We also found that the receiver operating characteristic curve of CHI3L1 yielded an AUC value of 0.955, which is slightly lower than the AUC values of the US FDA-recommended RA diagnostic factors, i.e., CRP (0.988) and cyclic citrullinated peptide (CCP, 0.995), but slightly higher than that of rheumatoid factor (0.865). The gene discussed is CHI3L1; the disease is rheumatoid arthritis.