CD68 and rheumatoid arthritis: In fact, a study searching for ST predictors of clinical differentiation in patients with seronegative undifferentiated peripheral arthritis reported that 6 out of 42 patients with a definite diagnosis after 1 year of follow up (2 RA, 2 SpA, 2 PsA) had higher histological CD68+ macrophage scores than patients persisting with undifferentiated arthritis (57).