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Background and Aims Correlation between fractional exhaled nitric oxide ( FeNO) and responsiveness to inhaled leukotriene D4 ( LTD4) and methacholine ( MCh) might be different. This study aims to determine the correlation between FeNO and airway responsiveness to LTD4 and MCh, and to compare the airway responsiveness to inhaled LTD4 and MCh and FeNO in non-smokers, patients without rhinitis and non-smokers without rhinitis. Methods In this cross-over study, asthmatic patients and healthy subjects underwent LTD4 and MCh inhalation challenge at a 2- to 14-day interval. The FeNO was measured by using NIOX MINO, a portable instrument, at the initial visit, before spirometry and inhalation challenge tests. Subgroup analyses were performed in asthmatic patients based on the categorisation of never-smoker group, non-rhinitis group and never-smoker without rhinitis group. Results Of 62 asthmatic patients enrolled, 43 did not have self-reported rhinitis (asthmatic patients without rhinitis), 56 were never-smokers (asthmatic non-smokers), giving rise to 37 non-smokers who did not have rhinitis (asthmatic non-smokers without rhinitis). Twenty-one healthy subjects were enrolled. Overall, Log10 FeNO correlated with Log10 PD20 FEV1- MCh but not Log10 PD20 FEV1- LTD4 or Log10( LTD4/ MCh potency ratio). Reduced FeNO was associated with significantly higher Log10 PD20 FEV1- MCh but not Log10 PD20 FEV1- LTD4, except for non-smokers. Compared with all asthmatic patients, asthmatic non-smokers without rhinitis were characterised by markedly reduced levels of Log10 PD20 FEV1- MCh but not Log10 PD20 FEV1- LTD4. The difference in all parameters did not reach statistical significance among asthmatic patients without rhinitis, asthmatic non-smokers and asthmatic non-smokers without rhinitis. Conclusion FeNO correlates with airway responsiveness to inhaled MCh but not LTD4, in asthmatic patients, particularly in asthmatic non-smokers without rhinitis. [ABSTRACT FROM AUTHOR]

Background: Response-dose ratio (RDR) and cumulative provocative dosage (PD) are useful indices reflecting airway responsiveness in asthma. Objectives: To compare the diagnostic value of RDR and PD, by conducting leukotriene D (LTD-BPT) and methacholine bronchial provocation test (MCh-BPT), in different asthma control levels. Methods: Healthy subjects and asthmatic patients underwent LTD-BPT and MCh-BPT, at 2-14-day interval. This entailed assessment of the distribution characteristics, correlation, and diagnostic value of PD inducing 20 % fall in forced expiratory volume in one second (PDFEV) and the RDR, defined as FEV fall (%) at the final step divided by the corresponding provocative dosage. Results: Twenty uncontrolled, 22 partly controlled, 20 controlled asthmatics, and 21 healthy subjects were enrolled. LogRDR was positively correlated with logPDFEV in both BPTs (all P < 0.05). Poorer asthma control was associated with significantly lower PDFEV and higher RDR (both P < 0.05). The differences in PDFEV and RDR between partly controlled and controlled asthma were unremarkable (both P > 0.05). Compared with logPDFEV, the logRDR yielded similar diagnostic values in both BPTs. A lower percentile of RDR (≤25th percentile) was associated with higher baseline FEV ( P < 0.05) and an increased proportion of well-controlled asthmatic patients. The combination of RDR and PDFEV led to an increased diagnostic value compared with either parameter alone. Conclusions: RDR is a surrogate of PDFEV for BPTs in asthma. This finding was not modified by different asthma control levels or the types of bronchoprovocants. [ABSTRACT FROM AUTHOR]