Comparison of Urinary Beta-2 Microglobulin Levels in Children with SSNS and Calcineurin Inhibitor-Treated SRNS.

BACKGROUND: While the utility of beta-2 microglobulin (β2M) has been explored in various renal conditions to identify tubulointerstitial damage, it has not been adequately studied in nephrotic syndrome. The primary objective of the study was to compare urinary β2M levels in children with steroid-sensitive nephrotic syndrome (SSNS) and steroid-resistant nephrotic syndrome (SRNS) in disease remission.

MATERIALS AND METHODS: This cross-sectional study was done at a tertiary care hospital between April 2019 and March 2020. Sixty children (2-18 years) with SSNS and SRNS (30 in each group) in remission were enrolled. SRNS patients were included after ≥1 year of treatment with calcineurin inhibitors (CNIs). Biochemical investigations were done to confirm remission; spot samples for urinary β2M were collected and estimation was done by an enzyme-linked immunosorbent assay (ELISA)-based kit.

RESULTS: Of the 60 children, 63% were boys. The median (interquartile range [IQR]) age at enrollment for SSNS and SRNS patients was 7 (4.1-9) and 11 (8.3-12) years, respectively. Urinary β2M levels were significantly higher in SRNS patients compared to SSNS patients (2.6 vs. 0.75 mg/ml, P < 0.0001). Patients who received cyclosporine for >2 years had higher median urinary β2M levels compared to those who received it for a shorter period (2.63 vs. 1.83 mg/ml, P = 0.03). Median β2M levels were higher in focal segmental glomerulosclerosis than minimal change disease (3.5 vs. 2.5 mg/ml).

CONCLUSION: Urinary β2M levels were higher in SRNS compared to SSNS disease in remission, and β2M levels correlated well with CNI use of >2 years. It appears to be a promising noninvasive tool to identify early tubular damage and progression in patients with nephrotic syndrome, especially SRNS.