Spirometric inclusion criteria of COPD patients in randomized clinical trials.

I read with interest the paper entitled, “Acute effects of indacaterol on lung hyperinflation in moderate COPD: a comparison with tiotropium”, that has been recently published on line in Respiratory Medicine(1). As I have had in the past a recurrent exchange of opinions with some of the Authors on the spirometric criteria for defining airflow limitation, [2], [3], [4], [5] and [6] and particularly on the relative value of the fixed ratio (FR) FEV1/FVC < 0.7 proposed by the GOLD initiative7versus the Lower Limit of Normal (LLN) of FEV1/VC,8 I carefully read the entry criteria of the study and I was surprised to verify that, similarly to previous studies,9 the same Authors, who heavily criticize the GOLD criteria to the point of requesting the endorsement not only of the Italian “scientific” respiratory societies but also of the Italian Ministry of Health10 continue to use the GOLD criteria in their clinical trials and practice. [1] and [9] I did notice that in this specific study1 they used both the post-bronchodilator FEV1/FVC < 0.7 and the LLN of FEV1/VC related to predicted values,8 but unfortunately they omitted to mention whether the values were pre- or post-bronchodilators, and whether the predicted values used to express the results were pre- or post-bronchodilator. As the methods were not described in details in the paper, I went to the study protocol11 and I found that the LLN of FEV1/VC was not mentioned in the protocol nor in the amendments, and that the only entry criteria for the study were the GOLD criteria.7 As I stated in previous correspondence, [2], [4] and [6] I do not believe that the use of one criterion or the other creates a major problem, but I have to admit that my opinion is not based on evidence. I think it would be interesting to give to the Authors the opportunity to provide this evidence, by publishing the individual data of FR and LLN not reported in the paper, and comment on discrepancies, if any!