First, classifying the bronchodilator response is arbitrary by definition in that it is continuous and not dichotomous. Thus, beyond any reasonable discussion on what best represents natural variability and effects of medication, no thresholds properly separate abnormal from normal responses. Drs Hansen and Porszasz1 claim that the perceptibility threshold is more sensitive than that of the ATS/ERS guidelines. We do not deny that this may be true in some patients, and we never suggested that a negative classic response is a marker of fixed airflow obstruction. Yet, the proposed threshold is often within the range of natural variability of the FEV1 and may not be applicable to all disease conditions. For instance, in asthma, the threshold is twice that of COPD and ironically similar3 to that of the ATS/ERS document.2 Second, in asthma, only 20% of the increase in dyspnea is related to airway narrowing or closure,4 whereas the rest has to do with feelings, emotion, and affection. Setting the threshold to low values may, therefore, increase the likelihood of false-positive results, depending on the patient’s personality. Third, data supporting the proposed threshold are scant3 and have never been reproduced by other authors. Fourth, the perceptive approach appears to be applicable only in a minority of patients in whom accuracy and repeatability of the forced expiratory maneuvers are very high. Given that FEV1 is a measurement of whole-lung mechanics inclusive of contrasting mechanisms, such as increase of airway size and airway collapsibility after the bronchodilator, the approach Drs Hansen and Porszasz propose to interpret the bronchodilator responses risks being unrealistic and void of clinical meaning. Fifth, these authors do not bring any evidence that categorizing the response on individual t tests is superior to the ATS/ERS guideline criteria.5 We agree with them that usefulness remains to be shown.