Pharmacogenetic tests predictive values

Several classic pharmacogenetic traits are listed in Table 8.1 and discussed below. For a variety of reasons, mostly reflecting the slow penetration of genetic thinking into clinical medicine and the limited predictive value of even the best-validated tests, these tests have been significantly underutilized. 

The low predictive values of pharmacogenetic tests for most polymorphic variants means there will be false positive (when PPV is low) and false negative (when NPV is low) test results. Both reduce the clinical utility of the tests. There are a number of reasons for the reduced predictive values. 

In light of the low predictive values of many pharmacogenetic tests, two other situations in which pharmacogenetic testing has been heralded need closer inspection their use in drug development and as a substitute for prescribing on an ethnic-racial basis. 

Since Congress gave it authority to regulate in vitro diagnostic tests in 1976, the FDA has included assessment of clinical validity based on data made available by the test s developer (Holtzman, 2000). In view of the paucity of published data on predictive values of pharmacogenetic tests, and the likelihood that many of them will be low (Table 9.2), data on clinical validity should be required before pharmacogenetic tests are used clinically.12... 

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