Abstract
The Seattle Angina Questionnaire (SAQ) is a widely used patient-reported measure of health status in patients with coronary artery disease. Comparisons of SAQ scores amongst population groups and over time rely on the assumption that its factorial structure is invariant. This study evaluates the measurement invariance of the SAQ across different demographic and clinical groups and over time. Data were obtained from the Alberta Provincial Project on Outcome Assessment in Coronary Heart Disease registry, a registry of patients who received coronary angiogram in Alberta, Canada. The studycohort consists of adult patients who completed the paper-based version of the 16-item Canadian version of the SAQ (SAQ-CAN) 2weeks and 1-year post-coronary angiogrambetween 2009 and 2016. Multi-group confirmatory factor analysis was used to assess configural, weak, strong, and strict measurement invariance across age groups, sex, angina type, treatment, and over time. Model fit was assessed using the comparative fit index and root mean square error of approximation. Of the 8101 patients included in these analysis, 1300 (16.1%) were at least 75years old, while 1755 (21.7%) were female, 5154 (63.6%) were diagnosed with acute coronary syndrome, 1177 (14.5%) received coronary artery bypass graft treatment, and 3279 had complete data on the SAQ-CAN at both occasions. There was evidence of strict invariance across age, sex, and angina type, and treatment groups, but partial strict invariance was established over time. SAQ-CAN can be used to compare the health status of coronary artery disease patients across population groups and over time.
Highlights
Patient-reported outcomes measures (PROMs), which are patients' appraisals of their health status and quality of life, are widely used to evaluate the effectiveness of treatment interventions, compare the health status of population groups, and assess the quality of care provided to patients[1,2,3]
While ACS patients generally reported higher average Seattle Angina Questionnaire (SAQ)-CAN domain scores on outdoor physical limitations, angina stability/burden, and treatment-related experiences, there was no significant difference in indoor physical limitations domain scores for ACS and stable angina patients
Of note is the finding that the hypothesis of strict measurement invariance of SAQ-CAN was established across sex, age, and disease groups, while partial strict measurement invariance was established across treatment groups
Summary
Patient-reported outcomes measures (PROMs), which are patients' appraisals of their health status and quality of life, are widely used to evaluate the effectiveness of treatment interventions, compare the health status of population groups, and assess the quality of care provided to patients[1,2,3]. Garrath et al [14] reported that the original factorial structure of the SAQ was not replicated in a sample of patients with stable angina but resulted in the emergence of the 15-item United Kingdom version of the SAQ with 3 domains. We are not aware of any study that has previously examined the measurement invariance of the SAQ or modified versions of the measure
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