The primary goal of testing for tuberculosis infection (TBI) is to identify people who are at increased risk for development of tuberculosis (TB) disease and therefore may benefit from TB preventive treatment (TPT).
TB Preventative Treatment Quick Reference(PDF, 111.82 KB)
Risk factors for the development of TB disease
A TB skin test (TST) or interferon-gamma release assay (IGRA) blood test is used to diagnose TBI.
How to Plant and Read a TST
Online TST/IGRA Interpreter
Use the Online TST/IGRA Interpreter to find out the estimated risk of TB disease for a person with a positive TST or IGRA, based on their clinical profile
What to do when TST/IGRA is positive
Rule out TB disease by completing symptom assessment, physical exam and chest x-ray.
Contraindications for TB skin test
- Past severe blistering TST reactions
- Extensive burns or eczema over testing sites
- Documented past TBI or TB disease with adequate treatment
- Current major viral infections
- Live vaccine in the past 4 weeks (Note: TST may be administered before or on the same day as live vaccine)
Common interpretation errors
Erythema vs. induration - Erythema or rash without induration occurs in 2-3% of persons tested. This does not indicate TBI.
BCG vaccine history - A history of BCG vaccination received in infancy can be ignored as the cause of a positive TST result in all persons aged 10 years and older.
Source: Canadian Journal of Respiratory, Critical Care, and Sleep Medicine, Volume 6, Issue sup1 (2022). Canadian TB Standards, 8th Ed.
