On the role of interleukin-6 and soluble interleukin-6 receptor as potential biomarkers for ulcerative colitis

The purpose of this study was to evaluate the use of IL-6, its soluble receptors, sIL-6R, and sgp130 as biomarkers in patients with ulcerative colitis. A total of 166 adult UC patients (514 measurements) were analysed for this study. Disease activity was monitored using disease activity scores, laboratory assessments and endoscopies. ELISA testing was used to determine the quantity of IL-6, sIL-6R and sgp130 in serum samples. 

A large proportion of IL-6 measurements were found to be below the detection limit of 3.13 pg/mL. IL-6 levels of patients with active UC were significantly increased compared to patients with inactive disease. However, 50% of active UC IL-6 measurements were below control levels. Furthermore, increases of up to 15% in median levels of sIL-6R and sgp130 were identified but these were not consistent with disease activity and deemed to be of negligeable clinical significance.

Indicators of UC disease activity were significantly associated with serum levels of IL-6 and positive associations were found with CRP, leukocytes and thrombocytes. Also, the IL-6 buffering ability of sIL-6R and sgp130 was underscored by the significant positive association between the two buffer components.

Given that only a small percentage of UC patients presented with increased levels of IL-6, this cytokine is not a suitable biomarker for the UC patient population. However, UC patients that qualify to receive treatment targeting IL-6 signalling could benefit from determining levels of IL-6 in serum to predict treatment success.