The authors made the following assumptions which underlie their estimate of the effectiveness:
(1)all gene tests are given at 25 years of age;
(2) the lifetime risk of colorectal cancer in general population is 6%;
(3) the median survival from colorectal cancer is 8 years;
(4)penetrance of the HNPCC genotype is 80%;
(5) the median age of diagnosis of HNPCC-related colorectal cancer is 45 years of age;
(6)the average number of years of life gained through the intervention is 20 years (9.76 years when discounted at 5%); and,
(7)implicit in the base case calculations,a 100% rate of accuracy of genetic testing.