Latent Tuberculosis Infections

For more information consult the Canadian Tuberculosis Standards, 7th edition, Chapter 4.

Mycobacterium tuberculosis infection is usually contained by an individual’s immune system and remains latent or dormant. The diagnosis and treatment of Latent TB Infection (LTBI) is an important intervention to reduce the future spread of tuberculosis (TB). 

The primary risk factor for acquiring TB infection is a history of having lived or spent time, in a community or country where TB is endemic.  The Canadian TB Standards does not recommend screening people who are at low epidemiological risk of having TB infections or at low risk of developing active TB disease (ex:  the general population, most immigrants), for LTBI. 

The goal of testing for LTBI is to identify people who are at increased risk for developing TB disease and would benefit from LTBI treatment. LTBI testing in not recommended as part of the diagnostic work-up of a person suspected of having active TB disease. The decision to test presupposes a decision to treat if positive for LTBI.

LTBI Tests

  • Tuberculin skin test (TST)
  • Interferon gamma release assay (IGRA) –available on a very limited basis with pre-approval from Cadham Provincial Laboratory

LTBI Assessment in Public Health Contact Investigations  (funded by MB Health)

  • Public Health (PH) is responsible for contact investigations
  • Patients with infectious active TB will be contacted by a public health nurse who will ask them questions about their activities during their period of infectivity in order to identify potential contacts
  • PH does an assessment of all contacts including TST testing—the cost of TSTs are covered in PH contact investigations
  • If a person attends a primary care provider or clinic with concerns that they have been exposed to someone with TB, refer the person to PH:  Winnipeg Regional Health Authority, Population and Public Health, Tuberculosis Services (WRHA PPH TB) 204-940-2274.
  • If a person attends for care and requests follow-up or treatment for a previous positive TST, contact PH for clarification of past TB history.

Other Reasons for doing LTBI Assessments (may not be funded by MB Health):

  • For clients where a planned treatment may increase the risk of a pre-existing LTBI to progress to active TB disease such as:
    • Prior to treatment with immunosuppressive therapies
    • Prior to organ or bone marrow transplantation
  • Students entering the health care field or pre-employment in a health care facility who require a baseline TST
  • Some Immigration physicals
  • Primary care clinics can consider TST testing for individuals with epidemiological risk factors for TB exposure and medical risk factor(s) for progressing to active TB disease
    • Prescribing clinicians can order Tuberculin from a pharmacy or immunization supplier; the cost is not covered by MB Health and either the client or clinic will need to cover the cost
    • Proper storage, use and attention to expiration dates of Tuberculin is necessary to ensure the reliability of TSTs
  • If active TB disease is suspected, a TST is not recommended
    • Diagnostic work-up for TB disease is based on symptom assessment, sputum samples and chest x-ray

LTBI Assessment is not recommended for:

  • Preadmission to personal care home facilities
  • Newcomers to Canada from countries with low TB rates
  • Preadmission to addictions treatment facilities
  • People with symptoms concerning for active TB disease
    • Diagnostic work-up for TB disease is based on symptom assessment, sputum samples and chest x-ray

LTBI treatment

  • LTBI treatment is available free of charge in MB
  • Treatment must be ordered on the designated MB Health prescription form  
  • LTBI treatment should be monitored by a clinician knowledgeable in TB care
  • Residents of the Winnipeg Health Region diagnosed with LTBI can be referred to:
    • Klinic Community Health, Access Downtown, BridgeCare (refugees only), Centre de Santé, and Access Fort Garry
    • Health Sciences Centre Pediatric Infectious Diseases for children < 17 years of age
    • Health Sciences Centre Chest Medicine for adults with complex health needs
  • Residents of Prairie Mountain Health Region:
    • Infectious Diseases on-call (Dr. Bookatz) 204-578-4000 (pgr) or 204-727-6451 ext.2202 (office)
  • Residents of Northern Health Region:
    •  Dr. Shadi Mahmoud: cell: 204-939-6076
    • When cell phone unavailable, hospital number for the HMO on call #204-677-2381

LTBI Treatment Regimens and Monitoring:

Information about screening:

Tuberculosis- Citizenship and Immigration Canada   

TB Screening for Clients of Addictions Programs