Cost-effectiveness analysis in severe mental illness: outcome measures selection

Abstract

Background: Most economic evaluations conducted in mental healthcare did not include widely recommended preference-based health outcomes like the QALY (Quality-Adjusted Life Years). Instead, studies have mainly been designed as cost-effectiveness analyses that include single outcome measures aimed at a (disease) specific aspect of health.

Aims of the study: To raise awareness about the potential problems related to the selection of outcome measures for economic studies in patient populations with severe mental illness. Furthermore, to make suggestions that may prevent these problems in future economic evaluations.

Methods: Data of a previously conducted economic evaluation assessing the cost-effectiveness of the HIT (Hallucination focused Integrative Treatment) intervention in patients with schizophrenia were used for the analyses presented in the current paper. Economic analyses based on the results of the selected primary health outcome (Positive and Negative Syndrome Scale: PANSS) were compared with results based on various other health outcomes assessed during the study, including QALYs.

Results: No relevant differences between groups were found on the single primary health outcome initially included in the cost-effectiveness analysis. In contrast, relevant and significant differences were identified on three of the four additionally assessed health outcomes. Conclusions based on the results of multiple cost-effectiveness analyses and acceptability curves were strongly in favour of the experimental intervention when including these three additional instruments. QALY results did not show differences between groups.

Discussion: Selecting between outcome measures for cost-effectiveness analysis in the field of mental healthcare appears to be a complicated process, which may have considerable consequences for the results of economic studies and subsequent policy decisions. It was argued that inconsistent results across the selected primary health outcome and additionally assessed health outcomes should explicitly be presented to decision-makers. Until there is consensus on a preference-based instrument suited for severe mental illness, QoL instruments could be applied instead of instruments aimed at specific aspects of health.

Implications for health policies: Decision-makers in the field of mental healthcare should be careful when interpreting results of economic studies that included outcome measures aimed at a specific aspect of health. Such instruments may provide too narrow a view on relevant changes in health and findings may be difficult to generalise. Due to current reservations on the use of QALYs in mental healthcare, QALY outcomes should be considered in the context of the results of additionally assessed health outcomes.