How do we value psychological outcomes in systematic reviews?

Article type
Authors
Richardson G, Bojke C, Bower P, Gardner C, Gately C, Lee V, Kennedy A, Rogers A
Abstract
Background: A previous systematic review of economic evaluations demonstrated that the majority of studies of self management interventions claim that these interventions are cost-effective. However, the measurement of effectiveness in these evaluations is often a psychological outcome measure (such as self-efficacy or autonomy) rather than a generic, utility based, outcome measure such as Quality Adjusted Life Years (QALYs). There is little evidence on the value of these psychological measures and, therefore, decision making becomes more complex.

Objectives: To determine whether a particular outcome measure, self-efficacy, is valued by consumers and whether consumers would trade improvements in self-efficacy for reductions in other characteristics such as health state.

Methods: Qualitative interviews, literature reviews and focus groups were used to identify the attributes that consumers felt were important to them. A discrete choice experiment (DCE), a questionnaire based stated choice method, was then used to explore the relative value of these attributes (characteristics). Initially, the DCE questionnaires were piloted on 27 people with chronic conditions and subsequently posted to a convenient sample of 511 chronically ill people.

Results: Four attributes were identified as being important to consumers, namely, health status, self-efficacy, GP access and level of isolation. These attributes were included in the DCE questionnaire. 359 of the 511 (70.2%) postal DCE questionnaires were returned. The results of the analysis were consistent with a priori expectations, that is, consumers preferred more 'health' to less, more 'self-efficacy' to less, quicker access to GPs, and less isolation, adding to the theoretical validity of the model. Consumers valued changes in the level of self-efficacy and were prepared to accept decrements in health status for improvements in self-efficacy.

Conclusions: Systematic reviews including psychological outcomes such as self-efficacy can be useful but require methods such as DCE to enable the estimation of the value of these outcomes.