ACP5 and arthritic joint disease: TNF-α was not only positively correlated with the number of TRAP+ osteoclast precursors (OCs) (r = 0.66; P = 0.000), but also with the radiographic damage scores (Sharp score r = 0.52; P = 0.001; BASRI r = 0.35; P = 0.02) and arthritis activity index PsAJAI (r = 0.41; P = 0.02) (Figure 3A–3D).