CPT® Code 85306

The CPT® Code 85306 refers to a laboratory test that measures the levels of free protein S, which is a vitamin K dependent glycoprotein found in the blood. This protein exists in both free and bound forms within the plasma and plays a crucial role as a non-enzyme cofactor in the activation of activated protein C (APC), a key component in the regulation of blood coagulation. A deficiency in protein S can lead to an increased risk of abnormal blood clotting, which may result in recurrent venous thrombosis or embolism. Such deficiencies are often linked to rare inherited genetic disorders, but they can also be acquired due to various conditions such as liver disease, vitamin K deficiency, disseminated intravascular coagulation (DIC), pregnancy, and certain inflammatory syndromes. In women, a deficiency in protein S is particularly concerning as it is associated with a heightened risk of fetal loss during pregnancy. The test for free protein S is primarily utilized to screen individuals for potential deficiencies. If a positive result is obtained, it is recommended to perform a follow-up test for total protein S to further classify the type of deficiency present. There are different types of protein S deficiency: Type I is characterized by low levels of both free and total protein S; Type III shows a decrease in only free protein S; and Type II presents with normal antigenic levels but decreased cofactor activity. 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 blood sample required for this test is collected through a venipuncture, and the analysis is conducted on platelet-poor plasma using a microlatex particle-mediated immunoassay method.