Relationships between a sign of rectal bleeding and the results of an immunochemical occult blood test, and colorectal cancer

A cross-sectional study based on medical check-up was carried out to invest igate the association between signs of rectal bleeding and colorectal cance r, and the results of an immunochemical faecal occult blood test. The 9625 patients received both an immunochemical faecal occult blood test using a t wo-consecutive-day method and colonoscopy. They were then divided into two groups, according to the results of a self-completed questionnaire on the s igns of rectal bleeding. The positivity rate of the immunochemical faecal o ccult blood test as well as the positive predictive value for colorectal ca ncer were determined in these two groups. The faecal occult blood test was positive in 9.3% of patients with rectal bleeding and in 4.4% of patients w ithout rectal bleeding, and the positive predictive value for colorectal ca ncer was 0.79 and 0.27 in patients with and without rectal bleeding, respec tively. This indicates a significant difference in the positivity rate (P < 0.001) as well as the positive predictive value (P < 0.05) between these t wo groups. The results suggest that there are positive associations between the signs of rectal bleeding and the results of immunochemical faecal occu lt blood test, and between the patients presenting with rectal bleeding and colorectal cancer. (C) 2000 Lippincott Williams & Wilkins.