The Influence of the Reference Values on the Interpretation of Lung Function in Children: Comparison of Global Lung Initiative 2012 and Polish 1998 Reference Values.

Interpretation of spirometry strongly depends on the applied predicted values. New Global Lung Initiative (GLI) reference values have recently been published but their influence on spirometry interpretation in children has not been widely evaluated. The aim of the study was to compare the interpretation of spirometry using GLI-2012 vs. Polish-1998 reference values. Spirometry results of 315 Caucasian children aged 4-18 were analyzed. Airway obstruction was defined as FEV1/FVC<LLN (lower limit of normal: 5th percentile, -1,64 standard deviation), while restrictive ventilatory pattern as FVC<LLN and FEV1/FVC>LLN. The findings were that FEV1 and FVC expressed as GLI-2012 or Polish-1998 z-scores differed significantly (p<0.05). The mean FEV1 z-score was -0.68±1.25 vs. -0.13±1.70 and the mean FVC was -0.34±1.08 vs. 0.30±1.15 for GLI-2012 and Polish-1998, respectively. There was no difference for FEV1/FVC z-scores. Obstructive and restrictive ventilatory patterns were diagnosed in 20.3% and 7.6% children using GLI-2012 values compared with 17.5% and 3.8% when using Polish-1998 reference values, respectively. In conclusion, the use of GLI-2012 reference values in the population of Polish children increases the number of detected lung function abnormalities compared with Polish-1998 reference values.