CPT® Code 80165

The CPT® Code 80165 refers to a laboratory test specifically designed to measure the concentration of free valproic acid, also known as dipropylacetic acid or depakote. Valproic acid is classified as an anticonvulsant medication, commonly utilized in the management of seizure disorders, the manic phase of bipolar disorder, and migraine headaches. The mechanism of action for valproic acid involves altering the levels of certain neurotransmitters in the brain, which helps to stabilize mood and prevent seizures. The test for total valproic acid, identified by CPT® Code 80164, serves multiple purposes, including monitoring the effectiveness of drug therapy, assessing patient adherence to the prescribed treatment regimen, and evaluating the potential for drug toxicity. In contrast, the test for free valproic acid, represented by CPT® Code 80165, is particularly useful in clinical scenarios where the total valproic acid concentration falls within the normal range, yet there are concerns regarding toxicity. This situation may arise in patients who exhibit altered or unpredictable protein binding capacity, which can lead to elevated levels of free valproic acid. To perform this test, a blood sample is collected through a separately reportable venipuncture, ideally just before the administration of medication, to capture the trough level of the drug. The laboratory analysis involves testing serum or plasma for total valproic acid using fluorescence polarization immunoassay techniques, while free valproic acid is quantified through enzyme multiplied immunoassay methods.