Does stool collection method affect outcomes in immunochemical fecal occult blood testing?

PURPOSE: This paper compares the positive predictive value of an immunochem ical fecal occult blood test for colorectal neoplasms between the stool spe cimens obtained during the digital rectal examination and those obtained du ring the routine screening. METHODS: In a medical check-up, 1,688 subjects received both an immunochemical fecal occult blood test and a colonoscopy. Fecal occult blood was tested by two methods: digital rectal examination an d routine screening. The positivity rate of an immunochemical fecal occult blood test and the positive predictive value for colorectal cancer and larg e adenomatous polyp were determined by these two methods. RESULTS: The posi tivity rate and the positive predictive value were 5.4 percent and 19.8 per cent (4.4 percent for cancer and 15.4 percent for adenomatous polyp) in the digital rectal examination method and 3.5 percent and 27.1 per cent (6.8 p ercent for cancer and 20.3 percent for adenomatous polyp) in the routine sc reening method, respectively. These figures indicate a significant differen ce in the positivity rate (P < 0.01) and the positive predictive value (P < 0.05) between these two methods. CONCLUSIONS: These findings indicate that the stool obtained by routine screening has a better positive predictive v alue than stool collected during the digital rectal examination.