the European community respiratory health survey ii is a multi-center study that uses the mefar™ dosimeter (brescia, italy) to assess bronchial responsiveness. ward et al. [1] reported that in some centers participating in the survey, there is potential for systematic variation in mefar™ dosimeter driving pressure, which could significantly affect between-center comparisons of bronchial hyperresponsiveness. they noted a wide range of driving pressures between centers, ranging from 70-245 kpa, with most outside the manufacturer's specification of 180 ± 5%. ward et al. [2] drew our attention to this issue when we were developing the quality control program for the survey. all centers were asked to check the dosimeter's driving pressure at least once a month and to report the results to the coordinating center. centers with readings below 160 kpa or above 180 kpa were advised to adjust the dosimeter. a website was set up with instructions on how to do this. reports from all centers except umea (sweden) showed that no center recorded a level below 160 kpa, with the highest value being 200 kpa in hamburg (germany). in hamburg, the equipment was adjusted and operated at approximately 180 kpa for the rest of the study. the mean pressure across all centers ranged from 160 kpa to 189 kpa (hamburg had a higher mean due to its driving pressure being 200 kpa for a period). although table 1 of the paper implies a substantial problem, the quality control program shows that variation exists, but the magnitude and its influence on between-center comparisons is much smaller than suggested. the letter from j. knox and d. jarvis is reassuring. although our initial concerns about excessive variation in mefar™ dosimeter driving pressures were not confirmed in most centers, the quality control program was validated. the range of mean pressures still seems to be outside the manufacturer's specifications. we proposed that our laboratory act as a "neutral" and confidence reference agency to collect calibration information. even so, our work to highlight a potential difficulty with the mefar™ dosimeter has been worthwhile. the article by rennard et al. and the editorial by dekhuijzen proposed that chronic obstructive pulmonary disease (copd) is underdiagnosed, underinvestigated, and has underestimated morbidity. the evidence lacks independent assessments of exercise tolerance and objective lung function measurements.the European community respiratory health survey ii is a multi-center study that uses the mefar™ dosimeter (brescia, italy) to assess bronchial responsiveness. ward et al. [1] reported that in some centers participating in the survey, there is potential for systematic variation in mefar™ dosimeter driving pressure, which could significantly affect between-center comparisons of bronchial hyperresponsiveness. they noted a wide range of driving pressures between centers, ranging from 70-245 kpa, with most outside the manufacturer's specification of 180 ± 5%. ward et al. [2] drew our attention to this issue when we were developing the quality control program for the survey. all centers were asked to check the dosimeter's driving pressure at least once a month and to report the results to the coordinating center. centers with readings below 160 kpa or above 180 kpa were advised to adjust the dosimeter. a website was set up with instructions on how to do this. reports from all centers except umea (sweden) showed that no center recorded a level below 160 kpa, with the highest value being 200 kpa in hamburg (germany). in hamburg, the equipment was adjusted and operated at approximately 180 kpa for the rest of the study. the mean pressure across all centers ranged from 160 kpa to 189 kpa (hamburg had a higher mean due to its driving pressure being 200 kpa for a period). although table 1 of the paper implies a substantial problem, the quality control program shows that variation exists, but the magnitude and its influence on between-center comparisons is much smaller than suggested. the letter from j. knox and d. jarvis is reassuring. although our initial concerns about excessive variation in mefar™ dosimeter driving pressures were not confirmed in most centers, the quality control program was validated. the range of mean pressures still seems to be outside the manufacturer's specifications. we proposed that our laboratory act as a "neutral" and confidence reference agency to collect calibration information. even so, our work to highlight a potential difficulty with the mefar™ dosimeter has been worthwhile. the article by rennard et al. and the editorial by dekhuijzen proposed that chronic obstructive pulmonary disease (copd) is underdiagnosed, underinvestigated, and has underestimated morbidity. the evidence lacks independent assessments of exercise tolerance and objective lung function measurements.