Maximising health or sufficient capability in economic evaluation? A methodological experiment of treatment for drug addiction

Conventional practice within the United Kingdom and beyond is to conduct economic evaluations with ‘health’ as evaluative space and ‘health maximisation’ as the decision making rule. However, there is increasing recognition that this evaluative framework may not always be appropriate, and this is particularly the case within public health and social care contexts. This paper presents a methodological case study designed to explore the impact of changing the evaluative space within an economic evaluation from health to capability wellbeing and the decision making rule from health maximisation to the maximisation of sufficient capability. Capability wellbeing is an evaluative space grounded on Amartya Sen’s capability approach and assesses wellbeing based on individuals’ ability to do and be the things they value in life. Sufficient capability is an egalitarian approach to decision making that aims to ensure everyone in society achieves a normatively sufficient level of capability wellbeing. The case study is treatment for drug addiction and the cost-effectiveness of two psychological interventions relative to usual care is assessed using data from a pilot trial. Analyses are undertaken from a health care and a government perspective. For the purpose of the study, Quality-Adjusted Life-Years measured using the EQ-5D-5L, Years of Full Capability equivalent and Years of Sufficient Capability equivalent, both measured using the ICECAP-A, are estimated. The study concludes that different evaluative spaces and decision making rules have the potential to offer opposing treatment recommendations. The implications for policy makers are discussed.