الفهرس 
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Abstract
SUMMARY UMMARYUMMARYUMMARYUMMARY
uberculosis is a common and in many cases lethal, infectious disease caused by mycobacteria usually mycobacterium tuberculosis. Tuberculosis typically attacks the lung, but can also affect other parts of the body.
Tuberculosis is a leading cause of worldwide preventable morbidity and mortality from an infectious agent. A definite diagnosis of tubercular pleural effusion can be difficult to make because of low sensitivity and / or specificity of noninvasive traditional diagnostic tools.
The QuantiFERON-TB Gold IN TUBE test is a whole-blood test for use as an aid in diagnosing Mycobacterium tuberculosis infection, including latent tuberculosis infection (LTBI) and tuberculosis (TB) disease. This test was approved by the U.S. Food and Drug Administration (FDA) in 2007.
Blood samples are mixed with antigens (substances that can produce an immune response) and controls.The antigens include mixtures of synthetic peptides representingM. tuberculosis proteins, (ESAT-6 , CFP-10, TB7.7). After incubation of the blood with antigens for 16 to 24 hours, the amount of interferon-gamma (IFN-gamma) is measured.
If the patient is infected with M. tuberculosis, their white blood cells will release IFN-gamma in response to contact with
the TB antigens. The QFT-G results are based on the amount of IFN-gamma that is released in response to the antigens.
Clinical evaluation and additional tests (such as a chest radiograph, sputum smear, and culture) are needed to differentiate between a diagnosis of latent TB or active TB.
The sensitivity of the QFT assay is >90% as determined using culture confirmed active TB as the gold standard. The specificity is 99.2% using young, healthy, low-risk people who have all previously been vaccinated with BCG QFT can be used for detection of latent infection of pulmonary and extrapulmonary TB (unlike culture methods that identify only active tb)
Advantages to using an IGRA such as the QuantiFERON-TB Gold IN TUBE test These include: Patients are not injected with a purified MTB protein (PPD) which avoids the possibility of a severe reaction to the TST. Improved patient compliance. No return visit is required to interpret the skin test. Automated colorimetric results as compared to subjective interpretation for the TST and provider office staff training is no longer required for interpretation of the TST.
The TB Gold test is the preferred method for people who have received a BCG vaccine. The TB Gold test involves only drawing blood from a patient, so it may be used in cases where subjecting a patient to a TB skin test may be contraindicated, such as children, patients who are immunocompromised, or on corticosteroids, or who have auto-immune diseases such as rheumatoid arthritis. If necessary, the TB Gold test can be repeated easily, since it only requires whole blood drawn from the patient, and the patient has not been previously or recently exposed to PPD, which could affect interpretation of the TB skin test.
Disadvantages and limitations of the test are:
Blood samples must be processed within 12 hours after collection while white blood cells are still viable.
There is limited data on the use of QFT-G in children younger than 17 years of age, among persons recently exposed to M. tuberculosis, and in immunocompromised persons (e.g., impaired immune function caused by HIV infection or acquired immunodeficiency syndrome [AIDS], current treatment with immunosuppressive drugs, selected
hematological disorders, specific malignancies, diabetes, silicosis, and chronic renal failure).
Errors in collecting or transporting blood specimens or in running and interpreting the assay can decrease the accuracy of QFT-G.
Limited data on the use of QFT-G to determine who is at risk for developing TB disease.
False positive results can occur with Mycobacterium szulgai, Mycobacterium kansasii, and Mycobacterium marinum.