For years physicians in the office setting have included a digital rectal exam and then tested stool captured by the gloved finger for occult blood.
A recent study published in the Annals of Internal Medicine compared the results of the single digital FOBT ( fecal occult blood test) with the take home FOBT kit which involves the patient testing 6 samples of stool at home presumably after following the dietary guidelines indicated in the literature found with the kit. 6 samples should be better than 1 in terms of sensitivity which is exactly what the researchers found in 2655 patients who also underwent screening colonoscopy.
The single FOBT test did badly, with a sensitivity of only 4.9% in detecting "advanced neoplasia" which was defined as tubular adenomas larger than 10 mm., adenomas with villous patterns, high grade dysplasia or invasive cancer. The six test kit did better with a sensitivity of 23.9%.
Specificities for the two tests were in the 90% plus range. The authors concluded that the single finger FOBT is a poor screening test and clearly it is not enough to do if the intent is screening for colon cancer or polyps. I would add that the six-sample method is certainly not a substitute for colonoscopy either.