A national screening programme for familial hypercholesterolaemia in New Zealand?

Abstract

Background: Familial hypercholesterolaemia (FH) is the commonest inherited lipid disorder with a prevalence of 2-5 per 1,000 for heterozygous FH in Western countries. It causes premature atherosclerotic cardiovascular disease (CVD) but routine CVD screening may not detect it or may detect it late. The aim of this thesis was to explore whether or not a national screening programme for FH should be considered in New Zealand. Methods: The best available evidence for screening for FH was identified and reviewed. An analysis was conducted on a prospective New Zealand cohort of 437,042 adults without established CVD who had undergone routine CVD screening in the Auckland and Northland regions using PREDICT electronic decision support software. The prevalence of FH as indicated by primary healthcare practitioners during CVD risk assessment and by pragmatic criteria (primarily lipid fractions) selected from international diagnostic criteria were investigated. In addition, the lipid levels of individuals and the proportion on lipid lowering medication (LLM) among those considered to have FH, were described. Results: International guidelines consistently support FH screening. The evidence supporting these guidelines is largely observational, and it is unlikely that undertaking a randomised controlled trial to evaluate FH screening would be regarded as ethical. The prevalence of FH according to primary healthcare practitioners was 19 per 1,000 of which 60% were on LLMs after risk assessment. This group had a mean low density lipoprotein (LDL) of 3.4 mmol/L and a mean total cholesterol/high density lipoprotein (TC/HDL) of 4.4 (corresponding values for the total cohort were 3.2 mmol/L and 4.1, respectively). The prevalence of FH (definite, probable or possible) according to international diagnostic criteria ranged from 0.025 to 28 per 1,000. Approximately 33 to 79% were on LLMs after risk assessment. This group had mean LDL of 5.3 to 9.7 mmol/L, and mean TC/HDL of 5.6 to 9.1. Discussion: The diagnosis of FH as indicated by primary healthcare practitioners during CVD risk assessment in this cohort appears unreliable given the relatively low concentrations of lipid fractions in this group. International diagnostic criteria appear more reliable, although they yielded widely differing ranges in FH prevalence. Irrespective of which criteria are used, there appears to be an opportunity to bridge the gap in CVD prevention for those with FH in New Zealand. New Zealand currently lacks a national registry and an infrastructure to systematically screen and manage FH adequately. A national screening programme run by the National Screening Unit and integrated with all levels of healthcare may complement public health efforts to reduce the burden of CVD in New Zealand.