of Sincalide would be made by directly observing and quizzing the patient during the actual infusion itself, and not by eliciting recollections at a follow-up interview. A similar lack of detail is noted with respect to the 2-week assessment and the subsequent final telephone follow-up. Finally, even were these extraordinary findings validated, elementary epidemiologic understanding dictates that it is impossible to evaluate a diagnostic study in a population where the prevalence of disease is nearly 100%. In this group, a diagnostic exam which calls every patient positive would be deemed to perform admirably, while the true ability to discriminate normal from abnormal would remain completely untested. Were this test to be ported to a population with a more normally distributed prevalence of disease, it is very possible that the specificity of this highly sensitive examination would be abysmal, leading to a large number of false positive normal patients. Since the study group only included a solitary patient without disease (who in fact experienced pain during Sincalide infusion), there is no way to evaluate specificity. It is an optimal time to revisit the validity and utility of the gallbladder ejection fraction as a marker of biliary dyskinesia in light of new standardized practice guidelines that have been recently promulgated by expert panels. A prospective clinical trial utilizing these newly codified best-