[Table of Contents]

Volume: 22S1 • April 1996

Guidelines for Preventing the Transmission of Tuberculosis in Canadian Health Care Facilities and Other Institutional Settings

IV. TB MANAGEMENT PROGRAM

B. Assessment and Classification of Risk of TB Transmission in the Facility

The designated personnel responsible for the TB management program should conduct annually and update, as required, an assessment of the risk of TB transmission within the health care facility. The assessed risk will enable the health care facility to establish appropriate HCW TB screening and surveillance programs (see Section IV.C) and to determine facility requirements (the number of isolation rooms, ventilation requirements in various areas of the health care facility (see Section IV.J) needed to manage patients with suspected or confirmed TB.

The risk of TB transmission in health care facilities in Canada varies on a continuum from low to high. HCWs are at very low risk if they never care for patients with TB and work in a health care facility where patients with TB are rarely seen. On the other hand, HCWs are at increased risk of exposure if they work in facilities that frequently admit patients with active TB and are present in areas where high-risk activities are performed (e.g., bronchoscopy and other cough-inducing procedures). For the large number of HCWs working in the majority of Canadian facilities, the risk is somewhere between these two extremes (27) . However, all facilities including those assessed to be at low risk for TB transmission should have a TB management program (see Section IV.A).

Determining health care facility risk

The health care facility risk of TB transmission can be assessed by the following:

• the number of individuals with active TB seen annually in the facility; and

the ratio of HCWs to the number of individuals with active TB seen annually at the facility (number of HCWs/number of individuals with active TB seen annually at the facility).

The following approach should be used to assess whether a health care facility is at high or low risk.

First stage

The risk is assessed by the number of individuals seen with active TB annually in the facility.

High-risk facility

• A facility is considered high risk if it has six or more individuals seen with active TB annually (36) .

Low-risk facility

• A facility is considered low risk if it has fewer than six individuals seen with active TB annually.

Facilities assessed to be at low risk should proceed to the next stage. Facilities found to have a high risk do not need to proceed to the second stage.

Second stage

Those facilities with less than six active TB cases seen annually should determine the ratio of HCWs to the number of individuals seen with active TB annually at the facility. This assessment acknowledges that smaller facilities are unlikely to report large numbers of patients with active TB but HCWs may have a higher risk of exposure to any individual patient because the overall number of HCWs is relatively small.

High-risk facility

• A facility where one or more patients with active TB were seen within the previous 12 months is considered high risk if the ratio of HCWs to the number of individuals that are seen with active TB annually at the facility is equal to or less than 100.

Example: A health care facility with 40 HCWs reporting five TB admissions per year (40 divided by 5 gives a ratio of 8).

Low-risk facility

• A facility is considered low risk if the ratio of HCWs to the number of individuals seen with active TB annually at the facility is greater than 100.

Example: A health care facility with 475 HCWs reporting three TB admissions per year (475 divided by 3 gives a ratio of 118).

Facilities where no individuals are seen with active TB annually are also at low risk.

N.B. In health care facilities with more than one physical site, the risk should be assessed separately for each site. Risk may also be assessed for specific areas within the facility (e.g., respiratory units) or in specific occupational groups (e.g., respiratory therapists).

Other suggested approaches for assessing the health care facility risk may be used as adjuncts to the first two methods when risk classification is problematic. These include cluster events or the annual TST conversion rate in HCWs (see section IV.C.2).

Determining activity risk

Reports of TB outbreaks summarized in Appendix A illustrate that HCWs working in different areas of the same health care facility have different risks of acquisition of infection from TB patients. The risk of infection appeared to be based more on the type of activities HCWs performed or assisted with (e.g., autopsy, bronchoscopy) rather than an occupational category of the HCW (e.g., nurse, physician). Therefore, in addition to assessing health care facility risk, it is also important to determine activity risk for the HCW.

Activities have been classified as high, intermediate or low risk of exposure to patients with active TB according to the following scheme:

High-risk activities are those demonstrated to have increased risk of infection. This includes the activities of personnel who are involved with:

• cough-inducing procedures;

• autopsy examinations;

• morbid anatomy and pathology examinations;

• bronchoscopy procedures;

• designated Mycobacterium laboratory procedures (manipulation of mycobacterial cultures);

• units where increased rates of TST conversion have been documented:

- where active cases of TB have not been identified; or

- where these conversions are not related to community acquisition of infection.

All personnel who perform duties on these units must be evaluated, including housekeepers, clerks and maintenance staff.

Intermediate-risk activities include activities of personnel who

• have regular direct patient contact and who work on units where patients with active TB are admitted.

• have minimal patient contact (e.g., work in medical records, administration); or have regular patient contact but rarely with patients with TB (e.g., obstetrics, gynecology, neonatal intensive care unit). The facility and activity risk assessment are used to determine the frequency of HCW TB screening and surveillance programs (see Section IV.C). The health care facility risk is also used to determine facility requirements for managing patients with suspected or confirmed TB (see Section IV.J).

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