Serum uric acid levels are associated with lupus nephritis in patients with normal renal function.

Uric acid has been recognised as a potential marker of endothelial dysfunction and kidney disease but there are scarce data about its importance in systemic lupus erythematosus (SLE) nephritis. This study aimed to evaluate serum uric acid (UA) levels in lupus nephritis (LN), by comparing SLE patients with normal renal function, with and without nephritis. Forty-six female SLE patients were consecutively selected and divided in two groups according to renal activity at the evaluation: presence of a recently diagnosed lupus nephritis (LN+, n = 18) and absence of lupus nephritis (LN-, n = 28). Age-matched healthy women were selected (CONTROL, n = 28). Patients with gout, creatinine clearance lower than 80 ml/min and use of drugs that interfere in UA were excluded. Laboratory and clinical data were analysed by appropriate tests. A multivariate analysis was performed, and a receiver operating characteristic (ROC) curve was plotted, and the area under the curve was calculated to assess the diagnostic strength of UA in LN. The mean age was similar among LN+, LN- and CONTROL groups (32.44 ± 6.09 vs. 30.68 ± 5.36 vs. 30.86 ± 5.00 years, p = 0.52). UA was significantly higher in LN+ compared to LN- (5.54 ± 1.67 vs. 3.65 ± 1.090 mg/dL, p < 0.001) and CONTROL (5.54 ± 1.67 vs. 3.92 ± 0.95 mg/dL p < 0.001). Multivariate analysis confirmed that high UA was an independent variable related to LN (p < 0.001). The cut-off value for UA using the ROC curve was 4.47 mg/dL (AUC 0.86, p = 0.00004, CI 95% 0.75-0.96). Lupus nephritis was associated with higher UA. Hyperuricemia as a predictor of renal damage in SLE needs to be evaluated in further studies.