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A2529 - Variability in FEV1 in Comparison to Forced Vital Capacity in Patients with Idiopathic Pulmonary Fibrosis
Author Block: S. Ashraf1, K. A. Wong2, P. Agarwala1, S. H. Salzman2; 1Pulmonary and Critical Care, NYU Wintrop Hospital, Mineola, NY, United States, 2Pulmonary and Critical Care, NYU Winthrop Hospital, Mineola, NY, United States.
Introduction: Idiopathic pulmonary fibrosis (IPF) is a progressive and chronic fibrosing lung disease of unknown etiology. Median survival from the time of diagnosis is approximately 3 years. Forced vital capacity (FVC) is the most commonly used physiological parameter in IPF clinical trials to assess severity of illness. Although FVC is widely accepted as a prognostic factor, the variability in its measurement in individual patients may limit its usefulness and reliability. By contrast, PFT interpretation guidelines from the American Thoracic Society and European Respiratory Society (Eur Respir J 2005; 26: 948-968) recommend rating severity of PFTs based on FEV1 rather than FVC, for obstructive and restrictive diseases. We seek to identify other physiological parameters which might show less variability in measurement in individual patients. Forced Expiratory Volume in the first second (FEV1) is one such parameter. We postulate that it may require less patient effort and coordination, therefore there will be less variability in results, thereby being a more reliable physiological parameter to monitor. Methods: We identified all patients in our outpatient practice that carried a diagnosis of IPF who underwent at least one pulmonary function test (PFT) between the years 2012 to 2017. All patients whose spirometry included two or more FVC maneuvers were included. Univariate analyses were performed using two-tailed paired t-tests to analyze the statistical differences between variations in measurement of FVC and FEV1 maneuvers within each individual testing session. Results: 46 patients were included and a total of 92 testing sessions of FVC and FEV1 were recorded. For each testing session the mean FVC and standard deviation (SD) of maneuvers were recorded. The mean measured FVC was 2.3L with an average SD of 0.14 over all maneuvers. This was shown to be higher in variance from measurements of FEV1, with an average of 1.83L and average SD of 0.06 over all maneuvers (P = 0.04). Conclusion: In patients with IPF, less variability was noted with FEV1 measurements compared to FVC measurement. This might make it a more useful parameter to follow in clinical trials as changes would be more likely to be due to biologic change than measurement variability.