Kay Roy

Exhaled breath condensate biomarkers in COPD

Biomarkers in chronic obstructive pulmonary disease may be useful in aiding diagnosis, defining specific phenotypes of disease, monitoring exacerbations and evaluating the effects of drugs. Exhaled breath condensate is a noninvasive means of sampling the airways, allowing biomarkers of airway inflammation and oxidative stress to be measured. In the present review, the use of exhaled breath condensate biomarkers in chronic obstructive pulmonary disease is explored and potential applications in diagnosis, disease phenotyping, exacerbation monitoring and clinical trials are considered. Exhaled breath condensate biomarkers are comprehensively reviewed in terms of method validation, reproducibility, disease specificity and sensitivity to detect changes in airway inflammation. The commonly used exhaled breath condensate methodologies in chronic obstructive pulmonary disease patients are shown to have considerable variability, due to technical issues concerning both sample collection and analysis. Despite these issues, there is still data to support the use of exhaled breath condensate biomarkers for monitoring chronic obstructive pulmonary disease exacerbations and the response to pharmacological intervention. Further improvements to sample collection and analysis methods will improve the sensitivity of these biomarkers. The use of cytokine arrays, mass spectrometry and nuclear magnetic resonance profiling of exhaled breath condensate has opened a new avenue for analysis, as hypothesis generation from such profiling may lead to further selection of biomarkers for specific analysis.

COPD phenotype description using principal components analysis

BackgroundAirway inflammation in COPD can be measured using biomarkers such as induced sputum and FeNO. This study set out to explore the heterogeneity of COPD using biomarkers of airway and systemic inflammation and pulmonary function by principal components analysis (PCA).Subjects and MethodsIn 127 COPD patients (mean FEV1 61%), pulmonary function, FeNO, plasma CRP and TNF-α, sputum differential cell counts and sputum IL8 (pg/ml) were measured. Principal components analysis as well as multivariate analysis was performed.ResultsPCA identified four main components (% variance): (1) sputum neutrophil cell count and supernatant IL8 and plasma TNF-α (20.2%), (2) Sputum eosinophils % and FeNO (18.2%), (3) Bronchodilator reversibility, FEV1 and IC (15.1%) and (4) CRP (11.4%). These results were confirmed by linear regression multivariate analyses which showed strong associations between the variables within components 1 and 2.ConclusionCOPD is a multi dimensional disease. Unrelated components of disease were identified, including neutrophilic airway inflammation which was associated with systemic inflammation, and sputum eosinophils which were related to increased FeNO. We confirm dissociation between airway inflammation and lung function in this cohort of patients.

The repeatability of interleukin-6, tumor necrosis factor-alpha, and C-reactive protein in COPD patients over one year.

Background Many of the systemic manifestations of chronic obstructive pulmonary disease (COPD) are mediated through increased systemic levels of inflammatory proteins. We assessed the long term repeatability of Interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and C-reactive protein (CRP) over one year and examined the relationships between these systemic markers in COPD. Methods Fifty-eight stable COPD patients completed a baseline and one-year visit. Serum IL-6, plasma CRP, and plasma TNF-α were measured. Repeatability was expressed by intraclass correlation coefficient (Ri) and the Bland–Altman method. Pearson correlations were used to determine the relationships between the systemic markers at both visits. Results There was moderate repeatability with a very high degree of statistical significance (p ≤ 0.001) between the two visits for all the systemic biomarkers (IL-6, CRP, and TNF-α). CRP was significantly associated with IL-6 at both visits (r = 0.55, p = 0.0001, r = 0.51, p = 0.0002, respectively). There were no other significant associations between the systemic markers at either of the visits. Conclusions Systemic inflammatory biomarkers IL-6, CRP, and TNF-α were moderately repeatable over a twelve month period in COPD patients. We have also shown that a robust and repeatable association between IL-6 and CRP exists.

Non-invasive biomarkers and pulmonary function in smokers.

Limited information exists regarding measurement, reproducibility and interrelationships of non-invasive biomarkers in smokers. We compared exhaled breath condensate (EBC) leukotriene B4 (LTB4) and 8-isoprostane, exhaled nitric oxide, induced sputum, spirometry, plethysmography, impulse oscillometry and methacholine reactivity in 18 smokers and 10 non-smokers. We assessed the relationships between these measurements and within-subject reproducibility of EBC biomarkers in smokers. Compared to non-smokers, smokers had significantly lower MMEF % predicted (mean 64.1 vs 77.7, p = 0.003), FEV1/FVC (mean 76.2 vs 79.8 p = 0.05), specific conductance (geometric mean 1.2 vs 1.6, p = 0.02), higher resonant frequency (mean 15.5 vs 9.9, p = 0.01) and higher EBC 8-isoprostane (geometric mean 49.9 vs 8.9 pg/ml p = 0.001). Median EBC pH values were similar, but a subgroup of smokers had airway acidification (pH < 7.2) not observed in non-smokers. Smokers had predominant sputum neutrophilia (mean 68.5%). Repeated EBC measurements showed no significant differences between group means, but Bland Altman analysis showed large individual variability. EBC 8-isoprostane correlated with EBC LTB4 (r = 0.78, p = 0.0001). Sputum supernatant IL-8 correlated with total neutrophil count per gram of sputum (r = 0.52, p = 0.04) and with EBC pH (r = −0.59, p = 0.02). In conclusion, smokers had evidence of small airway dysfunction, increased airway resistance, reduced lung compliance, airway neutrophilia and oxidative stress.

The reproducibility of adenosine monophosphate bronchial challenges in mild, steroid-naive asthmatics

AIMS Repeated adenosine monophosphate (AMP) challenges are used to assess drug efficacy in clinical trials of mild, steroid-naive asthmatics. Refractoriness has been reported after repeated challenges over short intervals. This study evaluated possible tachyphylaxis after repeated AMP challenges at 12 and 24 h in mild, steroid-naive asthmatics. METHODS This was an open, three-way crossover study. Twenty-six steroid-naive asthmatic subjects were randomized to the following AMP challenge regimens separated by 7-14 days: (A) challenge at 08.00 h, repeated 24 h later; (B) challenge at 08.00 h, repeated 12 and 24 h later; (C) challenge at 20.00 h, repeated 12 h later. Comparisons within day were assessed using 90% confidence intervals (CIs). Non-inferiority approach taken with 1 doubling concentration (DC) as a clinically relevant difference. RESULTS Regimen A: Significant increase in AMP reactivity at 24 h. Mean DC difference was 0.6 (90% CI 0.24, 0.96). Regimen B: No evidence of difference between AMP reactivity at 08.00 h and a repeated challenge 12 h later. Repeated challenge at 24 h caused a significant increase in provocation concentration (PC)(20) compared with 12 h (mean DC difference 0.48, 90% CI 0.02, 0.95) and 0 h (mean DC difference 0.82, 90% CI 0.49, 1.14 - the upper CI exceeds the criteria of 1 DC). Challenge regimen C: No difference between challenges; mean DC difference of 0.28 (90% CI -0.2, 0.76). CONCLUSION The small decline in AMP reactivity during repeated challenges was not consistently observed, and was small compared with the known effects of inhaled drugs.

Multiple flow rate modelling of nitric oxide in COPD – methodological concerns

Multiple flow rates FeNO data two-compartment mathematical modelling can estimate NO airway wall concentration (CawNO), airway wall diffusing capacity (DawNO), alveolar concentration (CalvNO) and maximal NO flux (JawNO). To compare modelling based on linear, non linear and mixed linear and non linear analyses in COPD. FeNO was measured using the Niox analyser (Aerocrine) at flow rates: 10, 30, 50, 100 and 200ml/s in 50 COPD patients and the data applied to 4 different methods. All methods showed that current smoking reduced CawNO. JawNO data differed between methods (Table 1). All the methods showed that current smoking did not affect CalvNO or DawNO. Comparison of the methods showed that CalvNO and DawNO data were significantly different between all methods, JawNO was different for most between method comparisons, while there was agreement between all the methods for CawNO. Smoking in COPD reduces CawNO , but not CalvNO and DawNO. JawNO, CalvNO and DawNO data are model dependent parameters. CawNO findings were model independent, and hence the most robust modelled parameter.