All patients with microscopic colitis who had biopsies of both the ascending and descending colon had positive slide review for at least one of the two sites, according to the findings of a single-center retrospective study.
“Microscopic colitis can be detected with 100% sensitivity by analyzing biopsy specimens from the ascending and descending colon. We propose a Western protocol (taking two biopsy specimens each from the ascending colon and the descending colon) in the evaluation of patients for microscopic colitis,” wrote Boris Virine, MD, of London (Ont.) Health Sciences Centre, Western University, together with his associates in Clinical Gastroenterology and Hepatology.
That is half the minimum number of samples recommended by current guidelines, the researchers noted. “The American Society for Gastrointestinal Endoscopy recommends two or more biopsy specimens from the right, transverse, left, and sigmoid colons; however, these recommendations were based on expert opinion rather than scientific evidence, and these guidelines have not been validated,” they wrote.
Microscopic colitis includes lymphocytic and collagenous subtypes, neither of which is grossly apparent on colonoscopy. “Endoscopists therefore often collect multiple random colonic biopsies, potentially oversampling, increasing times of colonoscopy and slide review,” Dr. Virine and his associates wrote.
To better pinpoint optimal biopsy sites and specimen numbers, they studied 101 patients consecutively diagnosed with biopsy-confirmed microscopic colitis at London Health Sciences Centre from 2017 through 2018. Patients with other colonic diseases were excluded from the study. Dr. Virine assessed all individual biopsy fragments, and another pathologist performed a second review of complex cases.
A total of 52 patients had biopsy-confirmed collagenous colitis – that is, normal crypt architecture, increased mononuclear inflammatory cells in the lamina propria, and a thickened subepithelial collagen band. Forty-two patients had lymphocytic colitis, defined as normal crypt architecture, increased mononuclear inflammatory cells in the lamina propria, and increased intraepithelial lymphocytosis. Seven patients had both disease subtypes.
For each patient, an average of nine (standard deviation, 4.9) biopsies had been collected. The most commonly sampled site was the ascending colon (biopsied in 47% of patients in whom at least one sample was labeled by site), followed by the descending colon (40%), rectum (21%), transverse colon (20%), sigmoid colon (15%), cecum (8%), and splenic and hepatic flexures (2% each). Diagnostic sensitivity was highest for the ascending colon (97%), transverse colon (96%), and sigmoid colon (91%) and lowest for the splenic flexure (75%), hepatic flexure (78%), and rectum (82%). The diagnostic sensitivity of the descending colon was 85%. However, all 39 patients with biopsies of both the ascending and descending colon had at least one biopsy that was positive for microscopic colitis (sensitivity, 100%).
“Based on the results of our study, collecting biopsy specimens from both the ascending and descending colons has the same overall sensitivity as following the guidelines,” the researchers concluded. “Because no single site in the colon was diffusely positive for microscopic colitis in 100% of cases, the possibility remains that collecting biopsy specimens from two sites could offer comparable sensitivity with biopsy specimens from each segment of the colon.”
No funding sources were reported. Dr. Virine and the senior author reported having no conflicts of interest. One coauthor disclosed ties to AbbVie, Allergan, Ferring, Janssen, Lupin Pendopharm, Pfizer, Shire, and Takeda.
SOURCE: Virine B et al. Clin Gastroenterol Hepatol. 2020 Feb 25. doi: 10.1016/j.cgh.2020.02.036.