The evaluation of cascade testing for familial hypercholesterolemia.

Familial hypercholesterolemia (FH) is an autosomal dominant disorder with a high risk of coronary heart disease at a young age that can be reduced by cholesterol-lowering drugs. Computer simulation was used to estimate the screening performance of three strategies of cascade testing for FH (a process of searching for relatives with FH once an individual is diagnosed with FH): (i) testing parents, siblings, and children (1st degree relatives) of an FH index case, (ii) testing (i) and testing 1st degree relatives of subsequently identified relatives with FH, and (iii) testing (ii) and also testing aunts, uncles, nephews, nieces, grandparents, and first cousins (2nd or 3rd degree relatives) when 1st degree relatives of an individual with FH are not available. For cascade testing to achieve detection rates of 80%, (i) 25%, (ii) 11%, and (iii) 8% of FH index cases who are unrelated need to be identified. To identify these unrelated FH index cases, (i) 45% (ii) 23%, and (iii) 17% of all individuals with FH need to be identified independently of cascade testing. Cascade testing is not a suitable method of population screening for FH, because a separate method of systematically identifying new FH index cases is required to achieve a reasonable level of FH detection in the population. Such an alternative systematic method of identifying new cases could itself be the method of population screening.