Vandana Das, Vanjare Nitin, Sundeep Salvi, Rahul Kodgule Department of Pulmonary Function Laboratory, Chest Research Foundation, Pune, Maharashtra, IndiaWe read the article by Balcan et al1 with great interest. The authors have reported a case–control study that included 115 females and looked at the association between exposure to biomass smoke and detection of COPD. Although the authors concluded a positive association, we are concerned about the issues related to the conduct of the study and discrepancies in the data reported. COPD cases in this study were defined based on pre-bronchodilator forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) ratio