Repeat stool testing for Clostridium difficile using enzyme immunoassay in patients with inflammatory bowel disease increases diagnostic yield

Background: The incidence and severity of Clostridium difficile infection (CDI) in patients with inflammatory bowel disease (IBD) is increasing. CDI is diagnosed by toxin enzyme immunoassay (EIA) or real-time polymerase chain reaction (PCR) performed on stool samples. An earlier study evaluating EIA in IBD patients with CDI suggested that more than one stool sample be tested to increase diagnostic yield. We investigated whether repeat stool testing improves diagnostic accuracy for CDI in hospitalized IBD patients compared to hospitalized patients with CDI and no IBD. Methods: We performed retrospective data analysis from January 2005May 2011 on 63,086 hospitalized patients who were tested for CDI using EIA or PCR. Of these, 2579 patients had IBD. Transition probabilities were calculated based on results from repeated tests. Results: Inclusive of all inpatients tested for CDI, 56,583 were tested using toxin EIA and 6503 were tested using PCR. In patients with no IBD, the first stool sample tested was positive in 90 and 94 with EIA and PCR respectively. In IBD patients tested using EIA, 101 were diagnosed with CDI. The first stool sample tested was positive in 81 of patients. Successive second and third stool samples yielded additional 14 and 5 CDI positive IBD patients. Conclusions: Approximately one in five IBD patients with CDI required repeat testing to yield a positive result with EIA. There are minimal diagnostic gains of repeat testing by EIA or PCR in patients without IBD. We recommend repeat stool testing for CDI when using EIA to increase diagnostic yield in IBD patients.