The recent multi-ethnic global lung initiative 2012 (GLI2012) reference values don't reflect contemporary adult's North African spirometry

Background: The applicability of the recent multi-ethnic reference equations derived by the ERS Global Lung Initiative (ERS/GLI) in interpreting spirometry data in North African adult subjects has not been studied.

Objective: To ascertain how well the recent ERS/GLI reference equations fit contemporary adult Tunisian spirometric data.

Population and methods: Spirometric data were recorded from 1192 consecutive spirometry procedures in adults aged 18-60 years. Reference values and lower limits of normality (LLN) were calculated using the local and the ERS/GLI reference equations. Applied definitions: large airway obstructive ventilatory defect (LAOVD): FEV1/FVC < LLN. Tendency to a restrictive ventilatory defect (TRVD): FEV1 and FVC < LLN and FEV1/FVC ≥ LLN. The spirometric profile, according to the two reference equations, was determined. Z-scores for spirometry from North African healthy subjects (n = 489) were calculated. If the average Z-score deviated by <± 0.5 from the overall mean, the ERS/GLI reference equations would be considered as reflective of contemporary Tunisian spirometry.

Results: Using Tunisian reference equations, 71.31%, 6.71% and 19.04% of spirometry records were interpreted as normal, and as having, LAOVD and TRVD, respectively. Using the ERS/GLI reference equations, these figures were respectively, 85.82%, 4.19% and 8.39%. The mean ± SD Z-scores for the contemporary healthy North African subject's data were -0.55 ± 0.87 for FEV1, -0.62 ± 0.86 for FVC and 0.10 ± 0.73 for FEV1/FVC.

Conclusion: The present study don't recommend the use of the recent ERS/GLI reference equations to interpret spirometry in North African adult population.