Can exhaled nitric oxide be a surrogate marker of bronchial hyperresponsiveness to adenosine 5'-monophosphate in steroid-naive asthmatic children?

Abstract

The interrelation between airway inflammation, bronchial hyperresponsiveness (BHR) and atopy remains controversial. The aim of this study was to document whether exhaled nitric oxide (eNO) may be used as a surrogate marker that predicts BHR to adenosine 5'-monophosphate (AMP) in steroid-naive school children with asthma. This study was a retrospective analysis of steroid-naive school age children with atopic and non-atopic asthma. All patients whose eNO levels had been measured and who had been challenged with both methacholine (MCH) and AMP were included. Receiver operation characteristic analysis was performed, in both the atopic and the non-atopic groups, to evaluate the ability of eNO to detect the BHR to AMP. One hundred and sixteen patients, sixty-nine (59.5%) of whom had been atopic, were included in the analysis. In the atopic group, eNO values were significantly higher in patients with BHR to AMP compared to those without BHR to AMP (51.9±16.9p.p.b. vs. 33.7±16.4p.p.b.; P<0.001), whereas in the non-atopic group, the differences were not statistically significant (29.7±16.9p.p.b. vs. 22.6±8.1p.p.b.; P=0.152). In the atopic group, eNO levels (R(2) : 0.401; β: 0.092; 95% CI: 1.19-14.42; OR: 7.12; P=0.008) were found to be the only independent factor for BHR to AMP, whereas none of the parameters predicted BHR to AMP in the non-atopic group. The best cut-off value of eNO that significantly predicts BHR to AMP was 33.3p.p.b. in the atopic group (P<0.001), whereas a significant cut-off value for eNO that predicts BHR to AMP was not determined in the non-atopic group (P=0.142). An eNO ≤17.4p.p.b. has 100% negative predictive values and 100% sensitivity and 60.47% PPV for prediction of BHR to AMP in the atopic group. Exhaled NO may be used to predict BHR to AMP in atopic but not in non-atopic steroid-naïve asthmatic children.