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Middlesex-London Health Unit

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TB Skin Tests and IGRAs

TB skin testing (TST) is a useful tool for diagnosing inactive tuberculosis. The test is not as helpful in the diagnosis of active TB and can produce a ‘false negative’ result in some patients with advanced disease and/or who are immunocompromised. For more information about TB skin tests, please view the Middlesex-London Health Unit’s TB skin testing Information Sheet (PDF 69KB).

The skin test is administered intradermally using the Mantoux technique of tuberculin skin testing. Interpretation of a TST should be done between 48-72 hours of administration. More information about the proper administration of the TST can be found under TB Resources by clicking on the Canadian Tuberculosis Standards(7th ed), the Tuberculosis Information for Health Care Providers (4th ed) guide or by ordering the Mantoux Tuberculin Skin Test training CD from the Canadian Lung Association.


The following persons should be tested for inactive TB:

  • Contacts of persons recently diagnosed with active pulmonary TB
  • Foreign-born persons and visitors from TB-endemic countries within 2 years of arrival to Canada
  • People who are at increased risk of progression to active TB disease
  • People with radiographic evidence of old, healed TB and no history of treatment
  • Health care workers at risk for occupational exposure to TB

Tb Skin Test Supplies

Tb Skin Test Supplies
  • Staff and residents in communal care, including correctional facilities, long-term care, and shelters/services for homeless/under housed
  • Persons from Aboriginal communities with high rates of TB

TB skin testing is also available at the health unit Immunization Clinic.

Interferon Gamma Release Assays (IGRAs)

Two Interferon Gamma Release Assays (IGRAs) are licensed for use in Canada: Quantiferon TB Gold and T-SPOT TB. Currently, these tests are not covered under the Ontario Health Insurance Plan (OHIP).  Quantiferon TB Gold testing can be obtained on a limited basis through Gamma-Dynacare Medical Laboratories. The cost for this testing is approximately $90.00.

For current recommendations on the use of IGRAs, please refer to Chapter 4 in the Canadian Tuberculosis Standards.

For testing information on Quantiferon TB Gold, contact Dynacare 112-230 Victoria Street, London Ontario at (519) 432-1560.

Date of creation: February 26, 2013
Last modified on: May 18, 2018


1Public Health Agency of Canada and the Canadian Lung Association/Canadian Thoracic Society. (2007). Canadian Tuberculosis Standards (6th ed.)