Aspetti critici nella conduzione degli screening del cancro colorettale mediante sangue occulto nelle feci

Screening program for CRC is a complex public health intervention, but available data suggest that it is now time to implement it. Screening by faecal occult blood testing (FOBT) is already realistic and feasible despite endoscopic alternative recently proposed. FOBT is based on the assumption that colorectal neoplasms usually bleed with some intensity and frequency, thus allowing for the early detection of CRC or adenomas. Several randomised controlled studies have demonstrated that screening by Hemoccult II, a guaiac-based FOBT, can reduce mortality from CRC by 13% to 33% depending on the study design. The test is very simple but it is poorly sensitive and non specific for human hemoglobin. Alternative ways of testing such as rehydration of the slides or the use of modified tests (Hemoccult-Sensa) increase sensitivity and readability but specificity of the test becomes a critical point. Immunochemical tests are specific for human hemoglobin, not requiring dietary restrictions, partially or fully automated in some versions. In some way they appear more cost effective than guaiac testing. Frequency of testing and overall organization of the screening program for CRC are discussed as well.