Pharmacogenetic tests clinical utility

IV. Why Are Most Pharmacogenetic Tests of Limited Clinical Utility ... 

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 this chapter, we provide an overview of the current state of pharmacogenetics in schizophrenia treatment. The most promising pharmacogenetic findings are presented for both antipsychotic response and commonly studied adverse reactions. The application of pharmacogenetics to schizophrenia treatment is discussed, with an emphasis on the clinical utility of pharmacogenetic testing and directions for future research. 

In these scenarios, the allele frequency of the variant is not considered to be different between the disease cohort and an appropriate control population. However, the hypothesis being tested is whether the polymorphism is associated with some relevant clinical characteristic, a defined phenotype, or a clinical subset of a heterogeneous syndrome. As discussed earlier, it may be difficult to ascertain disease risk when a variant from a single gene is one of several from multiple genes that together ascertain risk. Furthermore, disease modification effects may be part of a pharmacogenetic influence. In many cases, it is not ethical to withdraw or standardize therapy for all patients, so statistical methods need to be utilized to ascertain medication use as a confounder in analysis of a polymorphism s disease modification potential. 

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