Utility of measuring FEV0.75/FVC ratio in preschoolers with uncontrolled wheezing disorder.

Uncontrolled wheezing disorder is common in preschoolers and disease control assessment is challenging as parents frequently overestimate the extent to which their child's disease is controlled. This is the first study of forced expiratory volume in t s (FEVt)/forced vital capacity (FVC) ratio measurements (i.e. FEV1/FVC, FEV0.75/FVC and FEV0.5/FVC) in wheezy preschoolers in relation to disease control. Our objective was to evaluate whether FEVt/FVC ratios less than the lower limit of normal (LLN; z-score <-1.64) were associated with uncontrolled wheezing disorder in preschoolers.Valid FVC, FEV1, FEV0.75 and FEV0.5 values were obtained in 92 healthy and 125 wheezy (62% uncontrolled) children (3-5 years). Associations between spirometry value <LLN, disease classification (healthy/wheezy) and disease control classifications (controlled/uncontrolled disease) were estimated using logistic regression.FEV0.75/FVC or FEV0.5/FVC ratios <LLN were associated with wheezing disorder (OR 9.78, 95% CI 3.70-25.88 and OR 6.64, 95% CI 2.24-19.66; all p<0.001). Only an FEV0.75/FVC ratio <LLN was associated with uncontrolled wheezing disorder (OR 2.53, 95% CI 1.12-5.68; p=0.025).FEV0.75/FVC ratio is a useful surrogate outcome index to evaluate the control of the wheezing disease of preschoolers.