What is an IGRA Blood Test?

An Interferon-Gamma Release Assay (IGRA) blood test is a diagnostic tool used to detect prior or current infection with Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB). This blood test helps healthcare professionals assess an individual's immune response to TB bacteria, aiding in the diagnosis of both latent TB infection (LTBI) and active TB disease. Unlike the traditional tuberculin skin test (TST), the IGRA does not require multiple visits or elicit a reaction in individuals who have been vaccinated with the Bacille Calmette-Guérin (BCG) vaccine.

When is an IGRA Blood Test Ordered?

  1. Symptoms of TB Infection: Individuals exhibiting symptoms suggestive of TB, such as persistent cough, fever, night sweats, and unexplained weight loss, may be advised to undergo an IGRA blood test.

  2. Close Contact with TB Patients: Those in close contact with someone diagnosed with active TB are at risk of contracting the infection and may be recommended for IGRA testing.

  3. Healthcare Workers: Healthcare professionals exposed to patients with TB or individuals suspected of having the disease are often required to undergo regular IGRA testing as part of infection control measures.

  4. International Travel: Travelers visiting countries with high rates of TB may be advised to have an IGRA blood test before and after their trip to monitor for potential infection.

  5. Immigration Screening: Some countries mandate IGRA testing for individuals applying for visas or residency, particularly if they originate from regions with a high TB burden.

  6. High-Risk Groups: Individuals with weakened immune systems, such as those with HIV/AIDS, diabetes, and certain cancers, are more susceptible to TB infection and may benefit from regular IGRA testing.

Where to Get an IGRA Blood Test

IGRA blood tests are widely available through various healthcare facilities and laboratories. Here are some common options:

  1. Doctor's Office or Clinic: Many primary care physicians and specialists offer IGRA testing as part of their diagnostic services.

  2. Public Health Clinics: Local or regional public health departments often provide free or low-cost IGRA testing, especially for individuals at high risk of TB infection.

  3. Tuberculosis Clinics: Specialized TB clinics dedicated to diagnosing and treating TB disease may offer IGRA testing as part of their comprehensive services.

  4. Urgent Care Centers: Some urgent care facilities may offer IGRA testing, particularly if the patient presents with TB-like symptoms.

  5. Commercial Laboratories: Private laboratories, such as Quest Diagnostics and LabCorp, provide IGRA testing services for individuals who prefer more convenient or confidential testing options.

What to Expect During an IGRA Blood Test

The IGRA blood test is a simple procedure that typically involves the following steps:

  1. Blood Draw: A healthcare professional will collect a small blood sample from a vein in your arm using a needle and syringe.

  2. Processing: The blood sample is sent to a laboratory for processing and analysis using specialized equipment.

  3. Results: Results of the IGRA blood test are usually available within a few days. Your doctor will interpret the results and discuss them with you during a follow-up appointment.


The IGRA blood test is a valuable tool for diagnosing TB infection and helping healthcare professionals assess an individual's risk of developing active TB disease. Timely testing and appropriate treatment can help prevent the spread of TB and improve overall public health.


  1. What is the difference between an IGRA blood test and a TST?
    An IGRA blood test and a TST are both used to detect TB infection, but they work differently. The IGRA measures the immune response to TB bacteria, while the TST detects the presence of TB bacteria in the body.

  2. Is the IGRA blood test painful?
    The IGRA blood test involves a simple blood draw, similar to many other blood tests. The discomfort is usually minimal and lasts only a few seconds.

  3. How long does it take to get the results of an IGRA blood test?
    Results of an IGRA blood test are typically available within a few days. Your doctor will contact you to discuss the results and recommend appropriate next steps.

  4. Can I get an IGRA blood test if I've been vaccinated with the BCG vaccine?
    Yes, the IGRA blood test is not affected by the BCG vaccine. It can be used to diagnose TB infection in individuals who have received the BCG vaccine.

  5. What should I do if my IGRA blood test result is positive?
    A positive IGRA blood test result does not necessarily mean you have active TB disease. Your doctor will perform additional tests to determine if you have latent TB infection or active TB disease and recommend appropriate treatment if necessary.

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