SPDL1 and rheumatoid arthritis: In established RA (DD > 7 years), aCCP-positive patients had significantly higher levels of sPD-L1 (Figure 2A, median 1.0 vs. 23 pg/ml, Hodges–Lehmann (H–L) difference = 20, 95% CI = 0.0–39, and p = 0.016).