TY - JOUR T1 - Predicted Values for the Forced Expiratory Flow Adjusted for Forced Vital Capacity, a descriptive study JF - ERJ Open Research JO - erjor DO - 10.1183/23120541.00426-2020 SP - 00426-2020 AU - Claire A. Cox AU - Judith M. Vonk AU - Huib A.M. Kerstjens AU - Maarten van den Berge AU - Nick H.T. ten Hacken Y1 - 2020/01/01 UR - http://openres.ersjournals.com/content/early/2020/10/15/23120541.00426-2020.abstract N2 - Background The forced expiratory flows (FEFs) towards the end of the expiration may be more sensitive in detecting peripheral airways obstruction compared to the forced expiratory volume in the first second (FEV1) and forced vital capacity (FVC). However, they are highly variable. A partial solution is to adjust the FEFs for FVC (FEF/FVC). Here we provide reference equations for these adjusted FEFs at 25, 50, 75, and 25–75% of FVC, which are currently lacking.Methods We included pulmonary healthy, never-smoker adults, 14 472 subjects from Lifelines, a biobank for health research, and 338 subjects from the department's control cohorts (NORM and Fiddle). Reference equations were obtained by linear regression on 80% of the Lifelines dataset and validated on the remaining data. The best model was defined as the one with the highest adjusted R2-value. The difference in variability between adjusted and unadjusted FEFs was evaluated using the coefficient of variation.Results For all adjusted FEFs, the best model contained age, height, and weight. The adjustment improved the coefficient of variation of the FEF75 from 39% to 36% and from 43% to 40%, respectively in males and females. The highest percentage of explained variance by the reference equation was obtained for FEF75/FVC, 32%–38% for males, and 41%–46% for females, depending on the validation set.Conclusion We developed reference equations for FVC-adjusted FEF values. We demonstrated minimally, yet significantly improved variability. Future studies in obstructive airway diseases should demonstrate whether it is worthwhile to use these (predicted) adjusted FEF-values.FootnotesThis manuscript has recently been accepted for publication in the ERJ Open Research. It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJOR online. Please open or download the PDF to view this article.Conflict of interest: Mrs. Cox has nothing to disclose.Conflict of interest: Dr. Vonk has nothing to disclose.Conflict of interest: Dr. Kerstjens reports research grants from GSK, Novartis, and Boehringer, and fees for consultancies in advisory boards from other from GSK, Novartis, and Boehringer, all paid to his institutionConflict of interest: Dr. van den Berge reports grants paid to the University from Astra Zeneca, TEVA, GSK, Chiesi, outside the submitted work.Conflict of interest: Dr. ten Hacken has nothing to disclose. ER -