Day-to-day variation in plasma interleukin-6 concentrations in older adults

Cytokine. 2009 Sep;47(3):162-5. doi: 10.1016/j.cyto.2009.05.007. Epub 2009 Jul 14.


Interleukin-6 (IL-6) is a pro-inflammatory cytokine commonly used in studies as a means of assessing chronic inflammatory status. Despite the use of plasma IL-6 as a marker of chronic inflammation few studies exist that examine the variability of plasma IL-6 within and between individuals. The purpose of this study was to assess inter- and intra-variability of plasma IL-6 concentration in men and postmenopausal women. Sixteen healthy postmenopausal women and 5 men completed the 2-week study. Fasted venous blood samples were obtained on three consecutive mornings for two consecutive weeks (six blood draws per participant). Mean plasma IL-6 values were 2.00+/-1.74 pg/mL. Intra-variability was not significantly different (p>0.05) however inter-variability was significantly different (p<0.05). The index of individuality (II) was 0.20 and the standard error of the mean (SEM) was determined to equal 0.16 pg/mL (0.32 pg/mL; 1.96 SEM). An II of 0.20 demonstrates the need to carefully evaluate changes in plasma IL-6 concentration instead of utilizing population-based reference norms. In an older adult population until plasma IL-6 differences exceed 0.32 pg/mL such values could be considered normal fluctuation between trials and most likely not attributable to a nutrition intervention.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Cohort Studies
  • Female
  • Humans
  • Interleukin-6 / blood*
  • Male
  • Middle Aged
  • Postmenopause
  • Prospective Studies


  • Interleukin-6