ANAPC15 and rheumatoid arthritis: As shown in Figure 4A, presence of the five autoantibodies were more frequent in early‐stage RA (47.2% positive in anti‐ANAPC15, 54.7% positive in anti‐LSP1, 60.4% positive in anti‐PTMS, 56.6% positive in anti‐APBB1, and 56.6% positive in anti‐UBL7; p = 0.3548, 0.0439, 0.0094, 0.0281, and 0.0081, respectively; Figure 4A), compared with established stage (duration ≥2 years, n = 99) RA.