The estimation of sensitivity and specificity in colorectal cancer screening methods.

The sensitivity and specificity of three screening tests for colorectal cancer were evaluated using latent class analysis. This type of analysis is useful in situations where screening tests are performed on each person and follow-up diagnostic test results are not available for individuals with negative test results. Traditional methods of evaluation, which assume these individuals to be disease free, may be biased under these circumstances. In addition to providing the parameter estimates, the latent class technique gives standard errors and permits significance tests for differences in sensitivity and specificity. It was found that the radial immunodiffusion technique was significantly more sensitive (p less than 0.001) than either the rehydrated or nonrehydrated Hemoccult II tests for detecting occult blood in patients with cancer or adenoma. While comparable to the rehydrated Hemoccult II test in terms of specificity, the radial immunodiffusion technique was significantly less specific (p less than 0.01) than the nonrehydrated Hemoccult test. Similar results were observed when restricting the analysis to cancer only.