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

Extract 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 (i.e. fixed ratio) and/or statistical (i.e. 5th percentile, Z-score) cut-off point then defines the boundary between normal and abnormal, and the severity of impairment. Therefore, defining normal versus 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.