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Comparison of FEV 1 reference equations for evaluating a cystic fibrosis therapeutic intervention
Author(s) -
Konstan Michael W.,
Wagener Jeffrey S.,
VanDevanter Donald R.,
Pasta David J.,
Millar Stefanie J.,
Morgan Wayne J.
Publication year - 2017
Publication title -
pediatric pulmonology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.866
H-Index - 106
eISSN - 1099-0496
pISSN - 8755-6863
DOI - 10.1002/ppul.23751
Subject(s) - medicine , lung function , cystic fibrosis , significant difference , comparator , physical therapy , lung , physics , quantum mechanics , voltage
Objectives The Global Lung Function Initiative (GLI, 2012) developed reference equations for forced expiratory volume in 1 s (FEV 1 ). Previous equations were developed by groups led by Knudson (1983), Wang (1993), Hankinson (1999), and Stanojevic (2008). 1,2,4,6 We assessed how different prediction equations affect the conclusions from a therapeutic intervention study that evaluated the rate of percent predicted FEV 1 (ppFEV 1 ) decline. Methodology Using data from the Epidemiologic Study of cystic fibrosis (CF), we re‐analyzed our previous study evaluating the relationship of dornase alfa (DA) use with ppFEV 1 using the Knudson, Wang & Hankinson, Stanojevic, and GLI equations. The change in intercept and change in slope of ppFEV 1 from a 2‐year pre‐index period and 2‐year post‐index period were compared between the treated ( N = 2483) and comparator groups ( N = 6992, from 4110 unique patients). Results Change in intercept for the comparator group was similar across equations except that Wang & Hankinson values were more negative. The difference in change in intercept between the DA and comparator groups ranged from 3.38 to 4.02% predicted. The change in slope for the comparator group ranged from −0.58 to +0.30 ppFEV 1 /year, but the difference in change in slope between the DA and comparator groups was in a narrower range from +0.53 to +0.89 ppFEV 1 /year. Conclusions Although individual patient results are impacted by the choice of reference equations, the study conclusions from this evaluation of a therapeutic intervention were minimally affected. GLI equations are recommended for future studies, but prior results based on other equations should be accepted as reliable.