Cost-effectiveness of HLA-B*1502 Genotyping in Adult Patients with Newly Diagnosed Epilepsy in Singapore

Objective: Asians who carry the HLA-B*1502 allele have an elevated risk of developing Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) when treated with the antiepileptic drugs (AEDs) carbamazepine (CBZ) and phenytoin (PHT). With a focus on Singapore, this analysis identifies circumstances in which genotyping and targeted treatment with alternative AEDs that do not induce SJS/TEN is likely to be more cost-effective than 1) treatment with CBZ or PHT without genotyping or 2) providing a more expensive drug that does not induce SJS/TEN to all patients without genotyping.

Methods: A decision tree model was developed in TreeAge. The model takes into account costs of epilepsy treatments and genotyping, reductions in quality of life and increased costs resulting from SJS/TEN complications, the prevalence of the risk allele, the positive predictive value (PPV) of genotyping, life expectancy, and other factors.

Results: Compared with no genotyping and providing CBZ to all, genotyping results in an incremental cost-effectiveness ratio of $37,030/quality-adjusted life year (QALY) for Chinese patients, $7,930/QALY for Malays, and $136,630/QALY for Indians in Singapore.

Conclusions: Because of the different population allele frequencies of HLA-B*1502 among different ethnic groups, genotyping for HLA-B*1502 and providing alternate AEDs to those who test positive is cost-effective for Singaporean Chinese and Malays, but not for Singaporean Indians. Population frequency of HLA-B*1502, PPV, duration of treatment relative to life expectancy, and costs of alternative drugs are the key drivers influencing cost-effectiveness.