Time to remission of proteinuria and incidence of relapse in patients with steroid-sensitive minimal change disease and focal segmental glomerulosclerosis: the Japan Nephrotic Syndrome Cohort Study

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 (eCALB) and examined the association between eCALB 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 eCALB [µ l/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 m2, urinary protein excretion of 6.8 g/d, serum albumin of 1.4 g/dl, and eCALB of 2.27 μ l/min. eCALB was strongly associated with hypoalbuminemia, severe proteinuria, lipid abnormalities, and coagulopathy. In the multivariable analysis, a high eCALB 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 eCALB, which could substitute albumin kinetics, reflected the severity of MCNS, and a high eCALB was associated with recurrence.

Predictors of early remission of proteinuria in adult patients with minimal change disease: a retrospective cohort study

Previous studies reported conflicting results regarding an association between serum albumin concentration and the cumulative incidence of remission of proteinuria in adult patients with minimal change disease (MCD). The present study aimed to clarify the clinical impact of serum albumin concentration and the cumulative incidence of remission and relapse of proteinuria in 108 adult patients with MCD at 40 hospitals in Japan, who were enrolled in a 5-year prospective cohort study of primary nephrotic syndrome, the Japan Nephrotic Syndrome Cohort Study (JNSCS). The association between serum albumin concentration before initiation of immunosuppressive treatment (IST) and the cumulative incidence of remission and relapse were assessed using multivariable-adjusted Cox proportional hazards models. Remission defined as urinary protein < 0.3 g/day (or g/gCr) was observed in 104 (96.3%) patients. Of 97 patients with remission within 6 month of IST, 42 (43.3%) developed relapse defined as ≥ 1.0 g/day (or g/gCr) or dipstick urinary protein of ≥ 2+. Serum albumin concentration was significantly associated with remission (multivariable-adjusted hazard ratio [95% confidence interval] per 1.0 g/dL, 0.57 [0.37, 0.87]), along with eGFR (per 30 mL/min/1.73 m²: 1.43 [1.08, 1.90]), whereas they were not associated with relapse. A multivariable-adjusted model showed that patients with high eGFR level (≥ 60 mL/min/1.73 m²) and low albumin concentration (≤ 1.5 g/dL) achieved significantly early remission, whereas those with low eGFR (< 60 mL/min/1.73 m²) and high albumin concentration (> 1.5 g/dL) showed significantly slow remission. In conclusion, lower serum albumin concentration and higher eGFR were associated with earlier remission in MCD, but not with relapse.