Population-based Screening for Chronic Obstructive Pulmonary Disease Using the St. George’s Respiratory Questionnaire in Resource-limited Settings

Spirometry, while necessary for the diagnosis of COPD, remains a scarce and costly resource worldwide. Screening questionnaires may help to bridge the diagnostic gap. We evaluated the performance of the St. George's Respiratory Questionnaire (SGRQ) as a screening tool using spirometry-confirmed COPD as a gold standard. We screened adults aged ≥40 years for COPD in Bhaktapur, Nepal; Lima, Peru; and Nakaseke, Uganda. Participants completed SGRQs and pre-bronchodilator peak expiratory flow (PEF). We defined COPD as a post-bronchodilator FEV1/FVC Z-score < -1.645, evaluated the discriminative performance of the SGRQ using receiver operating characteristic curves, and identified the best threshold to screen for spirometry-confirmed COPD. We screened 10709 participants (mean age 56.3 years, 49.7% males, 15.4% current smokers). After exclusion for missing data and implausible values, we analyzed data of 10008 participants (94%). Prevalence of spirometry-confirmed COPD was 9.5%; mean (±SD) total SGRQ score was 7.9±11.9 points, and 20.3±19.4 points in participants with COPD and 6.6±9.9 points in those without COPD. The area-under-the-curve (AUC) for SGRQ as a screening tool for COPD was 0.77 (95% CI 0.75-0.79) and the best threshold was 10.75 points. When the SGRQ was combined with pre-bronchodilator PEF stratified by sex, the AUC increased to 0.84 (95% CI 0.82-0.85). A screening test that combined a total SGRQ score ≥12 points and/or pre-bronchodilator PEF <400 L/min for men and <250 L/min for women yielded a sensitivity of 91%, a specificity of 47% and negative predictive value of 98% to identify spirometry-confirmed COPD. SGRQ is an alternative screening tool for spirometry-confirmed COPD. Screening with the SGRQ in combination with PEF may help to identify people at-risk for COPD in resource-limited settings where spirometry is not readily available.