Defining IL‐6 levels in healthy individuals: A meta‐analysis

Abstract

Background Interleukin‐6 (IL‐6) is produced by and impacts different cell types in human. IL‐6 is associated with different diseases and viral infections, including COVID‐19. To our knowledge, no normal values were reported for IL‐6 in the blood of healthy individuals. We have reviewed and performed a meta‐analysis on a total of 140 studies, including 12,421 values for IL‐6 in the blood of healthy adult donors. Among these studies, 83 did not report a mean value and the standard deviation. Therefore, for the statistical analysis, we used the values reported in 57 studies, which included 3166 values for IL‐6. Results The reported values for IL‐6 in the blood of healthy donors varied between 0 and 43.5 pg/ml. The pooled estimate of IL‐6 was 5.186 pg/ml (95% confidence interval [CI]: 4.631, 5.740). As the age increased by 1 year, IL‐6 values increased by 0.05 pg/ml (95% CI: 0.02, 0.09; p < .01). Though the heterogenicity, as determined by I2 statistics, was high in our study, the differences in IL‐6 values are still at the level of a few pg/ml, which might be related to the differences in the conditions that influence IL‐6 production in the healthy population. Conclusions This is the first meta‐analysis reporting the levels of IL‐6 in the blood of healthy donors based on a large number of studies and donors. Therefore the 95% CI values determined in our study could well serve as a reference range for quick decision‐making in clinical interventions, particularly those aiming to inhibit IL‐6, especially urgent interventions, for example, COVID‐19.

Interleukin – 6 Serum Level and Single Nucleotide Gene -174 G/C promoter Polymorphism in Patients with Rheumatoid Arthritis / Iraq

“…A meta-analysis study included 140 different research found that the average concentration of IL-6 in the majority of healthy people ranged between 4.631 and 5.740 pg/ml (ng/l) 29 . These variation might be attributed to differences in the weight of these people and their muscle mass and contractility status 29 .…”

The Association of Systemic Interleukin 6 and Interleukin 10 Levels with Sarcopenia in Elderly Patients with Chronic Obstructive Pulmonary Disease

“…Therefore, plasma was used to measure these interleukin levels. 20 The patients gave 3 mL of peripheral venous blood in the early morning on an empty stomach. It was then centrifuged at room temperature (4000 rpm for 8 min), and the upper serum was stored in a refrigerator at −80°C.…”

Pathophysiology of Circulating Biomarkers and Relationship With Vascular Aging: A Review of the Literature From VascAgeNet Group on Circulating Biomarkers, European Cooperation in Science and Technology Action 18216

“…Additionally, IL-6 levels have been found to increase in an age-dependent manner in two cohorts of older individuals ( Puzianowska-Kuźnicka et al, 2016 ; Stevenson et al, 2018 ). Similarly, in a recent meta-analysis including 12421 values for IL-6 in the blood of healthy adult male and female donors, it was found that for every 1-year increase in age, there was a significant increase of IL-6 values by 0.05 pg/ml ( Said et al, 2021 ). Moreover, there is substantial evidence that IL-6 contributes to hypertension as levels of IL-6 have been correlated with blood pressure in hypertensive subjects and are reduced by treatment with angiotensin II-receptor blockade ( Vázquez-Oliva et al, 2005 ).…”