The current diagnosis of asthma is based mainly on symptoms and airway variability. The diagnostic value of using exhaled nitric oxide (FeNO) measurements at a flow rate of 50 ml/s to detect airway inflammation for asthma is still controversial. A recent study evaluated the predictive value of FeNO for bronchial hyperresponsiveness and the symptom correlation between FeNO and PC20 in patients with suspected asthma who had negative β2 agonist reversibility tests and underwent FeNO measurement and acetylcholine bronchial hyperresponsiveness (defined as a positive acetylcholine excitation concentration PC20 value ≤ 16 mg/ml that resulted in a 20% reduction in FEV1). This prospective study enrolled 174 patients with suspected asthma who had respiratory symptoms, an exertional expiratory volume in 1 second (FEV1) ≥ 70% predictive value, a negative β2 agonist reversibility test, and were not on hormone therapy. Standard symptom scores were completed in these patients and FeNO and acetylcholine excitation measurements were performed, and the association between PC20 values and FeNO was evaluated using ROC curves and logistic regression analysis. Results revealed that a total of 82 patients with PC20M ≤ 16 mg/ml had significantly higher FeNO levels (19 ppb vs. 15 ppb; p < 0.05). By performing ROC curve analysis, it was found that a cut-off FeNO value of 34 ppb was used to identify bronchial hyperresponsiveness with high specificity (95%) and positive predictive value (88%), but low sensitivity (35%) and negative predictive value (62%). On logistic analysis of all variables, FeNO (p = 0.0011) and FEV1 (p < 0.0001) were independent predictors of bronchial hyperresponsiveness, whereas age, sex, smoking and atopy had no effect on bronchial hyperresponsiveness. Daytime and nocturnal wheezing symptoms were correlated with increased FeNO levels (p < 0.001 and p < 0.05) This study found that FeNO > 34 ppb predicted the diagnosis of bronchial hyperresponsiveness in patients with suspected asthma with negative bronchodilator tests. In contrast, patients with FeNO ≤ 34 ppb did not exclude bronchial hyperresponsiveness and further acetylcholine provocation tests were required to establish the diagnosis.