Public preferences for health states with schizophrenia and a mapping function to estimate utilities from positive and negative symptom scale scores.

BACKGROUND: Schizophrenia is a common severe syndrome with a highly variable pattern of symptoms. The medications used to treat this disorder are expensive and may cause severe adverse effects. Little is known about how the public perceives health outcomes in schizophrenia or the potential adverse effects of antipsychotic medication. This complicates the use of standard cost-effectiveness analysis to set priorities for health resource allocation.
OBJECTIVE: In this study, we measured utility weights for a set of health states derived from Positive and Negative Symptom Scale (PANSS) scores, and a set of health states that included the presence of common adverse effects of medication, thus creating utility mapping function for clinical data.
METHODS: We presented a convenience sample of members of a large commercial Internet survey panel with digital video materials portraying eight different patterns of schizophrenia with varying levels of positive, negative and cognitive symptoms, and five common adverse effects of antipsychotic medications. We then elicited their standard gamble (SG) and visual analog scale (VAS) ratings using iMPACT3 computer program, with an automated error repair feature, deliberately over-sampling minority ethnic groups in the panel. We censored subjects with uncorrected errors in ratings and estimated utilities for each state by re-weighting responses to match United States population demographics.
SUBJECTS: 620 well-educated, ethnically diverse volunteers (54% Caucasian), who spanned a broad range of age groups and geographical regions of the US participated in this study.
RESULTS: Because of evidence of bias in ratings, 175 (29%) subjects with internal inconsistencies in ratings were censored from estimates of mean population utilities. In the remaining 441 subjects, SG utilities, re-weighted to match US population demographic profiles, ranged from 0.88 for mild schizophrenia to 0.47 extremely severe schizophrenia. Variability in the types of symptoms exhibited (positive, negative or cognitive) was less important to participants than the overall severity of each state. Modest reductions in symptoms (for example, from severe to moderate or moderate to mild) were associated with relatively large changes in utility (0.12-0.19). Adverse effects decreased utilities for states by amounts ranging from 0.09 (pseudo-parkinsonism) to 0.05 (obesity).
CONCLUSIONS: The public views schizophrenia is a very disabling syndrome and treatments that reduce symptoms produce important gains in utility, even if they do not induce a complete remission. Adverse effects significantly reduce utilities for states; therefore, cost-effectiveness analyses for this disorder should take adverse effects of treatment into consideration.