QuantiFERON Gold vs. QuantiFERON Gold Plus vs PPD Skin Testing
QuantiFERON is a form of Tuberculosis testing or “TB Testing” and is a requirement for employment for many different industries across the country. It can be required for industries that are subject to OSHA regulations and for companies that need their employees to work in or access a medical setting (HCIRs).
Healthcare industry representatives (HCIRs) are required to undergo a variety of vendor credentialing requirements. TB testing is often one of these requirements. HCIRs include traveling nurses, medical supply representatives, pharmaceutical representatives, etc. There are a couple of standards available for this procedure. The two standards for TB testing include a blood draw or skin test. Currently, the gold standard for blood drawn TB testing is a test called QuantiFERON Gold Plus. This test is an improved upon version of the QuantiFERON Gold. Another standard for TB testing used today is the PPD skin test. Throughout this article, we'll go over a background of QuantiFERON, as well as the differences between QuantiFERON Gold, QuantiFERON Gold Plus, and the PPD skin test.
What is QuantiFERON?
QuantiFERON (QFT) is a registered trademark for the blood draw that tests for latent tuberculosis (TB). Tuberculosis is a contagious disease rooted in a bacterium called Mycobacterium tuberculosis. TB infects a person's lungs and can spread throughout the body to the kidneys, spine, and even to the brain. If TB isn't treated properly, it can be fatal. In the United States today, it is believed that 13 million people carry the latent form of TB infection without knowing about it. This can develop into active TB, but it doesn't have to if detected and treated. This blood test for TB is considered an interferon-? release assay (IGRA). This is a whole-blood test that relies on peptides from three different TB antigens, including ESAT-6, CFP-10, and TB7.7. If the results to the TB antigens test above the cut-off point, the test subject is considered positive.
QuantiFERON Gold
This test was first established as an alternative to traditional TB skin tests that require two office visits. It has been approved for use in adults by the Food and Drug Administration (FDA) and recommended by the Center for Disease Control (CDC) for its numerous benefits. The CDC recommends this test to be used in place of a TB test for adults, but not along with. This test is recommended for adults who have received BCG (Bacillus Calmette–Guérin) vaccine. Benefits of using the QuantiFERON Gold Test over a TB skin test (TBT or PPD) include:
- Greater specificity
- One patient visit requirement (instead of 2-4)
- Results unaffected by BCG vaccine
- Results unaffected by booster phenomenon (greater sensitivity on subsequent TB tests which lead to false-positives)
- Savings realized from clinics due to the elimination of follow-up visits
- Results unaffected by reader bias
QuantiFERON Gold Plus
QuantiFERON Gold Plus is the new, improved version of the QuantiFERON Gold TB test. This is the same test with the same fundamental principles, but is more advanced at detecting TB. The Gold Plus test has been optimized in such an innovative way with the TB-specific antigens that elicit CD8 and CD4 T cell responses. This allows for a more accurate, comprehensive assessment of any cell-mediated immune responses to TB infection. This test is over 97% accurate at detecting a TB infection. Since this is a blood draw, there is no need for a follow-up visit to read the results, which are typically available within 24 hours. While this is a more efficient test overall, it's necessary for testing those who may be positive for TB, those who may have a low risk for disease progression, and those who suspect they may have latent TB. QuantiFERON hasn't been tested on pregnant women, those with HIV, or those who are under age 17. While the two tests are incredibly similar, the Gold Plus is superior due to its innovative advancements and higher accuracy rates. This is the new gold standard that most clinicians will use for testing TB.
How Does QuantiFERON Gold Plus Compare to the TB Skin Test?
As mentioned, the results of TB skin test might be skewed due to reader bias or human error in interpreting the results. There are 2-4 visits required of the patient in order to complete the skin test. TB skin testing is also more likely to show a false-positive result due to previous exposure to previous skin tests, as well as the BCG vaccine.
QuantiFERON has developed a more accurate and efficient method for testing that results in fewer false-positives, can be completed in less time, and cannot be skewed due to bias or previous TB test exposure. The QuantiFERON TB testing technology has been researched in over 1,300 clinical trials and studies, and this method has been empirically found to have the highest accuracy rates of any TB test available. Paired with the increased efficiency of testing, the QuantiFERON Gold Plus TB test is the preferred method for TB testing by clinicians today.
QuantiFERON Gold Plus vs T-SPOT
Want to learn what the differences betetween the two IGRA TB blood tests are?
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