Evaluating the Cost-Effectiveness of CYP2C19 Genetic Testing in Patients Who Have Experienced an Ischaemic Stroke or Transient Ischaemic Attack in England and Wales

OBJECTIVES: Anti-platelet therapy with clopidogrel is recommended to prevent further strokes in patients who have had an ischaemic stroke (IS) or transient ischaemic attack (TIA). However, clopidogrel is ineffective in patients with genetic variants of CYP2C19, which can be tested for in laboratories or using point-of-care (POC) tests. We aimed to assess cost-effectiveness of different CYP2C19 testing strategies in IS and TIA patients for a NICE diagnostic assessment.

METHODS: A hybrid decision tree and Markov model was developed to evaluate the costs and QALYs of testing strategies over a lifetime time horizon. Diagnostic strategies evaluated were: Laboratory testing; POC testing; and no testing. Diagnostic accuracy and treatment effect inputs were obtained from systematic literature reviews of diagnostic accuracy studies and RCTs, and other inputs taken from a large UK registry (SSNAP). The laboratory tests were assumed to be a ‘gold standard’ with assumed sensitivity and specificity of 1. Sensitivity of results to model assumptions and parameters were assessed in deterministic and probabilistic sensitivity analysis (PSA) and scenario analyses.

RESULTS: Both CYP2C19 testing strategies resulted in positive incremental QALYs and lower costs compared with the ‘no test’ strategy in both IS and TIA populations, with positive net monetary benefit (NMB) at a £20,000 per QALY willingness-to-pay threshold. PSA in the IS population found an average NMB of £6,138 and £6,214 for the Genomadix cube POC test, and lab test, respectively. In the TIA population PSA found an average NMB of £2,829 and £2,802, for the Genomadix cube POC test and lab tests, respectively. There was a positive NMB for both tests in all the scenario analyses conducted.

CONCLUSIONS: Testing for CYP2C19 mutations is cost-effective compared to not testing in both IS and TIA populations, with higher NMB for lab test in the IS population and POC test in the TIA population.