To assess the cost-effectiveness of alternative strategies for the treatment of suspected influenza in otherwise healthy adults and to identify future research priorities using value of information analysis.
A decision model was used to estimate the costs and effects, in terms of quality-adjusted life-years (QALYs) of amantadine, zanamivir, and oseltamivir for the treatment of influenza in otherwise healthy adults using data predominantly from meta-analysis of randomized controlled trials. Probabilistic sensitivity analysis using Monte Carlo simulation was conducted. The expected value of perfect information for the entire model and for individual parameters was calculated.
Based on mean costs and effects, zanamivir is dominated by oseltamivir. The incremental cost-effectiveness ratio for amantadine (compared with no treatment) is £11,000 and £44,000 for oseltamivir (compared with amantadine). The probability that amantadine is cost-effective at a willingness to pay of £30,000 per QALY is 0.74, falling to 0.49 at £20,000 per QALY. Global expected value of perfect information (EVPI) is £2 m over 15 years if a willingness to pay threshold of £30,000 per QALY is assumed rising to £9.6 m at £45,000 per QALY. EVPI for only one parameter exceeds £500,0000 at £30,000 per QALY: the quality of life for untreated influenza.
At traditionally accepted values of willingness to pay for health benefits, it is unlikely that additional research would be an efficient use of scarce resources. The only exception to this would be to examine the health-related quality of life impact of influenza in an untreated patient group. If a higher threshold value were acceptable, there are a small group of parameters that may warrant further investigation. These would, however, require comparative, potentially expensive, research studies.