Tuberculosis test, cell mediated immunity antigen response measurement; enumeration of gamma interferon-producing T-cells in cell suspension
CPT4 code
Name of the Procedure:
Tuberculosis Test, Cell Mediated Immunity Antigen Response Measurement; Enumeration of Gamma Interferon-Producing T-Cells in Cell Suspension
Commonly known as: Interferon-Gamma Release Assay (IGRA)
Summary
In this test, a sample of your blood is taken and exposed to specific antigens related to tuberculosis. The test measures the release of gamma interferon, a type of protein produced by T-cells in response to these antigens. It's an indirect method to determine if you have been infected with tuberculosis bacteria.
Purpose
This test is primarily used to diagnose latent or active tuberculosis infection. The goals are to detect whether the body’s immune system has been sensitized to tuberculosis bacteria and to aid in diagnosing TB infection, particularly in patients who have had a Bacillus Calmette-Guérin (BCG) vaccination or in those where skin testing is impractical.
Indications
- Symptoms of tuberculosis such as prolonged cough, weight loss, night sweats, or fever.
- Close contact with someone diagnosed with tuberculosis.
- Immunocompromised patients.
- Pre-screening for employment or school enrollment where TB testing is required.
- Prior vaccination with BCG.
Preparation
- No fasting or dietary restrictions are typically required.
- Inform the healthcare provider about any medications being taken, particularly immunosuppressive drugs.
- A brief medical history may be reviewed to assess risk factors for TB.
Procedure Description
- Blood Collection: A blood sample is drawn from a vein in your arm.
- Antigen Exposure: The blood sample is mixed with tuberculosis antigens.
- Incubation: The sample is then incubated to allow T-cells to respond.
- Gamma Interferon Measurement: The level of gamma interferon released by T-cells in response to the antigens is measured using specialized equipment.
No anesthesia or sedation is needed for this procedure.
Duration
The blood draw itself takes about 5-10 minutes, but results are typically available in a few days.
Setting
The blood sample collection is performed in a hospital, outpatient clinic, or a specialized testing center.
Personnel
- Phlebotomist or nurse for blood sample collection.
- Laboratory technician or specialist for the analysis of the sample.
Risks and Complications
- Common: Slight pain or bruising at the site of blood draw.
- Rare: Infection at the needle site, fainting, or dizziness.
Benefits
- Accurate detection of TB infection without interference from BCG vaccination.
- Results typically available within a few days, allowing for prompt diagnosis and treatment if necessary.
Recovery
There is no significant recovery time needed. Some patients might experience minor discomfort or bruising at the blood draw site. Follow any additional instructions provided by the healthcare provider.
Alternatives
- Tuberculin Skin Test (TST): An older test involving injecting a small amount of tuberculin under the skin and checking for a reaction, generally requiring two visits. However, it might give false-positive results in individuals who have received BCG vaccination.
Patient Experience
During the procedure, you might feel a brief pinch or sting when the needle is inserted for the blood draw. Post-procedure, the site might feel sore or show slight bruising. Any discomfort is typically minor and manageable with over-the-counter pain relief if necessary.