Reduced end-expiratory flows and prolonged expiratory times, which commonly exceed 6 s, occur in the initial stage of AO. The FEV1/FEV6 ratio can therefore lose sensitivity in early diagnoses, especially in aging patients, in whom the time required to complete the FVC maneuver increases.2 In two studies (references 22 and 25) included in the study by Hansen et al,2 it was possible to calculate the sensitivity of the FEV1/FEV6 ratio in patients with mild AO. The values decreased to 73% and 82%, respectively. In a recent study,3 we compared the sensitivity of FEV1/FVC ratio and FEV1/FEV6 ratio in patients with mild AO. The sensitivity for the FEV1/FEV6 ratio was only 75%. The exclusion of unpublished studies can introduce bias. In one such study (reference 10 in Soares et al3), 1,926 spirometry tests were evaluated. The sensitivity was for the FEV1/FEV6 ratio was 85.6%, but this value decreased to 74% among patients with mild obstruction.