Approximately 75-80% of patients have serum autoantibodies to the M-type phospholipase A2 receptor (PLAR2). In contrast, less than 10% of patients with secondary membranous nephropathy, other forms of glomerulonephritis, as well as healthy individuals are positive for autoantibody to the PLA2R antibody. An increase, decrease or disappearance generally precedes a change in the clinical status, thus the antibody titer has a predictive value with respect to clinical remission, relapse, or risk assessment after kidney transplantation. A test for colocalization of PLA2R and IgG4 of kidney tissue is recommended in seronegative samples to confirm or exclude a diagnosis of PLA2R antibody-mediated MGN.