CPT® Code 85400

The CPT® Code 85400 refers to a laboratory test that measures the activity of plasmin, a crucial serine protease enzyme produced by the liver. In its inactive form, plasminogen circulates in the bloodstream until it binds to a clot or cell surface, where it is activated into plasmin. This activation process is facilitated by various agents, including tissue plasminogen activator (tPA), urokinase plasminogen activator (uPA), kallikrein, and factor XII (Hageman). Once activated, plasmin plays a vital role in the breakdown of plasma proteins, particularly in the process of fibrinolysis, where it dissolves fibrin clots. Additionally, plasmin activates collagenases and contributes to the weakening of the walls of Graafian follicles, which is essential for ovulation. Beyond its role in reproductive health, plasmin is integral to wound healing, liver repair, and maintaining liver homeostasis. The test involves obtaining a blood sample through a separately reportable venipuncture, followed by analysis using fluorimetry to accurately measure plasmin activity.