Interobserver Variability and Feasibility of Polymerase Chain Reaction–Based Assay in Distinguishing Ischemic Colitis FromClostridium difficileColitis in Endoscopic Mucosal Biopsies

Abstract

Polymerase chain reaction (PCR)-based assays using stool samples are currently the most effective method of detecting Clostridium difficile. This study examines the feasibility of this assay using mucosal biopsy samples and evaluates the interobserver reproducibility in diagnosing and distinguishing ischemic colitis from C difficile colitis. Thirty-eight biopsy specimens were reviewed and classified by 3 observers into C difficile and ischemic colitis. The findings were correlated with clinical data. PCR was performed on 34 cases using BD GeneOhm C difficile assay. The histologic interobserver agreement was excellent (κ= 0.86) and the agreement between histologic and clinical diagnosis was good (κ = 0.84). All 19 ischemic colitis cases tested negative (100% specificity) and 3 of 15 cases of C difficile colitis tested positive (20% sensitivity). C difficile colitis can be reliably distinguished from ischemic colitis using histologic criteria. The C difficile PCR test on endoscopic biopsy specimens has excellent specificity but limited sensitivity.

Analysis of TaqMan Array Cards Data by an Assumption-Free Improvement of the maxRatio Algorithm Is More Accurate than the Cycle-Threshold Method

“…There is a number of reports related to the inter-rater agreement for diagnostic assays, particularly involving visual scoring [37–39], however those including PCR data are mostly focused at comparing this assay with other tests rather than the variability of PCR results issued by multiple operators [40]. To the best of our knowledge, this is the first study assessing the agreement between operators for the qPCR assay.…”

PCR vs “PCAren’t”

“…9 This study also emphasizes the critical importance of correlating molecular data with all available histologic, laboratory, and clinical information. Wiland et al 8 give an excellent example of this when they describe one of their cases that was histologically categorized as C difficile colitis, yet the patient tested negative by PCR-based stool assay. Upon clinical review, the patient had multiple convincing risk factors for ischemic colitis.…”