Validation of the Spanish activity questionnaire in COPD (SAQ-COPD) in patients with chronic obstructive pulmonary disease

Abstract

Purpose: The Spanish Activity Questionnaire in COPD (SAQ-COPD) is a short, simple physical activity (PA) measurement instrument for patients with chronic obstructive pulmonary disease (COPD). In this study, we analyzed its validity and sensitivity to change. Methods: Prospective scale validation study. An accelerometer (DynaPort MoveMonitor®) and the Yale Physical Activity Survey (YPAS) were used as reference standards. The analyses examined the criterion validity (Spearman correlations), internal consistency (Cronbach's alpha), factorial structure, test-retest reliability (intraclass correlation coefficient, ICC), sensitivity to change and receiver operating characteristic (ROC) curve to classify patients with low PA. Results: A total of 300 patients diagnosed with COPD were analyzed (73% males, mean age 66 ± 8 years, 40.3% with severe airflow limitation). Cronbach's alpha was 0.60 and Spearman's correlations with accelerometer measurements of PA [number of steps, metabolic equivalents (MET), physical activity level (PAL)] and YPAS ranged from 0.37 to 0.53 (all p < 0.001). ICC was 0.69 (95% CI 0.61-0.74) and the area under the ROC curve to identify low PA was 0.65 (95% confidence interval: 0.58-0.73). Significant variations in SAQ-COPD scores were found between groups defined by YPAS for change. Conclusion: The SAQ-COPD questionnaire is a valid instrument for classifying PA in patients with COPD. Correlations with other instruments provide criterion validity and also demonstrate good sensitivity to change.