Generalizing clinical data to the community: Estimated population prevalence of inflammatory biomarkers and lung function among people with obstructive lung disease

To estimate the real-world distribution of physician-assessed severity, spirometric characteristics and inflammatory biomarkers in adults with asthma and/or COPD by translating data from an observational study to a general population survey.

We used data from Australian participants with diagnoses of asthma and/or COPD from the observational NOVELTY study (NCT02760329) and a web-based survey of a nationally-representative population (ACTRN12619001572156); the survey included 57 patient-reported variables from NOVELTY. We developed an imputation model to estimate severity, spirometry and biomarkers in the population-based sample.

Participants with diagnoses of asthma and/or COPD in NOVELTY (n=818) were similar to those in the general population (n=1,510), except for older age, less smoking and greater inhaled corticosteroid use. Estimated prevalence of mild disease was 54%(asthma, 95%CI 38.3-69.4), 42%(asthma+COPD, 95%CI 24.4-60.4) and 51%(COPD, 95%CI 30.5-70.6). Estimated prevalence of post-bronchodilator FEV₁/FVC<0.7 was 39.8%(32.5-47.2), 53.9%(41.9-66.0) and 61.2%(51.0-71.4); of blood eosinophil count ≥0.3x10⁹/L was 24.3%(14.4-34.3), 23.0%(8.2-37.7) and 20.6%(10.2-31.1), and of FeNO≥25ppb was 42.6%(31.9-53.3), 33.8%(21.4-46.1) and 32.4%(21.5-43.2), respectively.

This study provides the first population-based estimates of disease severity, persistent airflow limitation and Type-2 biomarkers among Australian adults with asthma and/or COPD. Using a nationally-representative web-based survey together with a stratified observational study, we estimated that over half of community patients with asthma or COPD diagnoses had mild disease, and elevated FeNO was more prevalent than elevated blood eosinophils. The estimated prevalence of persistent airflow limitation (40% in asthma, only 61% in COPD) suggests potential for over/under-diagnosis in the community.