Recent advances in the understanding of the molecular genetics of cardiomyopathies present new challenges for clinicians that manage patients with these heart muscle diseases. Cardiologists in particular have to learn how to integrate this new knowledge into diagnostic strategies in order to improve the management of families with inherited cardiomyopathies. However the translational of this technology to routine practice is low. One reason for is probably the lack of data and uncertainties about the economic efficiency of such a strategy.
Wordsworth et al. recently published a cost-effectiveness study in Hypertrophic cardiomyopathy (HCM). HCM is the most common monogenic cardiac disorder and most frequent cause of sudden cardiac death (SCD) in young people and trained competitive athletes. Disease prevalence amongst adults is around 0.2% (1:500) and in recent studies the annual SCD rate from HCM is about 1% on average. HCM is caused by mutations in at least ten sarcomeric protein encoding genes and the inheritance is autosomal dominant, with the child of an affected parent having a 50% chance of inheriting the disease causing allele. The HCM phenotype is dynamic and the onset of cardiac expression (left ventricular hypertrophy diagnosed by echocardiography or ECG) may be delayed until adulthood, and sometimes until 40 to 60 years of age, a phenomenon known as age-related penetrance. Clinically, this presents a problem when assessing families with HCM, and the currently recommended follow-up strategy of relatives involves repeat evaluations every 1 to 5 years (according to age) with echocardiography and ECG.
The authors explored the cost-effectiveness of alternative methods of screening family members for HCM. They used an economic decision model comparing cascade screening by genetics, as opposed to clinical methods, for identifying individuals at risk of sudden death due to HCM. The model was built to estimate the lifetime resource costs and health outcomes (life years gained) of alternative strategies for assessing first degree asymptomatic family members of an individual diagnosed with HCM (proband). According to detailed information from the literature, various information and simulations were entered into the model including the familial structure (1 to 3 children, the youngest aged 18 years old), the yield of genetic testing (63% in the proband, then 50% in each child), the sensitivity and specificity of screening tests (such as those of ECG and echocardiography according to age-groups), and the natural history of the disease (such as the prevalence of sudden death major risk factors and related mortality rates). Costs of alternative screening strategies were evaluated according to UK estimation, including the cost of molecular testing (552 euros for the proband, 225 euros for a relative), of regular cardiac examination (ECG and echocardiography every 5 years), of associated consultations (cardiologist, geneticist sessions) as well as cost of ICD implantation (16910 euros), ICD replacement and follow-up.
The incremental cost per life year saved was 14397 euros for the cascade genetic compared with the cascade clinical approach, which is well bellow the acceptable threshold of 35000 euros per life saved (according to NICE decision making guidance, National Institute of Health and Clinical Excellence, UK). Genetic diagnostic strategies were more likely to be cost-effective than clinical tests alone. The costs for cascade molecular genetic testing were slightly higher than clinical testing in the short run, but this was largely because the genetic approach is more effective and identifies more individuals at risk.
The authors concluded that the use of molecular genetic information in the diagnosis and management of HCM is a cost-effective approach to the primary prevention of SCD in these patients. One explanation is that genetic strategy is able to discharge more individuals (individuals who do not carry the mutation) when compared to the clinical investigation.
This study represents a turning point as it is the first economic evaluation of the impact of genetic testing in hereditary cardiac diseases and the conclusion is clearly in favour of the use of genetic testing in familial screening.
Potential limitations of this economic decision model are related to the precise scenarios that were addressed but the authors carefully examined the detailed issues related to the strategies they evaluated. The price of genetic testing used for the proband was quite cheap and may have overestimated the real benefit of the genetic strategy, although such low price will be diffused very soon in many laboratories thanks to the coming next generation sequencing (NGS) that will revolutionize genetic practice. On the other hands, some points may have underestimated the benefit of genetic strategy as only first degree relatives were taken into account whereas other relatives may benefit from the cascade strategy thus amplifying the cost savings.
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