Is there any difference in pulmonary testing parameters due to spirometry reference values? A study in adolescents with idiopathic scoliosis.

The Global Lung Function Initiative (GLI 2012) presented multi-ethnic spirometry reference values that are recommended to be used instead previous Zapletals' reference values. The study aimed to compare the values of the pulmonary parameters calculated according to the Zapletals' versus the GLI 2012 reference values in adolescents with idiopathic scoliosis. Preoperative pulmonary testing and radiographic evaluation were performed in 39 adolescents (29 females, 10 males) aged 12-17 years. The thoracic Cobb angle ranged 50°-104°. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were measured. The percentages of predicted values of FVC (%FVC) and the FEV1 (%FEV1) were calculated according to the Zapletals' reference values and to the GLI 2012 reference values. The subgroup analysis was performed for the subjects with Cobb curve 50°-74° (N=26) versus the subjects with Cobb curve 75°-104° (N=13). Mean %FVC was significantly higher using the Zapletals' reference values 86.1%±16.4 versus 84.6%±15.6 using the GLI 2012 reference values, p=0.0116. Mean %FEV1 was significantly higher using the Zapletals' reference values 84.5%±18.2 versus 80.0%±16.3 using GLI 2012 reference values, p=0.000001. The subgroup analysis revealed significant difference of %FVC in moderate (p=0.033974) and no difference in severe curves (p=0.1993). The %FEV1 differences were significant in both moderate (p=0.000011) and severe curves (p=0.0334). The study demonstrated that a significant difference might be observed in the spirometry parameters due to the applied reference values. These differences might be taken into account during the spirometry examination interpretation.