Long-term repeatability of induced sputum cells and inflammatory markers in stable, moderately severe COPD.
OBJECTIVE
Neutrophilic inflammation is a major feature of COPD. Induced sputum is increasingly used to monitor inflammatory airway diseases. Although short-term repeatability of selected sputum markers has been extensively studied in several populations, data on the long-term repeatability of induced sputum markers in stable COPD are scant.


METHODS
Sputum supernatant of 12 patients with stable COPD was analyzed on three separate occasions with 4-weekly intervals. Sputum cells and inflammatory markers interleukin (IL)-8 and soluble intercellular adhesion molecule (sICAM)-1 were measured in supernatant using enzyme-linked immunosorbent assay. Repeatability of sputum markers was expressed by intraclass correlation coefficients (Ri).


RESULTS
Sputum induction was safe in all patients. None of the sputum parameters analyzed changed significantly throughout the study. The repeatability for cell differential counts in stable COPD was as follows: total cells, Ri = 0.07; neutrophils, Ri = 0.66; macrophages, Ri = 0.47; eosinophils, Ri = 0.49; and lymphocytes, Ri = 0.58. The repeatability of soluble markers was as follows: IL-8, Ri = 0.50; and sICAM, Ri = 0.58. Sputum neutrophils were negatively correlated with lung function on each separate occasion, whereas soluble markers were not correlated with sputum cells (p > 0.16, all correlations) or lung function (p > 0.24, all correlations).


CONCLUSIONS
Clinically stable, moderate COPD is associated with equally stable sputum inflammatory markers. Repeatability of induced-sputum markers of neutrophilic inflammation in stable COPD is satisfactory, even over extended periods of time. These data support the usefulness of serial monitoring of induced-sputum inflammatory markers in COPD.
Beeh
Kai M
KM
Pulmonary Department, Internal Medicine, University Hospital, Mainz, Germany. k.beeh@3-med.klinik.uni-mainz.de
Beier
Jutta
J
Kornmann
Oliver
O
Mander
Annette
A
Buhl
Roland
R
D000704:Analysis of Variance; D015415:Biomarkers; D005541:Forced Expiratory Volume; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism*; D016209:Interleukin-8 / Q000378:metabolism*; D007958:Leukocyte Count; D016014:Linear Models; D009504:Neutrophils / Q000378:metabolism*; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis*; D015203:Reproducibility of Results; D013147:Spirometry; D013183:Sputum / Q000166:cytology / Q000276:immunology*; D014797:Vital Capacity
D015415:Biomarkers; D016209:Interleukin-8; D018799:Intercellular Adhesion Molecule-1