Efficacy of corticosteroid therapy for IgA nephropathy patients stratified by kidney function and proteinuria.

BACKGROUND: Steroid therapy is one of the important therapies for IgA nephropathy (IgAN), but the features of the IgAN patients who have the benefit from this therapy remained unclear. METHODS: This retrospective observational study, using data of 874 patients with IgAN analyzed the proteinuria and kidney function of IgAN patients who had beneficial effect by steroid therapy. Two advantages of the present study were a large cohort and a long observational period. RESULTS: Corticosteroid therapy had ameliorated the kidney prognosis [incident rate ratio (IRR) 0.57 (95%CI 0.34-0.92), P = 0.029]. Because of interaction between kidney function and use of corticosteroid (P = 0.047), stratification analysis by kidney function revealed that prognosis of kidney function in IgAN patients whose eGFR was less than 60 ml/min/1.73m2 was ameliorated by corticosteroid therapy [IRR 0.50 (95%CI 0.26-0.97), P = 0.015); while, there was no change of kidney prognosis in IgAN patients whose eGFR was above 60 ml/min/1.73 m2. To make the target of corticosteroid therapy for IgAN patients more clear, IgAN patients, whose eGFR were less than 60 ml/min/1.73 m2, were stratified by proteinuria (1 g/day). In IgAN patients whose eGFR were under 60 ml/min/1.73 m2 and whose proteinuria were over 1.0 g/day, corticosteroid therapy seemed to ameliorate kidney function [IRR 0.39 (95%CI 0.19-0.86), P < 0.05]; while, there was obviously no change by corticosteroid therapy in IgAN patients whose eGFR were less than 60 ml/min/1.73 m2 and whose proteinuria were less than 1.0 g/day. CONCLUSION: Our results suggested that steroid therapy was especially effective for IgAN patients whose eGFR was less than 60 ml/min/1.73 m2 and whose proteinuria was more than 1.0 g/day.

Serum Uric Acid Level Predicts Progression of IgA Nephropathy in Females but Not in Males.

BACKGROUND: Immunoglobulin A nephropathy (IgAN) is one of most common forms of glomerulonephritis. At this point, the clinical impact of hyperuricemia on IgAN is not clear. The aim of the present study was to explore the clinical impact of hyperuricemia on the progression of IgAN. STUDY DESIGN: Multicenter retrospective cohort study. SETTING & PARTICIPANTS: 935 IgAN patients who were diagnosed by kidney biopsy at Osaka University Hospital, Osaka General Hospital, and Osaka Rosai Hospital. were included in this study. PREDICTOR: Uric acid levels at renal biopsy. OUTCOMES: The outcome of interest was the time from the kidney biopsy to the time when a 50% increase in the baseline serum creatinine level was observed, which was defined as "progression". MEASUREMENTS: The baseline characteristics according to the kidney biopsy at the time of diagnosis were collected from the medical records, and included age, gender, body mass index, hypertension, diabetes (use of antidiabetic drugs), serum levels of creatinine, urinary protein, smoking status, RAAS blockers and steroid therapy. RESULTS: An elevated serum uric acid level was an independent risk factor for progression in female patients (per 1.0 mg/dL, multivariate-adjusted incident rate ratio 1.33 [95% confidence interval 1.07, 1.64], P = 0.008) but not in male patients (1.02 [0.81, 1.29], P = 0.855). To control a confounding effect of renal function on an association between serum uric acid level and progression in female patients, age- and serum creatinine-matched and propensity score-matched analyses were performed, and these results also supported the effect by uric acid on kidney disease progression independent of basal kidney function. LIMITATIONS: A cohort analyzed retorospectively. CONCLUSIONS: This study revealed that an elevated uric acid level was an independent risk factor for ESKD in female IgAN patients. Therefore, uric acid might be a treatable target in female IgAN patients.