Background: Colorectal cancer (CRC) screening by guaiac fecal occult blood test (gFOBT) can reduce the mortality of CRC. The new immunochemical fecal occult blood test (iFOBT) has possibly improved sensitivity and specificity without any dietary restriction.
Objective: The present study aimed to evaluate the sensitivity, specificity, positive and negative predictive values of iFOBT for CRC detection compared to the colonoscopic and pathologic findings in known CRC cases.
Material and Method: A multicenter prospective study was conducted in three university hospitals in Bangkok, Thailand, between May and August 2006. Stool samples from 100 histologically-proven CRC patients and 64 control cases with normal colonoscopic findings were collected for iFOBT (OC-Light, Nagase, Singapore) without dietary restriction.
Results: The results showed the sensitivity, specificity, positive and negative predictive values of iFOBT for CRC detection to be 91.0% (95% CI: 83.8-95.2), 93.8% (95% CI: 85.0-97.5), 95.8% (95% CI: 89.7-98.4) and 87.0% (95% CI: 77.0-93.0) respectively. The sensitivity for CRC according to Dukes’ stage was 71.4% (Dukes’ A), 88.0% (Dukes’ B), and 96.7% (Dukes’ C or D). The sensitivity was 84.2% for proximal colon and 92.6% for distal colon and rectum.
Conclusion: The iFOBT revealed high sensitivity, specificity, positive and negative predictive values for CRC detection without dietary restriction. It should be considered as a noninvasive tool for CRC detection.

Keywords: Immunochemical fecal occult blood test, FOBT, Colorectal cancer, Sensitivity, Specificity, Accuracy