Fig 1

Flowchart showing an example of how the four epidemiologic parameters are related. In this example, a hypothetical cohort of one million Ashkenazi Jewish women is followed from age 20 to age 70. If the BRCA1 and BRCA2 mutation carrier rate is 1 in 40, then 25,000 mutation carriers are expected. Among these 25,000 mutation carriers, 10,000 (40% penetrance, Table 2) will develop breast cancer. When the clinical sensitivity estimate of 10% is applied (from Table 2), 90,000 women among nonmutation carriers are expected to develop breast cancer (10,000 / 0.1). The cumulative incidence is, therefore, 100,000 or 10%. Numbers in the remaining boxes in Fig. 1 are computed by subtraction.