Association of circulating plasma osteopontin (cOPN), but not circulating neutrophil gelatinase-associated lipocalin (cNGAL) with adjusted-mean systemic lupus erythematosus disease activity index (AMS) at the 6-month interval. (A) Baseline cNGAL in pediatric-onset systemic lupus erythematosus (pSLE) was lower in patients with persistently inactive disease over a 6-month period, but did not differentiate among patients with active disease at baseline, which improves (Active:I); remains persistently active (Active:P); or worsens over 6 months. (B) Increased 6-month AMS in pSLE is associated with baseline high cOPN (OPNhi; osteopontin levels in the top quartile) compared with cOPN in the bottom quartile (OPNlo), but not with baseline high cNGAL levels (NGALhi and NGALlo, also defined as top and bottom quartile, respectively). (C) cOPN at baseline correlates with 6-month AMS in pSLE (n = 42) and in adult-onset SLE (aSLE) (n = 23). (D) There is no correlation of baseline cNGAL levels in the total pSLE cohort or in aSLE. SLEDAI, SLE disease activity index.