An evaluation of spirometric reference equations for detecting obstructive airway disease in South African children: A cohort study
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Abstract
Background. Accurate diagnosis of obstructive lung disease in paediatric populations depends on the use of spirometry reference equations that reflect the regional and ethnic diversity of the population studied.
Objectives. To evaluate the diagnostic variability between the Global Lung Initiative 2012 (GLI2012) and Polgar reference equations in a multi-ethnic cohort of South African (SA) children.
Methods. This retrospective cohort study analysed spirometry data from 171 children, aged 6 - 18 years, attending a paediatric pulmonology clinic in Durban, SA, from January 2012 to December 2021. Key spirometry parameters (forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC) and FEV1/FVC ratio) were calculated using both the GLI2012 and Polgar reference equations. Diagnostic outcomes across ethnic groups were compared to assess the variability and potential diagnostic implications of each reference standard.
Results. Comparison of spirometry outcomes using the GLI2012 and Polgar reference equations revealed diagnostic variability across ethnic groups. GLI2012 identified a higher rate of obstructive lung disease, with abnormality rates of 24.6% among white children, 0.6% among black African children and 2.3% among Asian children, compared with Polgar, which reported rates of 23.9%, 0% and 1.6%, respectively. There was a statistically significant difference in FEV1/FVC ratios before and after administration of a bronchodilator between the two reference equations (mean (standard deviation) pre-bronchodilator FEV1/FVC ratio 0.86 (0.06) for both equations; post-bronchodilator ratio 0.88 (0.09) for GLI2012 and 0.85 (0.09) for Polgar (p=0.023)). There was no statistically significant difference in the proportion of children diagnosed with obstructive lung disease by age or ethnicity when comparing GLI2012 with Polgar.
Conclusion. This study underscores the diagnostic variability that arises from using global spirometry reference equations in a multi-ethnic paediatric population, particularly in SA. Future studies should include a more diverse ethnic representation to enhance data relevance.
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