| 1. QuantiFERON-TB Gold Plus (QFT-Plus) test is an in vitro diagnostic test using a peptide cocktail simulating ESAT-6 and CFP-10 proteins to stimulate interferon-y (IFN-y) from CD4+ and CD8+ T Iymphocytes. This is associated with Mycobacterium tuberculosis infection. |
| 2. The overall specificity and sensitivity of the QFT-Plus is 97.6% and 95.3% respectively. |
| 3. QFT-Plus does not cross react with previous BCG vaccinations. |
| 4. QFT-Plus is an indirect test for M. tuberculosis infection (including disease) and is intended for use in conjunction with risk assessment, radiography, and other medical and diagnostic evaluations. |
| 5. A negative result does not completely rule out TB infection. A false negative result can be due to the stage of infection (e.g. specimen obtained prior to the development of cellular immune response). |
| 6. QFT-Plus cannot distinguish between active and latent TB infection and cannot be used as a sole diagnostic test. |
| 7. In low risk individuals, weak positive (any TBAg minus Nil results between 0.35 to 0.60), should be interpreted with caution. Repeat testing on a new sample should be considered. |
| 8. A positive QFT-Plus result should be followed by further medical evaluation and diagnostic evaluation for active tuberculosis disease (e.g. TB DNA test, AFB smear and culture, chest X-ray). |
| 9. False positive QFT-Plus results may occur in patients with prior infection with M. kansasii, M. szulgai, or M. marinum. |
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| References: |
| 1. QuantiFERON-TB Gold Plus (QFT-Plus) ELISA Package Insert. QIAGEN. 02/2015 |
| 2. Centers for Disease Control and Prevention. (2010) Updated Guideline for using Interferon Gamma Assays to detect Mycobacterium tuberculosis infection - United States, MMWR 59 (RR-5) |
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| New generation of reagent in use and reference notes updated. Effective 01 Aug 2017. |