Preference-based measurement of health-related quality of life (HRQL) in children with chronic musculoskeletal disorders (MSKDs)

Background. Health-related quality of life can be measured by patients' health preferences (utilities or values). No method for measuring health state preferences has been standardized for children with arthritis or other musculoskeletal disorders (MSKDs). Such a method is needed for economic evaluations of current and new pediatric treatments. Objectives. 1) To assess the feasibility of utility measurements in children with MSKDs, 2) to test the validity of the Health Utility Index (HUI) for these children, 3) to assess whether rating scale values can be mathematically converted into meaningful standard gamble (SG) utilities, and 4) to study whether parents can act as proxies for their children with respect to health state preferences. Methods. Eighty parents of children with MSKDs were consecutively sampled. Their children, if 8 years of age or older (n = 55), were studied concurrently. Utilities of current health states were obtained by using the SG and the HUI in random order. In addition, health state preferences were assessed using categorical and analog rating scales. Traditional nonutility measures of health status (the Childhood Health Assessment Questionnaire [CHAQ] and the Activities Scale for Kids [ASK]) were also completed. Intraclass correlation coefficients (ICCs) were calculated to assess concordance between the different utility measures and also between the ratings of the parents and their children. Results. Children 8 years of age or older were able to express the strength of their health state preferences using the HUI and rating scales. Children older than 10 years of age were able to use the SG method. The health state utilities of the parents were higher than those of their children. The utilities varied widely depending on the elicitation method. The expected high agreement between the SG and the HUI was not found (ICC = 0.028 for parents, ICC = 0.016 for patients). Unlike the SG, the global utilities derived from the HUI agreed better with preferences derived from rating scales (ICC = 0.23-0.25) and correlated with traditional health status measures (with CHAQ, r = -0.56; with ASK, r = 0.46) both for parents and children. It was not possible to mathematically convert rating scale preferences into SG utilities. The SG utilities were unrelated to results from the rating scales, the CHAQ, and the ASK. Especially for parents, the SG utilities were very high, even when ratings of the other measures indicated poor health. Conclusions. Although it is possible to measure health utilities for children with MSKDs, the results are highly method dependent. The properties of the HUI in this population are more like those of the traditional health status measures rather than those of the SG. Preferences derived from rating scales, although easily performed, cannot readily be converted into SG utilities. Parents' ratings for their children are impaired by risk aversion.