Background: Variation of lung function is considered to be a hallmark of asthma. Although guidelines recommend measuring it as a diagnostic tool for asthma, the usefulness of this approach has not been studied in children.
Aim: To assess the usefulness of home spirometry in children with nonspecific lower respiratory tract symptoms, to diagnose or exclude asthma.
Methods: In school-aged children, referred by their general practitioner because of chronic respiratory symptoms of unknown origin, the diagnosis of asthma was made or excluded by a pediatric pulmonologist (gold standard), based on international guidelines and a standardized protocol. Additionally, children measured peak expiratory flow (PEF) and forced expiratory flow in 1 sec (FEV(1)) twice daily for 2 weeks on a home spirometer, from which diurnal variation was calculated. These results (index test) were not revealed to the pediatric pulmonologist. The value of home spirometry to diagnose asthma was calculated.
Results: Sixty-one children (27 boys) were included (mean age: 10.4 years; range: 6-16 years). Between asthma and no asthma, the mean difference in PEF variation was 4.4% (95% CI: 0.9-7.9; P = 0.016) and in FEV(1) variation 4.5% (95% CI: 1.6-7.4; P = 0.003). Sensitivity and specificity, based on the 95th-centile of the reference values for PEF and FEV(1) variation (12.3% and 11.8%, respectively) were 50% and 72% for PEF variation and 45% and 92% for FEV(1) variation. The likelihood ratio was 1.8 for PEF and 5.6 for FEV(1).
Conclusions: The contribution of home spirometry in the diagnostic process for asthma in schoolchildren with nonspecific respiratory symptoms is limited.