Performance
The T-SPOT.TB test difference
For many years, there was only one way to test for tuberculosis (TB): the tuberculin skin test (TST). This is no longer the case, as there are now two categories of tests to detect TB infection:
The tuberculin skin test1
The TST has been used to detect TB infection for over 100 years. They require an intradermal injection of a small amount of purified protein derivative (PPD), a TB antigen, into the skin. In 48-72 hours, the resultant induration is measured.
Interferon-gamma release assays
Interferon-gamma release assays (IGRAs), which include the T-SPOT®.TB test, are blood-based tests. The technology is based on the release of interferon-gamma secreted by individual effector T cells (both CD4+ and CD8+) after being stimulated by TB-specific antigens.
Accurate across patient populations |
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TB test considerations | IGRAs | TST | ||
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T-SPOT®.TB2 | QFT®-Plus3 | LIAISON® QFT-Plus4 | ||
Utility in immunocompromised patients |
Warning in package insert that the predictive value of a negative QFT®–Plus result in immunosuppressed persons has not been determined |
Limitation in package |
Studies have |
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Sensitivity and specificity > 95% |
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FDA-approved borderline zone | ||||
No cross-reactivity with BCG vaccine |
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Objective test results |
Consistent results |
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TB test considerations | T-SPOT®.TB | QFT®-Plus | LIAISON® QFT-Plus4 | TST |
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< 1% uninterpretable test results | 0.6% invalid rate5 | 2.5% indeterminate rate3 | 3.1% indeterminate rate | N/A |
Converison rate < 1% in serial testing | 0.8%6 | QFT®-Plus 4.3%7 QFT®-Gold 4.4%8 |
N/A* | N/A |
One tube with no refrigeration |
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TB test considerations | T-SPOT®.TB2 | QFT®-Plus3 | LIAISON® QFT-Plus4 | TST |
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On-site incubation or refrigeration of specimen is never required | N/A | |||
Single, streamlined blood collection and process |
3 possible collection methods requiring use of 1 or 4 tubes with up to 9 steps required |
3 possible collection methods requiring use of 1 or 4 tubes with up to 9 steps required |
N/A | |
A single visit is required |
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Unique CPT® code9 |
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CPT® code | 86481* | 86480* | 86480* |
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Applicable test | The T-SPOT.TB test | QuantiFERON®-TB Gold Plus (QFT®-Plus) | LIAISON® QFT-Plus |
Description | Tuberculosis test, cell mediated immunity antigen response measurement; enumeration of gamma interferon-producing T-cells in cell suspension | Tuberculosis test, cell mediated immunity measurement of gamma interferon producing antigen response | Tuberculosis test, cell mediated immunity measurement of gamma interferon producing antigen response |