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Tumour markers: current status and future applications.

A variety of tumour marker tests are available for three major intended uses: screening, diagnosis, and monitoring. For each use, performance characteristics need to be well established. The value of a marker depends heavily on two predominant performance parameters--sensitivity and specificity. These parameters must be established with respect to the intended clinical use of the marker. Therefore, it is important to balance the analytical/clinical sensitivity and the resultant claims for the test. The FDA review and evaluation of a tumour marker test focuses upon the intended use and the clinical utility of the marker. The sponsor must prove all specific claims. The data must support well-designed scientific protocols and clinical studies[1]. Generally, a tumour marker test is evaluated based on its intended clinical use, epidemiological sensitivity, specificity, and prevalence. A particular tumour marker test will have higher predictive value when it is applied to a population with a higher prevalence of the type of cancer being studied. Clinical utility for screening use may be limited by low prevalence [2].