Global Lung Function Initiative 2012 reference values for spirometry in South Italian children

•FEV1, FVC and FEV1/FVC GLI references do not fit values in normal Sicilian children.•GLI references yield low chance of spotting airway obstruction in Sicilian children.•Other reference equations differently fit lung function values in Sicilian children.•Analysis through Jarque-Bera test and bootstrap confidence intervals is recommended.•Before use, applicability of GLI references in local areas should be tested.

RationaleDespite the widespread use of the Global Lung Function Initiative (GLI) 2012 reference values, there is still the need of testing their applicability in local areas.ObjectivesThe aims of this study are to evaluate applicability of GLI reference equations in a large population-based sample of normal schoolchildren from Sicily, and to compare GLI and previous prediction equations in terms of spirometry test interpretation.MethodsGLI equations were evaluated in 1243 normal schoolchildren, 49% males, aged 7-16 years, height 116-187 cm. Normality assumptions for the GLI z-scores (FEV1, FVC, FEV1/FVC) were tested, and bootstrap confidence intervals for the mean (0 expected) and the variance (1 expected) were derived. GLI and other reference equations were compared in terms of probabilities to fall below the lower limit of normal (LLN).ResultsThe GLI z-score normality assumption held for males but not for females (p < 0.001). According to the mean z-score, predicted values were: slightly underestimated for FEV1 (0.15 in males, 0.07 in females); overestimated for FVC (−0.27 in males, −0.32 in females); highly underestimated for FEV1/FVC (0.75 in males, 0.81 in females). Variability was correctly estimated. The probability of FEV1