CPT® Code 85303

Protein C is a vital component of the body's natural anticoagulation system, playing a crucial role in regulating blood clotting. Deficiencies in protein C can lead to serious health issues, including recurrent thrombosis, which is the formation of blood clots in veins, and warfarin-induced skin necrosis, a condition where skin tissue dies due to inadequate blood supply. The CPT® Code 85303 specifically refers to the measurement of protein C activity in a patient's blood sample. This process involves diluting the blood sample and adding sodium citrate or citric acid to prevent clotting. The sample is then incubated in microwells that are coated with antibodies specific to human protein C, allowing the protein C present in the sample to bind to these antibodies. Following this binding phase, a detection antibody conjugated with horseradish peroxidase (HRP) is introduced. After washing away any unbound detection antibodies, a chromogenic substrate is added, which reacts to produce a colored product. The intensity of this color is then measured, providing a quantitative assessment of protein C activity. The primary purpose of ordering this assay is to evaluate whether a patient has a deficiency in protein C, which can significantly increase their risk for developing venous thromboembolism, a serious condition characterized by blood clots in the veins.