80197

Tacrolimus; quantitative measurement

CPT 80197 represents the quantitative measurement of tacrolimus, a potent immunosuppressive medication primarily used in solid organ transplantation to prevent graft rejection. Tacrolimus, also known as FK506, belongs to the calcineurin inhibitor class of drugs. It exerts its effect by binding to the FK-binding protein (FKBP12), which subsequently inhibits calcineurin, a phosphatase essential for the activation of T-lymphocytes. Because tacrolimus has a narrow therapeutic window, the concentration of the drug in the patient's system must be carefully managed. If the blood concentration is too low, the patient faces a significant risk of acute or chronic organ rejection. Conversely, supratherapeutic levels are associated with severe toxicities, including nephrotoxicity, neurotoxicity (such as tremors or seizures), glucose intolerance, and an increased susceptibility to opportunistic infections or secondary malignancies. Unlike many drugs that are measured in serum, tacrolimus is measured in whole blood because the drug is highly sequestered within erythrocytes, with red blood cell concentrations being significantly higher than plasma concentrations. The laboratory analysis is most commonly performed using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS), which provides high specificity and avoids cross-reactivity with inactive metabolites, or through automated immunoassays. Frequent monitoring is crucial during the initial post-transplant period, when dosing is being titrated, and continues at regular intervals throughout the life of the transplant to ensure long-term graft survival and minimize adverse drug effects.

Clinical Indications

  • Monitoring of therapeutic drug levels in patients following renal transplantation
  • Monitoring of therapeutic drug levels in patients following hepatic transplantation
  • Monitoring of therapeutic drug levels in patients following cardiac transplantation
  • Monitoring of therapeutic drug levels in patients following lung or heart-lung transplantation
  • Assessment of patient adherence to immunosuppressive therapy
  • Evaluation of suspected tacrolimus toxicity, including unexplained renal dysfunction or neurological symptoms
  • Adjustment of dosage when introducing or discontinuing medications known to interact with the cytochrome P450 3A4 system
  • Monitoring drug levels during transitions between immediate-release and extended-release tacrolimus formulations

Procedure Steps

  1. Verification of the clinical order for tacrolimus trough level measurement
  2. Collection of a whole blood sample via venipuncture, typically using an EDTA (lavender-top) tube
  3. Confirmation that the sample was drawn as a trough level, ideally immediately prior to the next scheduled dose
  4. Transport of the whole blood specimen to the laboratory, ensuring the sample is not centrifuged
  5. Preparation of the sample for analysis, which may involve protein precipitation or extraction in the case of LC-MS/MS
  6. Quantitative analysis of the tacrolimus concentration using an validated analytical method such as LC-MS/MS or immunoassay
  7. Calibration of the analytical equipment against known standards to ensure accuracy
  8. Review and validation of the results by laboratory personnel
  9. Electronic or manual reporting of the tacrolimus concentration in nanograms per milliliter (ng/mL) to the clinician

Coding Guidelines

  • Code 80197 is used for the quantitative measurement of tacrolimus. Do not use this code for qualitative or semi-quantitative assays.
  • This code should be reported once per assay performed, regardless of the number of times the drug is measured during a single encounter unless medically necessary for multiple checks.
  • If multiple different therapeutic drugs are measured (e.g., tacrolimus and mycophenolic acid), report each drug measurement with its specific CPT code.
  • For cyclosporine measurement, use CPT code 80158.
  • For sirolimus measurement, use CPT code 80195.
  • Do not report 80197 in conjunction with generic chemistry codes if the specific analyte code is available.
  • Venipuncture (e.g., 36415) may be reported separately depending on payer-specific policies and the setting of the blood draw.

Associated ICD-10 Codes