Urine-to-blood urea nitrogen ratio predicts proteinuria remission in nephrotic syndrome

Nephrotic syndrome (NS) carries a high risk of severe complications and kidney failure, necessitating reliable prognostic markers. Given the link between tubular injury and poor remission of proteinuria, markers of tubular function may be informative in NS. The urine-to-blood urea nitrogen ratio (UBUR) reflects tubular urea handling, yet its prognostic value in NS is unclear. We evaluated whether baseline UBUR predicts proteinuria remission in adult NS.

This multicenter retrospective study included patients with NS who underwent kidney biopsy between January 2012 and June 2022. Patients were followed from kidney biopsy until complete remission, dialysis initiation, death, or the end of the observation period (12 months after kidney biopsy).

A total of 237 patients (median age, 63 years; 47% female) were included, and divided into two groups based on a UBUR cutoff of 25.4 determined by the receiver operating characteristic curve. Patients with high UBUR had a significantly higher cumulative incidence of complete remission compared to those with low UBUR (P < 0.001, log-rank test). In multivariable Cox regression analysis, high UBUR independently predicted a greater likelihood of complete remission (hazard ratio 2.30 [95% confidence interval 1.47-3.61]). This association persisted in the subgroup analyses for podocytopathies, defined as minimal change disease and focal segmental glomerulosclerosis.

High UBUR independently predicts proteinuria remission in adults with NS. UBUR could have potential as a simple, valuable biomarker to help guide the management of NS.