 Each FEV1 is measured in triplicate at a given test or a given time point. The highest FEV1 volume, from the triplicate attempts, is used as the representative value. The highest and second highest FEV1 attempts should not differ by greater than 0.2 L. Up to 2 additional attempts may be measured if necessary, with a total of 3-5 attempts allowed for a given test. The accepted attempts have to be technically conforming to the current spirometry standards from the American Thoracic Society ATS. The current clinical normative lung volumes in conformity with the ATS guidelines will be used for calculating the predicted percentage. 