Health State Utilities for Patient's Current Health from Bipolar Type I Disorder

Abstract

Background: Bipolar Type I Disorder (BID) is a disabling mental disorder among young adults that places enormous psychological, social, and economic burdens on patients, their families, and health care systems and decreases quality of life (QOL). Few studies have investigated the quality-adjusted life-years (QALY), health state preferences, and utilities in patients with BID.

Aim of study: The aim of this study was to elicit health state utilities for current health among a sample of individuals with BID irrespective of their clinical conditions at the time of evaluation.

Methods: One hundred individuals with BID were consecutively enrolled in this cross-sectional study. Preferences were elicited from patients with visual analogous scale (VAS) and time trade-off (TTO). To assess quality of life, the Farsi version of the World Health Organization's QOL Instrument-Short Version (WHOQOL-BREF) was used. In addition, health state was assessed with the Short Form-36 (SF-36) health survey, and then a specially- derived reduced version of the SF-36 (the `SF-6D') was calculated as an alternative to existing preference-based measures of health for conducting economic evaluation of various interventions. Moreover, several clinical measures were administered to participants.

Results: The mean (S.D.) VAS, TTO, and SF-6D utility scores were 0.59 (0.21), 0.44 (0.33), and 0.61 (0.11), respectively. There were significant associations of most selected clinical characteristics with VAS and TTO scores. Additionally, there were strong correlations between all domains of WHOQOL-BREF and VAS scores as well as moderate to strong correlations with TTO scores. Furthermore, there were strong correlations between all scales of SF-36 scores and VAS scores as well as moderate to strong correlations between the scales of SF-36 scores and TTO scores.

Discussion: The current study showed that even unstable patients could evaluate their own health states. Furthermore, the present study showed substantial decrements in health-related life preferences among persons with BID. Additionally, the patients with most recent depressive or mixed episodes reported lower VAS scores than those with most recent manic episodes.

Limitations: This study was performed on a group of patients with BID in a referral psychiatric center. This sample can potentially make a selection bias. Furthermore, this study was cross-sectional.

Implications for health care provision and use: Generally, clinical features could explain more than half of the variances in VAS utility scores. Among all clinical features, severity of symptoms and duration of disease were among the main factors significantly associated with the utility decreases.

Implication for health policies: The present study data provide health state preferences useful for cost-utility and outcome-modeling studies as well as health policy and decision-making. Also, the evaluations were partially affected by severity of symptoms. Therefore, utilities obtained in this study can be utilized to develop QALY and provide utility values that can be used in economic models for cost-utility studies.

Implications for further research: The comparison of the utility in a group of patients in different mood episodes and in their controlled periods and calculating the proportion of each episode to total duration of disease and to the patient's life span in future investigations may add crucial information to the present knowledge. The evaluation of biological and non-biological therapies by measuring utility and health value as health output indicators is strongly suggested.