The factors associated with negative colonoscopy in screening subjects with positive immunochemical stool occult blood test outcomes

Background: The immunochemical fecal occult blood test (iFOBT) is an alternative method to colonoscopy that can be used for colorectal cancer (CRC) screening. If the iFOBT result is positive, a colonoscopy is recommended. In this retrospective study, we identify factors associated with negative colonoscopy and positive iFOBT results obtained during CRC screening.

Methods: We collected data for subjects who received a colonoscopy at Taipei Veterans General Hospital after receiving a positive iFOBT result during CRC screening from January 2015 to December 2015. Subjects' baseline data, medications, and co-morbidities as well as colonoscopy and histological findings were recorded. A negative colonoscopy result was defined as no detection of any colorectal neoplasia including non-advanced adenoma, advanced adenoma, and adenocarciona. Multivariate logistic regression analysis was conducted to identify the associated factors in screening subjects with positive iFOBT but negative colonoscopy results.

Results: 559 (46.3%) out of 1207 eligible study subjects received a colonoscopy with a negative result. Multivariate logistic regression analysis revealed that the use of antiplatelets [odds ratio (OR) = 0.654; 95% confidence interval (CI), 0.434-0.986], occurrence of hemorrhoid (OR = 0.595; 95% CI, 0.460-0.768), and the existence of colitis/ulcer (OR = 0.358; 95% CI, 0.162-0.789) were independent factors associated with negative colonoscopy but positive iFOBT results during CRC screening. The colon clean level, underlying diseases of gastrointestinal bleeding tendency (e.g., chronic kidney disease, cirrhosis), and the use of anticoagulant or nonsteroidal anti-inflammatory agents were not associated with negative colonoscopy and positive iFOBT results.

Conclusion: The use of antiplatelet agents and the presence of hemorrhoids and colitis/ulcers were factors associated with negative colonoscopy and positive iFOBT results.