Objective: Lung-function reference values play an important role in medical surveillance examinations of occupational and environmental respiratory diseases, in stipulation of preventive measures, in initiation of therapeutic measures, and in granting of benefits to which individuals with lung injuries or occupational lung diseases are entitled (e.g., bronchial asthma, pneumoconiosis, or farmer's lung disease). Prediction equations most widely used are based on studies performed more than 20 years ago and may not represent the findings obtained in today's population.
Methods: We recorded case histories and lung function values of 139 healthy subjects (spirometric and plethysmographic data, T(LCO)) and computed the differences of measured values minus predicted ones as recommended by different authors.
Results: The means of these differences can be seen as shifts in our group versus the theoretical (predicted) values of various authors. These shifts, the standardized mean values of residuals, and their probability as determined under the assumptions of the respective regression model and the number of subjects below the threshold limits are given. FVC, FEV1, and FEV1%FVC show mostly good agreement with the recommendations by Crapo et al., Roca et al., Glindmeyer et al., Brändli et al., and Berger et al. Our IVC and FVC values do not differ significantly from each other. Normative flow-volume curve parameters of various authors deviate widely, however, and are not compatible with the values of our control group. Plethysmographically measured volumes (FRC, TLC, and RV) are only insufficiently reflected by Quanjer's reference equations. Measured T(LCO) and K(CO) show good agreement with the predictions of Cotes et al.  for females but display less concurrence with the predictions for males.
Conclusions: Our results indicate that the ERS values of FVC, FEV1, and FEV1%FVC mainly applied in Europe should be verified. The much better-evaluated formulas of Brändli et al. are recommended. Furthermore, the age range between 60 and 70 years should be extrapolated from these formulas until better epidemiological data on lung function are available.