BACKGROUND: Available coronary artery disease (CAD)-specific health-related quality-of-life (HRQL) measures are not ideally suited for routine clinical practice. We report development of a valid and reliable CAD-specific short-form measure.
HYPOTHESIS: The Integrated Therapeutics Group (ITG) CAD-specific short-form HRQL measure is reliable and valid for assessing the health status of patients with CAD.
METHODS: In all, 409 patients (mean age 62.4 years) completed the 24-item CAD-specific HRQL questionnaire. Factor analysis was used to identify the scaling of the 24 CAD-specific items. Analysis of variance was used to reduce the number of items within each scale, and reliability (Cronbach's alpha), discriminant validity, and ceiling and floor effects of short-form scales were evaluated. Short-form scales were compared with the longer scales using relative validity coefficients. The CAD severity was assessed using New York Heart Association criteria, physician assessment, electrocardiogram results, the number of myocardial infarctions, and the number of CAD-specific medications. Clinical validity of short-form scales was then assessed based on their ability to discriminate across severity levels of these clinical criteria.
RESULTS: Four scales were identified: Extent of Chest Pain, Functioning and Well-Being, Activities Level-Physical, and Activities Level-Social. The 24-item questionnaire was reduced to a 13-item short form, with reliability exceeding 0.70 for all four scales. Relative validity estimates comparing short-form to original scales ranged from 0.68 to 2.58. Mean scores varied significantly (p < 0.05) by clinical severity, supporting the discriminant validity of the ITG CAD short-form scales.
CONCLUSIONS: The ITG CAD short form (used alone or with a general HRQL measure) is valid and practical for assessing patients with CAD.
