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-alpha (TNF-alpha), 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-alpha were measured. Repeatability was expressed by intraclass correlation coefficient (R(i)) 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

A comparison of exhaled nitric oxide measurements performed using three different analysers.

INTRODUCTION: Exhaled nitric oxide (NO) is an established technique for monitoring airway inflammation. We have compared exhaled NO measurements from 3 different analysers; Ecomedics (E), Niox (N) and Logan (L). METHODS: Thirty subjects (10 non-smoking healthy subjects, 10 non-smoking patients with asthma and 10 ex-smoking COPD patients) performed 3 repeated measurements of exhaled NO at a flow rate of 50 ml/s on each of the 3 analysers. Within analyser variability was determined by calculating the repeatability coefficient for each analyser. Differences between analysers were assessed by (1) the differences between group means and (2) the Bland Altman method to estimate the variability expected for an individual using the 3 analysers. RESULTS: The repeatability coefficients (expressed as ratios) were 1.12, 1.19 and 1.19 for N, E and L, respectively. There were significant differences (P<0.05) between analysers; the Logan analyser gave the highest group mean values and Ecomedics gave the lowest group mean values. Differences between analysers were observed in all subject groups (healthy, asthma, COPD). Similar results were obtained in the 3 groups when analysed separately. Bland Altman analysis gave the following ratios [data are mean ratio (95% limits of agreement)]; N:E 1.59 (1.02-2.50), L:N 1.23 (0.72-2.13), L:E 1.96 (1.09-3.57). CONCLUSION: Our findings indicate that exhaled NO measurements in healthy subjects and patients with airways disease differ according to the type of analyser used.