The recent multi-ethnic global lung initiative 2012 (GLI ₂₀₁₂ ) reference values don't reflect contemporary Mediterranean spirometry

Introduction. The applicability of the recent Multi-ethnic reference values derived by the GLI 2012 in interpreting spirometry data in Tunisian subjects has not been studied. Aims. To see if GLI 2012 Multi-ethnic and Tunisian prediction equations can be used interchangeably while interpreting routine spirometric data. Methods. Spirometric data were recorded from 1192 consecutive spirometry procedures in adults aged 18-63 years. Predicted values and lower limits of normality (LLN) were calculated using both regression equations. Applied d efinitions : large airway obstructive ventilatory defect (LAOVD): FEV 1 /FVC < LLN. Small AOVD (SAOVD): FEV 1 /FVC > LLN and FVC > LLN and FEF 25-75% < LLN. Tendency through a restrictive ventilatory defect (TRVD): FEV 1 and FVC < LLN. Mixed VD (MVD): FEV 1 /FVC and FEV 1 and FVC < LLN and FEV 1 < LLN. Z-scores for spirometry from Mediterranean healthy subjects (n=489) were calculated. If the average z-score deviated by < ±0.40 from the overall mean, the GLI 2012 reference values will be considered as reflective of contemporary Mediterranean spirometry. Results : According to Tunisian and GLI 2012 reference equations, the percentages of subjects with normal spirometry data, or having LAOVD, or SAOVD or a TRVD or a MVD, were significantly different, respectively, 35% vs 84%, 7% vs 4%, 37% vs 2%; 19% vs 9% and 3% vs 2%. The mean±SD Z-scores of the healthy group were -0.55±0.87 for FEV 1 , -0.62±0.86 for FVC, 0.10±0.73 for FEV 1 /FVC, 4.43±0.69 for FEF 75% and 0.07±0,93 for FEF 25-75% ). Conclusion . Our results don’t support the use of the GLI 2012 reference ranges to interpret spirometry in Mediterraneans.