Alternative cascade-testing protocols for identifying and managing patients with familial hypercholesterolaemia: systematic reviews, qualitative study and cost-effectiveness analysis.

Background

Cascade testing the relatives of people with familial hypercholesterolaemia is an efficient approach to identifying familial hypercholesterolaemia. The cascade-testing protocol starts with identifying an index patient with familial hypercholesterolaemia, followed by one of three approaches to contact other relatives: indirect approach, whereby index patients contact their relatives; direct approach, whereby the specialist contacts the relatives; or a combination of both direct and indirect approaches. However, it is unclear which protocol may be most effective.

Objectives

The objectives were to determine the yield of cases from different cascade-testing protocols, treatment patterns, and short- and long-term outcomes for people with familial hypercholesterolaemia; to evaluate the cost-effectiveness of alternative protocols for familial hypercholesterolaemia cascade testing; and to qualitatively assess the acceptability of different cascade-testing protocols to individuals and families with familial hypercholesterolaemia, and to health-care providers.

Design and methods

This study comprised systematic reviews and analysis of three data sets: PASS (PASS Software, Rijswijk, the Netherlands) hospital familial hypercholesterolaemia databases, the Clinical Practice Research Datalink (CPRD)-Hospital Episode Statistics (HES) linked primary-secondary care data set, and a specialist familial hypercholesterolaemia register. Cost-effectiveness modelling, incorporating preceding analyses, was undertaken. Acceptability was examined in interviews with patients, relatives and health-care professionals.

Result

Systematic review of protocols: based on data from 4 of the 24 studies, the combined approach led to a slightly higher yield of relatives tested [40%, 95% confidence interval (CI) 37% to 42%] than the direct (33%, 95% CI 28% to 39%) or indirect approaches alone (34%, 95% CI 30% to 37%). The PASS databases identified that those contacted directly were more likely to complete cascade testing (

Limitations

Systematic reviews were not used in the economic analysis, as relevant studies were lacking or of poor quality. As only a proportion of those with primary care-coded familial hypercholesterolaemia are likely to actually have familial hypercholesterolaemia, CPRD analyses are likely to underestimate the true effect. The cost-effectiveness analysis required assumptions related to the long-term cardiovascular disease risk, the effect of treatment on cholesterol and the generalisability of estimates from the data sets. Interview recruitment was limited to white English-speaking participants.

Conclusions

Based on limited evidence, most cost-effective cascade-testing protocols, diagnosing most relatives, select index cases by genetic testing, with services directly contacting relatives, and contacting second-degree relatives even if first-degree relatives have not been tested. Combined approaches to contact relatives may be more suitable for some families.

Future work

Establish a long-term familial hypercholesterolaemia cohort, measuring cholesterol levels, treatment and cardiovascular outcomes. Conduct a randomised study comparing different approaches to contact relatives.

Study registration

This study is registered as PROSPERO CRD42018117445 and CRD42019125775.

Funding

This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in

Familial hypercholesterolaemia is an inherited condition that causes raised cholesterol levels from birth and increases risk of heart disease if left untreated. After someone in a family is found to have familial hypercholesterolaemia (called an index case), their close relatives need to be contacted and checked to see if they have familial hypercholesterolaemia, using genetic or cholesterol testing. This is called ‘cascade testing’. We planned to find the most cost-effective and acceptable way to do this. The relatives could be contacted for testing by the index case (indirect approach), by a health-care professional (direct approach) or by a combination of both approaches. We found, based on looking at hospital records, that more relatives were tested if health-care professionals directly contacted relatives. In previous studies, slightly more relatives were tested for familial hypercholesterolaemia with a combination approach. Interviews with patients also suggested that the direct approach was the most effective, but the most acceptable and successful approach depends on family relationships: using one approach for some families and using both for other families. Furthermore, by looking at the health-care records of large numbers of patients, we confirmed that people with a recorded diagnosis of familial hypercholesterolaemia in general practice records have a much higher risk of heart disease than the general population, and this was especially so for those with previous heart disease and/or raised cholesterols levels when diagnosed. However, one-quarter of new patients with familial hypercholesterolaemia recorded in their records were not treated within 2 years, with less than one-third reaching recommended cholesterol levels. We used what we had learned to help us estimate the most cost-effective way to do cascade testing. This showed that if the health service directly contact all relatives simultaneously for further assessment, rather than the current approach whereby close (first-degree) relatives are contacted first, this was cost-effective and good value for money.