Change is coming? The concept of FEV₁ change score in predicting asthma exacerbations

Guidlines recommend that current asthma symptom control should inform asthma preventer treatment to reduce future asthma exacerbations. But current symptom control is not a reliable predictor of exacerbation. There is a need for an objective measure of lung function to support asthma preventer treatment decision-making in order to reduce risk for future asthma exacerbations in children with asthma. Historically FEV₁ was recommended as part of routine monitoring for childhood asthma, but not all current guidelines recommend regular FEV₁ measurements are made and this is, in part, due to a lack of evidence linking change in FEV₁ and future asthma outcomes. Recent work supports the use of conditional change score (Zc) as a method to express change in FEV₁ over time; Zc adjusts for age and interval between measurements and, unlike absolute change in FEV₁% or FEV₁ z score, Zc is not liable to regression to the mean. Changes in Zc are associated with future exacerbation risk and also future loss of asthma control. Rising and falling Zc are both associated with increased odds for future exacerbation whereas only falling Zc is associated with increased odds for future loss of asthma control. Randomised controlled trials are now required to determine the role of Zc in the management of childhood asthma.