Proteinuria selectivity index in renal disease

One of the main barriers to early detection and subsequent prevention of kidney diseases is the accessibility and feasibility of testing, especially in urine research. The proteinuria selectivity index (PSI or SI) is a method used to assess changes in glomerular permeability in glomerular diseases. It describes the pattern of proteinuria by comparing the clearance rates of large molecular proteins and transferrin, categorizing it as selective or nonselective. PSI is widely applied for kidney disease classification, prediction of corticosteroid efficacy, and prognosis. Herein, we reviewed the clinical applications and recent advancements of PSI in glomerular diseases, compared it with commonly used renal function biomarkers, and discussed the future research directions for PSI as a potential predictive marker for response to specific biologics.