CPT® Code 78120

The CPT® Code 78120 refers to a laboratory procedure specifically designed for the determination of red cell volume (RCV) through a single sampling method. This test utilizes radiolabeled tracers, primarily technetium 99m red blood cells (Tc-99m RBC), although chromium-51 sodium chromate labeled red blood cells may also be employed. The primary purpose of this procedure is to assess the volume of red blood cells in the body, which can be critical in diagnosing and managing various medical conditions. These conditions include hypovolemia, where there is a decreased blood volume; hypervolemia, characterized by an increased blood volume; anemia, which involves a deficiency of red blood cells; and polycythemia, where there is an excess of red blood cells. Additionally, this test is valuable in evaluating patients with orthostatic hypotension, hypertension, heart failure, shock or acute blood loss, as well as those undergoing dialysis, blood transfusions, or volume replacement therapies. The procedure begins with the collection of the patient's height and weight, followed by the establishment of venous access. A baseline blood sample is taken before the injection of the radiolabeled tracer, which is then allowed to circulate within the body. Subsequent venipuncture allows for the collection of blood samples, which may be taken as a single sample or multiple samples at predetermined intervals. The microhematocrit is measured from these samples, and the remaining blood is processed through centrifugation to separate the plasma from the red blood cells. The final data is calculated using specific formulas that compare the dilution factors of the radiolabeled tracer with standardized samples, taking into account the patient's individual height, weight, and hematocrit levels.