The Use of Exercise Challenge Testing and Fractional Exhaled Nitric Oxide in Diagnosis of Chest Tightness Variant Asthma in Children.

BACKGROUND: Chest tightness variant asthma (CTVA) in children presents with chest tightness as the sole manifestation. Diagnostic tests are needed given the lack of typical asthma symptoms. The present study aimed to investigate the diagnostic value of exercise challenge testing (ECT) and fractional exhaled nitric oxide (FeNO) in pediatric CTVA. METHODS: We included 98 children aged 6-13 years with chest tightness as the sole symptom for >4 weeks. All subjects underwent FeNO measurement, spirometry and ECT, and received 4-week budesonide/formoterol treatment. According to treatment responses, children were categorized into CTVA (n = 12) and non-CTVA (n = 86) groups. Differences in clinical characteristics and FeNO, spirometry, and ECT results were compared between the two groups. The FeNO and ECT diagnostic performances were determined using receiver operating characteristic (ROC) curve analysis. RESULTS: Children with CTVA exhibited significantly higher Mycoplasma pneumoniae IgG, total IgE, and FeNO values; greater post-ECT forced expiratory volume in 1 s (FEV1) fall; and more frequent sensitization to mites and pets than those without CTVA. Further logistic regression revealed that higher FEV1 fall (OR, 1.39; 95% CI: 1.11-1.74; p = 0.004) and higher FeNO values (OR, 1.04; 95% CI: 1.01-1.08; p = 0.014) were risk factors associated with CTVA. FEV1 fall and FeNO had similar areas under the ROC curve (AUCs) (0.79 vs. 0.78; p = 0.924), and their optimal CTVA-prediction cutoff values were 9.9% and 15.0 ppb, respectively. The AUC of FEV1 fall and FeNO combination was higher at 0.86 (95% CI: 0.78-0.93); however, no difference was observed using the single test (p > 0.05). Their combination exhibited a relatively higher sensitivity than that of FEV1 fall alone (0.75 vs. 0.67) and higher positive predictive value than that of FeNO alone (0.60 vs. 0.29). CONCLUSION: CTVA is a cause of unexplained recurrent chest tightness in children. FeNO ≥15.0 ppb and post-ECT FEV1 fall ≥9.9% are diagnostically valuable for CTVA in children, with their combination potentially contributing to greater diagnostic accuracy.