Interpreting the results of genetic tests for BRCA1 and BRCA2 mutations in patients requires careful consideration within a specialist genetics context. Positive test result indicates the presence of a pathogenic mutation, which confers a significantly increased lifetime risk of breast and ovarian cancer, necessitating tailored surveillance and risk-reducing strategies. Negative test result in a patient with a known familial mutation usually means the patient is not at increased genetic risk, but if no familial mutation is identified, a negative result does not exclude increased risk due to other factors. Variants of uncertain significance (VUS) require cautious interpretation and should be recorded in clinical genetics databases; their clinical implications are unclear and should not guide management decisions without further evidence.
Genetic testing should be preceded and followed by genetic counselling to explain the implications of positive, negative, or uncertain results, including the impact on the individual and their family. Testing is ideally first performed in an affected family member to identify a mutation before testing unaffected relatives. The probability of mutation carriage (usually ≥10%) guides eligibility for testing. Results should be integrated into a multidisciplinary care plan, including surveillance and preventive options, tailored to the individual's risk profile and preferences NICE CG164.