Original ArticlesComparison of Three Quality of Life Instruments in Stable Angina Pectoris: Seattle Angina Questionnaire, Short Form Health Survey (SF-36), and Quality of Life Index-Cardiac Version III☆
Introduction
Quality of life (QOL) is increasingly being applied as an endpoint in clinical trials, as a marker of health care quality, and as a component of disease management programs 1, 2. When used to supplement traditional endpoints of disease progression, such as morbidity and mortality, a better understanding of patient outcomes can be gained. Coronary artery disease (CAD) is a condition that is particularly well suited to the use of QOL measures because many interventions are directed toward improving quality of life rather than extending survival. Furthermore, in chronic conditions such as coronary artery disease, clinical outcomes, such as mortality and acute coronary syndromes, often need to be tracked for years before any meaningful conclusions about the quality of health care can be obtained. Further complicating these efforts is the continual evolution of medical care such that intervening changes in health care delivery can confound the interpretations of long-term outcome results and reduce their applicability to current clinical practice [3]. In contrast, QOL measures may often provide more responsive insights into health status and may prove to be useful mechanisms for guiding quality improvement processes.
Since its introduction into the CASS trial in the early 1970s, the Canadian Cardiovascular Society Classification (CCSC) [4] has been the most widely used system for grading severity of symptoms. Consequently, it remains the most interpretable measure of symptom severity to clinicians. Over the past 25 years, several new instruments have been introduced to provide broader, more refined and more psychometrically sound representations of QOL in ischemic heart disease. As part of a prospective randomized trial of anti-anginal therapy, three previously validated QOL instruments were administered: the Seattle Angina Questionnaire (SAQ) [5], the Short Form Health Survey (SF-36) [6], and the Quality of Life Index-Cardiac Version III [7]. These three instruments were specifically chosen because they represent a disease-specific measure of cardiovascular disease (SAQ), a global general health status measure (SF-36), and a more global QOL measure (QLI). The purpose of this article is to compare the reproducibility and responsiveness of these three QOL instruments with the Canadian Cardiovascular Society Classification (CCSC) in patients with chronic stable angina pectoris. The data presented describe the performance characteristics of each instrument against the CCSC; it is hoped that this information will assist researchers and clinicians who need to select quality of life measures for patients with coronary artery disease.
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Patients and Study Design
Participants were recruited from a Veterans Affairs Medical Center in the Pacific Northwest into the Quality of Life and Angina Research Trial (QUART). The QUART trial was designed to determine if long-acting once-a-day anti-anginal medications could improve quality of life and functional status in persons with CAD as compared with short-acting formulations. Inclusion criteria into this trial required individuals to be taking at least two regular medications for angina, have a medical diagnosis
Results
One hundred seven patients participated in the study. The average age was 65 years, all were men, and most were Caucasian (79.4%). A large percentage of the sample had significant medical co-morbidities at the time of study entry. These included a past history of myocardial infarction (68%), hypertension (75%), congestive heart failure (28%), coronary artery bypass graft surgery (39%), cardiac arrhythmias (30%), diabetes mellitus (39%), depression (37%), claudication (38%), arthritis (61%), and
Discussion
The purpose of this study was to compare the operating characteristics of three quality of life measures among a cohort of patients with coronary artery disease. Two criteria were used to facilitate this comparison. The first was an analysis exploring the relationship of these instruments to the clinical gold standard in assessing patients’ anginal status, the Canadian Cardiovascular Society Classification. The second criterion for comparison was the psychometric properties of the instruments:
Acknowledgements
Funding was provided by an unrestricted educational grant from Hoechst-Marion Roussel. Medications were provided in part by Key Pharmaceuticals. The authors thank Drs. Marguerite Kinney and Susan Heckbert for their thoughtful review of the manuscript.
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Accepted for publication on 11 March 1998.