We thank to H. Chen and co-workers for the interest in our recent paper in the European Respiratory Journal 1, and for raising an important point with good suggestions.
We agree with their opinion, missing data is one of the biggest problems in retrospective studies and we should have discussed this in more detail. However, we still think that the missing data of our study did not markedly influence our results and conclusion 1.
Although there were many missing data in the pulmonary function tests (PFT), the clinical course of most patients were well documented. As stated in our study, 81% of patients had improved or were stable after the initial treatment 1. Although follow-up PFT was variable, as the treatment duration was different for each case, …