This invention provides organic biomolecule markers (e.g., proteins) useful for differentiating minimal change nephrotic syndrome (MCNS) from focal segmental glomerulosclerosis (FCS), membranous nephrothropy (MN), and membranoproliferative glomerulonephritis (MPGN). This invention also provides organic biomolecule markers useful for evaluating the therapeutic value of agents for treating kidney disease.