Tuberculosis (TB): For health professionals

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Key information

TB is a serious but preventable and treatable infectious disease caused by the bacteria Mycobacterium tuberculosis (MTB). It is the leading cause of death for infectious diseases worldwide and is still present in Canada. While anyone can get TB, it disproportionately impacts people born outside of Canada and Inuit, First Nations and Métis populations.

TB can be diagnosed late or misdiagnosed as it has similar symptoms to other diseases and is not common in many parts of Canada.

Early testing, detection and treatment save lives and helps prevent the spread of TB.

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Disease progression

When MTB are inhaled, they enter the lungs and are taken up by immune cells (alveolar macrophages). Once a person is infected, their outcomes may vary based on a combination of the following factors.

Some factors that significantly increase the risk of progressing to TB disease include:

The most effective way to reduce transmission is to promptly diagnose, isolate and treat patients with TB disease.

TB is a notifiable disease in every Canadian province and territory. This means that cases must be reported to the corresponding provincial and territorial department of health.

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Signs and symptoms of TB disease

Signs and symptoms of TB disease depend on where the infection is located in the body. Pulmonary TB is the most common site of TB disease. However, TB can infect any site including extrapulmonary infections of the brain, bones, abdomen, and lymph nodes and other sites.

Extrapulmonary TB disease may present with systemic signs like fever, and symptoms specific to the site of infection. For example:

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Diagnosis

There are different diagnostic criteria and tests used for TB infection and TB disease.

Diagnosis of tuberculosis infection

The primary goal of testing for tuberculosis infection is to identify individuals who are at increased risk for developing TB disease in the future who would benefit from TB preventive treatment.

There are 2 accepted tests to identify TB infection:

  1. tuberculin skin test
  2. blood test (interferon gamma release assay)

Situations where one test is preferred over the other are outlined in the Canadian Tuberculosis Standards. Other tests and a clinical assessment are required for diagnosing TB disease.

TB diagnostic tests

Tuberculin skin test

A tuberculin skin test (TST), also called a Mantoux tuberculin test, is an antigen-based test for TB infection. The skin test is conducted by:

If the patient has been infected with TB previously, an induration (a hard, dense, and raised formation under the skin) will occur within 48 to 72 hours.

The area of induration should be objectively measured with a ruler. A measurement of less than 5 mm is generally considered negative. A measurement greater than 5 mm could be considered a positive result in some populations, whereas a threshold of 10 mm is used in others. For more details on the interpretation of TST results, including false positive and false negative results, please refer to the Canadian Tuberculosis Standards.

TB diagnostic tests

Blood test (interferon gamma release assay)

An interferon gamma release assay (IGRA) is a blood test that measures a person's immune response to MTB antigen to diagnose TB infection. IGRA is the preferred test when:

The BCG vaccine is not recommended for universal use in Canada but is still used in some high incidence communities and high incidence countries. There are 2 assays currently approved for use in Canada:

  1. QuantiFERON-TB Gold In-Tube Plus assay (QFT-Plus)
  2. T-SPOT.TB (T-SPOT)

If blood test results are indeterminate, invalid, or borderline, the blood test should be repeated or a TST performed.

If a TST or IGRA is thought to be a true positive, then the possibility of TB disease should be ruled out prior to starting treatment for TB infection.

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Tuberculosis disease

Testing for TB disease is recommended:

The recommended steps for diagnosing TB disease are as follows.

  1. Do a complete medical history and examination.
  2. Order a chest X-ray.
  3. Order laboratory tests.

Every effort should be made to obtain a microbiological diagnosis.

In Canada, the standard testing algorithm for tuberculosis disease includes the following tests:

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Prevention in health care settings

Exposure to people with undiagnosed pulmonary and laryngeal TB disease can occur in health care settings.

All health care settings should have a TB management or infection prevention and control program in place.

In a health care setting, infectious individuals should be placed in private (isolation) rooms. To contain the airborne pathogen and prevent the spread to other areas of the healthcare facility, isolation room must:

Other additional precautions may be used, such as:

When outside an airborne infection isolation room, masks should be worn by:

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Treatment

TB infection treatment

Prior to starting treatment for TB infection, it is critical to rule out TB disease as this could result in undertreatment and possible drug resistance.

First-line therapy

First-line therapy can either be rifapentine and isoniazid for 3 months (3HP) once-weekly or rifampin for 4 months (4R) daily.

Further information on treatment details, alternative regimens and considerations for special populations can be found in the Canadian Tuberculosis Standards.

Tuberculosis preventive treatment in adults

Drug access for treating TB infection

Rifapentine (Priftin®) is not authorized for sale in Canada but is accessible for treatment of TB infection under an exceptional circumstances regulatory pathway, via a federal notification on drugs for urgent public health needs. This allows its importation from the United States into Canada for the treatment of TB infection in combination with isoniazid.

To order Priftin®and for additional information, please contact Sanofi (the manufacturer) at ADECPriftin@sanofi.com.

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TB disease treatment

The standard regimen for TB disease should include 2 effective drugs at all times, and at least 3 effective drugs in the intensive phase.

First-line therapy for suspected drug sensitive TB disease

Intensive phase (first 2 months):

Continuation phase (following 4 months):

Treatment for drug-resistant TB is longer and requires a different combination of antimicrobial agents. Further information on treatment details and treatment of drug-resistance TB, including multi-drug resistant TB, can be found in the Canadian Tuberculosis Standards.

In addition, the standards can provide further guidance on the treatment of:

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Directly observed treatment

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Reporting forms

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