Repeated measures of FEV1 over six to twelve months: what change is abnormal?

Monitoring change in IEV 1 (ΔFEV 1 ) is useful for assessing adverse respiratory effects in an individual, but high variability impedes reliable recognition of accelerated decline. The American Thoracic Society (ATS) recommends a ≥15% year-to-year FEV 1 decline for clinical significance. To evaluate the applicability of this criterion in health monitoring programs, we examined the mean, lower 5th percentile, and lower 5% cutoff value of ΔFEV 1 determined from 2 tests at 6- and 12-month intervals using data obtained with ATS-recommended equipment and procedures in 389 white male workers, each with 3 to 11 spirometry tests over 5 years. Results indicate that when healthy working males perform spirometry according to ATS standards, a yearly decline in IEV 1 greater than 8% or 330 mL should not be considered normal, whereas the 15 % ATS criterion could be appropriate in clinical settings.