Background/Purpose: Hyperuricemia has been reported to be associated with chronic kidney disease (CKD) in several clinical conditions, and recent studies also observed an association between increased uric acid (UA) serum levels and renal damage in lupus. However, the predictive value of UA for the development of long-term renal dysfunction in lupus nephritis is unknown. The purpose of this study was to evaluate if the UA level may be considered a predictor of long-term renal outcome in patients with lupus nephritis.

Methods: 75 biopsy-proven lupus nephritis patients with more than 7 years follow-up were consecutively selected for this study. Clinical and laboratorial data were obtained using a standardized electronic chart database protocol carried out at 1-6 months interval. UA levels were measured in sera stored at -70ºC for all SLE patients at biopsy during nephritis flare and in 31 patients, for whom sera were available, at 6 and 12 months post-biopsy. The renal outcome was addressed after 7 years of follow-up to determine if UA was a predictor of good long-term renal outcome (Cr<1.5mg/dL in 7 years). SLE patients were divided in two groups according to the renal outcome [good outcome (Cr<1.5mg/dL in 7 years) and poor outcome (Cr≥1.5mg/dL in 7 years)] to assess whether UA levels at different time-points of follow-up were able to differentiate such groups. ROC curves were plotted to assess UA accuracy.

Results: At baseline, patients had mean SCr of 1.7±1.3 mg/dl, proteinuria of 5.7±4.7 g/24h, albumin of 2.4±0.8 g/dl, and SLEDAI scores of 9.5±5.0. Almost two thirds of the patients (66%) patients had positive anti-dsDNA and 28 patients (35%) had SCr≥1.5mg/dl. The distribution of histological classes among studied patients was: class II (6%), class III / IV (53%) and pure class V (36%). Serum UA levels were not able to differentiate good from poor long-term renal outcomes in patients with lupus nephritis at any of the time points analyzed: baseline, 6, 12 months (respectively p = 0.96, p = 0.76, p = 0.77). As expected, the ROC curve with higher AUC (12 months) showed a low accuracy (AUC=0.59). The cut-off for UA was 5.46mg/dL (Sensitivity=0.63, Specificity= 0.65, Positive Predictive Value=0.38, Negative Predictive Value=0.16, 95% CI=0.2-0.7, p<0.05). The AU was only associated with the current creatinine levels: at baseline (p=0.01), 6 months (p=0.03) and 12 months (p=0.01).

Conclusion: This study demonstrated that serum uric acid levels in lupus patients reflect solely the current renal function and it is not a good predictor of long-term renal outcome in lupus nephritis.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/is-uric-acid-level-a-predictor-of-long-term-renal-outcome-in-lupus-nephritis/