CPT® Code 85301

The CPT® Code 85301 refers to the assay for antithrombin III, which is a critical component in the body's coagulation system. Antithrombin III is a protein that helps regulate blood clotting by inhibiting thrombin and other clotting factors, thereby preventing excessive clot formation. The procedure involves taking a diluted blood sample and mixing it with antithrombin-deficient plasma, which lacks the necessary antithrombin III to facilitate normal coagulation. This mixture is then treated with intrinsic coagulation enzymes, an augmenting compound such as heparin, phospholipids, and an activator that initiates the contact phase of the intrinsic coagulation pathway. After these components are combined, calcium ions are added to the mixture to trigger the coagulation process. The time it takes for coagulation to occur is measured and compared to a reference standard, allowing for the determination of the antithrombin III activity level in the sample. In the specific method described for CPT® Code 85301, serum is added to a thrombin solution, and after a predetermined incubation period, the remaining thrombin activity in the plasma is measured. This assay is essential for diagnosing and managing conditions related to abnormal blood clotting, such as thrombosis or bleeding disorders.