Diagnostic Stability of Single Spirometry Compared to Repeat Spirometry for Airway Obstruction in Suspected COPD Patients: A Cross-sectional Study

Introduction: Obstructive airway diseases are a leading cause of respiratory morbidity and mortality worldwide, particularly Chronic Obstructive Lung Disease (COPD). The diagnosis of COPD is confirmed by a post-bronchodilator ratio of Forced Expiratory Volume in the first second (FEV1) to Forced Vital Capacity (FVC), i.e., FEV1/FVC <0.7. A repeat spirometry shows variability in a significant population. The Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines recommends repeating spirometry on a separate occasion if the post-bronchodilator FEV1/FVC is between 0.6 and 0.8. Aim: To determine the proportion of patients with diagnostic stability in the FEV1/FVC ratio after two weeks. Materials and Methods: This study was a cross-sectional study conducted in the Department of Pulmonary Medicine, Government Medical College, Thiruvananthapuram, Kerala, India from January 2019 to December 2019. in which 155 clinically suspected COPD patients with an FEV1/FVC ratio between 0.6 and 0.8 were recruited. A repeat spirometry was conducted two weeks later. The two post-bronchodilator FEV1/FVC ratios were compared, and the proportion of patients with diagnostic stability was determined. Fisher's-exact test and Pearson's Chisquare test were used to compare categorical variables between groups. The statistical significance of differences between means of variables among different independent groups was analysed using independent sample t -tests. A p-value <0.05 was considered statistically significant. Results: The mean age of the study population was 63.02 +/- 9.80 years. In present study, 118 (76.13%) out of 155 patients had stability in diagnosis, while 37 (23.87%) patients experienced a change in their diagnosis after repeat spirometry. The use of Inhaled Corticosteroids (ICS) and a history of Coronary Artery Disease (CAD) were associated with diagnostic instability (p<0.05). Conclusion: In present study, 23.87% experienced a change in their diagnosis after repeat spirometry. Hence, repeat spirometry should be done on a separate occasion as suggested by GOLD guidelines in patients with FEV1/FVC ratios between 0.6 and 0.8.