Economic evaluation alongside a randomised controlled crossover trial of modified group cognitive behavioural therapy for anxiety compared to treatment-as-usual in adults with Asperger Syndrome

Background: There is a growing interest in using group cognitive behavioural therapy (CBT) with people who have Asperger Syndrome (AS) and comorbid mental health problems. This study aims to assess the cost-effectiveness of modified group CBT for adults with AS experiencing co-occurring anxiety compared to treatment-as-usual. Methods: Economic evaluation alongside a pilot, multi-centre, single-blind, randomised controlled crossover trial. Costs from the UK public sector (National Health Service and Social Services) and societal perspectives, quality-adjusted life-years (QALYs), incremental net (monetary) benefit (INB), expected value of perfect information, expected value of sample information, expected net gain of sampling, and efficient sample size of a future trial are reported. Results: Over 48 weeks, from the societal perspective, CBT results in additional costs of £6647, with only a 0.015 incremental gain in QALYs, leading to a negative INB estimate of £6206 and a 23% probability of cost-effectiveness at a threshold of £30,000/QALY. Results from sensitivity analyses support the unlikely cost-effectiveness of CBT, but indicate the potential for cost-effectiveness over longer time horizons. Eliminating decision uncertainty is valued at £277 million and the efficient sample size for a future trial is estimated at 1,200 participants per arm. Limitations: Relatively small sample size and prevalence of missing data present challenges to the interpretation of the results. Conclusions: Current evidence from this small pilot study suggests that on average, modified group CBT is not cost-effective. However, there is much decision uncertainty so such a conclusion could be wrong. A large, full scale trial to reduce uncertainty would be an efficient investment for the UK health economy