In stark contrast, circulating CTHRC1 levels were significantly increased in the RA cohort when compared to either control, OA or ReA groups with an average level of 20.39 ng/ml, a median level of 8.28 ng/ml, and a maximum level of 96 ng/ml (Kruskal-Wallis test, p < 0.001, Figure 1). Here, CTHRC1 is linked to rheumatoid arthritis.