CPT® Code 85421

The CPT® Code 85421 refers to a laboratory test specifically designed to measure the levels of plasminogen antigen in the blood. Plasminogen is a protein produced by the liver that circulates in an inactive form until it binds to a clot or cell surface, where it is then activated to plasmin. This activation process is facilitated by various factors, including tissue plasminogen activator (tPA), urokinase plasminogen activator (uPA), kallikrein, and factor XII (Hageman). The measurement of plasminogen antigen is crucial for evaluating patients who may have inherited genetic deficiencies related to plasminogen, such as hypoplasminogenemia (Type I deficiency) or dysplasminogenemia (Type 2 deficiency). Type I deficiency is characterized by a systemic disorder that impairs extracellular fibrinolysis, leading to the formation of fibrin-rich pseudomembranous lesions, particularly noticeable in the conjunctiva, known as ligneous conjunctiva. In this type, there is a parallel decrease in both immunoreaction and functional activity, but it does not increase the risk of thrombophilia. Conversely, Type 2 deficiency presents with normal or slightly decreased levels of circulating plasminogen, yet the functional activity is significantly reduced. The test is performed by obtaining a blood sample through a separately reportable venipuncture, and the analysis is conducted using enzyme-linked immunosorbent assay (ELISA) on serum, plasma, or cultured cells.