If an individual is identified as at risk for LTBI or active TB disease, then the TST or IGRA test is ordered and performed. A positive test result may indicate the presence of TB bacteria, but it does not differentiate between LTBI or 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 who have a track record of not returning for the second TST reading appointment. IGRAs are also preferred for individuals who have been vaccinated with BCG. The TST is preferred for children under the age of 5 years.
