A new study shows the underutilized test could reveal an additional 9% of asthma diagnoses and potentially 8% of asthma-COPD overlap syndrome cases.
Srinadh Annangi, MD
A new assessment of data from the National Health and Nutrition Examination Survey (NHANES) presented at the CHEST 2019 Annual Meeting in New Orleans this week showed the often underutilized post-bronchodilator spirometry test may help more clearly determine distinctions between COPD and asthma—and conditions which may overlap them.
Led by Srinadh Annangi, MD, of the University of Kentucky College of Medicine, investigators sought to determine the role of bronchodilator in bettered COPD screening and respiratory disease diagnosis. They noted the test’s limited presence in practice comes in spite of clinical recommendation to use post-bronchodilator ratio of forced expiratory volume in 1 second (FEV1) over forced vital capacity (FVC) in diagnosis.
The team used NHANES data analyzed from 2007-2013. Subjects ≥40 years or older with spirometry studies meeting the American Thoracic Society (ATS) quality standards were included. Blood eosinophil counts and FEV1 change were used to define blood eosinophilia and bronchodilator reversibility.
The NHANES-listed question of “Has a doctor or health care professional ever told you that you have asthma?” was used to define asthma history. ACOS risk was identified by 2 of the following: post-bronchodilator FEV1/FVC < 0.7, FEV1 change of ≥400 ml, or asthma history—along with any 1 minor criteria listed.
The observed patient population included 8002 subjects ≥40 years old who had completed pre-bronchodilator spirometry testing. Of those, 625 met ATS spirometry quality standards and had an initial FEV1/FVC < 0.7. Of these patients, 381 (61%) had post-bronchodilator FEV1/FVC < 0.7—confirming irreversible airway obstruction.
Of the 381 patients, 12 (3.1%) had asthma history and bronchodilator reversibility; 16 (4.2%) had asthma history and blood eosinophilia; 2 (0.7%) had FEV1 change of ≥400 ml and blood eosinophilia. Investigators noted ACOS was more likely than lone COPD in these patients.
Of the remaining 244 patients, 24 (9.8%) had bronchodilator reversibility—10 of which having eosinophilia, making asthma more likely. Another 18 of the patients with bronchodilator reversibility, and 6 of the 10 patients with reversibility and eosinophilia had no prior asthma history.
These patients would likely be diagnosed incorrectly as having COPD if pre-bronchodilator FEV1/FVC was noted considered. The implication of the finding could be even greater in such a patient population.
“Not performing bronchodilator testing routine and relying on pre-bronchodilator FEV1/FVC ratio will lead to COPD overdiagnosis in 40% of subjects,” Annangi said in a statement.
Indeed, investigators concluded COPD overdiagnosis could occur in 39% of subjects, and called for further evaluation for potential asthma in 9.8% of the subjects observed in their study.
Another 8% of patients diagnosed with COPD likely have ACOS as well, based on post-bronchodilator spirometry values and recommended criteria.
The study, “Role of Bronchodilator Testing in Identifying COPD, Asthma, and Asthma-COPD Overlap Syndrome: NHANES III Analysis,” was presented at CHEST 2019.