Quality and reproducibility of spirometry in COPD patients in a randomized trial (UPLIFT®)

SummaryBackgroundThis study explores spirometry quality and reproducibility in the Understanding Potential Long-term Impacts on Function with Tiotropium (UPLIFT®) trial.MethodsFour-year, randomized, double-blind, placebo-controlled, multicenter trial in 5993 patients with chronic obstructive pulmonary disease. Within-test variability of pre- and post-bronchodilator forced expiratory volume in 1 s (FEV1) was compared across study visits. Between-test variability of best pre- or post-FEV1 values between two visits 6 months apart was compared at the start, middle and end of the trial.ResultsThree or more acceptable maneuvers were obtained in 93% of visits. Within-test variability of pre- and post-FEV1 (mean standard deviation: 0.092 and 0.098 L) decreased during the trial. Between-test variability also decreased: pre-FEV1 (visit 3-5 = 0.141 ± 0.138 L; visit 9-11 = 0.129 ± 0.121 L; visit 17-19 = 0.121 ± 0.122 L); post-FEV1 (0.139 ± 0.140, 0.126 ± 0.123, 0.121 ± 0.122 L, respectively), and was dependent on age, sex, smoking status and disease stage, but not on bronchodilator response or study treatment.ConclusionSpirometry quality in UPLIFT® was good and improved during the trial. Between-test variability across patient subgroups suggests that relevant cut-offs for individual disease monitoring are difficult to establish.Trial registration numberNCT00144339.