Public health aspects of breast cancer gene testing in Canada. Part 2: selection for and effects of testing

Criteria set by clinical services for referral for counselling and genetic testing are variable and often arbitrary. Empirical data and computer models are available to estimate the probability of being a mutation carrier, based on family and personal history. Surveys show that high proportions of women at risk of cancer and of women in the general population are interested in being tested, but this may be based on inflated perceptions of personal risk and limitations in understanding of the tests used and their implications. A high proportion of women with a positive family history have a greatly overestimated perception of their own risk, and even expert counselling has little impact on this. This risk perception may produce psychological distress and may reduce participation in screening programs. Counselling, while improving understanding, may also have little impact on prior interest in being tested. Interest in being tested relates to a wish to assess the risk for children, and hazards include potential health insurance discrimination. Testing may result in a reduction of psychological disturbance in those shown to be non-carriers, with little change in those shown to be carriers, but unwillingness to be tested may be related to psychological distress. The impact of publicity concerning genetic testing on perceptions of risk and on psychological disturbance, and the subsequent impact of counselling and intervention, require further assessment.