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

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Background:Interleukin‐6 (IL‐6) is produced by and impacts different cell types inhuman. IL‐6 is associated with different diseases and viral infections, includingCOVID‐19. To our knowledge, no normal values were reported for IL‐6 in the bloodof healthy individuals. We have reviewed and performed a meta‐analysis on a totalof 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 between0 and 43.5 pg/ml. The pooled estimate of IL‐6 was 5.186 pg/ml (95% confidenceinterval [CI]: 4.631, 5.740). As the age increased by 1 year, IL‐6 values increased by0.05 pg/ml (95% CI: 0.02, 0.09;p< .01). Though the heterogenicity, as determined byI2statistics, was high in our study, the differences in IL‐6 values are still at the levelof a few pg/ml, which might be related to the differences in the conditions thatinfluence IL‐6 production in the healthy population.Conclusions:This is the first meta‐analysis reporting the levels of IL‐6 in the blood ofhealthy 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 quickdecision‐making in clinical interventions, particularly those aiming to inhibit IL‐6,especially urgent interventions, for example, COVID‐19.
Original languageEnglish
JournalJournal of Medical Virology
Publication statusPublished - 2021

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