Published models and local data can bridge the gap between reference values of lung function for children and adults.

The aim of this study was to create reference equations for pulmonary function tests (PFTs) that span the age range from childhood to young adulthood. PFT results (forced vital capacity (FVC), forced expiratory volume in one second (FEV1), ratio of FEV1 to FVC (FEV1/FVC), total lung capacity (TLC), transfer factor) of 348 healthy 13-24 yr old Caucasian never-smokers from a local population study were compared with 13 selected sets of published reference equations. Predicted and observed PFT results differed significantly for 63 of 92 reference equations tested, and most equations accounted poorly for the increase in PFT variables which takes place during adolescence. We selected the equations with the best fit and adjusted their parameters, so that the level and variance of predicted values agreed with the local data. For subjects older than 18 yrs, we selected the European Community for Steel and Coal (ECSC) equations. For subjects younger than 18 yrs, we chose European summary equations for FVC, FEV1, and FEV1/FVC, and recent British equations for TLC and transfer factor. The customized reference equations are the best available (maximum likelihood) for analysing PFTs of patients tested in our laboratory. Our approach can be used whenever generally accepted reference equations are lacking and a local sample of normal subjects is available.