S100A8 and rheumatoid arthritis: Notably, plasma levels of S100A8/A9 alarmin are increased in RA flare compared to levels found in healthy controls (mean 59 ng/mL, range 46–107 ng/mL, Fig. 3E), and exhibit a trend showing a marked increase in S100A8/A9 with DAS28 score >5 consistent with reports of association of S100A8/A9 in the highest quartile with severity in RA [13].