Diagnostic value of post-bronchodilator pulmonary function testing to distinguish between stable, moderate to severe COPD and asthma

The first criteria, post-bronchodilator FEV1 < 80% of the predicted value in combination with a post-bronchodilator FEV1/FVC ratio of < 70%, had an accuracy of 70% to diagnose COPD. This combination was very sensitive (100%) in diagnosing COPD, but it was not specific (38%). The second BDR criteria, defined as an increase of < 12% and 200 mL of initial FEV1 and criterion number 3, an increase of < 9% of predicted FEV1, were less sensitive (55% and 59%, respectively), but more specific (81% and 76% respectively) to diagnose COPD. Our findings suggest that the current recommended spirometric indices are not optimal in differentiating between COPD and asthma.