Quality of life (QOL) instruments have begun to play an increasingly important role in the evaluation of health care delivery systems. Although many such scales exist, it can be argued that the SF-36 scale has had the largest impact of the QOL scales. However, the methodological weaknesses of these types of assessment have also come under question (Merbitz, et al., 1989, Groenvold, 1999). To illustrate these methodological issues a subsample of approximately 3,600 individuals (all individuals with SF-36 scores) was drawn from the Medical Outcomes Study 1986-1992 Radius database (Tarlov et al., 1998). The responses to the SF-36 at baseline, 12, 24, and 48 months were examined using Rasch Rating Scale analysis (Wright & Masters, 1982) to determine the suitability of the scale evaluating outcomes. These analyses indicate several major problems that must be addressed if the scales are to be used as an appropriate indicator of quality of care. The first issue is one of dimensionality. The fit of these data to the measurement model suggest that the scale may be multi-dimensional. Second, the raw scores assigned to the various items may contribute to the unintentionally high weighting for certain items on the scale. Third, the ordinal nature of the scores may have an impact on the interpretation of the results. The methodology used in this analysis can be used as a guideline for the type of psychometric analysis to which all QOL scales should be subject to prior to implementation.
Learning Objectives: At the conclusion of this presentation the participants will be able to: 1. Understand appropriate analytic tools for ordinal and interval data 2. Evaluate the psychometric properties of quality of life scales 3. Assess multidimensionality of quality of life scales
Keywords: Quality of Life, Methodology
Presenting author's disclosure statement:
Organization/institution whose products or services will be discussed: None
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.
The 128th Annual Meeting of APHA