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TST

IGRA

Tuberculin is injected under the skin and produces a delayed-type hypersensitivity reaction if the person has been infected with M. tuberculosis

Blood is drawn for testing; test measures the immune response to the TB bacteria in whole blood

 

Requires two or more patient visits to conduct the test

Requires one patient visit to conduct the test

Results are available 48 to 72 hours later

Results can be available in 24 hours (depending on the batching of specimens by the laboratory and transport)

Can cause boosted reaction

Does not cause boosted reaction

Reading by HCW may be subjective

Laboratory test not affected by HCW perception or bias

BCG vaccination can cause false-positive result

BCG vaccination does not cause

false-positive result and infection with most nontuberculous mycobacteria does not cause false-positive result

A negative reaction to the test does not exclude the diagnosis of LTBI or TB disease

A negative reaction to the test does not exclude the diagnosis of LTBI or TB disease

For more information on IGRAs please review the IGRA section in this chapter.