Comparison of Choi’s and GLI-2012 Reference Equations for Spirometry in Korean Adults

Objective: In this study, we compared predicted spirometric values, Z-scores, and diagnostic classifications derived from Choi’s reference equations and Global Lung Function Initiative (GLI)-2012 Northeast Asian (NEA) equations in order to evaluate the level of agreement and interchangeability of these models in Korean adults Design: Retrospective cross-sectional study Methods: We analyzed spirometry data from 1,988 healthy adults aged 20–86 years, and computed predicted values and Z-scores for Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 s (FEV1), and FEV1/FVC ratio using Choi’s regression formulas and the GLI-2012 Lambda–Mu–Sigma-based algorithm. We examined agreement between equations using Spearman correlations, chi-square tests, and Cohen’s κacross both conventional spirometric diagnostic categories and Z-score–based severity classifications. Results: Although we observed strong correlations for predicted values and Z-scores (ρ = 0.933–0.995), the two equations produced systematic differences. GLI-2012 yielded lower predicted FVC and FEV1,but higher predicted FEV1/FVC ratios compared with Choi’s equations. These differences significantly altered the diagnostic classification (χ 2 = 2696.42, p < 0.001)with moderate-to-substantial agreement (κ= 0.709). Z-score–based severity classifications demonstrated fair-to-moderate agreement (κ = 0.184–0.417) due to the wider dispersion of GLI-2012-derived Z-scores. Conclusions: Despite demonstrating strongrank-order correlations, Choi’s and the GLI-2012 NEA reference equations yielded notable differences in the predicted values, Z-scores, and diagnostic classifications. These discrepancies indicate that the interpretation couldvary depending on the selected reference equation, underscoring the importanceof using population-appropriate and nationally consistent spirometric referencestandards in Korea.