The TST or IGRA test is ordered and performed if an individual is identified as at risk for LTBI or active TB disease. A positive test result may indicate the presence of TB bacteria, but it does not differentiate between LTBI and active TB.
If the TST or IGRA test is positive, additional tests should be performed to determine if the person has active TB disease or latent infection. A TB medical evaluation may take place, to include:
- physical history,
- chest radiograph, and
- diagnostic microbiology (acid-fast smear and culture).
Note: IGRAs are preferred for individuals with a track record of not returning for the second TST reading appointment and those vaccinated with BCG. The TST is preferred for children under the age of 5.
