Epidemiological studies have established a relationship between low levels of serum vitamin D and reduced lung function in healthy adults, and asthma onset and severity in children. However, no study has examined the relationship between vitamin D levels and exercise-induced bronchoconstriction in asthmatic children.We evaluated the relationship between 25-hydroxyvitamin D concentrations and baseline forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁) and change in FEV₁(ΔFEV₁) after a standardised exercise challenge in 45 children with intermittent asthma.Only 11% of the children had desirable serum vitamin D levels (at least 30–40 ng·mL⁻¹). A positive correlation was found between serum 25-hydroxyvitamin D and both FVC (r = 0.34; p = 0.037) and FEV₁(r = 0.32; p = 0.037). Subjects with a positive response to the exercise challenge (ΔFEV₁≥10%) presented lower serum levels of 25-hydroxyvitamin D than children with a negative challenge (mean±sd16.2±5.2versus23.4±7.0 ng·mL⁻¹, respectively; p = 0.001).Our results indicate that hypovitaminosis D is frequent in asthmatic children who live in a Mediterranean country. In those children, lower levels of vitamin D are associated with reduced lung function and increased reactivity to exercise.

Recurrent wheezing in children

Measuring biomarkers (e.g. volatile organic compounds [VOCs]) in exhaled breath is an attractive approach to monitor airway inflammation in asthma and other lung diseases. Olfactive technology by electronic nose (e-Nose) has been applied to identify VOCs in exhaled breath. We compared e-Nose respiratory patterns in a pediatric cohort with asthma classificate children with different asthma control. This cross-sectional study involved 38 children: 28 with asthma and 10 healthy controls . The asthmatic patients were categorized as having controlled (AC), partially controlled (APC) or uncontrolled asthma (ANC) based on level of asthma symptom control according to Global Initiative for Asthma (GINA). Clinical exams, exhaled breath collection for generating e-Nose VOC profiles, and spirometry were performed. Exhaled breath samples were obtained using a commercial electronic nose (Cyranose 320; Smith Detections, Pasadena, CA, USA). The discriminative ability of breathprints were investigated by principal component analysis and penalized logistic regression. The e-Nose was able to discriminate between the CON (controls) + AC and the ANC + APC group with an area under the curve [AUC] of 0.85 (95% confidence interval [CI] 0.72 to 0.98) and a cross-validated AUC of 0.80 (95% CI 0.70 to 0.85). Sensitivity and specificity calculated using the Youden index were 0.79 and 0.84, respectively. Exhaled biomarker patterns were easy to obtain with the device and were able to differentiate children with uncontrolled symptomatic asthma from asymptomatic controls.