Table 3 Risk of bias assessment for studies reporting on incidence and prevalence of active TB disease and latent TB infection in health care workers

Adams: Prevalence and determinants of TB infection in health care workers, unpublished

UNCLEAR: Participation in the study was voluntary. 505/764 HCWs participated in the study.

Incidence and prevalence of LTBI and TB disease: LOW (TB diagnosed using standard procedures)

Risk factors for TB: HIGH (HCWs completed questionnaires which are prone to information bias)

UNCLEAR: Community vs. occupational exposure to TB; HIV status of all of the HCWs not known

McCarthy et al. [22]

(linked to Van Rie et al. [23])

UNCLEAR: Participation in the study was voluntary. 120/450 eligible HCWs and 79/296 eligible medical students participated in the study.

Incidence and prevalence of LTBI: LOW (latent TB infection diagnosed using standard procedures)

Risk factors for TB: HIGH (HCWs completed questionnaires which are prone to information bias)

UNCLEAR: Community vs. occupational exposure to TB. However, HIV status of all participants was assessed.

Ayuk et al. [20]

UNCLEAR: Not all HCWs completed questionnaire

Incidence and prevalence of TB disease: LOW

Risk factors for TB: HIGH (HCWs completed questionnaires which are prone to information bias)

UNCLEAR: Community vs. occupational exposure to TB; HIV status of all of the HCWs not known

Claassens et al. [15]

LOW: Although authors report that health care facilities were randomly selected there is no explanation of how the randomisation process was conducted.

Incidence of TB disease: HIGH (In each health care facility a questionnaire was completed by the facility manager to indicate the number of HCWs who were registered in that facility and who had been on TB treatment from January 2006 to December 2008.

UNCLEAR: Community vs. occupational exposure to TB; HIV status of all of the HCWs not known

Dwadwa et al: Health worker access to HIV/TB prevention, treatment and care services in Africa: situational analysis and mapping of routine and current best practices, unpublished

UNCLEAR: Six of the facilities were randomly selected although there is no explanation of how this was conducted. Four of the facilities were specifically selected based on current best practice as recommended by the Department of Health and AIDS and TB Directorates.

Number of TB cases: HIGH (Data obtained from questionnaires and interviews

UNCLEAR: Community vs. occupational exposure to TB

Kranzer et al. [6]

UNCLEAR: It is not clear how the community health workers (CHWs) were selected, if all of the CHW were selected to participate or if participation was voluntary

Prevalence of TB disease: LOW (standard TB diagnostic techniques used)

UNCLEAR: HIV status of all of the HCWs not known

Naidoo et al. [24]

UNCLEAR: Although authors state that a randomly selected sample of dentists was approached to participate in the study, it is not clear how this randomisation process was conducted. Only 78 of the 100 dentists participated

Prevalence of LTBI: LOW (LTBI diagnosed with Mantoux tests)

UNCLEAR: It is not clear where the dentists practiced or the demographics of their patients; Community vs occupational exposure to TB; HIV status of all of the HCWs not known

Balt et al. [26]

LOW: Detailed review of health staff records at the four dedicated TB centres

Incidence of TB disease: LOW

UNCLEAR: Community vs. occupational exposure to TB

Malangu et al. [5]

LOW: A pre-designed data collection form was used to extract data from claims submitted to the Compensation Commissioner from January 2007 to December 2009

Cases of TB disease: LOW (Data based on reported cases of TB. However, it is well known that there is underreporting of TB among HCWs with regards to occupational diseases. This may introduce detection bias and affect the external validity of the study)

UNCLEAR: possible underreporting of TB cases; Community vs occupational exposure to TB; HIV status of all of the HCWs not known

Jarand et al. [25]

LOW: Retrospective case record review of all patients with XDR-TB in Eastern and Western Cape province from 1996 to 2008

UNCLEAR: it is not known how study authors determined whether patients were health care workers

UNCLEAR: Community vs. occupational exposure to TB

Mehtar et al. [29]

LOW: Retrospective review of occupationally acquired TB case reports

Cases of TB disease: LOW (Data based on reported cases of OATB. However, it is well known that there is underreporting of TB among HCWs with regards to occupational diseases. This may introduce detection bias and affect the external validity of the study)

UNCLEAR: Underreporting of TB cases; Community vs occupational exposure to TB; HIV status of all of the HCWs not known

Naidoo et al. [16]

LOW: Retrospective record review. All HCW with TB treated at 8 specified public sector hospitals were included if records confirmed HCW status

Incidence of TB disease: LOW (However, it is possible that HCWs seeking TB treatment may not have stated their occupation, resulting in underreporting of TB cases and information bias)

UNCLEAR: Underreporting of TB cases; Community vs occupational exposure to TB; HIV status of all of the HCWs not known

O’Donnell et al. [17]

UNCLEAR: Although hospital database was used to identify MDR-TB and XDR-TB admissions the study relied on HCW self-reporting their occupation.

Incidence of TB disease: LOW (However, it is possible that HCWs seeking TB treatment may not have stated their occupation, resulting in underreporting of TB cases and information bias)

UNCLEAR: Underreporting of TB cases; Community vs occupational exposure to TB; HIV status of all of the HCWs not known

Tudor et al. [18]

LOW: Data abstracted from occupational health employee medical charts using a standardized chart audit form

Incidence of TB disease: LOW

UNCLEAR: Underreporting of TB cases; Community vs occupational exposure to TB; HIV status of all of the HCWs not known

Van Rie et al. [23]

UNCLEAR: Participation in the study was voluntary. 120/450 eligible HCWs and 79/296 eligible medical students participated in the study.

Prevalence of LTBI: LOW

LTBI was diagnosed using TST and IGRAs

UNCLEAR: Community vs occupational exposure to TB. HIV status of all participants was assessed.

Wilkinson et al. [21]

LOW: Staff TB data was extracted confidentially from the anonymized tuberculosis control programme register.

Incidence of TB disease: LOW (Case ascertainment is known to be complete because tuberculosis treatment cannot be obtained anywhere else in the district and all staff illness episodes are recorded in personnel files)

UNCLEAR: Community vs occupational exposure to TB; HIV status of all of the HCWs not known