Sensitivity and specificity of IgM-RF testing for the diagnosis of RA was 76.1% (68.6%–82.5%) and 77.7% (72.1%–82.7%), respectively, whereas in patients with early disease, IgM-RF revealed a sensitivity of 68.2% (45.1%–86.1%). Here, CD40LG is linked to rheumatoid arthritis.