IGRA assesses for past exposure to Mycobacterium tuberculosis. It is more specific for the bacteria than the Tuberculin Skin Test and is not affected by past BCG vaccination. More information can be found in the Canadian TB Standards, 7th edition, Chapter 4.
Each year, World Tuberculosis (TB) Day is observed on March 24. This annual event commemorates the date in 1882 when Dr. Robert Koch announced his discovery of Mycobacterium tuberculosis, the bacillus that causes tuberculosis (TB).
The Windsor-Essex County Health Unit strongly recommends that all employees/volunteers in all healthcare settings have pre-employment baseline TB screening.
If a TST or IGRA is required, it should be administered and read before immunization or delayed for four weeks after vaccination.
Have all equipment ready. Tubersol® 5 tuberculin units of PPD is recommended. Check expiry dates. Use a disposable tuberculin syringe and a ¼ to ½", 26 or 27 gauge needle with a short bevel.
|
TST result |
Situation in which reaction is considered positive* |
|---|---|
|
0-4 mm |
|
Latent TB Infection (LTBI) |
OR |
Active TB Disease |
|---|---|---|
|
TB germ has entered the body, but is not growing (dormant) |
Status |
The Long Term Care Homes Act 2007, Ontario Regulation 79/10, and Retirement Homes Act 2010, Ontario Regulation 166/11, require screening for tuberculosis.
TB infection is defined as the presence of latent or dormant Mycobacterium tuberculosis bacteria, with no clinical evidence of active disease.