Statistical Analysis
Analyses were performed using SPSS Statistics v21.0 (IBM, Chicago, IL,
USA). Normally-distributed continuous data were expressed as mean and
standard deviation, and not-normally distributed continuous data as
median and interquartile ranges (IQR). Group comparisons were carried
out using student´s t-test, Mann–Whitney U-test or ANOVA as appropriate
for the continuous, and the chi-square test or Fisher test for
categorical variables. The correlation coefficients between serum
periostin level and other clinical variables were determined using
Spearman‘s rank correlation coefficient. Association of severe asthma
classes with clinical variables was examined using regression models
adjusted for potential confounders, including age, aeroallergen
sensitization, BMI z-score, blood eosinophil count and serum periostin
level. The odds ratio (OR) and 95% confidence interval (CI) were
reported. The diagnostic performances of serum periostin levels to
identify children with severe asthma were determined by receiver
operating characteristic (ROC) curve analysis. Sensitivity, specificity,
positive predictive value (PPV), and negative predictive value (NPV)
were calculated for the selected cut-off point. A P level
<0.05 was considered significant.