CPT® Code 85293

The CPT® Code 85293 refers to a laboratory test known as the high molecular weight kininogen assay, also referred to as the Fitzgerald factor assay. This test is specifically designed to measure the activity of high molecular weight kininogen (HMWK), which is a crucial plasma protein produced by the liver. In its inactive form, HMWK circulates in the bloodstream until it encounters an injury to the epithelium, at which point it binds with prekallikrein and factor XI. This interaction is essential for the activation of factor XIIa, which plays a significant role in the intrinsic pathway of the clotting cascade. A deficiency in HMWK is a rare condition that typically does not lead to spontaneous or excessive bleeding. Instead, it is often identified when a patient presents with an abnormal bleeding time test, specifically the activated partial thromboplastin time (PTT). The underlying causes of HMWK deficiency are usually linked to rare inherited genetic disorders; however, it can also be acquired in patients suffering from liver disease or disseminated intravascular coagulation (DIC). To perform this assay, a blood sample is collected through a venipuncture, which is reported separately. The plasma obtained from this sample is then subjected to a clotting activity assay to evaluate the functionality of HMWK in the coagulation process.