2025 CPT code 85306
Effective Date: N/A Pathology and Laboratory - Hematology and Coagulation Feed
Clotting inhibitors or anticoagulants; protein S, free
Modifiers may apply. Modifier 91 is used for repeat testing. Modifier 90 indicates the test was performed by an outside laboratory.
Medical necessity must be established by the patient's signs, symptoms, and clinical history suggestive of a protein S deficiency, such as venous or arterial thromboembolism, recurrent pregnancy loss, or a family history of protein S deficiency.
The laboratory analyst performs all technical steps to determine the free protein S level in patient plasma. This typically involves methods such as latex immunoassay, where patient plasma is combined with a reagent. This reaction is measured, and changes indicate free protein S levels.
In simple words: This blood test measures the amount of free protein S, a natural blood thinner. Low levels can increase the risk of blood clots.
This test measures the level of free protein S in the patient's plasma. Protein S is a vitamin K-dependent anticoagulant protein that acts as a cofactor to activated protein C. Approximately 40% of protein S circulates unbound (free) and is the only fraction with anticoagulant function. This test is typically ordered to initially assess for protein S deficiency, which can lead to venous or arterial thrombosis and possibly recurrent pregnancy loss. It's also used to investigate suspected acquired protein S deficiency related to vitamin K deficiency, liver disease, or oral anticoagulant therapy.
Example 1: A patient with a family history of blood clots presents with unexplained deep vein thrombosis. The physician orders a free protein S test (85306) to evaluate for a possible inherited deficiency., A pregnant woman experiences recurrent miscarriages. Her physician orders a free protein S test (85306) to determine if a protein S deficiency is a contributing factor., A patient on long-term anticoagulant therapy is experiencing unstable levels of anticoagulation. The physician orders free protein S (85306) along with other coagulation tests to monitor the effectiveness of therapy.
Documentation should include the reason for testing, relevant medical history (e.g., personal or family history of thrombosis, pregnancy complications), and current medications. If the test is being used to monitor anticoagulation therapy, dosage information should be included.
- Revenue Code: T1H - LAB TESTS - OTHER (NON-MEDICARE FEE SCHEDULE)
- Specialties:Hematology, Pathology, Internal Medicine, Obstetrics and Gynecology
- Place of Service:Independent Laboratory, Hospital Outpatient, Outpatient Clinic