Researchers at the University of Utah and Myriad Genetics investigated the use of positive and negative ‘predictive value’ analysis as one tool for health care workers to use to interpret BRCA1 and BRCA2 test results. A predictive positive decreases the risk of a false positive test. A predictive negative test decreases the risk of a false negative test. Results from their experiments show including the family history of the following relatives serves as useful predictive factors for interpreting the results of a BRCA1 and/or BRCA2 test:
- a person with a relative with ovarian cancer
- a relative with male breast cancer
- bilateral cancer in a patient
- breast cancer in a patient below 40 years of age
- breast cancer in one relative who is below 50 years of age
Using the relative family criteria listed above, a predictive value test is extremely useful for women whose pretest probability of breast and/or ovarian cancer is between 10 and 40%. The likelihood of a false-positive test decreases as the pretest probability increases. The false-positive rate for a person with a 10% pretest probability is 5%, while the false-positive rate for a woman with a 40% pretest probability is 1%. The likelihood of a false negative result increases as the pre-test probability of a mutation increases. The false-negative rate for a person with a 10% pretest probability is 2%, while the false-positive rate for a woman with a 40% pretest probability is 9%. The risk of a false positive test result is 0% for a woman with a pre-test probability of a mutation greater than 50%. For a woman with a pre-test probability of a mutation greater than 50%, the risk of a false negative, however, begins at 13% and increases.
Dr. Susan Neuhausen at the University of Utah reports, “The predictive value of BRCA1 and BRCA2 testing is comparable to breast biopsies and mammograms.”
Reference
Bansal, A., et al., “The Predictive Value of BRCA1 and BRCA2 Mutation Testing,” Genetic Testing, 4(1), 45-48, 2000.
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