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Tuberculosis Infection Screening by Interferon-Gamma Release Assay (IGRA) - Quantified

Published: August 9, 2026Updated: August 16, 2026

This blood test measures your immune response to tuberculosis bacteria. It helps determine if you’ve been exposed to TB bacteria, even if you don’t have active symptoms.

Quick summary

["IGRA detects past or recent TB exposure without requiring symptoms or active infection."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
53703-5
Short code
M bovis tuberc IFN-g Pnl Bld
Synonyms
M bovis tuberc IFN-g Pnl Bld
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What This Test Measures

The test uses a small sample of your blood to detect interferon-gamma, a protein released by your immune cells when they recognize TB-specific antigens. This response indicates whether your body has encountered TB bacteria.

How the Test Works

Two TB-specific antigens are added to your blood sample. If your immune system has been exposed to TB, it will release interferon-gamma. The test quantifies this response to provide a numerical result.

Why It’s Done

IGRA is often used for screening high-risk groups (e.g., travelers, immunocompromised individuals) or before certain procedures (e.g., surgery) to identify latent TB infection.

Preparation

No special preparation is needed. You may eat or drink normally before the test, but avoid smoking for 1 hour before drawing blood.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IGRA Quantified (Tuberculosis)

Frequently asked questions

If your result is positive, further testing (like a chest X-ray or sputum culture) may be needed to check for active TB. A negative result means no recent TB exposure was detected, but it doesn’t rule out past infection.
A positive IGRA result suggests latent TB infection, which can be treated with antibiotics to prevent active disease. Follow-up with your healthcare provider is important.
How long does it take to get results?
Results are typically available within 3–5 business days. Your healthcare provider will discuss the meaning of your specific result during your follow-up.
Can I get TB from a positive IGRA test?
No, IGRA detects exposure to TB bacteria, not active infection. Active TB requires additional testing and treatment, which your doctor will guide you through.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy