CPT® Code 78191

The CPT® Code 78191 refers to a laboratory test known as a platelet survival study. This test is designed to measure the lifespan of platelets, which are also known as thrombocytes. Platelets are critical components of the blood, produced in the bone marrow, circulating throughout the bloodstream, and stored in the spleen. They play a vital role in the process of hemostasis, which is the formation of blood clots to prevent excessive bleeding. Under normal circumstances, platelets have an average lifespan of approximately 8 to 9 days. Abnormal platelet counts can indicate various health issues. An elevated platelet count, known as thrombocytosis, occurs when the platelet level exceeds 400,000 per microliter of blood. This condition can arise from several underlying factors, including anemia, cancer, inflammation, or infection, and may lead to an increased risk of thrombotic events such as strokes or infarctions. Conversely, a reduced platelet count, termed thrombocytopenia, is identified when the platelet level falls below 100,000 per microliter. This condition can result from a variety of causes, including the effects of certain medications, inherited disorders, malignancies such as leukemia or lymphoma, kidney dysfunction, or excessive alcohol intake. The platelet survival study is particularly useful for monitoring the impact of various disease states, environmental influences, and the effects of prosthetic materials or therapeutic interventions on platelet function. Additionally, this test can help evaluate the procedures involved in the collection and storage of transfused platelets. The process begins with obtaining a blood sample through venipuncture or an intravenous line, followed by a baseline platelet count. The sample is then processed through centrifugation to isolate platelet-rich plasma. A radioisotope tracer, specifically 111-Indium Oxine, is introduced to the platelets, which are then incubated and re-injected into the patient. Subsequent blood draws are performed at specified intervals—20 minutes, 2 hours, 3 hours, 4 hours, and daily for a duration of 1 to 10 days—to assess platelet survival over time.