New technologies have been based on blood and cellular products of
neoplasia. Fecal occult blood tests (FOBTs) based on
guaiac (i.e. GFOBTs) have been proved to be effective, but their impact on mortality is modest. When GFOBTs are reconfigured to provide improved sensitivity for
cancer, their specificity often becomes unacceptable. Fecal immunochemical tests (FITs) targeting the human
hemoglobin molecule have been shown to have better sensitivity for
neoplasia without an unacceptable deterioration in specificity. The new stool-sampling technologies for FITs also improve population participation rates in screening. Most recently, quantitative FITs have become available; these provide flexibility for the end-user as a desired sensitivity: specificity ratio can be selected that is feasible in the context of available colonoscopic resources. A multi-target fecal
DNA test, comprising a test for undegraded
DNA and certain common mutations, was found more sensitive for
cancer, but not for
adenoma, than the early GFOBTs. A more recent version including an epigenetic marker for the
vimentin gene has further improved sensitivity for
cancer, but performance relative to GFOBT or FIT is not clear. These 'fecal
DNA tests' have not proved to be more specific for
neoplasia than tests that detect blood.
CONCLUSIONS: FIT should replace GFOBT as the first test in two-step screening of large populations. It is not yet clear that tests targeting nonhemoglobin molecular events provide a clear advantage over FIT.