Impact of using the multi-ethnic global lung initiative as a spirometry reference equation: Retrospective cross-sectional study in Egyptians

Context: Spirometry interpretation is largely affected by the reference equation. European Coal and Steel Community/European Respiratory Society reference equation 93 (ECSC-ERS93) is widely used in Egypt, despite the endorsement of multiethnic global lung initiative equation (GLI-2012) by many international societies as a reference. Aim: We aimed to investigate the interpretive impact of shifting from ECSC-ERS93 to GLI-2012 among Egyptians. Methods: Acceptable pre-bronchodilator spirometry tests for Egyptian subjects, obtained between January 2022 and July 2024 were included, excluding those with age and anthropometric limits of ECSC-ERS 93 equation. Interpretation of spirometric results (normal, preserved ratio impaired spirometry (PRISm), spirometric obstruction, spirometric restriction, and mixed pattern 'obstruction & restriction') according to GLI- 2012 and ECSC-ERS93 were compared, in addition to severity classification of obstructive and restrictive abnormalities. Results: Five hundred thirty-five subjects were included in the final analysis, 56% of whom were males, and an age range of 18-70 years. According to ECSC-ERS93, 314 (59%) were classified as normal, 29 (5.5%) as PRISm, 108 (20%) spirometric restriction, 44 (8%) obstructive and 40 (7.5%) as having mixed abnormality, Application of GLI-2012 changed the interpretation of 93 (17.4%) subjects (p