Instability in the COPD Diagnosis upon Repeat Testing Vary with the Definition of COPD

Background
A low FEV1/FVC from post-bronchodilator spirometry is required to diagnose COPD. Both the FEV1 and the FVC can vary over time; therefore, individuals can be given a diagnosis of mild COPD at one visit, but have normal spirometry during the next appointment, even without an intervention.
Methods
We analyzed two population-based surveys of adults with spirometry carried out for the same individuals 5-9 years after their baseline examination. We determined the factors associated with a change in the spirometry interpretation from one exam to the next utilizing different criteria commonly used to diagnose COPD.
Results
The rate of an inconsistent diagnosis of mild COPD was 11.7% using FEV1/FVC <0.70, 5.9% using FEV1/FEV6 1.
Conclusions
Using FEV1/FEV6