[Screening for colo-rectal neoplasms by the study of fecal occult blood]

Occult blood testing has been proposed as a screening tool for colorectal cancer. At the present time guaiac testing is considered the most suitable for mass screening. The specificity of the test is affected by diet. For this reason it is necessary to adhere to a meat-free diet while the necessity of eliminating peroxidase containing foods as uncooked vegetables and fruit is controversial. The sensitivity of guaiac test is affected by the intermittence of colorectal cancer bleeding, by the quantity of ascorbic acid and fibers in the diet and by the development modality of the test. The experience of the authors is based on a screening protocol applied on some populations in the province of Florence (Italy). The protocol is based on guaiac test and an anamnestic selection of high-risk patients. 6029 patients have performed guaiac test. In 1159 patients, the results of occult blood testing and sigmoidoscopy have been compared. This analysis accounts for a predictive value of 50%, a specificity of 95.6%, and a sensitivity of 68% for carcinomas and 21.3% for adenomas. In conclusion, guaiac testing seems to warrant a good cost/benefit ratio but because its sensitivity is too low, it is necessary to include other selective tools (the anamnestic questionnaire) as well as an over-all major effort in the research of more sensitive ways of testing.