Isoelectric focusing and selectivity index in IgA nephrotic syndrome

Proteinuria in 13 patients with IgA nephritis with nephrotic syndrome (IgANS) was analysed by isoelectric focusing (IEF) and compared with 12 patients with minimal change nephrotic syndrome (MCNS) (n = 8) or focal global sclerosis nephrotic syndrome (FGS) (n = 4) to determine the pattern of proteinuria on IEF and to assess the value of IEF and protein selectivity index (SI) as predictors of response to therapy with predisolone or cyclophosphamide. Steroid/cyclophosphamide responsive patients with IgANS had SC:UA (cationic serum albumin with anionic urine albumin) or SA:UC (anionic serum albumin with cationic urine albumin) IEF patterns and steroid/cyclophosphamide unresponsive patients with IgANS had an SC:UC (cationic serum albumin with cationic urine albumin) IEF pattern. The majority of patients with MCNS or FGS who had an SA:UC IEF pattern were steroid responsive. SI was a better predictor of steroid/cyclophosphamide responsiveness in patients with IgANS (r = 0.78, p < 0.002 compared to IEF, r = 0.64, p < 0.02).