Abstract

Biomarkers able to predict progression and treatment responsiveness are of paramount importance in glomerulonephritis. In IgA Nephropathy (IgAN) at present the most powerful prognostic predictor is the level of proteinuria; the predictive value of proteinuria may be enhanced by measurement of its high molecular weight components which are reliable markers of alteration of glomerular filtration barrier. Aim of the review is to summarize recent literature on predictive value of functional outcome in IgAN patients of the new biomarker FE IgG/SG: Fractional Excretion of IgG divided by non obsolescent glomeruli defined Surviving Glomeruli (SG). In 132 non-crescentic IgAN patients, FE IgG/SG < vs ≥ 0.00010 predicts progression (ESRD and eGFR reduction ≥50%) in 2% vs 87.5% of 68 untreated and in 0%vs36% of 64 patients treated with ACE-inhibitors. In patients with SG < 80% (57 + 14%) progression rate is 100% vs 0% if FE IgG/SG is ≥ vs < 0.00010. In 34 crescentic IgAN patients FE IgG/SG < vs ≥ 0.00034 predicts progression in 5%vs83% and in 0%vs89% of 23 patients treated with Steroids and Cyclophosphamide. In patients with FE IgG/SG ≥ 0.00034 and sCr ≥ 1.74 mg/dL progression prediction is 100%. In conclusion this biomarker based on combination of Fractional Excretion of the high MW protein IgG with nephron loss is a powerful outcome predictor in IgAN patients and represents a validation in a human disease of some progressive mechanisms hypothesized by the “remnant kidney” progression theory. The review also outlines some recent patents on the biomarkers for nephropathy.

Keywords: Fractional excretion of IgG, IgA nephropathy, outcome prediction, surviving glomeruli (SG)