Questionnaire, peak expiratory flow useful for COPD screening when spirometry unavailable

Key takeaways:

• This study included adults in Nepal, Peru and Uganda.
• Discriminative performance improved after adding sex-specific pre-bronchodilator peak expiratory flow to St. George’s Respiratory Questionnaire score.

When spirometry is unavailable, physicians can use the St. George’s Respiratory Questionnaire score plus peak expiratory flow to screen for COPD, according to data published in American Journal of Respiratory and Critical Care Medicine.

“If you are a physician working in a low- and middle-income country with limited resources, a screening tool based on checklists and peak expiratory flow may help you to identify individuals with COPD more easily and help you be more effective with the utilization of available resources and referral to spirometry,” William Checkley, MD, PhD, professor of medicine at Johns Hopkins University, told Healio.

“If you work in a high-income country and have access to an arsenal of lung function testing or [a] pulmonary function laboratory, this may not have a direct impact on your day-to-day work,” Checkley said. “But even in high-income countries, many individuals without COPD do not undergo spirometry and are given a clinical diagnosis only. Screening tools like the one in our work may also help.”

Checkley and colleagues studied 10,008 adults (mean age, 57 years; 50% men) in Nepal, Peru and Uganda to determine if the St. George’s Respiratory Questionnaire (SGRQ) can be used to screen for COPD and what threshold has the best discriminative performance.

Notably, Checkley and colleagues previously assessed the discriminative accuracy of three different screening tools — the COPD Assessment in Primary Care to Identify Undiagnosed Respiratory Disease and Exacerbation Risk; the COPD in Low- and Middle-Income Countries Assessment questionnaire; and the Lung Function Questionnaire — to identify COPD in the same three countries.

“Many low- and middle-income countries are experiencing a significant increase in COPD cases due to a variety of risk factors that include tobacco smoking, exposure to biomass fuels, occupational exposures and dusty environments, and a high burden of respiratory infections, pneumonia and tuberculosis throughout the lifespan,” Checkley told Healio.

“These same countries lack the infrastructure to diagnose and manage COPD,” Checkley continued. “Spirometry is frequently lacking in many health centers in resource-poor settings, making it difficult to identify many cases of COPD.”

In addition to the SGRQ, researchers captured pre-bronchodilator peak expiratory flow (PEF) for each individual.

Within the total cohort, 9.5% had COPD confirmed via spirometry. In terms of SGRQ scores, adults with vs. without COPD had a greater total score (mean, 20.3 points vs. 6.6 points), according to the study.

Based on the SGRQ score alone, researchers observed an area under the curve (AUC) of 0.77 (95% CI, 0.75-0.79); however, this value improved with the addition of sex-specific pre-bronchodilator PEF measured by the Piko-1 (AUC, 0.84; 95% CI, 0.82-0.85).

“Simple tools like questionnaires and a peak flow meter could help to identify people at risk or those with the disease,” Checkley told Healio.

The study noted that 10.75 points was the “best threshold to screen for spirometry-confirmed COPD” in the analysis of the SGRQ score alone, as this threshold achieved 81% specificity and 61% sensitivity.

In the assessment of pre-bronchodilator PEF by the Piko-1 to screen for COPD, men had a higher best threshold than women (310 L/minute vs. 224 L/minute).

With consideration to the best thresholds found for the SGRQ and sex-specific pre-bronchodilator PEF by the Piko-1, researchers reported favorable performance measures when the SGRQ threshold was at least 12 points and/or the pre-bronchodilator PEF threshold was less than 400 L/minute for men and less than 250 L/minute for women.

This tool identified spirometry-confirmed COPD with 91% sensitivity, 47% specificity and 98% negative predictive value, according to the study.

Lastly, researchers looked at the discriminative performance of pre-bronchodilator PEF by spirometry rather than by the Piko-1 in 8,037 adults and found a higher AUC in the model combining SGRQ and sex-specific pre-bronchodilator PEF (0.9; 95% CI, 0.89-0.92).

“Low-cost screening tools such as ours can be easily implemented and target individuals who would benefit from confirmatory spirometry,” Checkley told Healio. “These types of programs should be considered a best-buy intervention for COPD diagnosis/management for many low- and middle-income countries where there is a lack of access to spirometry and/or pulmonary specialists.”

Looking ahead, Checkley said research on this topic could delve deeper into the factors that help detect COPD.

“[Future studies may conduct an] evaluation of a parsimonious set of questions (about symptoms, risk factors and environmental exposures) in combination with a simple peak expiratory flow assessment to help to identify patients with COPD more readily,” Checkley told Healio. “Implementation trials of screening tools may aid in the diagnosis and/or management of patients with COPD in low- and middle-income countries.”

For more information:

William Checkley, MD, PhD, can be reached at wcheckl1@jhmi.edu.