Latent Tuberculosis Infection (LTBI): For health professionals

• Individuals with latent tb infection (LTBI), as known as tb infection, are infected with Mycobacterium tuberculosis, but do not have active TB disease.
• LTBI occurs when the TB bacteria is dormant for months to years with no symptoms.
• While it is estimated that about 5 to 10% of people with LTBI will develop active TB disease over their lifetime, lifetime risk of developing active TB disease depends on individual risk factors, including time since exposure and medical history.
• The major risk factor for LTBI in Ottawa for all age groups is having lived in an area with a high prevalence of TB – which leads to an increased risk of tuberculosis exposure (See WHO list of countries with high TB disease burden)
• LTBI is reportable to Ottawa Public Health.

• The rates of latent TB infection (LTBI), as known as TB infection, in Ottawa have been higher than the Ontario-less-Ottawa rates for the last 10 years.
• Please see Ottawa Public Health’s Diseases of Public Health Significance in Ottawa dashboard for updated epidemiology.

• Individuals with latent TB infection (LTBI), also known as TB infection, remain asymptomatic and do not transmit the infection in this state.
• Because sub-clinical TB (a continuum of active TB disease where the patient remains asymptomatic, but TB can be isolated from sputum) is also asymptomatic, it is important to rule out active TB disease before treating LTBI.
• It is important that all cases of LTBI be counselled on the signs and symptoms of active TB disease, which can mimic other respiratory illnesses or systemic diseases, and seek assessment by a healthcare provider.

Risk factors for LTBI:

• Individuals with increased risk of tuberculosis exposure, or contacts of a person diagnosed with pulmonary tuberculosis

• Individuals born in tuberculosis endemic countries
• Individuals with certain medical comorbidities that increase the risk of developing tuberculosis disease, such as HIV infection, diabetes and chronic renal failure
• Individuals who are homeless or under housed
• People who use injection drugs
• Indigenous peoples from areas with high tuberculosis incidence
• Health care workers, depending on the setting
• Residents of correctional facilities
• Residents of long-term care homes and retirement homes < 65 years of age
• Travellers to countries with high TB incidence

• A thorough clinical evaluation is advised to rule out active TB disease.
  
• The diagnosis of latent TB infection (LTBI), also known as TB infection, requires patient history, a physical exam, and testing.
• There are two tests available in Ottawa to support a diagnosis of LTBI: the tuberculin skin test (TST) or an Interferon-Gamma Reactive Assay (IGRA) blood test.
• Please be aware that currently the IGRA test is only available at select laboratories and the cost is not covered by OHIP.  See the Canadian Tuberculosis Standards for more information on the utility of IGRA.
• For more information on testing, please see Ottawa Public Health’s Tuberculin Skin Test page.
• The Online TST/IGRA Interpreter can be extremely useful to aid with interpretation of TST and / or IGRA results, taking into account the type of exposure to TB, the age of the patient, previous BCG vaccination and other risk factors. Testing for LTBI is NOT recommended in the following situations:
  • In persons who have a low risk of infection and
  • if infected, to support a tuberculosis disease diagnosis in adults and adolescents >12 years of age.
  • For routine mass screening of individuals outside of contact investigations or occupational screening programs; and
  • For the monitoring of tuberculosis disease treatment response.

A suspect or confirmed case of latent TB infection (LTBI), also known as TB infection, can be reported to Ottawa Public Health next business day by fax or phone. 

• Monday to Friday from 8:30 am to 4:30 pm:
  • Fax 613-580-9640 or
  • Call 613-580-2424, extension 24224 and leave a detailed, confidential message including your contact information
• The reporting form (bilingual, pdf - 333 KB) (This document is currently not in an accessible format) is available on our website, along with information on how to order medications for LTBI (bilingual, pdf - 316 KB) (This document is currently not in an accessible format).

Prior to offering treatment for latent TB infection (LTBI), also known as TB infection, persons with a positive TST require the following to rule out active TB disease:

• Physical exam: assessment of symptoms suggestive of possible active TB disease* and review of risk factors for active TB disease, such as contact history or other medical illnesses. If a cough is present for 3 or more weeks with no other diagnosis, sputum for acid-fast bacteria smear and culture should be ordered.
• Chest x-ray: if not performed within the past year or if any other symptoms compatible with active TB disease* are present. Indicate TST result on the chest x-ray requisition.

* Symptoms of active pulmonary TB disease include cough (especially if productive or bloody and/or associated with pain), fever, weight loss, fatigue and/or night sweats. Symptoms of active extrapulmonary TB disease include lymphadenopathy, pleural effusion and abdominal or bone and joint involvement, as these may be present concomitantly.

Treatment of LTBI and Medication

The Canadian Tuberculosis Standards (2022) has detailed information on drugs, dosage, side effects and monitoring for LTBI. Table 1 from this chapter of the Canadian TB Standards (2022) is linked here  for your convenience, although it can be accessed as a “pop out” table from the link above.

LTBI medication is provided at no cost to the patient when ordered through OPH. Please note that the first-line regime rifapentine and isoniazid (3HP) noted in the Canadian TB Standards is currently only available through a collaboration between OPH and the Ottawa Hospital, as it is a Special Access medication. 

For patients who cannot or will not start or complete treatment for LTBI, please ensure they are provided education regarding the signs and symptoms of active TB disease. OPH provides a patient fact sheet on TB your convenience.

Prevention

• The development of active TB disease occurs with greatest frequency in the first 2 years after infection.
• The primary strategy to prevent TB is targeted screening of individuals and groups who may be at high-risk (e.g., people who came from a country with a high burden of TB, etc.).
• Treating LTBI, referred to as tuberculosis preventive treatment (TPT), will not only significantly reduce the risk of the patient developing TB disease in the future, but will also prevent future spread of TB.

All suspected and confirmed cases of latent TB infection (LTBI), also known as TB infection, are reportable to Ottawa Public Health.

Treatment for LTBI is only available free of charge to the patient if it is ordered through Ottawa Public Health.

Ottawa Public Health participates in surveillance of LTBI and reports to the Ministry of Health as per Ministry requirements. Current rates of latent TB infection can be searched in the Diseases of Public Health Significant in Ottawa Dashboard.

Please report LTBI to Ottawa Public Health by fax or phone:

• The reporting form (bilingual, pdf - 333 KB) is available on our website, along with information on how to order medications for LTBI (bilingual, pdf - 316 KB) (These documents are currently not in an accessible format).

• Tuberculosis, Ottawa Public Health
• Patient fact sheet, Ottawa Public Health

Diagnosis of latent TB infection (LTBI), also known as TB infection: Canadian Tuberculosis Standards 8^th Edition. Chapter 4: Diagnosis of tuberculosis infection

Treating LTBI, referred to as tuberculosis preventive treatment (TPT) Canadian Tuberculosis Standards 8^th Edition. Chapter 6: Tuberculosis preventive treatment in adults

For information about tuberculin skin testing, please visit Tuberculin Skin Test, Ottawa Public Health

Please also see this downloadable PDF on how to administer tuberculin skin test.

The Online TST/IGRA Interpreter can be extremely useful to aid with interpretation of TST and / or IGRA results, taking into account type of exposure to TB, age, previous BCG vaccination and other risk factors.

The LTBI reporting form (bilingual, pdf - 333 KB) and information on how to order medications for LTBI (bilingual, pdf - 316 KB) (These documents are currently not in an accessible format).