Variability of serum levels of tumor necrosis factor-alpha, interleukin 6, and soluble interleukin 6 receptor over 2 years in young women

Cytokine. 2005 Apr 7;30(1):1-6. doi: 10.1016/j.cyto.2004.08.008.


Serum levels of tumor necrosis factor-alpha (TNF-alpha), interleukin 6 (IL-6), and soluble interleukin 6 receptor (sIL-6R) have been studied as risk factors of cardiovascular disease in longitudinal studies. However, it is unknown about their long-term intra-individual variations and whether single measurements of these cytokines and receptor are reliable biomarkers in epidemiological studies. In this study, serum levels of TNF-alpha, IL-6, and sIL-6R were assayed by ELISAs in 36 young, healthy women from whom three blood samples were collected at 12-month intervals over 2 years, and the intraclass correlation coefficients (ICC) were estimated. The ICC of 0.73 (95% CI=0.49-0.79) for TNF-alpha was comparable to those of other commonly used biomarkers, justifying its use in epidemiological studies. The ICC of 0.48 (95% CI=0.25-0.58) for IL-6 was not optimal. However, IL-6 has been demonstrated as a consistent risk factor for cardiovascular disease, suggesting it could still be a useful biomarker if its disease association is substantial. The ICC of 0.36 (95% CI=0.10-0.47) for sIL-6R was relatively low, and multiple samples would need to be collected in prospective studies for this receptor.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Analysis of Variance
  • Biomarkers / metabolism
  • Cardiovascular Diseases / blood
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Humans
  • Inflammation
  • Interleukin-6 / blood*
  • Papillomavirus Infections / blood
  • Prospective Studies
  • Receptors, Interleukin-6 / blood*
  • Reference Values
  • Reproducibility of Results
  • Risk Factors
  • Time Factors
  • Tumor Necrosis Factor-alpha / biosynthesis*


  • Biomarkers
  • Interleukin-6
  • Receptors, Interleukin-6
  • Tumor Necrosis Factor-alpha