Published ahead of print on February 23, 2006, doi:10.1164/rccm.200506-975OC
© 2006 American Thoracic Society doi: 10.1164/rccm.200506-975OC
Variability of Spirometry in Chronic Obstructive Pulmonary DiseaseResults from Two Clinical TrialsDivision of Pulmonary and Critical Care Medicine, The Johns Hopkins University School of Medicine; Center for Clinical Trials, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland; Division of Pulmonary and Critical Care Medicine, University of Utah School of Medicine, Salt Lake City, Utah; Division of Pulmonary and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; and Division of Biostatistics, University of Minnesota School of Public Health, Minneapolis, Minnesota Correspondence and requests for reprints should be addressed to Laura B. Herpel, M.D., The Johns Hopkins University School of Medicine, Division of Pulmonary and Critical Care Medicine, 5501 Hopkins Bayview Circle, Baltimore, MD 21224. E-mail: lherpel{at}jhmi.edu Objective: Our goal is to determine short-term intraindividual biologic and measurement variability in spirometry of patients with a wide range of stable chronic obstructive pulmonary disease severity, using datasets from the National Emphysema Treatment Trial (NETT) and the Lung Health Study (LHS). This may be applied to determine criteria that can be used to assess a clinically meaningful change in spirometry. Methods: A total of 5,886 participants from the LHS and 1,215 participants from the NETT performed prebronchodilator spirometry during two baseline sessions. We analyzed varying criteria for absolute and percent change of FEV1 and FVC to determine which criterion was met by 90% of the participants. Results: The mean ± SD FEV1 for the initial session was 2.64 ± 0.60 L (75.1 ± 8.8% predicted) for the LHS and 0.68 ± 0.22 L (23.7 ± 6.5% predicted) for the NETT. The mean ± SD number of days between test sessions was 24.9 ± 17.1 for the LHS and 85.7 ± 21.7 for the NETT. As the degree of obstruction increased, the intersession percent difference of FEV1 increased. However, the absolute difference between tests remained relatively constant despite the severity of obstruction (0.106 ± 0.10 L). Over 90% of participants had an intersession FEV1 difference of less than 225 ml irrespective of the severity of obstruction. Conclusions: Absolute changes in FEV1 rather than percent change should be used to determine whether patients with chronic obstructive pulmonary disease have improved or worsened between test sessions.
Key Words: forced expiratory volume • obstructive lung diseases • reproducibility of measurements • spirometry • vital capacity This article has been cited by other articles:
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