Objective  To evaluate the diagnostic value of three consecutive qualitative fecal occult blood tests (FOBTs) for colorectal polyps and cancer.

  Methods  We retrospectively reviewed patients who underwent three consecutive FOBTs in one week before a standard colonoscopy from August 2006 to April 2013 in Peking Union Medical College Hospital.The sensitivity and specificity of positive FOBT(1, 2, or 3 times) for diagnosing colorectal neoplasms(including polyps and cancer)were calculated. The impacts of colorectal neoplasm's location, amount, size, and histological features on FOBT results were also evaluated.

  Results  A total of 303 patients154 males and 149 females, aged (59.5±15.0)years were enrolled in this study. Colorectal neoplasms were recognized in 165 patients, in whom 119 patients were diagnosed with colorectal polyps and 46 with cancer. As for colorectal polyps, the sensitivity and specificity of positive FOBT were 71.4% and 52.7% for one time, 41.2% and 67.4% for two times, and 22.7% and 79.9% for three times. As for colorectal cancer, the sensitivity and specificity were 91.3% and 49.4% for one time, 80.4% and 72.0% for two times, and 54.3% and 84.8% for three times. Neoplasms in the left half colon and advanced neoplasms were significantly related to positive FOBTs (P=0.001).

  Conclusions  Three consecutive qualitative FOBTs can be used as a screening tool for colorectal polyps and cancer. Location and histological features of polyps may influence FOBT results.