CD40LG and rheumatoid arthritis: The area under the curve (AUC) of circulating RF_IgA, RF_IgG, and RF_IgM levels in predicting RA was 0.79 (95% CI: 0.74-0.83, P < 0.001), 0.73 (95% CI: 0.68-0.78, P < 0.001), and 0.87 (95% CI: 0.84-0.91, P < 0.001), respectively.