It is mandatory to report TB infection and disease to Public Health. Patient consent is not required for reporting this information.


  • Report a new active, reactivated or suspect TB case.
  • All suspected and confirmed TB cases must be reported to Public Health.
  • All persons with a positive skin test must be reported to Public Health.
  • TB medications for prophylaxis and treatment are free through Public Health.

Who should be tested for Latent TB infection (LTBI)?

The following persons should be tested for latent TB infection (LTBI):

  • Contacts of persons recently diagnosed with active pulmonary TB
  • Foreign-born persons and visitors from TB-endemic countries, especially immigrants who have arrived in the last two years
  • People who are at increased risk of progression to active TB disease due to impaired immunity
  • People with radiographic evidence of old, healed TB without history of treatment

There are two accepted tests for identification of latent TB infection

1) Tuberculin Skin Test (TST)

The tuberculin skin test is used to detect individuals infected with M. tuberculosis. The skin test is administered intradermally using the Mantoux technique. Reading and interpretation of a TST should be done within 48 to 72 hours of administration.

2) Interferon Gamma Release Assay (IGRA)

In 2010, the Canadian Tuberculosis Committee provided an update to an Advisory Committee Statement, Recommendations on Interferon Gamma Release Assays for the Diagnosis of Latent Tuberculosis Infection.

Two Interferon Gamma Release Assays (IGRAs) are licensed for use in Canada: Quantiferon TB Gold and T-SPOT TB.

However, neither are presently covered under the Ontario Health Insurance Plan (OHIP). Quantiferon TB Gold testing can be obtained on a limited basis through Gamma-Dynacare Medical Laboratories.

For patient service centres that offer Quantiferon TB Gold testing, visit the Gamma-Dynacare website or call 1-800-565-5721. At the current time, the cost for this testing is approximately $90.00.

Other commercial laboratories may also offer IGRA testing in the future.

How to evaluate and treat latent TB infection (LTBI)?

Treatment for latent TB infection should be initiated only after active TB disease has been ruled out.

Refer Patient to TB Specialist if:

  • Child (< five years)
  • Pregnant
  • Immunocompromised
  • Contact of drug-resistant TB
  • Abnormal chest x-ray
  • History of liver disease
  • History of alcohol/substance abuse/misuse

How to do a skin test

  • Administer 0.1 mL of 5 tuberculin units (5-TU) of purified protein derivative (PPD), injected intradermally on volar aspects of the forearm.2
  • If no wheal appears, inject another 0.1 mL of PPD 5 cm from the previous site or in the other arm.1
  • Record the time, date, lot number, expiry date and dose of PPD injected and the site(s) of injection.3
  • Patients should wait 15 minutes after injection to monitor signs of anaphylaxis.
  • An emergency kit with epinephrine should be available in case of an adverse reaction.
  • Tests should be read and recorded after 48 to 72 hours by a trained health professional.2
  • Measure induration not erythema across the width of the arm (i.e. transverse to the long axis of the forearm) and record in mm.2

Contraindications for skin test

  • Patients with documented active TB or a clear history of treatment for TB infection or disease
  • Patients with severe blistering tuberculin reactions in the past
  • Patients with extensive burns or eczema
  • Patients with major viral infections or live-virus vaccinations in the past month, e.g., MMR

A skin test may be administered before, on the same day or 30 days after a live-virus vaccination, e.g., MMR.1

Not a contraindication for skin test

  • Pregnancy
  • Patients with a history of Bacille Calmette-Guerin (BCG) vaccination 2

Why do a two-step skin test?

  • Assists in establishing a true baseline result for people who will be getting serial TB skin tests.
  • A positive skin test may gradually wane over the years. The initial skin test completed as part of the two-step process may stimulate the immune response, and a positive reaction may occur when the person is retested one to 4 weeks later. This delayed response is called thebooster phenomenon.2
  • If a baseline is not measured through two-step skin testing, a positive skin reaction on subsequent tests may be interpreted as a conversion (i.e. recent TB infection), when in fact the positive skin reaction may represent the booster phenomenon (i.e. previous TB infection).

Who should get a two-step skin test?

People who are beginning a schedule of skin testing at regular intervals should have a 2-step as their initial test.

  • Health care professionals
  • Corrections staff
  • Travellers who are going to an area with a high prevalence of TB for one month or more 2
  • Residents of long-term care facilities
  • Shelter staff 3

How to do a two-step skin test

  • Administer 0.1 mL of 5-TU of PPD intradermal as usual for each test.2
  • If the reaction on first skin test is negative, a second skin test is administered one to four weeks later.2
  • If the reaction on the first skin test is positive, a second skin test should not be administered.
  • If either the first or second skin test is positive, the person should be evaluated further to rule out active TB disease (i.e., medical evaluation re: risk factors for TB, chest radiography, and in presence of symptoms, sputum for acid fast bacilli smear and culture).
  • For people on a regular TB screening schedule, only the initial round of testing needs to be two-step. Once baseline is established, subsequent routine testing (i.e., annually) is one-step only.

Skin testing for patients who are contacts of an active TB case

  • Administer 0.1 mL of 5-TU of PPD intradermal as usual for each test.2
  • Perform an initial skin test as soon as exposure to an active case of TB is identified.
  • Conversion of a skin test from negative to positive after exposure to an active case may take eight to 12 weeks. Therefore if the reaction on the first skin test is negative, administer a second skin test eight to 12 weeks after the contact’s last possible exposure to the active case.2
  • If the reaction on the first skin test is positive, a second skin test should not be administered.
  • Under some circumstances a single post 8 week skin test may be warranted. Please contact Public Health.
  • If either the first or second skin test is positive, the person should be evaluated further to rule out active TB disease (i.e. medical evaluation re: risk factors for TB, chest radiography, and in presence of symptoms, sputum for acid fast bacilli smear and culture).2
  • There is no indication for two-step skin testing for a contact of active TB. Skin test conversion can occur as early as two weeks. It is difficult to differentiate true conversion from the booster phenomena. Any change in skin test reactivity must be considered as a true conversion.2
  • Contacts are identified by Public Health and provided with documentation for further follow-up from their physicians

How to report a TB Skin Test

TST reaction size Results are significant (considered positive) for:
0 – 4 mm
• Patient with significant immunocompromise with other TB risk factors.
5 – 9 mm • Household or close contact of a TB case.
• Patient with abnormal chest radiograph.
>10 mm • Patient who is healthy with no known TB risk factors.
*All clients with significant immunocompromise (including HIV) are at high risk for developing TB disease and should be seen by an ID Specialist or TB clinic.
  • Skin test results should be recorded in mm of induration, not simply as “positive” or “negative”.2
  • Erythema should not be included in the measurement of a skin test. Redness does not indicate TB infection.2
  • Store PPD preparation between two and 8 degrees Celsius.
  • Date the vial of tuberculin when first opened. Discard a vial of tuberculin preparation that has been opened and used after one month, as potency may be reduced.3


  • 1Aventis Pasteur. (2000). Tuberculin Skin Test Guidelines.
  • 2Canadian Lung Association. (2000). Canadian Tuberculosis Standards. (5th ed.). Ottawa: Canadian Lung Association.
  • 3Ontario Ministry of Health and Long Term Care. (1998). Ontario Ministry of Health Tuberculosis Protocol.
TB Infection OR TB Disease
TB germ has entered the body but is not growing (dormant/inactive)
TB germ has entered the body and is growing (replicating/active)
Positive Skin Test
Skin Test
May be positive or negative
No active TB disease
Chest x-ray
(or e.g., CT scan, MRI)
Most show active TB on x-ray of chest OR on x-ray/ CT scan/MRI of other parts of the body (e.g., lymph node, spine, kidney)
No TB germs in sputum
May have TB germs in sputum
No symptoms
Symptoms which become worse over time (e.g., cough, chest pain, chills, weakness, weight loss, night sweats, coughing up blood, swollen lymph node)
Not contagious
Cannot pass TB germ to anyone else
If disease is in the lungs and not properly treated with medication
Person is at risk of developing disease in the future
Associated Risks
Person has disease and must be treated to prevent disease from getting worse or spreading to others
May be prescribed medication to prevent disease from developing
Needs treatment with several medications for six months or longer to cure the disease
  1. Report a new active, reactivated or suspected TB case
  2. Refer your patient to a TB clinic. TB cases should be managed by a specialist with experience with TB cases. If your patient is less than five years old, HIV positive and/or MDR, they must be referred to a TB clinic (or HIV clinic) for treatment.
  3. Order medication. Call 416-338-7600 and ask to speak with staff in the TB Prevention and Control Program. Have the patient’s address available so that your call may be transferred to the appropriate team.
  4. Toronto Public Health will be following your patient throughout their treatment and will contact you if we become aware of any issues such as lab results or treatment non-compliance.
  5. Notify Toronto Public Health of any treatment changes or patient issues e.g. side effects, missed appointments, travel plans and free medication ordering.
  6. If you have any questions, please call 416-338-7600 and ask to speak with staff in the TB Prevention and Control Program.

Treatment guidelines

Additional resources