Page 205 - fourth year book

COMMUNICABLE DISEASES (T.B)

Two-step TST testing for TB infection and TB disease

B. Interferon Gamma Release Assays (IGRAs)

- It detects the presence of M. tuberculosis infection by measuring the
immune response to TB proteins in the whole blood.

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

Indication

- People who have received BCG, (unlike the TST, IGRAs is not affected
by prior BCG vaccination).

- People who have a difficult time returning for a second appointment
to look for a reaction to the Tuberculin Skin Test (TST)

Results and interpretation:

 Positive IGRA: means that the person has been infected with TB
bacteria. Additional tests are needed to determine if the person has
latent TB infection or TB disease then the health care worker can
provide treatment as needed.

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