Genetic testing for mutations in BRCA1 and BRCA2, two genes predisposing to
breast and ovarian cancers, is available to women with a relevant family h
istory. The aim of this study was to estimate the positive and negative pre
dictive value of clinical sequence analysis of these genes. A reference gra
ph showing positive and negative predictive values over a range of pre-test
risk was derived, taking into account the sensitivity and specificity of a
full-sequence analysis test. High positive and negative predictive values
were found for women with pre-test risk between 4% and 40%, a range of risk
commonly seen in clinical testing. The predictive value of full sequence a
nd single-site analysis of BRCA1 and BRCA2, therefore, compares favorably w
ith other diagnostic medical tests. Our results provide a numerical estimat
e of the predictive value of BRCA testing, and as such, provide a valuable
tool to healthcare providers and families as they interpret BRCA1 and BRCA2
test results.