Validation of the Spanish Activity Questionnaire in COPD (SAQ-COPD) in Patients with Chronic Obstructive Pulmonary Disease

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 (R)) 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.