Proton pump inhibitors reduce the accuracy of faecal immunochemical test for detecting advanced colorectal neoplasia in symptomatic patients

Abstract

BACKGROUND: The faecal immunochemical test (FIT) is used in colorectal cancer (CRC) screening and for the detection of advanced colorectal neoplasia (AN) in symptomatic patients, but its accuracy could be improved. Our objective was to assess the impact of proton pump inhibitors (PPI) on the accuracy of the FIT in the detection of AN, namely advanced colorectal adenoma and CRC. METHODS AND FINDINGS: We performed a prospective study of 1002 individuals referred for a diagnostic colonoscopy at Bellvitge University Hospital from September 2011 through to October 2012. An exhaustive interview was performed by a gastroenterologist, prescription drug dispensing database was reviewed and the patient was given a FIT prior to colonoscopy. The positivity threshold of FIT used was ≥ 20 μg Hb/g feces and the main outcome was AN. AN was detected in 13.2% (133) of patients. The accuracy of FIT for detecting AN in the PPI users and non-PPI users were: sensitivity 43.0% vs 65.6%, P = 0.009; specificity 86.9% vs 92.3%, P = 0.010; and, predictive positive value 34.4% vs 55.5%, P = 0.007, respectively. In multivariate analysis, adjusting for potential confounders, PPIs were associated with false positives in AN detection by FIT (OR 1.63 CI 95% 1.02-2.59, P < 0.037). The ROC curve for the FIT in the detection of AN in the PPI users and non-PPI users was 0.68 (CI 95% 0.61-0.76) and 0.85 (CI 95% 0.79-0.90). CONCLUSIONS: PPI therapy reduces the accuracy of FIT for detecting AN in symptomatic patients.