Serum glomerular albumin permeability activity: association with rapid progression to end-stage renal disease in focal segmental glomerulosclerosis

BACKGROUND: Focal segmental glomerulosclerosis (FSGS) is a major cause of renal failure. Sera of some FSGS patients increase glomerular albumin permeability (P(alb)) during in vitro testing and cause proteinuria in experimental animals. OBJECTIVES: To determine whether permeability activity of FSGS serum (P(alb) activity) is associated with rate of progression to renal replacement therapy (RRT). DESIGN: This is an observational study based on medical and demographic information and P(alb) activity testing. SETTING: Studies were performed at Medical College of Wisconsin. PATIENTS: Serum was submitted by patients’ nephrologists for measurement of P(alb) activity. Each patient had had a biopsy diagnosis of FSGS, had reached ESRD and was on dialysis or had a functioning transplant. MEASUREMENTS: P(alb) activity, clinical characteristics and time between biopsy diagnosis and RRT (T-RRT) were recorded for each patient. METHODS: P(alb) activity was measured using established in vitro techniques. RESULTS: P(alb) and T-RRT were inversely correlated. Neither P(alb) nor T-RRT varied with demographics or medications. Kaplan–Meier survival curves showed that patients with P(alb) ≥ 0.5 progressed to RRT more rapidly than others. LIMITATIONS: Only patients who had reached RRT were included. Limited clinical information was available for each patient. Central verification of biopsy characteristics was not performed and detailed descriptions of renal histology were not available. CONCLUSIONS: P(alb) activity is associated with the rate of progression to RRT in patients with FSGS. Additional observations will be needed to verify that P(alb) activity predicts prognosis and is useful in stratifying patients for clinical decision making or treatment trials.