Is serum uric acid a predictor of long-term renal outcome in lupus nephritis?

Abstract

Recent studies observed an association between increased serum uric acid (SUA) levels and renal damage in lupus. However, the predictive value of UA for the development of long-term renal dysfunction in lupus nephritis (LN) is still unknown. The aim of this study was to evaluate if SUA may be a predictor of long-term renal outcome in LN. Eighty biopsy-proven LN patients > 7years of follow-up were selected. SUA levels were measured in sera stored at - 70°C. All patients had serum stored from LN baseline, and 32 also had stored serum from 6 and 12months after LN. Renal outcome was addressed after 7years of follow-up to determine if SUA could be a predictor of long-term renal outcome. A good long-term renal outcome in 7years was defined as a creatinine clearance (CrCl) ≥ 90.0mL/min/1.73m2, and poor if CrCl < 90mL/min/1.73m2. Patients were divided in two groups according to the renal outcome to assess whether SUA levels at different time points of follow-up could differentiate such groups. An ROC curve was plotted to assess accuracy. SUA levels at baseline and 6months were not able to differentiate good from poor long-term renal outcomes in LN (respectively p = 0.37, p = 0.28), but at 12months (p = 0.02), they could clearly differentiate the two groups. ROC curve (12months) accuracy was 0.76. SUA cutoff was 6.05mg/dL (sensitivity = 0.67, specificity = 0.89, positive predictive value = 0.85, negative predictive value = 0.73). SUA levels < 6.05mg/dL at 12months of follow-up is a predictor of good long-term renal outcome in lupus nephritis. • Previous studies reported an association between increased serum uric acid level and short-term renal damage in lupus patients. • The predictive value of serum uric acid for the development of long-term renal dysfunction in lupus nephritis was never assessed. • At 12months of follow-up serum uric acid clearly differentiated good from poor long-term renal outcome in lupus nephritis. • SUA level < 6.05mg/dL at 12months of follow-up was a predictor of good long-term renal outcome in lupus nephritis.