Elevated serum uric acid is associated with renal arteriolopathy and predict poor outcome in patients with lupus nephritis.

ABSTRACT

OBJECTIVES: Increased serum uric acid (SUA) levels are well known to be concomitant of cardiovascular and kidney diseases, and have been proposed to be implicated in the development of arteriolar damage. The aim of the present study was to assess the association between SUA levels, renal damage and its implication for outcome in patients with lupus nephritis (LN). METHODS: This retrospective study included 194 cases with biopsy proven LN at the Affiliated Hospital of Qingdao University between January 2013 and June 2021. We reviewed clinical, laboratory and histologic data of patients and analysed the correlation between SUA levels, renal damage and the primary outcome (death or ESRD). Biopsy-proven arteriolar damage was defined by the presence of arteriolar hyalinosis and/or intimal thickening. RESULTS: Compared to LN patients without hyperuricemia, LN patients with hyperuricaemia presented with higher BP, hyperlipidaemia, lower eGFR, lower haemoglobin, lower serum albumin, worse renal arteriolar damage and proteinuria, and also higher SLEDAI score, activity index and chronicity index (p<0.05). At logistic regression analysis, SUA was independently related to the presence of arteriolar damage. For each 100 µmol/L increase in SUA levels the risk for arteriolar damage raised by 53.8% (hazard ratio [HR] =1.538; 95% CI 1.147-2.063; p=0.004) after adjustment for haemoglobin, serum creatinine and erythrocyte sedimentation rate. Cox regression analysis showed that female (HR=3.180; 95% CI 1.216-8.313; p=0.018), white blood cell count (HR=1.111; 95% CI 1.027-1.202; p=0.009), SUA (HR=1.100; 95% CI 1.023-1.253; p=0.035), serum creatinine (HR=1.800; 95% CI 1.348-2.404; p<0.001), and renal arteriolar damage (HR=3.117; 95% CI 1.022-9.511; p=0.046) was significantly associated with development of ESRD or death in patients with LN after adjustment for several potential confounding factors. Furthermore, for each 100 µmol/L increase in SUA levels, the risk of ESRD or death increased by 10%. CONCLUSIONS: SUA levels are directly associated with renal arteriolar damage and poor prognosis in LN patients. Hyperuricaemia is an important predictor for poor prognosis in patients with LN.