Response--dose ratio is a surrogate of cumulative provocative dosage for bronchial provocation tests in asthma

Clinical implications of concentration of alveolar nitric oxide in asthmatic and non-asthmatic subacute cough

Asthma is an important cause of subacute cough. The concentration of alveolar nitric oxide (CANO) is a sensitive inflammatory indicator in peripheral airways, and it has received much less attention than the fraction of exhaled nitric oxide (FeNO₅₀). The main objective of this study was to explore the correlation between CANO and clinical parameters in asthmatic and non-asthmatic subacute cough, which might promote understanding of the clinical utility of CANO in these special patient populations. 155 patients with subacute cough were included consecutively, of which 25 were diagnosed as asthmatic. Data for demographic characteristics, FeNO₅₀, CANO, baseline spirometry, bronchial provocation test (or bronchodilation test) and response dose ratio (RDR) were collected. Differences between the asthmatic and non-asthmatic groups were analyzed. Spearman's correlation coefficient (ρ) was used to evaluate the correlation between FeNO₅₀, CANO and other clinical parameters. In patients with subacute cough, baseline CANO values did not differ between asthmatic and non-asthmatic patients (4.4(1.3, 11.4) versus 4.0(2.1, 6.8) ppb,P> 0.05). Besides, CANO exhibited a stronger association with pulmonary function parameters when compared with FeNO₅₀. For asthmatic subacute cough, CANO was inversely correlated with FEV₁/FVC (ρ= -0.69,P< 0.01) and small airway parameters including MEF25 (ρ= -0.47,P< 0.05) and MMEF (ρ= -0.45,P< 0.05). For non-asthmatic subacute cough, CANO was inversely correlated with MEF25 (ρ= -0.19,P< 0.05) and RDR (ρ= -0.21,P< 0.05). In subacute cough, asthmatic and non-asthmatic patients had similar values of baseline CANO. In both asthmatic and non-asthmatic subacute cough, CANO exhibited a stronger association with pulmonary function parameters when compared with FeNO₅₀. A low CANO value in non-asthmatic subacute cough corresponded to a higher value of RDR, which implied a stronger tendency towards airway responsiveness.

Adenosine monophosphate is not superior to histamine for bronchial provocation test for assessment of asthma control and symptoms

BACKGROUND

Adenosine monophosphate (AMP) may reflect airway inflammation and hyperresponsiveness, but relationship between AMP and histamine (His, a conventional stimulus) bronchial provocation test (BPT) in asthma is not fully elucidated.

OBJECTIVES

To compare both BPTs and determine their utility in reflecting changes of asthmatic symptoms.

METHODS

BPTs were performed in a cross-over fashion, at 2-4 day intervals. Cumulative doses eliciting 20% FEV₁ fall (PD₂₀ FEV₁ ), diagnostic performance and adverse events (AEs) were compared. Patients with PD₂₀ FEV₁ lower than geometric mean were defined as responders, otherwise poor responders. Patients with uncontrolled and partly controlled asthma, who maintained their original inhaled corticosteroids therapy, underwent reassessment of airway responsiveness and asthmatic symptoms 3 and 6 months after.

RESULTS

Nineteen uncontrolled, 22 partly controlled and 19 controlled asthmatic patients and 24 healthy subjects were recruited. Lower PD₂₀ FEV₁ geometric means were associated with poorer asthma control in His-BPT (0.424 μmol vs 1.684 μmol vs 3.757 μmol), but not AMP-BPT (11.810 μmol vs 7.781 μmol vs 10.220 μmol). Both BPTs yielded similar overall diagnostic performance in asthma (area under curve: 0.842 in AMP-BPT vs 0.850 in His-BPT). AEs, including wheezing and tachypnea, were similar and mild. Ten patients with uncontrolled and 10 partly controlled asthma were followed-up. At months 3 and 6, we documented an increase in PD₂₀ FEV₁ -AMP and PD₂₀ FEV₁ -His, which did not correlate with reduction asthmatic symptom scores. This overall applied in responders and poor responders of AMP-BPT and His-BPT.

CONCLUSION

Despite higher screening capacity of well-controlled asthma, AMP-BPT confers similar diagnostic performance and safety with His-BPT. AMP-BPT might not preferentially reflect changes asthmatic symptoms.

Responsiveness to methacholine, but not leukotriene D4, correlates with fractional exhaled nitric oxide in asthma

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.