The QuantiFERON®-TB Gold Plus (TB Test) test contains 1 test with 5 biomarkers.
Brief Description: The Quantiferon TB Gold Plus test is a blood test used to detect tuberculosis (TB) infection. It is based on the principle of measuring the immune response to Mycobacterium tuberculosis, the bacteria that causes TB. This test is considered an alternative to the traditional tuberculin skin test (TST).
Also Known As: TB Test, Tuberculosis Test, IGRA Test, Interferon-Gamma Release Assay Test.
Specimen Type: Serum
Test Preparation: No preparation required
When and Why a Quantiferon TB Gold Plus Test may be Ordered
A Quantiferon TB Gold Plus test may be ordered in the following situations:
Screening for Latent TB Infection: It is commonly used to screen individuals who may have been exposed to TB or are at higher risk of infection, such as close contacts of TB cases, health care workers, and immigrants from TB-endemic regions.
Diagnosis of Active TB: The test may be ordered to support the diagnosis of active TB in individuals with symptoms suggestive of TB, such as persistent cough, fever, weight loss, and night sweats.
What a Quantiferon TB Gold Plus Test checks for:
Tuberculosis is a communicable disease caused by infection with M. tuberculosis complex. Infection results in either acute disease or Latent TB Infection (LTBI), a non-communicable asymptomatic condition. The main purpose of diagnosing the latent stage is to consider medical treatment for preventing overt disease. Until recently, the tuberculin skin test was the only available method for diagnosing LTBI.
QuantiFERON®-TB gold eliminates false positive skin test due to BCG vaccination and most Non-Tuberculous Mycobacteria (NTM) and is an objective, reproducible qualitative test. There are no side effects or adverse reactions due to patient hypersensitivity, and no "booster effect", whereby the first test induces a false positive response on re-testing. There is no need for follow-up patient visits to obtain test results.
The TB blood test has several advantages over a skin test. Blood testing requires only one visit to the lab while skin testing requires multiple visits to a doctor's office. Blood testing for Tuberculosis is typically more accurate than a skin test. Skin testing has a higher likelihood of false positive results, especially if a person has been previously vaccinated for TB.
Other Lab Tests Ordered alongside a Quantiferon TB Gold Plus Test
When a QuantiFERON TB Gold Plus test is ordered, it might be part of a broader evaluation for tuberculosis or other related health issues. Here are some tests commonly ordered alongside it:
Complete Blood Count (CBC):
- Purpose: Provides a broad picture of overall health, including red and white blood cells and platelets.
- Why Is It Ordered: To assess general health status and detect signs of infection or other health issues that may be relevant in the context of TB diagnosis or treatment.
Liver Function Test:
- Purpose: To assess liver health.
- Why Is It Ordered: Certain medications used in the treatment of TB can affect liver function, so baseline and ongoing liver function tests are important.
Kidney Function Test:
- Purpose: To evaluate kidney function.
- Why Is It Ordered: To ensure that kidney function is adequate, especially considering that some TB medications can affect kidney health.
Blood Glucose and Hemoglobin A1c (HbA1c):
- Purpose: To assess blood sugar control, particularly in individuals with diabetes.
- Why Is It Ordered: Diabetes can increase the risk of developing active TB and can affect the management of TB treatment.
These tests, when ordered alongside a QuantiFERON TB Gold Plus test, provide a comprehensive view of an individual’s health status in relation to TB infection and are critical for diagnosing, managing, and monitoring tuberculosis. The specific combination of tests will depend on the individual's risk factors, symptoms, and overall health condition.
Conditions or Diseases Requiring a Quantiferon TB Gold Plus Test
The Quantiferon TB Gold Plus test is primarily used for:
Screening for Latent TB Infection: Individuals who may have been exposed to TB or are at higher risk of infection are screened to detect latent TB infection. This includes individuals living in close contact with active TB cases, health care workers, and those from TB-endemic regions.
Diagnosis of Active TB: The test aids in the diagnosis of active TB when symptoms and other clinical findings are suggestive of TB disease.
Utilization of Quantiferon TB Gold Plus Test Results by Health Care Providers
Health care providers use the results of the Quantiferon TB Gold Plus test to:
Identify Latent TB Infection: A positive result indicates exposure to TB bacteria and the presence of a latent infection, requiring further evaluation and possible treatment to prevent the development of active TB disease.
Support Diagnosis of Active TB: A positive result, along with other clinical findings, assists in confirming the diagnosis of active TB, prompting initiation of appropriate treatment and infection control measures.
Guide Treatment Decisions: The test results, in combination with other diagnostic information, help determine the need for TB treatment, the duration of treatment, and the choice of specific anti-TB medications.
It's important to note that the interpretation of Quantiferon TB Gold Plus test results should consider the individual's clinical history, risk factors, and exposure history. Consultation with a health care provider experienced in TB management is essential for accurate interpretation and appropriate patient care.
Most Common Questions About the QuantiFERON TB Gold test:
Understanding the QuantiFERON-TB Gold Test
What is the QuantiFERON-TB Gold test?
The QuantiFERON-TB Gold test, also known as the QFT-GIT, is a blood test used to detect Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB). It measures the immune system's reaction to TB proteins and helps determine if a person has been infected with TB bacteria.
Why is the QuantiFERON-TB Gold test performed?
The QFT-GIT is performed as a part of routine TB screening in people who are at risk for TB or may have been exposed to TB bacteria. This could include health care workers, immigrants from areas with high TB rates, or those living in close quarters with an individual diagnosed with TB.
TB Infection and Its Implications
What is the difference between latent TB infection and TB disease, and how does the QuantiFERON-TB Gold test relate to them?
Latent TB infection means that an individual has the TB bacteria in their body, but it's not active, so they don't have symptoms and can't spread it to others. TB disease means the bacteria are active and can cause symptoms. The QuantiFERON-TB Gold test can detect both conditions as it identifies if TB bacteria are present, regardless of whether they're active.
If my QuantiFERON-TB Gold test comes back positive, does it mean I have TB disease?
No, a positive QFT-GIT test only means that you have been infected with TB bacteria. It doesn't indicate whether the infection is latent or has progressed to TB disease. Further diagnostic tests, such as a chest x-ray and sputum culture, are necessary to confirm TB disease.
What happens if I have a positive QuantiFERON-TB Gold test but no symptoms of TB?
If you have a positive QFT-GIT but no symptoms, it's likely you have latent TB infection. You can't spread TB to others, but treatment is typically recommended to prevent the latent infection from progressing to TB disease.
Understanding Test Results
How are the results of the QuantiFERON-TB Gold test interpreted?
The results of the QFT-GIT are usually reported as positive, negative, or indeterminate. A positive result indicates TB infection, a negative result indicates no infection, and an indeterminate result suggests the test couldn't conclusively determine your TB status, possibly due to a lab error or immune system suppression.
Can the QuantiFERON-TB Gold test yield false positive or false negative results?
Yes, false positives can occur if the immune system reacts to the test despite the absence of TB bacteria. False negatives can occur if the immune system fails to react to the test despite the presence of TB bacteria, which can happen in people with weakened immune systems.
What should I do if my QuantiFERON-TB Gold test results are indeterminate?
Indeterminate results usually require retesting. They can occur if your immune system response is insufficient to give a clear result, often due to immune system suppression or lab error.
Health Implications and the QuantiFERON-TB Gold Test
What health implications are associated with a positive QuantiFERON-TB Gold test result?
A positive QFT-GIT result indicates that you've been infected with TB bacteria. This puts you at risk for developing TB disease, especially if your immune system becomes weakened. It's essential to consult with your healthcare provider for potential treatment to prevent the infection from becoming active.
Can the QuantiFERON-TB Gold test detect TB in people with HIV?
Yes, the QFT-GIT can detect TB infection in people with HIV. However, the test's sensitivity might be reduced in individuals with HIV, particularly those with advanced immune suppression.
The QuantiFERON-TB Gold Test in Medical Practice
How often should I get a QuantiFERON-TB Gold test?
The frequency of testing depends on your risk of TB exposure. High-risk individuals, like healthcare workers in settings where TB is prevalent, might need routine annual testing. If you're not at high risk, retesting is usually only needed if you believe you've been exposed to TB bacteria.
Can the QuantiFERON-TB Gold test be used in children?
Yes, the QFT-GIT can be used in children over the age of two. However, it's not as sensitive in young children compared to adults, so additional testing might be necessary.
Further Insights into the QuantiFERON-TB Gold Test
Why would I get a QuantiFERON-TB Gold test instead of a TB skin test?
The QFT-GIT has some advantages over the skin test, including requiring only one patient visit, having fewer false positives due to prior Bacillus Calmette–Guérin (BCG) vaccination, and it doesn't rely on patient perception for the interpretation of results.
If I've had the BCG vaccine, will the QuantiFERON-TB Gold test give a false positive?
Unlike the TB skin test, the QFT-GIT is not affected by previous BCG vaccination and is less likely to give a false-positive result in this scenario.
Can the QuantiFERON-TB Gold test detect drug-resistant TB?
The QFT-GIT cannot identify drug-resistant TB as it only detects the presence of TB bacteria, not its susceptibility to specific drugs.
How does pregnancy affect the results of the QuantiFERON-TB Gold test?
Pregnancy does not significantly impact the results of the QFT-GIT. If you're pregnant and at high risk for TB, testing might be recommended.
What impact do immunosuppressive medications have on the QuantiFERON-TB Gold test results?
Immunosuppressive medications, such as corticosteroids or drugs used for autoimmune diseases or after organ transplantation, can decrease the body's immune response, potentially leading to a false-negative QFT-GIT result.
Can the QuantiFERON-TB Gold test determine if I'm contagious?
No, the QFT-GIT cannot determine if you're contagious. It only detects TB infection. Additional tests, such as a sputum culture, are required to determine if you have active TB disease and are potentially contagious.
Can the QuantiFERON-TB Gold test help monitor the effectiveness of TB treatment?
No, the QFT-GIT is not typically used to monitor treatment effectiveness. The test cannot differentiate between active and latent TB, and the immune response it measures can remain positive even after successful treatment.
What factors can interfere with the accuracy of the QuantiFERON-TB Gold test?
Several factors can interfere with the accuracy of the QFT-GIT, including lab error, improper blood collection or handling, recent TB exposure (within 8 weeks), age (less accurate in children under 2), and immune system suppression.
Can the QuantiFERON-TB Gold test detect TB meningitis?
No, the QFT-GIT cannot specifically detect TB meningitis. While it can detect TB infection, it can't identify the location of the infection in the body. TB meningitis is typically diagnosed with other tests, such as a lumbar puncture.
How do underlying health conditions affect the results of the QuantiFERON-TB Gold test?
Underlying health conditions, especially those that affect the immune system, can affect the results of the QFT-GIT. For instance, conditions like HIV, certain types of cancer, or autoimmune diseases can suppress the immune system response and potentially lead to false negatives.
Can the QuantiFERON-TB Gold test diagnose non-tuberculous mycobacterial (NTM) infections?
No, the QFT-GIT cannot diagnose NTM infections. It's specifically designed to detect Mycobacterium tuberculosis, the bacterium that causes TB.
What should I do if I think I've been exposed to TB, but my QuantiFERON-TB Gold test is negative?
If you think you've been recently exposed to TB (within the last 8 weeks), but your QFT-GIT is negative, you should consult with your healthcare provider. It's possible for the test to be negative if your immune system has not yet reacted to the bacteria. Retesting may be recommended.
What does a negative QuantiFERON-TB Gold test result mean for my health?
A negative QFT-GIT result typically means that you're not infected with TB bacteria, which reduces your risk for developing TB disease. However, no test is 100% accurate, and it's possible to have a false negative, especially if your immune system is suppressed or you've been recently infected.
We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.