Clinical validity refers to the predictive value of a test for a
given clinical outcome (e.g., the likelihood that cancer will
develop in someone with a positive test). It is primarily
determined by the sensitivity and specificity with which a test
identifies people with a defined clinical condition within a
given population. Sensitivity of a test refers to the proportion
of people who test positive for a clinical condition among those
who actually have the clinical condition; specificity refers to
the proportion of people who test negative for a clinical
condition among those who do not have the clinical condition. In
the case of genetic susceptibility to cancer, clinical validity
can be considered at two levels: - Does a positive test identify
a person as having an increased risk of cancer? - If so, how
high is the cancer risk associated with a positive test? Thus,
the clinical validity of a genetic test is the likelihood that
cancer will develop in someone with a positive test result. This
likelihood is af