Population-Based Screening for Chronic Obstructive Pulmonary Disease Using the St. George's Respiratory Questionnaire...

Rationale: Spirometry, although necessary for the diagnosis of chronic obstructive pulmonary disease (COPD), remains a scarce and costly resource worldwide. Screening questionnaires may help to bridge the diagnostic gap. Objectives: We evaluated the performance of the St. George's Respiratory Questionnaire (SGRQ) as a screening tool using spirometry-confirmed COPD as a gold standard. Methods: We screened adults aged 40 years and older for COPD in Bhaktapur, Nepal; Lima, Peru; and Nakaseke, Uganda. Participants completed SGRQs and prebronchodilator peak expiratory flow (PEF). We defined COPD as a postbronchodilator FEV₁/FVC Z-score less than -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. Measurements and Main Results: We screened 10,709 participants (mean age, 56.3 yr; 49.7% male; 15.4% current smokers). After exclusion for missing data and implausible values, we analyzed the data of 10,008 (94%) participants. Prevalence of spirometry-confirmed COPD was 9.5%; mean SGRQ scores were 7.9 points (SD = 11.9) for the total population, 20.3 points (SD = 19.4) for participants with COPD, and 6.6 points (SD = 9.9) for participants without COPD. The area under the curve for SGRQ as a screening tool for COPD was 0.77 (95% confidence interval, 0.75-0.79), and the best threshold was 10.75 points. When the SGRQ was combined with prebronchodilator PEF stratified by sex, the area under the curve increased to 0.84 (95% confidence interval, 0.82-0.85). A screening test that combined a total SGRQ score of 12 points and higher and/or prebronchodilator 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. Conclusions: 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.