CPT® Code 85305

The CPT® Code 85305 refers to a laboratory test that measures the total levels of protein S, which is a vitamin K dependent glycoprotein found in the blood. This single chain protein exists in both free and bound forms within plasma. Protein S plays a crucial role in the coagulation process by acting as a non-enzyme cofactor for activated protein C (APC), which is essential for regulating blood clotting. A deficiency in protein S can lead to an increased risk of abnormal blood clotting, resulting in conditions such as recurrent venous thrombosis and embolism. This deficiency can be inherited as a rare genetic disorder or acquired due to various factors including liver disease, vitamin K deficiency, disseminated intravascular coagulation (DIC), pregnancy, and inflammatory syndromes. Women with protein S deficiency face a heightened risk of fetal loss during pregnancy. The total protein S test is particularly useful for subtyping known deficiencies, as it can differentiate between Type I, Type II, and Type III deficiencies based on the levels of free and total protein S present. Prior to testing, patients are advised to avoid anticoagulants such as warfarin or coumadin for a period of two weeks to ensure accurate results. The test is performed on platelet-poor plasma obtained from a blood sample collected through venipuncture, and the analysis is conducted using a microlatex particle-mediated immunoassay method.