Bronchial hyperreactivity features in children 3-6 years old with different asthma patterns

At pre-school age group, there are wheezing phenotypes who share same clinical symptoms, but treatment of them are different. Differential diagnosis between these children are not easy to do at clinical practice. Pathophysiological mechanisms underlying these phenotypes are thought to be different. Direct and indirect bronchial provocation tests may provide clues about the pathophysiology of bronchial asthma by means of determining bronchial hyperreactivity. Therefore, this study in asthma patients between the ages of 3-6 who monitored regularly, was performed to investigate the difference of airway hyperreactivity in the phenotypes of asthma.The number of responders to methacholine and adenosine 5?-monophosphate (AMP) bronchial provocation tests in persistent wheezing group are more than episodic viral wheezing group. Leading to a 15% decrease in transcutaneous oxygen pressure (PC15PtcO2) dose of methacholine in children with persistent wheezing, was lower than children with episodic viral wheezing. Thereof the degree of airway hyperresponsiveness was more severe in children with persistent wheezing than the children with viral induced wheeze. However, the difference between the two groups in terms of dose of AMP PC15PtcO2 was not detected. For both groups, the there was not found correlation between methacholine and AMP PC15PtcO2. Using receiver operation characteristic (ROC) curve the optimal cut-off was 0.24 mg/ml for PC15PtcO2 methacholine, for episodic and persistent wheezing discrimination with a sensitivity of 87.2%, a specificity of 55%. The positive likelihood ratio (LR) of PC15PtcO2 methacholine was 1.94, and a negative LR was 0.23. The area under curve was found to be insignificant for adenosine 5?-monophosphate. Peripheric blood eosinophil counts was significantly higher in children with persistent wheezing compared to the children with episodic viral wheeze. On the other hand no significant difference was observed in median serum IgE concentration of the patient groups. Also, no significant correlation was found between blood eosinophil count and either PC15PtcO2 methacholine or PC15PtcO2 AMP; airway hyperresponsiveness in both groups.Our study demonstrated that at present, neither direct nor indirect challenge tests are capable of discriminating asthma between the wheezing phenotypes in preschool-age children.