A J-shaped association between serum uric acid levels and poor renal survival in female patients with IgA nephropathy.

Recently, low serum uric acid (SUA) levels and high SUA levels, have emerged as risk factors for cardiovascular disease, as well as for the incidence of acute kidney injury and chronic kidney disease (CKD). However, the effect of low SUA on the progression of CKD remains unclear. To evaluate the association between SUA and renal prognosis in patients with immunoglobulin A nephropathy (IgAN), one of the most common causes of CKD, we retrospectively followed 1218 patients who were diagnosed with primary IgAN by kidney biopsy between October 1979 and December 2010. Patients were divided into three groups on the basis of SUA level tertiles: low (L group), middle (M group) and high (H group) tertiles (<6.1, 6.1-7.0, and >7.0 mg dl, respectively, for men and <4.4, 4.4-5.3, and >5.3 mg dl, respectively, for women). The risk factors for developing end-stage renal disease (ESRD) were estimated using a Cox proportional hazards model. After a median follow-up of 5.1 years, 142 patients (11.7%) developed ESRD. The hazard ratio (95% confidence interval) showed a J-shaped trend with the tertiles in both men (1.18 (0.55-2.54), 1.00 (reference), and 1.80 (1.01-3.10) in L, M and H groups, respectively) and women (2.73 (1.10-6.76), 1.00 (reference) and 2.49 (1.16-5.34) in L, M and H groups, respectively). Notably, low SUA was significantly associated with incident ESRD in women. This finding suggests that SUA has a J-shaped association with ESRD in patients with IgAN, especially women.