Rationale
A recent update of the GLI equation (Bowerman, 2022) provides race-neutral equations for spirometry parameters replacing the multi-ethnic approach (Quanjer, 2012). The impact of this update is investigated on FEV1 and FVC using a large sample from UK biobank (UKBB). 

Methods 
From the UKBB, 20263 non-smoking subjects without lung disease are selected from 16 ethnic groups. They all performed  spirometry with acceptable quality. FEV1 and FVC Z-scores are computed based on 2022 equation for each ethnicity and compared to average z-values based on 2012 equations. 

Results 
While using the new global equation leads to averaged z-scores deviating less from zero overall, non-zero averages are still observed for non-European ethnicities (Figure 1). For example, over 25% of African and Indian ethnicities fall below lln.  

Conclusion 
The impact of ethnicity is reduced with the global equation. However, it does not represent specific subpopulations, especially non-European. It can lead to systematic bias either because such populations have below average lung function or because the equations are not fit for these ethnicities. It might still be useful to look at ?normality? within the context of ethnicity and outcome. 

Figure 1: Comparing global  to multi-ethnic equations.  Dotted lines represent mean and upper/lower limits of global normal population.