Screening for colorectal cancer: alternative faecal occult blood tests.

Hemoccult-based colorectal cancer (CRC) screening, while shown to be effective in randomized controlled trials, is suboptimal; alternative faecal occult blood tests which are either modifications of current guaiac-peroxidase tests or newer technologies (immunochemical), are available and show real promise. The goals of the alternative tests are improved sensitivity with acceptable specificity and improved compliance by screenees. The process of demonstrating superiority to Hemoccult need not include mortality as an endpoint, but must involve a direct comparison in large numbers of screenees (say 20,000) with cancer yields, apparent specificity and compliance determined for each test. Only the more sensitive and more readable guaiac test, HemoccultSENSA, and the immunochemical test Immudia-HemSp (the international version is HemeSelect) have undergone such extensive testing and could be considered as acceptable alternatives to Hemoccult for population-based screening. Even then, the test positivity rate of HemoccultSENSA warrants checking in a pilot study in the target population because it may pose a problem of specificity in some populations.