Hyperuricemia as a marker for progression of immunoglobulin A nephropathy

BACKGROUND The variable clinical and histopathological manifestations of immunoglobulin A nephropathy (IgAN) make it difficult to predict disease progression. A recent study showed that hyperuricemia, a condition common in hypertension and vascular disease, may contribute to renal dysfunction and histological changes including renal arteriosclerosis, tubular atrophy, and interstitial fibrosis. Herein, we investigated the clinical significance of uric acid level at the time of biopsy, as a marker of IgAN progression. METHODS We included 193 patients with biopsy-proven IgAN. Renal disease progression was defined as serum creatinine elevation above 1.2 mg/dL or over 20% elevation from baseline. Hyperuricemia was defined as a serum uric acid level ≥7.3 mg/dL in men and ≥5.3 mg/dL in women, which were 1 standard deviation above the mean value in the normal subjects. RESULTS The hyperuricemia group (n=50) had higher blood pressure, body mass index, and serum creatinine, and a greater amount of proteinuria and a lower glomerular filtration rate than the nonhyperuricemia group (n=143). Hyperuricemia increased the risk of IgAN progression (odds ratio, 4.53; 95% confidence interval, 1.31-15.66). The disease progression group (n=26) had a greater frequency of hyperuricemia, hypertension, and nephrotic range proteinuria than the nonprogression group (n=119). The renal survival analysis showed that the hyperuricemia group had a higher rate of IgAN disease progression. CONCLUSION Hyperuricemia at the time of diagnosis is an important marker for IgAN progression.