CPT® Code 85520

The CPT® Code 85520 refers to a laboratory test known as the heparin assay. This test is specifically designed to measure the levels of plasma unfractionated heparin (UH) and/or low molecular weight heparin (LMWH) antibodies, commonly referred to as Heparin Anti-Xa. Heparin is a widely used anticoagulant medication that plays a crucial role in both the prevention and treatment of blood clots. The formation of antibodies in response to heparin occurs when it interacts with a protein on the surface of platelets known as platelet factor 4 (PF4). This interaction results in the creation of a heparin-PF4 complex, which the immune system recognizes as foreign. In response, the immune system produces antibodies against this complex. The presence of these antibodies can lead to the activation of platelet production, which in turn triggers the release of more PF4. This cascade of events can result in a serious condition known as immune-mediated heparin-induced thrombocytopenia (HIT type II). HIT type II is characterized by a combination of low platelet counts, the presence of HIT antibodies, and an increased risk of excessive clotting. To perform the heparin assay, a blood sample is collected through a procedure known as venipuncture, which is separately reportable. The test itself involves analyzing platelet-poor plasma using a chromogenic assay, a method that allows for precise measurement of heparin levels and the associated antibodies.