As shown in Figure 1(a), among the biomarkers, differences in the median serum level of PCT were statistically significant between the early RA (0.065 ng/ml) and OA groups (0.025 ng/ml) (p < 0.0001) or between the RA (0.065 ng/ml) and healthy groups (0.024 ng/ml) (p < 0.0001). Here, CALCA is linked to rheumatoid arthritis.