Are you curious about the Igra Test? If so, you're in the right place. In this blog, we'll uncover all the essential information and insights about the Igra Test that you need to know. We'll delve into Interferon-Gamma Release Assays (IGRAs) and help you understand what they are. You'll learn about the mechanisms behind IGRAs, including how they work, their advantages, and their limitations. We'll also walk you through the process of administering an IGRA Test, step by step. Plus, we'll decode the IGRA test results and explain how to interpret them. Additionally, we'll explore different scenarios for IGRA Test use and discuss why companies and the US Immigration Service require an IGRA test. Finally, we'll provide pre- and post-IGRA test guidelines to help you prepare for the test and know what to expect afterward. So let's dive in and get all your questions answered!

Delving into Interferon-Gamma Release Assays (IGRAs)

Interferon-Gamma Release Assays (IGRAs) are diagnostic tests used for detecting tuberculosis (TB) infection. These tests work by measuring the immune response to specific antigens produced by Mycobacterium tuberculosis, the bacteria that causes TB. IGRAs have advantages over other tests, such as greater specificity and a lack of influence from the BCG vaccine or the majority of nontuberculous mycobacteria. They play a crucial role in diagnosing latent tuberculosis infection (LTBI), especially in individuals at higher risk, such as those with HIV or recent exposure to TB. Different types of IGRAs, like Quantiferon and T-SPOT.TB, have applications in clinical practice, providing valuable insights for healthcare providers regarding TB diagnosis and management. Understanding the interpretation and significance of IGRA test results is essential for accurate patient evaluation and appropriate intervention, making interferon-γ release assays an important tool in the fight against TB.

Understanding the IGRA Test to detect tuberculosis

The IGRA test, an essential tool for detecting latent tuberculosis infection, involves a blood test that measures the release of interferon-gamma in response to TB-specific antigens. This test is more specific than the tuberculin skin test and does not cross-react with BCG vaccination. With just a single patient visit, the IGRA test provides results within 24-48 hours, making it a convenient option for individuals at high risk of TB exposure. This includes healthcare workers and those who have recently immigrated from countries with a high burden of TB. By understanding the IGRA test, we can effectively identify and manage latent TB infections.

The Mechanism behind IGRAs

Interferon-Gamma Release Assays (IGRAs) are a type of blood test used to detect tuberculosis (TB) infection. They work by measuring the release of interferon-gamma, an immune response, when exposed to specific TB antigens, including ppd. This test offers several advantages over other TB testing methods. It is more specific than the tuberculin skin test (TST) and does not cross-react with the BCG vaccine, providing reliable results. The process of conducting an IGRA test involves collecting fresh blood samples and stimulating them with TB antigens. The results are then interpreted as either positive or negative for TB infection. However, IGRAs also have limitations and challenges, including false-positive results in patients with non-TB mycobacterial infections or immunosuppression. Despite these challenges, IGRAs play a crucial role in the diagnosis and control of TB, offering valuable insights for effective TB testing and management strategies.

How does it work?

The IGRA test detects tuberculosis infection by measuring the immune response to specific antigens. A small blood sample is mixed with TB antigens, and if the person has been exposed to TB, their immune system will produce a measurable reaction.

Advantages and Limitations of IGRAs

IGRAs offer distinct advantages over the tuberculin skin test (TST). They have higher specificity and sensitivity, leading to more accurate results. Another benefit is that IGRAs can detect both latent and active tuberculosis (TB) infections, providing comprehensive diagnostic capabilities. Additionally, IGRAs require only one patient visit and provide quicker test results compared to the TST. Unlike the skin test, IGRAs are unaffected by prior BCG vaccination, ensuring accurate results. However, it's essential to note that IGRAs have limitations in certain populations, such as immunocompromised individuals. Considering these advantages and limitations, IGRAs serve as a valuable tool for the diagnosis of TB infections, including the tb vaccine.

The Process of Administering an IGRA Test

The process of administering an IGRA test involves collecting a blood sample from the individual and stimulating the immune system to release interferon-gamma. This diagnostic test, which stands for Interferon-Gamma Release Assay, is used to detect latent tuberculosis infection. The collected blood sample is then analyzed in a laboratory to measure the amount of interferon-gamma released, indicating the presence of a TB infection. Compared to traditional tuberculin skin tests, IGRA tests are considered more accurate and reliable. The results of the IGRA test can help healthcare professionals determine if further testing or treatment is necessary for the individual.

Steps Involved in IGRA Testing

The process of IGRA testing involves several steps. Firstly, a blood sample is collected from the individual. This blood sample is then sent to a laboratory for analysis. In the lab, the blood sample is exposed to specific antigens that stimulate an immune response. After an incubation period, the level of immune response is measured using specialized equipment. The results of the IGRA test, which can help diagnose tuberculosis infection, are typically available within a few days. By following these steps, healthcare professionals can gather valuable information about a patient's tuberculosis status.

Decoding IGRA test results: Can a BCG vaccine affect results?

Decoding IGRA Test Results

The IGRA test, or Interferon-Gamma Release Assay, is a diagnostic test used to detect tuberculosis (TB) infection. It helps healthcare professionals interpret the results of the test, which can be positive, negative, or indeterminate, including a positive tst. Factors such as the presence of HIV, BCG vaccination, and the progression from latent TB infection to active TB disease can affect the accuracy of the IGRA test results, leading to false positive results. If you receive a positive or indeterminate IGRA test result, further testing and evaluation may be necessary. Compared to other tuberculosis diagnostic tests, the IGRA test has its advantages and limitations.

How to Interpret IGRA Test Results

Interpreting IGRA test results involves analyzing the immune responses to tuberculosis (TB) antigens. A positive result suggests a TB infection, while a negative result indicates no infection or early stages. Indeterminate results require further evaluation to determine the presence of TB bacteria.

Scenarios for IGRA Test Use

The IGRA test, also known as the interferon gamma release assay, is widely used for tuberculosis (TB) infection detection. Healthcare providers utilize the IGRA test to screen individuals at high risk for TB. It is often combined with other diagnostic methods, like the tuberculin skin test (TST). The IGRA test helps determine if a person has been exposed to TB bacteria and if treatment is needed. Particularly, it is valuable for individuals who have received the BCG vaccine, as it can differentiate between vaccine-related immunity and active TB infection. By assessing various scenarios, the IGRA test plays a crucial role in identifying and managing TB infections.

Who should consider getting an IGRA test?

Considering an IGRA test? It's recommended for those exposed to TB or at high risk of contracting it. This includes healthcare workers, individuals with weakened immune systems, and those in close quarters with someone with TB. Also used to screen for latent TB infection before immunosuppressive therapy. Talk to your healthcare provider to determine if an IGRA test is right for you.The former test quantitates the amount of IFN-γ produced in response to the ESAT-6 and CFP-10 antigens from Mycobacterium tuberculosis , which are distinguishable from those present in BCG and most other non-tuberculous mycobacteria .

Why do companies and the US immigration service require an IGRA TB test?

Companies and the US Immigration Service require IGRA tests to screen for tuberculosis (TB) infection in the United States. TB is a contagious disease that poses a risk to public health. The IGRA test helps identify individuals exposed to TB bacteria and at risk of developing active TB disease, ensuring the safety of employees, customers, and the public.

Pre- and Post-IGRA Test Guidelines

Pre- and Post-IGRA Test Guidelines: To ensure accurate results, it's important to follow certain guidelines before and after undergoing an IGRA test. Before the test, it's crucial to understand the purpose of the IGRA test, which is often recommended for individuals who have been exposed to tuberculosis (TB) or are at high risk of contracting TB. Pre-test guidelines include avoiding medications or substances that may affect the test results. During the test, be prepared for a blood test to detect the immune response to specific TB antigens. After the test, it's essential to interpret the results correctly and take any necessary follow-up steps. It's also important to consider the limitations and potential risks associated with the IGRA test.

Preparing for the IGRA Test

When preparing for the IGRA test, it is important to follow certain guidelines. If applicable, fasting requirements should be adhered to before taking the test. Inform your healthcare provider about any medications you are currently taking. Before the test, avoid smoking or using any tobacco products, as they can potentially affect the results. It is recommended to wear loose-fitting clothing to allow easy access to the arm for blood sample collection. Additionally, staying hydrated by drinking plenty of water before the IGRA test is essential. By following these preparations, you can ensure accurate and reliable results.

What should I expect after the test?

After completing the Igra test, expect your results in a few days. Positive results may require further medical evaluation for tuberculosis. Negative results indicate no infection or an inactive infection. Follow up with a healthcare professional for next steps or treatment recommendations.

How do you interpret IGRA test results?

Interpreting IGRA test results involves measuring interferon-gamma (IFN-g) levels. A positive result suggests exposure to tuberculosis (TB), but not active TB disease. A negative result indicates no current TB infection or an inability to mount an immune response. Intermediate or indeterminate results may require further testing or clinical evaluation.

How does the IGRA Test Impact Clinical Decisions?

The IGRA test plays a crucial role in clinical decision-making for tuberculosis (TB). It helps healthcare providers determine the need for further testing or treatment by identifying TB infection and assessing the risk of active TB disease. The results, along with other clinical information, guide healthcare providers in making informed decisions.

Is the Quantiferon Gold Plus Test the Same as an IGRA Test or a TST?

The Quantiferon Gold Plus Test is indeed a type of IGRA (Interferon-Gamma Release Assay) test, used to detect tuberculosis infection by measuring the immune response to TB antigens. It is an updated version of the original Quantiferon Gold Test and offers high accuracy and advantages over traditional tuberculin skin tests (TST).

What Happens If Your IGRA Test Results Are Positive?

If your IGRA test results are positive, it means you have been exposed to the bacteria that cause tuberculosis (TB). Further testing, like a chest X-ray, is done to confirm active TB disease. Positive results without active TB may require preventive treatment. Consult a healthcare provider for evaluation and guidance.

Where Can You Buy an Affordable IGRA Test Near You?

Discounted Labs sells the most affordable IGRA test (Quantiferon Gold Plus) on the market.

How Does Discounted Labs Work?

1-     Click on the Lab Near You page to ensure we serve your state and that a location is near you. 

2-     If a location is near you, go to Quantiferon Gold Test and add it to the shopping cart. 

3-     If you have a discount coupon code, add it to your cart. You will earn points for every purchase you can redeem in future orders.

4-     If you don't have an account with us, you will be asked to create one by adding your name, address, gender, and date of birth. Note: You cannot place an order for someone else unless you create an account for them.

5-     Place your order by using a credit card.

6-     You will receive three emails: an order confirmation & detailed instructions within minutes about how to download your lab requisition form to take to the lab near you.

7-     Print the lab requisition form (PDF file). 

8-     Take that form to the  lab near you . You can walk in, but we suggest you make an appointment to cut down on potential waiting (instructions on how to do so are on our "Find a Location" page). Get your blood drawn at the lab.  

9-    Your results will be ready within 2-7 business days (Depending on the test. Sensitive hormone tests done by liquid chromatography/mass spectrometry LC/MS take 5-7 business days). You will receive them by email as soon as they come in.

Please contact us if you have any questions. We also have answered a lot of questions in our Frequently Asked Questions page

More Facts About TB Testing

  • Children less than 2 years old should have the TB skin test instead of the TB blood test.
  • The TB blood test is one of two types of tests used to detect TB.
  • A persistent cough that has lasted for three weeks or longer.
  • A TB blood test takes a single visit to complete, and the test results are typically available within 24 to 48 hours after the blood sample is collected.
  • A small needle is inserted into the vein, and a sample of blood is collected into up to three vials.
  • The results of the TB blood test may be available within 24 to 48 hours after taking the blood sample.
  • Experts recommend testing at least 6 to 8 weeks after exposure to TB.
  • QuantiFERON (QFT) is an interferon-γ release assay (IGRA) that aids in the evaluation of tuberculosis (TB) infections (latent or active) and is recommended by the CDC as an alternative to the tuberculin skin test (TST) in certain situations.
  • The QFT has been shown to be more accurate than the TST in identifying people who may have a latent TB infection.
  • A meta-analysis calculated a pooled sensitivity for TST at 70% (23 of 25 studies in developed countries) and a pooled sensitivity for QFT at 84% (13 studies in developed countries).
  • One study reported up to a 32% reduction in cost compared to the TST.
  • If a positive QFT result is the discrete referral decision driver vs. a positive TST (using the data in the study), a QFT positive result might have reduced the chest x-ray referral by 37.5% in the group with no BCG vaccination, who also had a prior TST inoculation history.
  • A QFT positive result might also have reduced the referrals within all study participants by 60% (including the sum of no BCG/no TST history; BCG; and TST/no BCG history participants).
  • Approximately 11 million individuals in the US are currently infected with LTBI, so it is critical for patients to be screened for TB infection prior to the initiation of immunosuppressive treatment, including biologic agents for autoimmune diseases.
  • For such people, an alternative is to assume, without additional testing, that the initial result is a false positive.
  • These tests are mostly developed for the field of tuberculosis diagnosis , but in theory, they may be used in the diagnosis of other diseases that rely on cell-mediated immunity, e.g., cytomegalovirus, leishmaniasis, and COVID-19 .
  • The former test quantitates the amount of IFN-γ produced in response to the ESAT-6 and CFP-10 antigens from Mycobacterium tuberculosis , which are distinguishable from those present in BCG and most other non-tuberculous mycobacteria.


In conclusion, the IGRA test is a valuable tool for diagnosing certain infections and conditions. It provides accurate and reliable results that can help guide clinical decisions and treatment plans. Understanding the mechanism behind IGRAs and how to interpret the test results is crucial for healthcare professionals and individuals seeking testing. It is important to follow pre- and post-test guidelines to ensure accurate results. If you are considering getting an IGRA test, consult with your healthcare provider to determine if it is necessary for your specific situation. Remember, early detection and proper management can make a significant difference in your health outcomes. If you're looking for an affordable IGRA test near you, please visit our website for more information.


  1. Centers for Disease Control and Prevention. (n.d.). Testing for TB Infection. Retrieved July 22, 2023, from
  2. Gerald, L., Blumberg, H., & Burzynski, J. (2021). Tuberculosis. In: Ferrets, Rabbits, and Rodents (4th ed.). Retrieved July 22, 2023, from
  3. Minnesota Department of Health. (n.d.). Tuberculosis (TB) Facts - Interferon-Gamma Release Assays (IGRAs). Retrieved July 22, 2023, from