One in 5 adults diagnosed with asthma, chronic obstructive pulmonary disease (COPD), or both asthma and COPD in a primary care setting have asthma-COPD overlap (ACO) based on the criteria established by the Respiratory Effectiveness Group (REG) ACO Working Group, according to a study published in Annals of the American Thoracic Society, with characteristics and prevalence rates that vary across the 3 source populations of patients.
To ameliorate the paucity of evidence about individuals with ACO in primary care, the REG conducted this cross-sectional study of patients ≥40 years old ≥2 primary care visits during a 2-year period. The data were derived from the United Kingdom’s Optimum Patient Care Research Database. The objectives of the study were to estimate disease prevalence and describe ACO characteristics in patients with COPD, asthma, or both, and to compare the characteristics and prevalence of ACO among the 3 populations. Patients were classified using diagnostic codes, and ACO was defined by the presence of all of the following: current or former smoker ≥40 years old, postbronchodilator airflow limitation (forced expired volume in 1 second/forced vital capacity <0.7), and ≥12% and ≥200 mL reversibility in postbronchodilator forced expired volume in 1 second.
The study included 2165 patients (1015 with COPD only, 755 with asthma only, and 395 with both asthma and COPD). The overall ACO prevalence was 20% (95% CI, 19%-23%). Patients with ACO were a mean age of 70 (standard deviation, 11 years), 40% were women, 66% were obese or overweight, 73% were former smokers, and 27% were current smokers. The following comorbid conditions were common in patients with ACO: 53% had diabetes, 36% had cardiovascular disease, 30% had hypertension, 23% had eczema, and 21% had rhinitis. ACO prevalence was higher in patients diagnosed with both asthma and COPD (32%) compared with patients diagnosed with asthma only (14%; P <.001) or COPD only (20%; P <.001). Sex and prevalence of comorbid conditions were not significantly different across the 3 populations, but demographic and clinical characteristics varied.
The study had several limitations: including patients from only 1 country, possible selection bias, and missing data.
The investigators concluded that the significant variation in characteristics of patients with ACO and in the patterns of some of the comorbid conditions suggests, “ACO as defined in our report likely comprises a heterogeneous set of subpopulations. While use of information recorded by clinicians in primary care offered the opportunity for our results to be more generalizable, our study also highlights the disadvantage of relying on clinical documentation (ie, potential for missing data or variable quality of information). Nevertheless, we recommend use of the REG ACO Working Group definition in other patient populations to estimate the prevalence of ACO, and longitudinal studies using observational and clinical trial designs to understand the functional consequence in ACO patients in primary care settings.”
Krishnan JA, Nibber A, Chisholm A, et al. Prevalence and characteristics of asthma-COPD overlap in routine primary care practices [published online June 4, 2019]. Ann Am Thorac Soc. doi:10.1513/AnnalsATS.201809-607OC