Spinelli F, Garufi C, Truglia S, et al. - Osteopontin (OPN) was measured in the serum and urine of SLE people with active lupus nephritis (LN) (n = 14), LN in remission (n = 20), SLE without kidney involvement (n = 22) and age- and gender-matched healthy controls (HC, n = 20) in order to assess OPN as a biomarker of renal involvement in individuals with SLE and associate its levels with disease activity and laboratory characteristics. In both groups of individuals and controls, OPN levels were significantly greater in urine than in serum. Irrespective of the phase of renal activity, serum OPN levels were greater in the LN individuals vs HC and in SLE cases without renal involvement. SLE people without renal involvement and controls explicated comparable serum levels. A relationship between low complement levels and OPN serum levels in individuals with LN was discovered. Furthermore, a greater percentage of individuals with LN, in comparison with SLE without LN and HC, exhibited abnormal serum OPN. Thus, data propose that serum OPN could be taken into consideration as a biomarker of renal involvement, without distinguishing between active and remission LN.