Purpose of review
Screening and prevention of colorectal cancer is a public health priority. Fecal occult blood testing is a popular screening test because of its simplicity, noninvasiveness, and demonstrated mortality benefit. At the same time, guaiac tests suffer from poor sensitivity, limited ability to detect early lesions, the need for annual testing, low population compliance, and high costs of follow-up for false-positive tests. These limitations have sparked many innovations in stool testing.
Recent studies suggest that both community intervention and physician awareness are needed to improve patient compliance with fecal occult blood testing and colorectal cancer screening in general. Despite the low costs of the guaiac test, the high false positives and high false negatives of fecal occult blood testing lead to high costs and low cost-effectiveness when compared with endoscopic techniques. Fecal DNA testing promises to improve the performance characteristics of stool testing. Small trials of multitarget assays demonstrate a sensitivity for colorectal cancer of 62 to 91% and a sensitivity for adenomas of 26 to 73%. The specificity of these assays is high, ranging from 93 to 100%. The major drawback of fecal DNA testing, compared with other fecal colorectal cancer screening tests, is the cost.
Preliminary data on fecal DNA tests show better performance characteristics than fecal occult blood tests. In their current form, however, it is not clear that the added sensitivity merits the additional cost. These tests must be studied in larger cohorts of asymptomatic patients before adequate comparison can be made to established colorectal cancer screening techniques.