IV. TB MANAGEMENT PROGRAM

[Table of Contents]

Volume: 22S1 • April 1996

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

C. HCW TB Screening and Surveillance Programs

The goal of the HCW TB screening and surveillance component of the TB management program is to ensure that the annual rate of acquiring infection with M. tuberculosis in HCWs does not exceed the annual rate of acquiring infection in an average Canadian community (e.g., no more than one TST negative HCW in 1,000 (0.1%) would develop a positive TST per year) (39) . In communities where there is a high rate of active TB cases, the occupational TB screening program may identify individuals who were infected in the community rather than in an occupational setting. Liaison between the health care facilities TB program and the public health authorities will be required to determine if this situation exists.

Screening is "the presumptive identification of unrecognized disease or defect by the application of tests, examinations or other procedures that can be applied rapidly. Screening tests identify apparently well persons who probably have a disease from those who probably do not. A screening test is not intended to be diagnostic. Persons with positive or suspicious findings must be referred to their physicians for diagnosis and necessary treatment" (40) .

Surveillance is the continuing scrutiny of all aspects of occurrence and spread of a disease that are pertinent to effective control. This includes the systematic collection and evaluation of morbidity and mortality reports, special reports describing any results of outbreak investigations, isolation and identification of infectious agents by laboratories and information regarding infection levels in the population (screening programs). Data such as these should be summarized into a report that is distributed to all who need to know the results of surveillance activities (40) .

The objectives of HCW TB screening and surveillance programs are as follows:

to establish the HCW's current TB infection status;
to identify HCWs with inactive TB infection and, when appropriate, to offer them preventive therapy to decrease their risk of developing active TB;
to identify HCWs with active TB and ensure that they are appropriately treated;
to document conversion rates, i.e., negative to positive;
to determine if the HCWs identified above acquired their infection within the facility or from the community;
to ensure public health authorities are notified, as required; and
to monitor the effectiveness of the TB management program.

To achieve these objectives, it is necessary to develop and maintain a HCW TB screening and surveillance program and ensure appropriate follow-up of all tested individuals (see Figure 5 and 6). This will require collaboration between the health care facility, the public health authorities and the physician providing ongoing personal health care.

FIGURE 5
Pre-Placement and Initial Screening Tests

FIGURE 6
Initial and Ongoing TST Screening

N.B. The term health care workers (HCWs) refers to all paid and unpaid persons working in the health care facility (including health care facility staff, physicians, volunteers and students).

Designated personnel (e.g., those in the occupational health department) should be responsible for the TB screening and surveillance program. Results of screening must be recorded on the HCW's record as well as summarized in TB surveillance program data.

All HCWs (pre-placement and presently employed) should have their TB infection status documented. Ideally, this is performed at initiation of employment. Results of TST testing should be reported in millimetres (mm) and interpreted to be either a negative or positive TST (see Appendix B). Results of clinical investigations (e.g., chest x-rays) of HCWs who are known to have a documented positive TST test, or to have inactive or active TB should also be documented. Results of ongoing screening tests should also be recorded.

Health care facilities cannot preclude hiring people because of their TB infection status. However, local ordinances may enable health care facilities to require documentation of TB infection status from all employees, physicians, students and volunteers in order to protect the health of other workers and patients.

Employers have reported greater success in encouraging HCWs to participate in screening programs when screening is performed in conjunction with some other required activity (e.g., orientation, before identification is issued or re-issued, mandatory updating of certification in cardiovascular resuscitation). Personnel responsible for the TB screening and surveillance program need to elicit the cooperation of supervisors to ensure adherence to screening and surveillance program requirements.

1. Pre-Placement and Baseline Screening

All HCWs in all health care facilities must be assessed for their TB infection status upon hiring. The TB infection status of current employees must also be on record. HCWs who are not directly employed by the health care facility (e.g., students, volunteers, physicians) must provide documentation of their TB infection status prior to starting work in the health care facility. Documentation must indicate whether the HCW is TST negative or positive (include size of reaction recorded in millimeters) and whether the HCW has received preventive therapy for inactive TB or treatment for active TB.

Screening to be performed at pre-placement or verification of current TB infection status
Initial HCW screening tests should be performed as outlined in Figure 5 and Appendix B.

After a two-step TST has been documented, all future testing will require only one TST. Although it is not harmful to the HCW to repeat a two-step TST, it is not necessary to do so.

Rationale for two-step testing: the boosting phenomena
Two TST tests are required because the immune system loses its ability to produce a positive TST reaction over time and may require an additional stimulus to "boost" a limited response. A "boosting" phenomenon occurs because the antigenic stimulus of the first TST test causes the immune system, in someone previously infected in whom immunity has waned, to recover its ability to generate a positive TST response in subsequent testing.

Example: An individual was unknowingly exposed to and infected with M. tuberculosis as a child. The individual had their first TST as an adult and the response was negative. A year later, this person was documented to have a 12 mm TST (positive response). The assumption is that this individual has been exposed to someone with active TB since the last test. This assumption may be in error. If a second TST had been applied 7 to 21 days after the first test, the individual might have been documented as having a 12 mm response due to the boosting phenomenon. If the second test had been performed 7 to 21 days after the initial negative test, it would have been recognized that the individual had boosted, that he or she had been exposed to someone with TB in the past and should be followed in the screening program as being TST positive.

Ideally, TST testing should be performed so that the boosting phenomenon can be distinguished from conversion reactions. Performing the second test 7 to 21 days after the first test decreases the risk of interpreting the second test, when positive, as being the result of new infection (e.g., a TST conversion). Boosting can be reliably demonstrated 7 days after the first TST in immunocompetent individuals.

Individuals who are immunocompromised and infected with M. tuberculosis may not be able to develop a positive TST.

Repeated TSTs in an individual without prior infection or BCG vaccination will not lead to a positive test result.

Performing a two-step TST
A TST test is applied and read. If this first test is negative, a second skin test is applied 7 to 21 days later. The results of the second test are used to determine if the individual's TB infection status is positive or negative (see Appendix B). Individuals found to be positive should be assessed as outlined in Figure 5. If the first test is positive, the person is documented as being TST positive and a second test is not given. The individual should be assessed as outlined in Figure 5.

Response to individuals with positive TST results
All individuals with positive TST reactions should be investigated clinically and be informed about their risk of developing active TB (see Table 2) and issues pertinent to taking INH preventive therapy (see Section IV.D.7 and Appendix C). Preventive therapy should be initiated only when active TB has been excluded. HCWs found to have active TB should be treated as outlined in Appendix D. Public health authorities should be notified.

Table 2 Risk of Future TB Disease in Persons with a Positive TST Reaction
TB reactors of unknown duration who > 5 years old with no additional risks	0.1% per year are
Newly infected persons:
- recent significant skin test	3%-5% in the first year
- household contact	2.5%-5% in the first year
Abnormal chest radiograph in an individual with inadequate past therapy (implies a large residual bacillary load)	1%-4.5% per year
Chronic medical conditions	Risks are increased but estimates not available
HIV+	14% over 2 years
(Reprinted from the Am Fam Physician 1991;43:463).

2. Ongoing Surveillance Programs for HCWs

Ongoing surveillance for TB in HCWs includes BOTH regular ongoing screening of HCWs (see this section) and post-exposure screening (see Section IV.D.7). All HCWs who have a negative TST should undergo TST screening as outlined below. HCWs who have previously been treated for TB, were given preventive therapy for TB or have a documented positive TST should not undergo further TST testing or routine chest x-rays. They should be educated regarding the symptoms of active TB and instructed to seek medical evaluation as soon as possible if these symptoms develop.

Determining the frequency of ongoing surveillance programs for HCWs
Table 3 indicates the recommended frequency of ongoing HCW TB screening based on the health care facility risk and activity risk (see Section IV.B).

Cluster events or unexpectedly high TST conversion rates
Table 3 provides a general guide to the frequency of ongoing HCW screening. However, ongoing HCW TST screening may reveal the occurrence of cluster events. A cluster event is considered to have occurred when two or more TST conversions are documented within a 3-month period among HCWs in a specific area or occupational group and when epidemiologic evidence suggests transmission within the facility (36) . A cluster event may also be considered to have occurred when the conversion rate is 1 HCW in 1,000 per year and when epidemiologic evidence suggests transmission within the facility.

If either or both of these situations is documented during routine TST testing of HCWs:

the source and circumstances of transmission should be identified, if possible, and changes in the TB management program instituted, if required;
further HCW testing should occur every 3 months for at least two consecutive periods until no further TST conversions are documented;
once no further conversions are documented, the frequency of ongoing TST testing may return to the pre-cluster screening frequency; and
public health authorities should be notified.

Record keeping
The occupational health service or a designated staff member should keep records of the results obtained from TST screening or the documented TST status provided by HCWs and record and update changes in the health status of HCWs. The confidentiality of these records must be maintained while complying with provincial regulations to report individuals with new inactive or active TB. Essential information includes the following:

job title, position, locations, hours worked;
date of employment or beginning of work in the health care facility;
documentation of TB status performed at pre-placement or at the start of the TB screening program;
results of regular ongoing TST screening;
record of TB exposure results of post-exposure screening;
management plans for follow-up and/or therapy for infected individuals;
education provided; and
counselling provided.

Table 3 Frequency of Ongoing HCW Surveillance for TB
Activity Risk	Health Care Facility Risk
	High*	Low Þ
High¹	every 6 months	annually
Intermediate²	annually	post-exposure⁴
Low³	post-exposure4	post-exposure⁴

* High a. >or= 6 individuals with TB seen annually or b. 1 or more individuals with TB are seen and the ratio of HCWs to TB cases <or= 100
Þ Low a. < 6 individuals with TB seen annually or b. the ratio of HCWs to TB cases > 100
NOTES: (refer to Section IV.B) 1 High-risk activities include activities of personnel who are involved with cough-inducing procedures, autopsy, morbid anatomy and pathology examinations, bronchoscopy and designated mycobacterium laboratory procedures. 2 Intermediate-risk activities include activities of personnel who have regular direct patient contact and work on units with patients with active TB (all personnel, including housekeepers, clerks and maintenance staff). 3 Low-risk activities include activities of personnel who have minimal patient contact (e.g., working in medical records, administration) or regular patient contact but rarely with patients with TB (e.g., obstetrics, gynecology, neonatal intensive care unit). 4 See Section IV.D.7.

Separate reports should describe the results of post-exposure screening and regular ongoing screening (see Section IV.D.8 and, for an example, Appendix E). These data should be reviewed and reported on an annual basis as part of the health care facility TB risk assessment (see Section IV.I). Computerization of records should facilitate record retrieval and notification of individuals requiring follow-up, but is not essential.

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	Last Updated: 1996-09-24		Important Notices