Serum amyloid a in clinical practice

Abstract

Serum amyloid A (SAA) is an acute phase first class protein discovered a quarter of the century ago. Its concentration depends on clinical findings of the patient, illness activity and the therapy applied. SAA increases moderately to markedly (100-1000 mg/l) in bacterial and fungal infections, invasive malignant diseases, tissue injuries in the acute myocardial infarction and autoimmune diseases such as rheumatoid arthritis and vasculitis. Mild elevation (10-100 mg/l) is often seen in viral infections, systemic lupus erythematosus and localized inflammation or tissue injuries in cystitis and cerebral infarction. SAA as sensitive, non-invasive parameter is used in organ transplantation where early and correct diagnosis is needed as well as where prompt therapy is required. Besides acute kidney allograft rejection, SAA is used in the diagnosis of rejection after liver transplantation, simultaneous pancreas and kidney transplantation and also in bone marrow transplantation (acute "graft vs. host disease"). Simultaneous determination of C-reactive protein (CRP) and SAA may point to acute kidney allograft rejection. Standard immunosuppressive therapy with cyclosporine A and prednisolone significantly suppresses the acute phase CRP reaction both in operation itself and acute rejection, but not in infection. On the other hand, SAA rejection in operation, acute allograft rejection and infection is present in spite of cyclosporine A and steroids therapy. Different reaction of SAA and CRP in transplant patients to cyclosporine A therapy helps in differentiation between the infection and rejection. Although CRP and SAA are sensitive and acute phase reactants, their serum concentrations cannot be valued as prognostic and diagnostic criteria without creatinine serum concentration and clinical findings. In addition, they offer important information for clinical diagnosis as well as the kind of therapy.