86480

Tuberculosis test, cell mediated immunity antigen response measurement; gamma interferon

CPT code 86480 describes an in vitro laboratory blood test used for the detection of Mycobacterium tuberculosis infection. It measures the cell-mediated immune response, specifically the release of interferon-gamma (IFN-g) by white blood cells after they are stimulated by synthetic peptides representing specific M. tuberculosis antigens. This test is commonly known as an Interferon-Gamma Release Assay (IGRA), with the most notable commercial example being the QuantiFERON-TB Gold Plus test. Unlike the traditional tuberculin skin test (TST), IGRAs are not affected by prior BCG (Bacille Calmette-Guerin) vaccination, significantly reducing the likelihood of false-positive results and making it the preferred testing method for patients with a history of receiving the BCG vaccine. The laboratory procedure involves drawing a whole blood sample from the patient into specialized collection tubes that contain the specific TB antigens (ESAT-6, CFP-10) as well as positive and negative controls. The phlebotomist or laboratory technician must ensure proper mixing of the blood with the antigens. The tubes are then incubated at a precise temperature (usually 37 degrees Celsius) for a designated period, typically 16 to 24 hours. During this incubation, if the patient has been previously infected with M. tuberculosis, their sensitized T-lymphocytes will recognize the antigens and secrete interferon-gamma. Following incubation, the blood samples are centrifuged to separate the plasma. The laboratory then performs an enzyme-linked immunosorbent assay (ELISA) on the plasma to quantify the exact concentration of interferon-gamma produced. The test results are determined by comparing the interferon-gamma levels in the TB antigen tubes to those in the control tubes. The final report will indicate whether the test is positive, negative, or indeterminate. A positive result strongly suggests infection with M. tuberculosis, but it is important to note that this assay cannot clinically distinguish between latent tuberculosis infection (LTBI) and active tuberculosis disease. Physicians must correlate the IGRA results with the patient's medical history, physical examination, chest radiography, and microbiological studies such as sputum smears and cultures to make a definitive diagnosis and formulate an appropriate treatment plan. This CPT code specifically applies to assays that measure the total gamma interferon level, and should not be confused with testing that enumerates the specific T-cells producing the interferon.

Clinical Indications

  • Screening for latent tuberculosis infection (LTBI) in asymptomatic individuals.
  • Evaluating patients with clinical signs and symptoms of suspected active tuberculosis.
  • Routine screening of healthcare workers, military personnel, or other high-risk occupational populations.
  • Evaluating patients prior to initiating immunosuppressive therapies, such as TNF-alpha inhibitors or biologics, to prevent reactivation of LTBI.
  • Testing individuals who have previously received the BCG vaccine, where tuberculin skin tests (TST) may yield false-positive results.
  • Contact tracing and evaluation of individuals with known or suspected exposure to a person with active tuberculosis.
  • Screening immunocompromised patients, such as those with HIV/AIDS or those undergoing organ transplantation.

Procedure Steps

  1. Collect a whole blood sample from the patient via venipuncture directly into specialized, manufacturer-provided collection tubes containing TB antigens (e.g., ESAT-6, CFP-10) and control substances.
  2. Thoroughly mix the blood with the antigens by shaking or inverting the tubes according to the specific manufacturer's instructions.
  3. Transfer the tubes to an incubator and maintain them at 37 degrees Celsius for 16 to 24 hours to allow T-lymphocytes to process the antigens and secrete interferon-gamma.
  4. Following the incubation period, centrifuge the blood collection tubes to physically separate the plasma from the cellular components.
  5. Extract the plasma from each tube to be used in the enzyme-linked immunosorbent assay (ELISA).
  6. Perform the ELISA testing procedure to quantitatively measure the concentration of interferon-gamma present in the plasma of each tube.
  7. Compare the quantitative results from the TB antigen tubes against the results from the positive (mitogen) and negative (nil) control tubes.
  8. Interpret the final assay values to determine if the result is positive, negative, or indeterminate.
  9. Generate a final laboratory report detailing the quantitative findings and qualitative interpretation for the ordering provider.

Coding Guidelines

  • Report CPT code 86480 for the in vitro measurement of gamma interferon produced in response to M. tuberculosis antigens (e.g., QuantiFERON-TB Gold).
  • Do not report 86480 in conjunction with 86481 (enumeration of gamma interferon-producing T-cells in cell suspension) for the same test; 86481 is intended for ELISPOT-based methodologies such as the T-SPOT.TB test.
  • Do not report 86480 for a traditional tuberculin skin test (PPD); use code 86580 for the skin test.
  • When billing 86480, ensure that the corresponding ICD-10-CM diagnosis code accurately reflects the medical necessity for the test, such as screening, suspected exposure, or pre-immunosuppressant evaluation.
  • If an indeterminate result requires the test to be repeated on a newly collected blood sample, the repeated test may be coded again, provided appropriate modifiers (e.g., modifier 59 or 91) are appended per payer policy.
  • Routine screening for employment or school purposes may not be a covered benefit under some insurance plans, including Medicare; verify coverage and utilize an Advance Beneficiary Notice (ABN) if necessary.

Associated ICD-10 Codes