Assessing the Impact of Different Spirometric Equations on Asthma Severity and Control Among Children in Jordan: A Retrospective Study

<b>Background:</b> Accurate assessment of lung function among asthmatic children is crucial for effective disease management. The Global Lung Initiative (GLI) has developed widely used spirometric reference equations. However, locally derived equations may better reflect regional population characteristics and more accurately predict asthma control status. The impact of using local versus GLI equations, particularly the newly developed race-neutral equations, remains under investigation. This study examined how the choice of spirometric equation affects asthma assessment. <b>Method:</b> Spirometry was conducted on a sample of 438 asthmatic children (257 boys), and asthma control was assessed using the Global Initiative for Asthma Symptoms test (GINA-AST). Reference values, <i>z</i>-scores, and lower limits of normality (LLNs) were calculated for each child using both local and GLI reference equations. Concordance between equations was assessed using Cohen's kappa, and the sensitivity and specificity of each equation in detecting asthma control status were evaluated. <b>Results:</b> Significant differences were found in spirometry values across equations. The local equation displayed the highest sensitivity for detecting uncontrolled asthma and showed the greatest agreement with GINA-AST. Mean FEV₁ <i>z</i>-scores varied across equations, though intraclass correlation coefficients (ICCs) were high. <b>Conclusions:</b> This study highlights the substantial impact that the choice of spirometric equation has on asthma control assessment. Local equations may offer greater diagnostic sensitivity, potentially leading to more accurate disease classification and improved management outcomes.