Assessment of bronchoreversibility in severe emphysema.

To define bronchoreversibility they unfortunately followed the American Thoracic Society/European Respiratory Society (ATS/ERS) guideline recommendations for FEV1 responses [2]. These guidelines require both a 12% increase in FEV1 and a 200-mL increase in FEV1 to indicate a positive test, levels which are based on expert opinions rather than statistical analysis of individual patients. Consequently, they found that, on average, ATS/ERS guideline-defined bronchoreversibility was found in only 8.5% of tests. The 544 NETT patients had a FEV1 of 700¡220 mL. Thus, on average, to increase their FEV1 by 200 mL would require a sizeable increase of 28.5%, much more than 12%.