Urinary retinol-binding protein as a prognostic marker in the treatment of nephrotic syndrome.

We studied the urinary levels of retinol-binding protein (urRBP), an index of proximal tubular dysfunction, in patients with nephrotic syndrome before and approximately 2 months after the beginning of steroid therapy as a predictor of response to therapy which included for some patients courses of immunosuppressive drugs. Those patients with minimal-change disease, mesangial proliferative glomerulonephritis, and focal-segmental glomerulosclerosis who had normal pretreatment urRBP levels were responsive to treatment; occasionally, responsive patients had an initially elevated urRBP level which normalized during treatment. Contrariwise, those patients with abnormally high levels of urRBP which did not normalize during treatment did not respond to treatment. The chance of a patient with minimal-change disease, mesangial proliferative glomerulonephritis, or focal-segmental glomerulosclerosis and a pretreatment urRBP level equal to or >1.0 mg/l being resistant to steroid treatment is 30 times that of a patient with a urRBP level <1.0 mg/l and even higher, if we consider the levels obtained during treatment.