Steve young is an infectious disease specialist leading a large reference lab which supports a network of 14 hospitals. Interferon gamma concentration from the plasma is measured by elisa. Comparison of two commercially available gamma interferon. Qiagen, germantown, md interferon gamma release assay igra received fda clearance in 2017 and will replace the prior version of the assay, the qftgold intube qftgit. If the results to the tb antigens test above the cutoff point, the test subject is considered positive. Blood tests recommended over skin tests to check for tb in. Blood collection and handling training guide quantiferon.
Mazurek gh, jereb j, lobue p, iademarco mf, metchock b, vernon a. Hivinfected persons should be tested for ltbi as soon as their hiv status becomes known. A quantiferon gold test is considered positive if the result is. The test requires viable white blood cells, so the igra blood sample must be received and tested by a laboratory within a. The interferongamma release assay igra was recently developed to overcome the limitations of the tst, and it is expected to be more useful for the diagnosis of tb infection 3, 4. Quantiferon and t spot are tests for mycobacterium. Tb testing the differences between quantiferon gold. All igra testing was performed before the patients were prescribed antitb. An interferon gamma release assay igra blood test screens for exposure to tb by indirectly. The quantiferontb gold plus qftplus assay is an in vitro diagnostic test that utilizes a peptide cocktail simulating esat6 and cfp10 proteins to stimulate cells in heparinized whole blood. Dallas positive results with respect to the presence of latent tuberculosis infection ltbi in patients with renal failure were more consistent with the use of quantiferontb gold plus qftg plus testing compared with the use of quantiferontb gold intube qftgit testing a cohort study of patients with renal failure, who were undergoing dialysis or had. Comparison of two commercially available gamma interferon blood tests for immunodiagnosis of tuberculosis. Director, denver metro tb program property of presenter.
Costeffectiveness of interferon gamma release assays vs. Tb and quantiferontb gold in tube qfngit tests for diagnosing mycobacterium tuberculosis infection. This is similar to the tb elispot and is particularly suitable for. Dallas positive results with respect to the presence of latent tuberculosis infection ltbi in patients with renal failure were more consistent with the use of quantiferontb gold plus qftg plus testing compared with the. Despite the indication of a preference, use of the alternative test fdaapproved igra or tst is acceptable medical and public health practice. The tuberculin skin test versus quantiferon tb goldr in predicting. In these settings, igras may be more specific than tst for latent tb infection. This is a wholeblood test that relies on peptides from three different tb antigens, including esat6, cfp10, and tb7. For anyone who has had a tst tb skin test, i am curious what advantages a tst test has over an igra tb blood test. Gamma interferon release assays for detection of mycobacterium. Interpretation of igra results a view from the clinical lab. It offers advantages over the conventional tuberculin skin test tst for diagnosing ltbi. Interferongamma release assays igras test for tuberculosis. Tuberkulosekontakt mit dem tbquantiferontest nach weisen.
Overall, there were 32 cases with a followup of a second igra. The two standards for tb testing include a blood draw or skin test. Blood collection training guide 042017 3 quantiferontb gold is an indirect test for mycobacterium tuberculosis infection and is intended for use in conjunction with risk assessment, radiography and other medical and diagnostic evaluations. This test is an improved upon version of the quantiferon gold. Frequency and significance of indeterminate and borderline. There are two approved tests in the usa by the fda. Quantiferon tb gold plus for the diagnosis of tuberculosis.
Learn why 14 hospitals and a reference lab discontinued the tb skin test. Comparison of the quantiferontb gold plus and quantiferon. Neither test is licensed for use in active tb, so should not be used as either a rulein or a ruleout test in this clinical setting. Nevertheless, the skin test is still recommended, according to the new guidelines, if the igra test is not available or difficult to do in a particular setting, or because it is more expensive than the skin test to perform. The consistent positivity that was demonstrated was 82. Since igras are more costly and technically complex to do than the mantoux test, in their 2011. The quantiferon gold test is one of two commercially available tuberculosis tb interferon. Selection of the most suitable test or combination of tests for detection of m.
What does an indeterminate result in quantiferon gold in. It is intended for adults tested with standard tuberculin 5 tu ppds, or 2 tu rt23 andor a commercial interferon gamma release assay. Comparative study between using quantiferon and tuberculin. Data were collected retrospectively from case notes.
Whole blood is stimulated overnight with mycobacteria tuberculosis tb specific antigens, positive control or a nil control. Although there are several reasons for an indeterminate qftit, a common explanation is an immunocompromised state involving inadequate tcell response eg, corticosteroids, hiv, cancer. Igra test for tb measures the t cell release of interferon ifn gamma after being stimulated by antigens unique to mycobacterium tuberculosis bacterium. Interferongamma release assays igras are in vitro blood tests of cellmediated immune response that aids in the diagnosis of mycobacterium tuberculosis infection. The quantiferon tb gold test qftg is a wholeblood test for use as an aid in diagnosing mycobacterium tuberculosis infection, including latent tuberculosis infection ltbi and tuberculosis tb disease.
It seems like, in general, tb skin tests are more painful than a blood draw although many people dont experience too much pain. Use of interferongamma release assays for diagnosis of latent. Who recommends that either tst or igra can be used to test. Senior director, medical and scientific affairs, tb diagnostics. Blood tests recommended over skin tests to check for tb in most cases. Comparison of the sensitivity of quantiferontb gold in. Children with borderline or positive mantoux test results, or in whom there was clinical concern, were referred for consultant assessment andor igra quantiferon gold. Tb in testing for latent tuberculosis infection among hivinfected adults. Quantiferontb gold plus qftplus is a wholeblood test or interferongamma release assay igra that can measure a persons immune reactivity and aid in diagnosing mycobacterium tuberculosis infection. Position statement on interferong release immunoassays in the detection of latent tuberculosis infection. The following tool estimates the risk of active tuberculosis for an individual with a tuberculin skin test reaction of. Annual testing should be considered for hivinfected persons who are tst. The pros and cons of the quantiferon test for the diagnosis of tuberculosis, prediction of disease progression, and treatment monitoring. The tb blood test can be done instead of a tb skin test mantoux.
Interferongamma release assays igras blood tests for. Conversion to a positive test occurs most commonly with igra. Interpretation of igra results a view from the clinical lab edward a. For the detection of latent tb each has advantages and disadvantages. Understanding understanding igraigra resultsresults. Igra methods quantiferontb gold in tube qfg and tspot. Quantiferon, also known as qft, is the registered trademark of the test for tuberculosis infection or latent tuberculosis. Next generation tb testing with quantiferon tb gold plus.
The tuberculosis tb blood test, also called an interferon gamma release assay or igra, is a way to find out if you have tb germs in your body. Discrepancy between the tuberculin skin test and the wholeblood interferon gamma assay for the diagnosis of latent tuberculosis infection in an intermediate tuberculosisburden country. In 2007, the fda approved the nextgeneration igra, the quantiferontb gold in tube test qftgit cellestis limited. Since igras are more costly and technically complex to do than the mantoux test, in their. Qftgit, the third generation test, has replaced qft and qftgold qftg, which are no longer marketed. Either an igra or a tuberculin skin test tst may be performed to screen for tb, but in most cases the igra is now the preferred test. It does not mean intermediate or borderline positive. Igra are based on the principle that individuals who are infected with tb have primed memory t cells, which, upon reexposure to specific tb antigens, will be activated and stimulated to release interferon gamma. Abdelsamea a 1 yasser mahmoud ismail a 2 sahar mohamed a. Tuberculin skin test tst and interferongamma release assays igra april 2018 bob belknap m. Qiagens quantiferontb gold plus is the more accurate, more dependable and patientcentered way to detect tuberculosis. The quantiferontb gold test qftg is a wholeblood test for use as an aid in diagnosing mycobacterium tuberculosis infection, including latent tuberculosis infection ltbi and tuberculosis tb disease. Individuals living in highincidence settings, regardless of test results particularly african gold mines where close quarters and frequent hiv coinfection produce some of the highest tb rates in the world, is uncertain. An indeterminate quantiferon gold intube qftit simply means the result cant be interpreted.
A quantiferon tb gold test, known as a qftg, is one of the igras interferon gamma release assays and is approved by the fda known as a diagnostic tool for latent tuberculosis infection ltbi, this tb blood test measures how the immune. Use of the quantiferontb gold interferongamma release. Tuberculin skin test tst and interferongamma release. However, longitudinal studies have shown that a significant number of test reversions and conversions. P175 mantoux or gamma interferon igrawhich test is best. Quantiferon test for tuberculosis is a type of interferongamma release assay igras. This test was approved by the us food and drug administration fda in 2005. Igras are in vitro blood tests of cellmediated immune response to relatively tbspecific antigens such antigens are absent in the bcg vaccine and most nontuberculous mycobacteria. There are a couple of standards available for this procedure. Currently available fdaapproved igra assays for mtb include quantiferon tb gold qiagen and tspot tb oxford immunotec assays. The igra test measures the release of a substance called gamma interferon by white blood cells in a sample of blood when the cells are exposed to specific tb antigens.
Is your doctor or employer asking you to take a test for tb infection. Quantiferon is an elisa based interferon gamma release assay. This test is used to check for a latent tuberculosis infection latent tuberculosis tb infection is a noncommunicable form of tubercular infection in. Can igras be given to persons receiving vaccinations. Quantiferon is cheaper and easier to use in the lab, can be prepared and stored and batched. Igras have sensitivity age screened with both tst and two igra assays quantiferon gold intube test qftgit and tspot, the igras were found to have high specificity. More frequently detected in those with active tb disease vs. Quantiferon and t spot for mycobacterium tuberculosis detection there are two reasons to screen for tuberculosis. As with tst, live virus vaccines might affect igra test results. The diagnosis of ltbi is based on information gathered from the medical history, tst or igra result, chest radiograph, physical examination, and in certain circumstances, sputum examinations. Guidelines for using the quantiferontb gold test for detecting mycobacterium tuberculosis infection, united states. Comparative study between using quantiferon and tuberculin skin test in diagnosis of mycobacterium tuberculosis infection author links open overlay panel sohair a. One is the quantiferon tb gold intube test qftgit, and the other is the tspot tb test.
Currently, the gold standard for blood drawn tb testing is a test called quantiferon gold plus. Comparing interferongamma release assays with tuberculin skin. Comparison of mantoux and quantiferon tb gold tests for. Comparison of the sensitivity of quantiferontb gold intube and. Igraigra tst cheaper two visits igra more expensive. Comparison of mantoux and quantiferon tb gold tests for diagnosis of latent tuberculosis infection in army personnel. Caution in interpretation should be used when testing certain populations because of limited data on the use of igras see updated guidelines for using interferon gamma release assays to detect mycobacterium tuberculosis infection, united states. There are currently two types of commercial igras available, the quantiferontb gold intube test qftgit and the tspot. Tuberculosis tb reactivation is a rare but significant complication of organ transplantation, and screening of all transplant candidates for latent infection is recommended with either an interferon. Tb showed higher overall sensitivity than qftgit 91.