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 (Palb) during in vitro testing and cause proteinuria in experimental animals. OBJECTIVES To determine whether permeability activity of FSGS serum (Palb 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 Palb activity testing. SETTING Studies were performed at Medical College of Wisconsin. PATIENTS Serum was submitted by patients' nephrologists for measurement of Palb activity. Each patient had had a biopsy diagnosis of FSGS, had reached ESRD and was on dialysis or had a functioning transplant. MEASUREMENTS Palb activity, clinical characteristics and time between biopsy diagnosis and RRT (T-RRT) were recorded for each patient. METHODS Palb activity was measured using established in vitro techniques. RESULTS Palb and T-RRT were inversely correlated. Neither Palb nor T-RRT varied with demographics or medications. Kaplan-Meier survival curves showed that patients with Palb ≥ 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 Palb activity is associated with the rate of progression to RRT in patients with FSGS. Additional observations will be needed to verify that Palb activity predicts prognosis and is useful in stratifying patients for clinical decision making or treatment trials.