FEV ₁ Q: the quest for an optimised measure of lung function impairment goes to the Global South

<title>Extract</title> The interpretation of spirometry has traditionally involved the comparison of an individual's raw values to a statistical distribution of a reference population of presumably healthy individuals controlling for non-modifiable factors associated with lung function (age, height and sex). A numerical (<italic>i.e.</italic> fixed ratio) and/or statistical (<italic>i.e.</italic> 5th percentile, Z-score) cut-off point then defines the boundary between normal and abnormal, and the severity of impairment. Therefore, defining normal <italic>versus</italic> abnormal spirometry, as well as the severity of impairment, ultimately relies on the make-up of the underlying reference population, which has come under increased consideration.