Posttransplantation monitoring of high-density lipoprotein-associated serum amyloid A protein: a new diagnostic aid in the detection of renal allograft rejection.

The concentrations of serum amyloid A protein, a high-density lipoprotein-associated protein synthesized in the liver, were monitored in 66 recipients of cadaveric renal allografts. Acute graft rejection episodes were associated with dramatic elevations of serum amyloid A. Electrofocusing and immunoblotting of rejection sera showed a polymorphic serum amyloid A pattern similar to that obtained with control (apo) serum amyloid A isolated from the high-density lipoprotein fraction of plasma. Rejections in patients receiving cyclosporine alone as posttransplantation immunosuppressive medication were characterized by significantly higher serum amyloid A levels than in those receiving cyclosporine in combination with methylprednisolone. Due to the dramatic rejection-induced serum amyloid A elevation, limit values could be used which combined high sensitivity (87-96%) with reasonably high predictive value of a positive test (82%). The serum amyloid A test was applicable also in patients with initially nonfunctioning or poorly functioning grafts. It is concluded that monitoring of the serum amyloid A concentrations offers a valuable noninvasive aid in the early diagnosis of acute renal allograft rejection, including patients with acute tubular necrosis of the graft.