Limitations of the faecal occult blood test in screening for colorectal cancer

Background. A screening test should be acceptable, safe, Introduction simpl e, accurate, reliable, effective, and inexpensive. Screening for colorectal cancer with the faecal occult blood test is done to reduce the incidence a nd mortality from colorectal cancel: How does this test measure up to these requirements? Methods. The characteristics of faecal occult blood test are described by m eans of clinical epidemiology, analysing its compliance, sensitivity specif icity, positive predictive value, and its test performance in Bernoulli tri als. A decision tree and a Markov model are used to compare the cost-effect iveness of screening strategies involving faecal occult blood test and colo noscopy Results. After 5-10 years, patient compliance in a faecal occult blood test screening programme falls below 50%. Over 80% of the patients are likely t o leave the programme before its completion. Although the rest itself may s eem safe and simple, the high rate of false-positive, outcomes exposes many subjects To the potential complications of colonoscopy The high rate of fa lse-negative tests gives patients with colorectal cancer a false sense of s ecurity and delays their proper diagnostic work-up. In populations with low prevalence rates of colorectal cancel; faecal occult blood test becomes ve ry inaccurate in diagnosing colorectal cancer; as its positive predictive v alue falls below 5%. Its long-term test performance is unreliable in that i t comes to depend on the frequency with which the test is repeated. Arty ne gative or positive test result can be achieved by varying the frequency of test repetition. Screening by colonoscopy every five or ten years is more c ost-effective than screening by annual faecal occult blood rest in preventi ng, the occurence of colorectal cancer and its associated mortality Conclusions. Screening strategies for colorectal cancer involving faecal oc cult blood test should be abandoned.