Use of the quality of well-being self-administered version (QWB-SA) in assessing health-related quality of life in depressed patients

Abstract

Background: This study evaluated the cross-sectional and longitudinal relationship between depression severity and the Quality of Well-Being scale self-administered version (QWB-SA) in subjects diagnosed with current major depression. Methods: The research design was prospective and observational. Data were collected on a convenience sample of 58 subjects. Additional measures included the Quality of Well-Being scale interviewer-version (interviewer-QWB), Hamilton Rating Scale for Depression (HRSD-17), Beck Depression Inventory, and each were collected at baseline, 4 weeks, and 4 months postmedication treatment. Results: Cross-sectional and longitudinal QWB-SA scores were significantly correlated with depression severity and the interviewer-QWB. Treatment response, defined as 50% improvement in HRSD-17, was associated with 0.10 and 0.16 unit changes in the QWB-SA at 4 weeks and 4 months, respectively. The QWB-SA was significantly and negatively correlated with cross-sectional and longitudinal depression severity. Limitations: The study design was observational and used a convenience sample of subjects. Conclusions: The QWB-SA is less expensive to administer than the interviewer-QWB and is a useful alternative for determining the effectiveness and cost-effectiveness of treatments for depression relative to other physical and mental illness treatments.

Introduction

Outcomes assessment is an essential element of providing quality healthcare, and cost-effectiveness analysis is a common component of outcomes assessment (Ellwood, 1988, Smith et al., 1997). Cost-effectiveness analysis produces a ratio of net healthcare costs to net health benefits and can inform health policy decisions regarding the most efficient distribution of healthcare resources (Weinstein and Stason, 1977, Wells and Sturm, 1996). One of the requirements of cost-effectiveness analyses is for the units of effectiveness to be comparable across a wide range of programs because all programs compete for limited healthcare resources. For example, in order to compare programs for the treatment of a particular mental illness or between treatments of physical and mental illnesses, a common or generic measure of effectiveness is needed.

A panel on Cost-Effectiveness in Health and Medicine convened by the US Public Health Service recommended quality-adjusted life years (QALYs) as the common unit of effectiveness for use in studies intended to inform healthcare resource allocation decisions (Gold et al., 1996). By measuring effectiveness in units of QALYs, diverse treatments can be compared using the same metric. There are a handful of measures that provide effectiveness results in QALY units (Kaplan et al., 1976, EuroQol Group, 1990, Feeny et al., 1995), but there is no consensus on which measure is most appropriate. Furthermore, many of the existing measures have not been evaluated in samples of patients with mental health disorders.

The interviewer-administered Quality of Well-Being Scale (interviewer-QWB) (Kaplan et al., 1978) can measure QALYs and was designed for use in cost-effectiveness analyses, yet there have been significant limitations to its widespread use. A primary criticism is that it is more expensive and difficult to administer than self-administered measures, thus limiting its usefulness in research and clinical settings. In addition, the interviewer-QWB includes a complex pattern of branching and probe questions. In response to these criticisms, a self-administered version of the QWB (QWB-SA) was developed (Kaplan et al., 1997).

The content of the QWB-SA is similar to the interviewer-QWB. The primary differences are the mode of administration and an expanded symptom/problem complex section, which includes additional mental health items. The QWB-SA can be printed on two sides of a single page, is available in a scannable form, and usually takes less than 7 min to complete. The QWB-SA includes the same four subscales (symptoms/problem complex, mobility, physical activity, and self-care/social role activity) as the interviewer-QWB.

Comparison between the interviewer-QWB and QWB-SA demonstrated comparable scores and similar test–retest reliability using the same scoring algorithm in both instruments (Kaplan et al., 1997). A scoring algorithm specific to the QWB-SA is now available and several investigations are underway to document the usefulness of the QWB-SA in a wide variety of clinical settings.

In prior analyses, the original interviewer-QWB was found to be sensitive to cross-sectional and longitudinal depression severity, and interviewer-QWB scores for patients with major depression were similar to those of patients with chronic physical illnesses (Pyne et al., 1997a, Pyne et al., 1997b). This paper is the first to present validation data of the cross-sectional and longitudinal relationships between the QWB-SA, interviewer-QWB, and depression severity in a sample of patients diagnosed with unipolar or bipolar major depression. We hypothesized that (1) the QWB-SA would strongly and positively correlate with the interviewer-QWB and (2) the QWB-SA would strongly and negatively correlate with cross-sectional and longitudinal depression severity.