High Albumin Clearance Predicts the Minimal Change Nephrotic Syndrome Relapse

KEY POINTS: Albumin kinetics not only reflected the pathophysiology of minimal change nephrotic syndrome but was also a predictor of relapse. The high estimated 24-hour albumin clearance predicts the minimal change nephrotic syndrome relapse. The 24-hour albumin clearance can easily be calculated from only serum albumin and urinary protein excretion, which are routine laboratory measurements. BACKGROUND: Although albuminuria leakage that occurs in minimal change nephrotic syndrome (MCNS) may be related to the disease state, albumin kinetics in MCNS has never been evaluated. In this study, we investigated albumin kinetics in adult Japanese patients with MCNS by the estimated 24-hour albumin clearance (eC(ALB)) and examined the association between eC(ALB) and relapse. METHODS: We retrospectively identified 103 adult patients with a histological diagnosis of MCNS from four hospitals in Japan (2010–2020). The primary outcome is the first relapse in 2 years after complete remission after corticosteroid therapy. The eC(ALB) [µl/min] was defined as (2.71828((0.0445+0.9488×log(urinary protein)) [g/24 hours])/(serum albumin [g/dl]×1440 [min/24 hours]) for women and (2.71828((-0.1522+0.9742×log(urinary protein)) [g/24 hours])/(serum albumin [g/dl]×1440 [min/24 hours]) for men. RESULTS: Relapse was observed in 44 patients (103 kidney biopsy samples; 42.7%). The mean patient age was 41.0 years. Patients had an eGFR of 71.0 ml/min per 1.73 m(2), urinary protein excretion of 6.8 g/d, serum albumin of 1.4 g/dl, and eC(ALB) of 2.27 μl/min. eC(ALB) was strongly associated with hypoalbuminemia, severe proteinuria, lipid abnormalities, and coagulopathy. In the multivariable analysis, a high eC(ALB) was significantly associated with relapse after adjusting for age, eGFR, time to complete remission, and urinary protein excretion (adjusted hazard ratio, 5.027; 95% confidence interval, 1.88 to 13.47; P = 0.001). CONCLUSIONS: This study revealed that eC(ALB), which could substitute albumin kinetics, reflected the severity of MCNS, and a high eC(ALB) was associated with recurrence.