Spirometric reference values in the occupational medicine practice

Introduction: Spirometry is the main pulmonary function test routinely employed in the occupational medicine practice. Its interpretation depends on the choice of the theoretical reference values. Therefore, our objective was to retrospectively evaluate the differences in the spirometric interpretation according to the reference values used. Methods: A total of 2462 spirometries performed during health surveillance programs were analyzed. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and FEV1/FVC ratio were compared according to three different reference values: the European Coal and Steel Community (ECSC) 1971, the European Respiratory Society (ERS) 1993, and the Global Lung Initiative (GLI) 2012. Results: The GLI 2012 provided significantly higher predicted mean FVC and FEV1 values compared to the ERS 1993 and significantly lower compared to the ECSC 1971. The GLI 2012 were able to detect all the obstructive deficits and mixed patterns diagnosed with ECSC 1971 and ERS 1993, in addition to others not diagnosed by these two latter reference values. The number of restrictive patterns identified through the GLI 2012 was significantly reduced and increased compared to those diagnosed using the ECSC 1971 and the ERS 1993, respectively. Discussion: In comparison to the GLI 2012, the ERS 1993 values significantly underestimated obstructive and restrictive alterations. Conversely, the ECSC 1971 significantly underestimated obstructive changes, while overestimated restrictive patterns, compared to GLI. Although the GLI reference values may provide a correct spirometric interpretation, their validation in an Italian worker population is necessary to confirm their possible use in routine occupational health programs.