PT  - JOURNAL ARTICLE
AU  - Claire A. Cox
AU  - Judith M. Vonk
AU  - Huib A.M. Kerstjens
AU  - Maarten van den Berge
AU  - Nick H.T. ten Hacken
TI  - Predicted values for the forced expiratory flow adjusted for forced vital capacity, a descriptive study
AID  - 10.1183/23120541.00426-2020
DP  - 2020 Oct 01
TA  - ERJ Open Research
PG  - 00426-2020
VI  - 6
IP  - 4
4099  - http://openres.ersjournals.com/content/6/4/00426-2020.short
4100  - http://openres.ersjournals.com/content/6/4/00426-2020.full
SO  - erjor2020 Oct 01; 6
AB  - 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 1 s 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.FEFs may be more sensitive in detecting peripheral airway obstruction compared to FEV1 or FVC. However, they are highly variable. Adjusting the FEF by dividing it by FVC may partially solve this. This article provides FVC-adjusted FEF reference equations. https://bit.ly/2IG2fsx