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Responsiveness of EQ-5D utility indices in alcohol-dependent patients

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Abstract

Introduction

The EQ-5D provides community-based preference weights (utilities) for calculating quality adjusted life years (QALYs) in cost-utility analysis. This study aimed to analyze the responsiveness of EQ-5D-based utilities in patients with alcohol dependence.

Methods

In an observational longitudinal cohort study of alcohol-dependent patients (N = 52), three different EQ-5D-based utilities (EQ-Index United Kingdom, United States, and Germany) were calculated and compared with the scores of the WHOQOL-BREF (mental domain), HoNOS (total score), and GAF at baseline and at 18 months. Patients were categorized with more/same/less problems according to their self reported consumption of alcohol (patient-based anchor) and their problem status due to alcohol consumption using a question of the HoNOS scale (clinician-based anchor). Effect sizes (ES) were used to compare longitudinal changes in scores within each group; regression analysis was used to derive difference scores in health status associated with a shift from “same” to “less” problems according to the two anchors.

Results

ES were rather trivial to medium for all EQ-5D indices (ranging from |0.10| to |0.59|) related to a shift from “same” to “less” problems in the two anchors. Differences in scores of the EQ-5D indices revealing a shift from “same” to “less” problems according to the two anchors were not significant.

Conclusions

These results suggest that the EQ-5D indices are less responsive and require larger patient samples to detect meaningful clinical differences compared to the other used instruments. Additional research is needed to compare societal and clinical views on relevant change in health status in this patient group.

Introduction

The EQ-5D is a short generic patient rated questionnaire measuring health-related quality of life (HRQOL). For various countries (including the United Kingdom, Germany, and the United States) there is an index score assigned to all possible health states described by the EQ-5D according to a set of preference values derived from general population surveys (Dolan, 1997, Greiner et al., 2005, Shaw et al., 2005). This index score might help evaluate changes in health status, reflecting the preferences of the community (Dolan, 1999), and is typically used to calculate quality adjusted life years (QALYs) in cost-utility analysis (Drummond et al., 1997, Gold et al., 1996).

In the field of alcohol dependency, first results could corroborate that the EQ-5D reflects psychopathology and mental aspects of HRQOL in patients with alcohol dependency (Günther et al., 2007, Foster et al., 2002). Beyond these results, the EQ-5D has to reveal responsiveness, i.e. the ability to detect a meaningful change in health status, which results from evaluating the relationship between changes in clinical endpoints and changes in an instrument's outcome over time in either observational or clinical trials (Guyatt et al., 1987, Revicki et al., 2000). In practice, no gold standard determines if the score changes are meaningful from the patient's, clinician's or decision maker's perspective. Recently, the Food and Drug Administration (FDA) in the Unites States has raised a draft on patient reported outcomes including methods to calculate responsiveness and to interpret the detected differences (Food and Drug Administration, 2006). Thus, the recommended best practice for evaluating responsiveness is the calculation of various distribution-based estimates (i.e., effect size, standardized response mean, standard error of measurement) under several anchor-based criteria (i.e., patient or clinician ratings of global improvement).

This study aimed to compare and contrast the responsiveness of several community preference-based scores of the EQ-5D in alcohol-dependent patients with the responsiveness of composite summary scores of instruments measuring mental quality of life, psychopathology and social functioning.

Section snippets

Sample

Patients suffering from an alcohol dependence according to the International Statistical Classification of Diseases (ICD-10, F10.2) (World Health Organization, 1992) were interviewed at admission and the second time after a period of 18 months. More detail about patients characteristics have been provided elsewhere (Günther et al., 2007, Roick et al., 2005).

Measures

A standard version of the EQ-5D was administered, comprised of five items relating to problems in the following dimensions: “mobility”,

Demographic characteristics and change in health status

Of the 103 patients joining the study at baseline, 51 dropped out, and 52 completed the follow-up. The mean age of patients completing the study was 50.6 years with a S.D. of 12.0 at baseline. The age ranged from 24 to 79 years, and the majority (71.2%) was male. More than one quarter of all patients was married (26.9%), and almost one half lived alone (49.5). On average, 9 years had passed since the first diagnosis of alcohol dependence. At baseline, mean scores of patients completing the

Discussion

The results suggest that the EQ-5D indices were considerably less responsive than the HoNOS, and the GAF, and somewhat less responsive than the WHOQOL-BREF. In order to better understand the meaning of these findings, two issues should be taken into account: (1) differences in the scope of measurement between the instruments, i.e. that the EQ-5D was primarily developed as an instruments to measure outcome for QALY analysis in economic evaluation rather than eliciting HRQOL in clinical trials;

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