Decision thresholds with genetic testing.

A genetic test is a test for the presence or absence of a genetic mutation. A positive test outcome that reveals a mutation associated with increased risk for a disease may lead a patient to seek preventive treatment provided that the penetrance (probability of developing the disease given the mutation) is sufficiently high. We derive the test threshold and the test-treatment threshold, which confine the mutation probability interval for the use of the genetic test. Test and treatment costs as well as a low penetrance rate of the mutation narrow this interval. We illustrate the model with parameters of the test for BRCA1 and BRCA2 genes as well as of preventive treatment options for breast cancer.