A study being presented at the CHEST Annual Meeting 2019 found that routine use of post-bronchodilator spirometry values prevents the overdiagnosis of chronic obstructive pulmonary disease (COPD) and better identifies patients with asthma-COPD overlap syndrome (ACOS).Researchers used data from the National Health and Nutrition Examination Survey III from 2007 to 2012 to identify patients aged ≥40 years with spirometry studies meeting the American Thoracic Society (ATS) quality standards. Researchers used eosinophil count ≥300 cells/μL and forced expiratory volume in one second (FEV1) change >12% and >200 mL with bronchodilator testing to define blood eosinophilia and bronchodilator reversibility, respectively.
Probable ACOS was defined with two major criteria: post-bronchodilator FEV1/forced vital capacity (FVC) <0.7 in cases with an asthma history or FEV1 change ≥400 mL in cases without an asthma history, as well as one minor criteria: bronchodilator reversibility or blood eosinophilia. Probable asthma cases were considered a post-bronchodilator FEV1/FVC ≥0.7 with bronchodilator reversibility and/or blood eosinophilia. Patients self-identified whether they had received an asthma diagnosis from a healthcare professional.
The study included 8,002 patients who completed pre-bronchodilator spirometry testing, 625 of whom met the ATS spirometry quality standards and had a pre-bronchodilator FEV1/FVC <0.7. Among these patients, 381 (61%) had a post-bronchodilator FEV1/FVC <0.7, 12 (3.1%) had a history of asthma and bronchodilator reversibility, 16 (4.2%) had a history of asthma and blood eosinophilia, and two (0.7%) had FEV1 change ≥400 mL and blood eosinophilia, making ACOS more likely than COPD alone in these patients.
The remaining 39% of cases (n=244) had a pre-bronchodilator FEV1/FVC <0.7 but post-bronchodilator ≥0.7 and may be overdiagnosed as having COPD; 24 patients (9.8%) had bronchodilator reversibility alone, while 10 had bronchodilator reversibility and eosinophilia, making asthma more likely.
Eighteen of the 24 patients with bronchodilator reversibility and six of 10 with bronchodilator reversibility and eosinophilia had no prior history of asthma and would likely be misdiagnosed with COPD if just the pre-bronchodilator FEV1/FVC ratio was considered.
“Post-bronchodilator spirometry values, along with the recommended criteria for ACOS help identify 8% of COPD [patients] who likely have ACOS,” the authors concluded.
Annangi S, Yataco AC. Role of bronchodilator testing in identifying COPD, asthma, and asthma-COPD overlap syndrome: NHANES III analysis. Presented at the CHEST Annual Meeting 2019. October 19-23, 2019; New Orleans, Louisiana.