QuantiFERON-TB Gold Plus Test - More Information

The QuantiFERON-TB Gold Plus test, sometimes known as an IGRA test, is an FDA-cleared blood test that screens for tuberculosis (TB). This test measures how your white blood cells respond to specific TB antigens (including ESAT-6 and CFP-10). A positive result means that your immune system has been sensitized to TB bacteria - Mycobacterium tuberculosis. The QuantiFERON-TB test is a screening test and does not diagnose active tuberculosis or prove you are contagious.

Through Accesa Labs, people can order a QuantiFERON-TB Gold Plus test online, get tested at a local lab, and get results electronically as soon as they are available (typically in 6 days or less - usually faster).

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Who Should Get the QuantiFERON-TB Gold Plus Test?

The QuantiFERON-TB Gold Plus blood test is ordered in a wide range of situations when one needs documented tuberculosis screening:

• Healthcare students
  Students entering healthcare professions usually need tuberculosis screening before starting.
• Vendor credentialing
  Medical device, pharmaceutical sales, and other healthcare representatives often need to provide TB testing documentation through vendor credentialing platforms to access clinical settings. Confirm that the test result is accepted by the platform before ordering.
• College student requirements
  Some universities require proof of tuberculosis clearance before enrollment.
• People who have had the BCG vaccine
  The QuantiFERON-TB Gold Plus test typically does not result in a false positive from prior BCG vaccination.
• People with a positive or unclear PPD test result
  The IGRA test is more reliable in these situations and can obviate the need for repeated chest x-rays.
• Residents or staff in higher-exposure settings
  Individuals who work or live in places like correctional facilities, homeless shelters, and long-term care facilities sometimes need or want periodic TB screening.
• Immigration medical exams
  Confirm that this test is acceptable with the civil surgeon.

Organizations managing TB testing compliance for multiple employees, contractors, or students can use Accesa Labs' software tools to place and track group orders from a single account. Get started at the Organization Signup page.

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QuantiFERON-TB Gold Plus Test - How It Works

The QuantiFERON-TB Gold Plus test is used to screen people who might have been exposed to tuberculosis in the past. Through Accesa Labs, people can order a QuantiFERON-TB blood test online and get tested at a local lab. The price includes the physician lab order, all lab test fees, and secure electronic PDF results.

This QuantiFERON-TB test is a type of IGRA, or interferon-gamma release assay, test. It works by measuring how reactive one's immune system is when exposed to components of the tuberculosis bacteria. When triggered, the white blood cells in the body will release a special chemical called interferon-gamma that can be measured through this TB blood test. Specifically, this QuantiFERON-TB Gold Plus test helps assess proteins related to tuberculosis bacteria - mycobacterial proteins ESAT-6, CFP-10 and TB 7.7. People who have been exposed to M. tuberculosis will typically show high levels of interferon-gamma while healthy people who have not been exposed will have low levels of interferon-gamma. This test is often ordered with titer tests such as the hepatitis B titer, MMR titer and varicella titer and occasionally with drug testing.

QuantiFERON-TB Gold Plus - Testing Process

If you need to get the QuantiFERON-TB Gold Plus blood test near you, you likely have some nearby options available. Most standard lab locations are able to perform the QFT test. To get a TB blood test, you will need to go to the lab and the lab staff will draw your blood, typically into a single lithium-heparin tube at most locations. Some locations may still use the four-tube collection format (a Nil tube, TB Antigen tube, TB2 Antigen tube, and Mitogen tube). After collection, the whole blood sample will be incubated for a period of time (no special isolation, washing or culturing required) and the QuantiFERON results will be ready after that.

If you click on the sample results link above, you can see what a QuantiFERON-TB Gold test lab report looks like. In this particular sample lab report, the QuantiFERON test results say negative which indicates a negative results. The numbers reported next to the Nil, Mitogen-Nil and TB-Nil rows indicated that the controls for the test (the additional vials of blood) were successfully performed as a comparison to the actual blood test. More specifically, the Nil vial checks for possible false positives, the mitogen control helps check for false negatives and the TB antigen tube helps with the patient's sample.

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TB Blood Test vs. TB Skin Testing

Traditionally, TB screening has been done through a TB skin test, also known as a PPD test or a Mantoux test. To get a TB skin test, one needs to visit a medical office and receive a small injection of a substance known as a protein purified derivative (PPD) in the forearm. After 48-96 hours, the forearm needs to be checked and measured by a medical provider to see if any swelling, or induration, has developed at the site of the injection. If a raised swelling above a certain size is noted on the second visit, a chest x-ray is required to make sure that tuberculosis is not present in the lungs. As a result, the TB skin test requires a minimum of two visits and possibly more if the TB skin test is read as positive.

As opposed to the TB skin test, the TB blood test is more convenient as it only requires one visit to a laboratory. During the lab visit, a simple, nearly painless blood draw is performed and the specimen is processed by the lab using specialized equipment. In contrast to the TB skin test, a second visit is not required for a TB blood test. And, because the QuantiFERON test uses sophisticated lab machinery instead of relying on manual skin measurements by a medical provider, this TB blood test is more accurate, particularly in borderline cases.

What if one tested positive to a TB skin test previously? For people who have tested positive on a TB skin test, the QuantiFERON-TB Gold Plus blood test is a good choice. Most people who have had a positive TB skin test in the past are required to get a chest x-ray to demonstrate that active tuberculosis is not present in the lungs. The TB blood test, on the other hand, can often differentiate between a false positive and a false negative skin test without the need for a chest x-ray.

The QuantiFERON-TB Gold Plus test has demonstrated improved accuracy in regards to statistical test specificity relative to the skin test. More specifically, the QuantiFERON-TB blood test is reported to have a specificity of greater than 99% versus as low as 59% for the TB skin test. This increased QuantiFERON test accuracy is partially due to the fact that QuantiFERON blood testing results are not subject to interpretation error or bias from the medical provider reading the PPD test. The TB skin test, on the other hand, requires the person interpreting the test to accurately measure the size of swelling, or induration, on the patient and even one millimeter can make the difference between a positive or negative for latent tuberculosis. In addition to its benefits in testing people who have received the BCG vaccine previously, the TB gold blood test is of value to anyone (e.g. a healthcare worker) who suspects they may have had a false positive TB skin test in the past.

Infrequently, people will need to get something called a two-step tuberculosis test for compliance reasons. The two-step TB test was originally designed to check for evidence of tuberculosis activity in people who may have been infected with M. tuberculosis and have lost some ability to react to the skin test. During the two-step TB test, one needs to get two TB skin tests over the course of multiple weeks, requiring a lot of time and multiple office visits. TB blood testing is a great alternative to the two-step TB test as it is not affected in the same way as the skin test by these "boosting" effects. In place of a two-step TB test requirement, the TB blood test still only requires one visit to draw the blood and process it.

To summarize, there are specific circumstances in which the IGRA blood test is preferred over the TB skin test. As mentioned, the TB blood test is helpful for people who have received the BCG vaccination previously. Generally speaking, the CDC now recommends that the IGRA test can be used as an alternative to the tuberculosis skin test for screening purposes.

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QuantiFERON-TB Gold Plus Blood Test Results

Conservatively, QuantiFERON TB blood test results typically take approximately six business days to be reported. For many people in busy metropolitan areas, TB blood test results can be available in as soon as three business days. A negative QuantiFERON lab report, when accurate, is the best result. It indicates that evidence of tuberculosis exposure cannot be found in the blood specimen. A negative lab test is similar to a negative TB skin test and, in most cases, does not require a chest x-ray for confirmation or other diagnostic studies.

What does a TB blood test result mean? Positive or indeterminate QuantiFERON TB blood test results typically mean that you will need to get a chest x-ray to confirm that you do not have active tuberculosis. Negative QuantiFERON Gold results imply that you do not have latent tuberculosis at the time the blood was drawn. In cases of indeterminate QFT tests, newer algorithms are being studied and may be helpful alternatives to immediate imaging.

If you are wondering how long your QuantiFERON-TB Gold Plus blood test result is good for, the answer is it really depends on who is asking for it. Broadly speaking, many organizations recommend annual TB blood testing for screening. That being said, every organization has its own recommended guidelines as far as how often one needs to be screened for tuberculosis. Tuberculosis screening guidelines have been created in consideration of the risk of possible TB exposure in the work or school environment. The best way to know for sure when you need to get another QuantiFERON-TB Gold Plus test is to ask the person or organization requiring the test to see what their requirements are. If you are simply getting tested for your own reasons, then retesting can be performed at any time and based on one's comfort level. After all, someone who has a negative TB blood test result but is exposed to tuberculosis the very next day will have a positive result on a future retest.

The QuantiFERON-TB IGRA test was approved by the FDA in 2001 and is now the predominant tuberculosis screening method at most hospitals, health systems, and universities in the United States.

Tuberculosis - An Overview

Tuberculosis is an infectious disease caused by M. tuberculosis that has been part of human history for a long time. M. tuberculosis usually infects the lungs but can also infect other parts of the body. Tuberculosis is very contagious, spreading from person to person from infected droplets. People who have been exposed to TB may or may not have symptoms. When symptoms of tuberculosis are present (i.e. "active" tuberculosis), they classically consist of coughing with blood-tinged sputum, weight loss and night sweats. However, many people who have been exposed to tuberculosis do not have symptoms (i.e. "latent" tuberculosis). Screening for latent tuberculosis is important because it can turn into active tuberculosis at a later date. This is why ongoing tuberculosis screening - particularly in people like healthcare and school workers and students who are at a higher risk of tuberculosis exposure - is so important for protecting communities.

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How To Get Tested At Accesa Labs

1. Order online. Add the QuantiFERON-TB Gold Plus test to your cart and complete the order. The listed price includes lab fees and the physician order review and lab order.
2. Choose a lab location. Pick a convenient participating lab. No insurance is required.
3. Visit the lab for a blood draw. Only one visit is required. No fasting is necessary.
4. Receive your results. Download your report and submit it to your employer, school, or credentialing platform. If the result is positive or indeterminate, follow up with a clinician before assuming clearance.

Accesa Labs makes QuantiFERON-TB Gold Plus testing fast, affordable and secure. No health insurance is required and there are no hidden costs.

More TB Blood Test Information

- CDC - IGRA