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 <or= 0.001) between the two visits for all the systemic biomarkers (IL-6, CRP, and TNF-alpha). 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-alpha 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.
Kolsum
Umme
U
North West Lung Research Centre, University of Manchester, South Manchester University Hospitals Trust, Wythenshawe, Manchester, UK. ukolsum@meu.org.uk
Roy
Kay
K
Starkey
Cerys
C
Borrill
Zoë
Z
Truman
Nick
N
Vestbo
Jørgen
J
Singh
Dave
D
D000368:Aged; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D018836:Inflammation Mediators / Q000097:blood*; D015850:Interleukin-6 / Q000097:blood*; D008168:Lung / Q000276:immunology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry; D029424:Pulmonary Disease, Chronic Obstructive / Q000276:immunology* / Q000503:physiopathology; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000097:blood*; D014797:Vital Capacity
D015415:Biomarkers; C508600:IL6 protein, human; D018836:Inflammation Mediators; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D002097:C-Reactive Protein