Clinical utility of urinary soluble CD163 in evaluation of lupus nephritis patients

Aim of the workTo assess urinary soluble CD163 (sCD136) in systemic lupus erythematosus (SLE) patients compared to healthy controls. In addition to determine its association with different SLE clinical features, laboratory investigations and pathological indices focusing on those suggest renal disease activity.Patients and methodsThe study included 58 SLE patients and 30 controls. SLE disease activity index (SLEDAI) was assessed and patients subdivided into active lupus nephritis (ALN) (renal SLEDAI ≥ 4) and no-renal activity (NRA) SLE patients (renal SLEDAI = 0). Urinary sCD163 was measured by Enzyme-Linked Immunosorbent Assay (ELISA). Urine values were normalized to urinary creatinine excretion. Renal biopsies were performed in 21 ALN patients.ResultsThey were 54 females and 4 males with a mean age 31.8 ± 9.1 years and disease duration 6.2 ± 4.8 years. They were 31 with ALN and 27 NRA SLE patients. Urinary sCD163 level was significantly higher in SLE patients (1.85 ± 0.3) than controls (0.5 ± 0.36, p < 0.001). In ALN, it was significantly higher (2.91 ± 2.52) compared to NRA SLE patients (0.64 ± 0.38) and controls (p < 0.001 in both). The optimum cut-off value above which normalized urinary sCD136 can predict renal activity was > 0.82 with sensitivity of 90.3%, specificity of 88.89%, p < 0.001. Urinary sCD163 significantly correlated with renal (r = 0.75, p < 0.001) but not with extra-renal SLEDAI. It correlated with activity index of renal biopsy (r = 0.46, p = 0.038).ConclusionUrinary sCD163 is a potential biomarker for LN activity. Its level is associated with clinical features, laboratory investigations and pathological indices that indicate renal disease activity.