Because the vast majority of RA patients in our study were undergoing treatment at the time of study and most patients were diagnosed with low to moderate disease activity, we divided patients with RA into two groups based on the DAS28-CRP score to evaluate the ability of CTHRC1 to monitor disease severity and activity: patients who were in remission or had low disease activity (DAS28-CRP < 3.0) and patients with moderate to high disease activity (DAS28-CRP > 3.0). Here, CRP is linked to rheumatoid arthritis.