Chapter 14: Prevention and control of tuberculosis transmission in healthcare settings

Figures & data

Table 1. Ventilation recommendations for selected areas in healthcare facilities.

Area/Function	Minimum total ACH ^a			Relative pressurization ^b (CSA 2019)	Exhaust ^b , ^c (CSA 2019)
	CDC 2019 ^49	CSA 2019 ^50	ASHRAE 2021 ^51
AIIR	12	12	12	Negative	Dedicated ^d
Ambulatory care clinic	NA	9	4	Negative ^e	Dedicated ^d
Autopsy (general zone)	12	20	12	Negative ^e	Dedicated ^d
Bronchoscopy	12	20	12	Negative	Required ^f
ED waiting rooms	12	12	12	Negative	Dedicated ^d
ED trauma room, life support	15	15	15	Positive	NR
General diagnostic imaging suites (includes CT, MRI, X-ray, ultrasound)	6 ^g	9	6	Equal	NR
Microbiology laboratory ^h	6	NA	6	NA	NA
Operating rooms	15	20	20	Positive	NR
Anteroom for operating rooms used for patients with airborne infection	NA	9 ^i	NA	Negative to operating rooms and contiguous space ^j	Air removed from anteroom and from the operating rooms shall be exhausted to the outdoors
Patient room in an acute care facility	6	4-6	4 ^k	Equal	NR
Resident room in a LTCH	2	4	2	Equal	NR
Resident gathering areas in a LTCH	4	NA	4	NA	NR
Sputum induction/ pentamidine aerosol administration	NA	NA	12	NA	Local ^l

This table provides key information related to ventilation and does not replace information found in the relevant standards and guidelines. For further details, consult the complete guidelines and/or standards. Adapted from tables in the CDC, ⁴⁹ CSA ⁵⁰ and ASHRAE ⁵¹ documents.

Abbreviations: ACH, air changes per hour; CDC, Centers for Disease Control and Prevention; CSA, Canadian Standards Association; ASHRAE, American Society of Heating, Refrigerating and Air-Conditioning Engineers; AIIR, airborne infection isolation room; NA, not addressed; ED, emergency department; NR, no requirement; CT, computed tomography; MRI, magnetic resonance imaging; LTCH, long-term care home; HVAC, heating, ventilation, and air conditioning; HEPA, high-efficiency particulate air.

a As per CSA, “minimum air change rate can be defined by either the supply or the exhaust depending on the situation. If defined by the exhaust flow rate, supply shall be chosen/configured to ensure consistent air quality and to meet heating and cooling needs. In all cases, the minimum outdoor air change rate shall be maintained.” ⁵⁰

b Recommendations from CSA (2019) ⁵⁰ only. See full versions of ASHRAE (2021) ⁵¹ standard or CDC (2019) ⁴⁹ guideline for further detail on relative pressurization (or pressure relationship) and exhaust (or direction of air movement).

C Clinics/facilities that have rooms where airborne disease is of concern and/or aerosol-producing medical procedures are performed should have ventilation for negative directional airflow for airborne disease prevention (e.g., dedicated exhaust or HEPA-filtered exhaust). ⁵⁰

d An exhaust system that extracts air from spaces or through equipment of similar function that cannot be recirculated or transferred. ⁵⁰

e For patient care areas or an area that is intended for the provision of services that directly supports patient care areas. ⁵⁰

f High-level air separation requirements shall apply. ⁵⁰

g X-ray (diagnostic and treatment). ⁴⁹

h The Canadian Biosafety Standard (Second Edition 2015) describes the HVAC requirements associated with specific laboratory activities (ie, diagnostic or research). ⁵²

i Value extrapolated from “Anterooms for special precautions rooms”. ⁵⁰

j As per CSA, anterooms shall be provided for operating rooms used for patients with airborne infectious disease (e.g., TB). The anteroom pressure shall be maintained negative to both the operating room and the contiguous space; air shall flow from the operating room into the anteroom and from the corridor into the anteroom. ⁵⁰

k For single-bed patient rooms using Group D diffusers, a minimum of 6 total ACH shall be provided and calculated based on the volume from finished floor to 6 feet (1.83 metres) above the floor. ⁵¹

l Rooms or booths used for these procedures shall be provided with local exhaust ventilation designed to capture contaminants as close to the source of emission as possible. ⁵⁰

Table 2. Time needed (by number of air changes per hour) to remove airborne microorganisms after generation of infectious droplet nuclei has ceased. ^a

Air changes per hour	Minutes required for removal of airborne microorganisms
	99% removal	99.9% removal
2	138	207
4	69	104
6	46	69
12	23	35
15	18	28
20	14	21

a This table was adapted from the CDC recommendations. ²⁵

Figure 1. Isolation of patients with, or being evaluated for, respiratory tuberculosis (TB) in healthcare settings.^ASee Section 4.1.3; ^BSee Section 4.1.4; ^CSee Chapter 3: Diagnosis of Tuberculosis Disease and Drug-resistant Tuberculosis; ^DSee Chapter 5: Treatment of Tuberculosis Disease. Abbreviations: AIIR, airborne infection isolation room; IPC, infection prevention and control; PHA, public health authority.

Table 3. Suggested framework for TB transmission risk algorithm and contact follow-up. ^a

Transmission Risk Factors	Transmission Risk Level	Criteria for Contacts
		Patient with low risk of progression to active TB	Patient with high risk of progression to active TB	Staff
Aerosol-generating medical procedure	Very high	Not applicable	Not applicable	Any staff present without appropriate personal protective equipment
Laryngeal TB	Very high	2-12 hours of cumulative exposure in shared air space	2-3 hours of cumulative exposure in shared air space	≥12 hours of cumulative exposure in shared air space
Smear-positive respiratory TB OR cavitation on chest x-ray	High	4-24 hours of cumulative exposure in shared air space	2-12 hours of cumulative exposure in shared air space	4-36 hours of cumulative exposure in shared air space
Smear-negative respiratory TB AND no cavitation on chest x-ray	Low	20-48 hours of cumulative exposure in shared air space	4-24 hours of cumulative exposure in shared air space	20-60 hours of cumulative exposure in shared air space

Abbreviations: TB, tuberculosis .

a Framework adapted from St. Michael’s Hospital (Toronto) Exposure Investigation Guidelines for Patients & Staff Exposed to Pulmonary Tuberculosis (personal communication MP Muller) and Toronto Public Health’s Structured Risk-based Tool for Contact Investigations (see Chapter 11: Tuberculosis Contact Investigation and Outbreak Management). The framework was expanded to include range of exposure durations used by other jurisdictions.

Table 1a. Epidemiological investigations reporting TB exposures in healthcare settings, linked to a health care worker index case

Author, Ref, Year	Setting, Country	Index/Source Case Characteristics	Transmission (Yes/No) & Associated Risks	Study Population & Contact Investigation Details	TB/LTBI Screening & Testing	Transmission Outcomes
Acute Care Settings
Balmelli^15 2014	Acute care hospital Switzerland	Index: HCW from a high TB endemic region found to be infectious due to abrupt onset of productive cough, weakness, and malaise	No HCW did not undergo pre-employment TB screening; lack of baseline TST data limited HCW exposure assessments	All HCW and patients in contact with index for any period of time in the 2 weeks before symptom onset	Questionnaire on demographics, risk factors and duration of contact with index case, 2 step TST, IGRA	Active TB cases linked to exposure event: None TST conversions linked to exposure event: 6 to 10/101 HCW and patient contacts (variability in 2 step TST and IGRA conversions)
Orenstein^35 2013	Acute care hospital Canada	Index: HCW dx with active TB, assumed to be infectious for 6 months prior to diagnosis	No Delivery of care by a HCW with an active TB infection to Oncology and Palliative care patients	All HCWs in contact with index case; all patient and family contacts	Not reported	Active TB cases linked to exposure event: None TST conversions linked to exposure event: 9/121 HCW contacts
Hazard^13 2016	Acute care hospital, nutritional service department employees United States	Index: HCW with no patient contact	Yes Kitchen located in a confined basement of the facility with a dedicated exhaust system independent from healthcare facilities other ventilation systems	All current and former (previous 6 months) staff (limited to kitchen) included in CI; Routine HCW TB screening identified a high frequency of TST conversions in nutritional service employees prompting a CI	Symptom questionnaire, 2 step TST, clinical assessment of contacts with previous positive TST results	Active TB cases linked to exposure event: 4 HCW contacts (nutritional service staff). 1 HCW was identified with MTB + sputum 4 years post exposure event, TST negative during CI and annual screening TST conversions linked to exposure event: 20/224 nutritional service staff contacts Index case confirmed by spoligotype and MIRU
Merte^38 2014	Dental Clinic United States	Index: HCW with active pulmonary TB, female, mid-40 yrs, known untreated LTBI, lived in a high TB endemic region, cough, fever, fatigue, weight loss; 4+ AFB, CXR indicative of infection	No Lack of baseline TST data limited HCW exposure assessments, HCW worked for approx. 6 months while infectious,	HCW, patients, and household contacts of index; 462 patient contacts without previous documented TST	Symptom questionnaire, 2 step TST, clinical evaluation and CXR for contacts with previous positive TST results	Active TB cases linked to exposure event: None TST conversions linked to exposure event: 1/19 HCW contacts, 0/1 household contact
Romagnoli^36 2012	Acute care hospital, Neonatology unit Italy	Index: HCW who worked at multiple healthcare facilities	Yes None reported	All Patient in the maternity ward 3 months before the birth of the index case and 2 days after the last working day of the HCW with active TB	IGRA for newborn contacts > 12moa, and follow-up test at 3 moa; TST, CXR and clinical assessment for contacts with documented positive TST results	Active TB cases linked to exposure event: 1 Patient. dx. with pulmonary extra-pulmonary TB at 4 moa at another hospital TST conversions linked to exposure event: None Active TB cases matched by DNA finger printing
Long-term and Residential Care Settings
Khalil^11 2013	Long-term care and residential care facility Canada	Index: HCW presenting with cough, fever, night sweats, and pleuritic chest pain; immigrant from an endemic region; Baseline TST at hire was documented to be negative Source case: Chart review suggests a resident with active TB may have been symptomatic up to 12 months prior to dx.	Yes Patient care to residents; Baseline TST at hire available for 40% of staff; Ventilation in a tested dining room, common room, and most resident rooms <4 ACH	Residents or staff (including volunteers) who shared indoor airspaces daily and/or >4 hr per week with index case; Family members or visitors who shared indoor airspaces for >2-4 hr per week with index case	2 step TST, CXR for TST positive contacts, and suspicious CXR followed up with chest computerized tomography scan and sputum samples for culture; concentric circle approach to CI	Active TB cases linked to exposure event: 3 resident contacts TST conversions linked to exposure event: 9/121 HCW contacts, 15/146 resident contacts, none among visitor and household contacts Active TB cases matched by genotyping
Mor^37 2018	Nursing Home Israel	Index: HCW from a high TB endemic region found to be infectious following productive cough, fever, malaise, weakness and loss of appetite	Yes Patient care to residents; HCW CXR abnormal but permitted to work at facility	Resident and staff contacts of index case	Symptom screen interview, 2 step TST, concentric circle approach to CI	Active TB cases linked to exposure event: 1 HCW contact and 2 resident contacts TST conversions linked to exposure event: 26/68 resident contacts, 2/32 HCW contacts

Table 1b. Epidemiological investigations reporting TB exposures in healthcare settings, linked to a patient or long-term care resident (patient) index case

Author, Ref, Year	Setting	Index/Source Case Characteristics	Transmission (Yes/No) & Associated Risks	Study Population & Contact Investigation Details	TB/LTBI Screening & Tests	Transmission Outcomes
Acute Care Settings
Bucher^17 2016 Freytag^39 2016 ^A	Acute care hospital Germany & United States	Source: Patient. organ donor treated for TB 40+ years ago, no recent TB symptoms identified Index: Patient. 70 yrs, kidney organ recipient, clinical deterioration at 6 weeks post transplant Index: Patient. 60 yrs, liver transplant recipient, died from TB infection 15.5 months post transplant	Yes Donor derived TB not considered among solid organ transplant recipients; AGMP and invasive medical procedures (e.g. surgical wound debridement, general anesthesia, endotracheal intubation) performed without airborne precautions	Individuals cumulatively exposed to the index patient >40hrs or continuously for >8hrs	Not reported	Active TB cases linked to exposure event: 1 HCW contact. This HCW was excluded from the initial post exposure CI TST conversions linked to exposure event: Not Reported Active TB cases matched by WGS
de Perio^23 2014	Acute care hospital United States	Index: Patient. with pulmonary TB, AFB positive, reported to have difficulty hearing (i.e. required close interactions to interpret communications)	Yes Delay in TB dx. and initiation of IPC measures; patient care (e.g. ED evaluation) performed without airborne precautions; NIOSH assessment identified issues with AIIR pressure sensor calibrations, ACH, direction of air flow and pressure differential (several AIIR did not meet CDC recommendation); doors between anteroom and hallways open when AIIR were occupied	HCW with a TST conversion during outbreak year or self-reporting exposure to index patient; HCW exposures identified by shift records	TST, AFB, staff interviews	Active TB cases linked to exposure event: 1 HCW contact (nursing assistant); 1 household contact (spouse of index case) TST conversions linked to exposure event: 19/41 HCW contacts Report Active TB cases to be related
Grisaru-Soen^14 2014	Acute care Children’s hospital Israel	Index: Patient. 26 day old premature infant with congenital TB, 5 day history of recurrent vomiting and respiratory failure at admission, mother originating from endemic region with suspect diagnosis for pulmonary TB	Yes Delay in TB dx. and initiation of IPC measures; AGMP and patient care (e.g. mechanical ventilation, bronchoalveolar lavage) performed without airborne precautions	NICU PICU patients, staff, or visitors >24 in the same room as index case	TST contacts >5 years of age; physical examination for contacts <3 months of age; CXR; 2 step TST for adult contacts	Active TB cases linked to exposure event: 1 (mother of infant) TST conversions linked to exposure event: 3/35 staff contacts, 1/75 NICU & PICU patient contacts, 3/22 PICU visitors, 8/58 NICU visitors
Holden^18 2018	Acute care hospital, ER and ICU United Kingdom	Index: Patient. 50 yrs, lower respiratory tract infection, history of sustained weight loss, productive cough at admission, marginally housed, CXR showed cavitation	Yes Delay in TB dx. and initiation of IPC measures due to misdiagnosis of pneumonia, AGMP and patient care performed without airborne precautions, Discontinuation of airborne precautions without considering symptoms after 14 days of anti-TB treatment.	All HCW with >4hrs of contact with index Patient, HCW present during AGMP or in close proximity during invasive procedures; family members of HCW with active TB; concentric circle approach to CI	Symptoms questionnaire, IGRA, CXR	Active TB cases linked to exposure event: 1 HCW contact. This HCW was excluded from the initial post exposure CI TST conversions linked to exposure event: 7/8 ICU HCW contacts Active TB cases matched by WGS
Jonsson^24 2013 Kan^40 2013^A	Acute care hospital Denmark	Index: Patient. 50 yrs, HIV+, history of IDU, 6 week history of coughing and weight loss at admission, died at hospital	Yes Delay in TB dx. and initiation of IPC measures due to misdiagnosis of pneumonia, AGMP (e.g. bronchoscopy) and patient care performed without airborne precautions, discontinuation of airborne precautions without sputum analysis results, lack of baseline TST data limited HCW exposure assessments, socialization among ward patients, shared patient rooms, personal care assistance to roommate of index	Initial CI was limited to HCW with major exposure to index patient, then expanded to include all HCW at the ward	TST, IGRA, CXR	Active TB cases linked to exposure event: 3 HCW contacts; 4 patient contacts. 1 HCW was excluded from the initial post exposure CI TST conversions linked to exposure event: 15/36 HCW contacts, 4/15 patient contacts, 5/7 social contacts. Some active TB cases matched by RFLP
Khatami^34 2017	Acute care Children’s hospital and pediatric operating room Australia	Index: Patient. 12 yrs male; 5 day history of acute onset fever, dyspnea, cough, and malaise at admission; CXR abnormal	No Delay in TB dx. and initiation of IPC measures; AGMP and patient care performed without airborne precautions (e.g. daily chest physiotherapy, general anesthesiology, video-assisted thoracoscopic surgery, frequent blood collection, chest drain, central venous catheter insertion, bronchoalveolar lavage); shared patient rooms; lack of baseline TST data limited HCW exposure assessments	HCW assessed to be close contacts of index case; patients who shared a room with the index case >8 hrs; concentric circle approach to CI	2 step TST and IGRA, CXR and assessment at chest clinic for contacts with documented positive TST	Active TB cases linked to exposure event: None TST conversions linked to exposure event: Initial CI group 4/38 HCW contacts and expanded CI group 2/51 HCW contacts (physiotherapists and anesthesiologists)
Medrano^12 2014	Acute care hospital United States	Index: Patient. mid 20 yrs, HIV+, history of being marginally housed, prison inmate admitted to hospital, died at hospital, previously infected and treated for another TB strain, PCR positive for MTB but no viable samples for genotyping Source: inmate from the same jail who shared the same holding cell for <10 hrs	Yes Delay in TB dx. and initiation of IPC measures due to misdiagnosis of pneumonia; inadequate respiratory risk assessment at admission; patient often walked the halls of the hospital floor	All HCW, correctional staff, patients, and visitors to the floor housing the index case NOTE: Routine HCW TB screening identified a high frequency of TST conversions prompting the CI	TST, IGRA, TB symptom screen for contacts with documented positive TST results, CXR and sputum culture for symptomatic contacts	Active TB cases linked to exposure event: 3 HCW contacts (2 nurses and a social workers); 6 other hospital contacts (patients, visitors, correctional staff) TST conversions linked to exposure event: 87/318 of all hospital contacts; 23/30 HCW contacts (on the same floor as index case); 12/67 patient and visitor contacts Active TB cases (with positive culture results) matched by WGS
Townes^41 2016	Ambulatory care United States	Index: Patient. at Rheumatology clinic on immunosuppressive medication, cough	No Delay in TB dx. and initiation of IPC measures due to misdiagnosis of pneumonia; inadequate respiratory risk assessment at clinic visit	Anyone who shared the clinic airspace with index case >2hrs	Symptom assessment; 2 step TST and/or IGRA; CXR and symptom assessment for contacts with previous positive IGRA results	Active TB cases linked to exposure event: None TST conversions linked to exposure event: None among HCW and patient contacts; 7/17 community contacts
Long-term and Residential Care Settings
Harris^22 2013	Long-term care facility joined to an Acute care hospital United States	Index: LTC resident 68 yrs, male with a history of laryngeal cancer, diabetes, hypertension, COPD, cerebrovascular accident, abnormal CXR 9 months prior to TB dx.	Yes Delay in TB dx. and initiation of airborne precautions; AGMP without airborne precautions (e.g. repeated mucus/secretion suction, routine tracheostomy care; re-insertion of tracheostomy tube); shared negative pressure room <2-3hrs ACH with airflow from index to secondary case; group dinning and recreation activities among LTC residents	Resident/patient, visitor and staff contacts of index case in LTC (ventilator-dependent care and sub-cute care units); Hospital staff and patient contacts of index case	TST and IGRA, sputum sample culture, clinical assessment, CXR recommended for LTC contacts	Active TB cases linked to exposure event: 2 resident contacts (a roommate of index case, and a resident of a room across the hall from index at LTC site) TST conversions linked to exposure event: 7/64 patient or resident contacts, 5/239 HCW contacts (LTC staff). No TST conversions among hospital contacts Active TB cases matched by RFLP

^A-Companion articles. Articles identified as companion articles provide supplementary information about a specific epidemiological investigation. Where such articles exist, the additional information is included in the table.

Table 1c. Observational studies reporting on TB exposures in healthcare settings

Author, Ref, Year	Setting, Country	Study Population	Transmission (Yes/No) & Associated Risks	Transmission Outcomes
Uppal^20 2014	Acute care hospital Canada	All HCW, Patient and Visitor exposures to active TB cases (n = 15) at the hospital in 2011; Ten significant exposures identified among (n = 7) active TB infections	No Delay in TB dx. and initiation of airborne precautions; Advanced age, atypical presentation of TB infection, comorbid infections, errors in ordering and interpreting microbiological or CXR results	Root cause analysis found 70% of the significant exposure incidents among active TB patients were linked to delay in TB dx. and initiation of airborne precautions No TST conversions among HCW following significant exposures identified
de Vries^16 2017	Not specified Netherlands	HCW with TB identified in a national registry (n = 131), analysis of factors contributing to infection transmission from patients to HCW	Delay in TB dx. led to TB infection transmissions among 47% of HCW in the sample	24% of TB cases (n = 32) in registry were categorized as transmissions in healthcare settings, between patients and HCW; majority linked to delays in TB dx. Roles of HCW infected with TB at the workplace were nurse (n = 15), medical doctor (n = 6), bronchoscopy assistant (n = 3), autopsy assistant (n = 3), medical equipment sterilisation assistant (n = 2), laboratory assistant (n = 1), pathology assistant (n = 1), and medical assistant (n = 1)
Muzzi^21 2014	Acute care hospital Italy	HCW exposures (n = 388) to pulmonary and respiratory TB patients (n = 14) due to delayed dx. or airborne precautions	Patient comorbidities linked to delayed dx. cirrhosis, advanced cancer, chronic kidney disease, HIV and diabetes	TST conversions linked to exposure event: 3.7% (n = 9) of exposed HCW assumed TST negative at baseline (n = 255), were positive at 3 months post exposure by 2 step TST
Schepisi^10 2015	Various acute & outpatient healthcare settings Multiple countries	HCW diagnosed with respiratory active TB (n = 177) among studies reporting confidence interval outcomes	Yes Medical procedures linked to transmission were tooth extractions and hemodialysis	Meta-analysis estimated active TB among exposed individuals to be: 0.11% (95% Confidence Interval 0.04–0.21) for infants, 0.38% (95% Confidence Interval 0.01–1.60) for children, 0.09% (95% Confidence Interval 0.02–0.22) for adults and 0.00% (95% Confidence Interval 0.00–0.38) for HCWs.

Abbreviations: TB, tuberculosis; LTBI, latent TB infection; HCW, health care worker; TST, tuberculin skin test; IGRA, interferon-gamma release assay; dx, diagnosis; CI, contact investigation; MTB, mycobacterium tuberculosis; MIRU, mycobacterial interspersed repetitive units; AFB, acid-fast bacillus; CXR, chest radiograph; Patient, patient; moa, months of age; DNA, Deoxyribonucleic acid; ACH, air changes per hour; AGMP, aerosol-generated medical procedure; WGS, whole genome sequencing; IPC, infection prevention and control; ED, emergency department; NIOSH, National Institute for Occupational Safety and Health; AIIR, airbone infection isolation room; CDC, Centers for Disease Control and Prevention; NICU, neonatal intensive care unit; PICU, pediatric intensive care unit; ER, emergency room; ICU, intensive care unit; HIV, human immunodeficiency virus; IDU, injecting drug user; RFLP, Restriction fragment length polymorphism; PCR, polymerase chain reaction; LTC, long-term care; n, number.

Table 2a. Tuberculosis (TB) exposures in healthcare or long-term care settings linked to absent or sub-optimal baseline TB screening in health care workers (HCWs)

Research Question: Have absent or sub-optimal baseline TB screening in HCWs been linked to TB exposures in healthcare or long-term care facilities? This body of evidence informs Chapter 14 recommendations on HCW testing and treating for TB infection
Study	Setting	Trans- mission	Study Design	Quality	Directness	Critical Appraisal Results^A
Balmelli^15 2014	Acute	No	Weak	Medium	Direct	Study Number: Three epidemiological investigations provide limited evidence of a TB exposure from an infectious HCW in a health care setting, and link exposures to absent or sub-optimal baseline TB screening. Furthermore, Jonsson et al. reports that a contact investigation of exposed HCW was limited due to missing baseline tuberculin skin test data. Study Quality: The identified studies were assessed to be of low to medium quality by two appraisers. Consistency of Results: Three studies consistently identified missing or sub-optimal screening of HCWs upon hire as primary and attributed causes of exposure. This evidence is considered consistent. Directness: These studies report missing or sub-optimal baseline screening of HCW to have led to TB transmission from infectious HCWs to colleagues and other patients. The remaining study (Jonsson et al.) provides indirect evidence that baseline TB testing data is valuable to post-exposure contact investigations. Generalizability: Overall, this evidence is generalizable to Canadian hospital and long-term care settings. Strength of Body of Evidence: Weak to Moderate
Khalil^11 2013	LTC	Yes	Weak	Low	Direct
Mor^37 2018	LTC	Yes	Weak	Low	Direct
Jonsson^24 2013	Acute	Yes	Weak	Medium	Extrapolation
Overall			Weak	Low - Medium	Direct

^ARating the quality of the overall body of available evidence for specific recommendations was conducted using the Public Health Agency of Canada Critical Appraisal Toolkit (CAT). Moralejo D, Ogunremi T, Dunn K. Critical Appraisal Toolkit (CAT) for assessing multiple types of evidence. Can Commun Dis Rep. 2017;43(9):176-81. https://doi.org/10.14745/ccdr.v43i09a02

Table 2b. Tuberculosis (TB) risk (latent or active TB infection) among health care workers (HCWs) compared to non-HCW populations in low-incidence countries

Research Question: Is TB risk (latent or active TB infection) among HCWs in low-incidence counties higher when compared to the general population? This body of evidence informs Chapter 14 recommendations on HCW testing and treating for TB infection
Study	Country	HCW vs. non-HCW	Study Design	Quality	Directness	Critical Appraisal Results^A
Diel^77 2018	Germany	Higher TB risk	Weak	Medium	Extrapolation	Study Number: Five studies report on TB risk among HCWs vs. non-HCW or general population groups. Three studies used population-based surveillance data, providing direct evidence that TB risk is similar between HCWs and non-HCWs, and any identified differences were not statistically significant. Two studies provide evidence that can be extrapolated to describe TB risk among HCWs. Youakim compared TB occupational compensation claims in British Columbia, Canada from 1999-2008, and found registered nurses to be at increased risk of TB infection claims, compared to other occupation groups. An analysis of TB clusters by Diel et al. found HCW were more likely to be associated with a case cluster linked to transmission at work, compared to non-HCWs. Study Quality: Included studies were assessed to be of medium quality Consistency and Directness of Results: The three studies providing direct evidence are consistent, concluding no evidence of elevated TB risk among HCWs, compared to non-HCWs. Two studies provide evidence that can be inferred to suggest that HCWs, such as nurses, are at increased risk for occupational TB exposures and transmissions. Generalizability: Overall, this evidence is generalizable to Canadian hospital and long-term care settings. Strength of Body of Evidence: Moderate Note: A systematic review by the World Health Organization found TB risk to be elevated among HCW compared to the general public in high and low burden countries. However, this review was not limited to recent evidence (inclusion criteria: studies published after 1946)
Davidson^4 2017	United Kingdom	Similar TB risk	Moderate	Medium	Direct
Gehanno^9 2017	France	Similar TB risk	Weak	Low	Direct
Lambert^6 2012	United States	Similar TB risk	Weak	Medium	Direct
Youakim^8 2016	Canada	Higher TB risk	Weak	Medium	Extrapolation
Overall		Similar TB risk	Weak	Medium	Direct

^ARating the quality of the overall body of available evidence for specific recommendations was conducted using the Public Health Agency of Canada Critical Appraisal Toolkit (CAT). Moralejo D, Ogunremi T, Dunn K. Critical Appraisal Toolkit (CAT) for assessing multiple types of evidence. Can Commun Dis Rep. 2017;43(9):176-81. https://doi.org/10.14745/ccdr.v43i09a02

Table 2c. Tuberculosis (TB) exposures linked to delayed diagnosis and initiation of airborne precautions in patients or residents

Research Question: Have delayed diagnosis of TB and initiation of airborne precautions in patients or residents been linked to TB exposures in healthcare or long-term care facilities? This body of evidence informs Chapter 14 recommendations and good practice statements on identifying individuals with respiratory TB in the healthcare settings.
Study	Setting	Trans- mission	Study Design	Quality	Directness	Critical Appraisal Results^A
de Perio^23 2014	Acute	Yes	Weak	Medium	Extrapolation	Study Number: Ten observational studies, nine outbreak investigations and a single cross-sectional study, provide evidence to support delayed diagnosis and initiation of airborne precautions among active TB cases can lead to TB transmission in healthcare settings. In many of the reported investigations, at least one active TB infection among investigated contacts was linked to an index patient with a missed or delayed diagnosis by common epidemiology or infection strain. The cross-sectional study by Uppal et al., reports atypical presentation of TB infections and delays in TB diagnosis as the root causes of many TB exposures identified in a single healthcare facility. Study Quality: Across studies, quality was variable, from low to medium. Consistency of Results: The majority of studies were from acute care settings, but exposure events, contact investigations and findings were variable. All of the included studies identified delays in diagnosis and initiation of airborne precautions as infection prevention and control gaps linked to exposure event. Directness: These studies provide direct evidence to confirm TB transmission in healthcare settings due to gaps in infection prevention and control measures linked to exposure events, particularly delays in diagnosis and prompt initiation of airborne precautions. Generalizability: Overall, this evidence is generalizable to Canadian hospital and long-term care settings. Strength of Body of Evidence: Moderate
Grisaru-Soen^14 2014	Acute	Yes	Weak	Low	Direct
Holden^18 2018	Acute	Yes	Weak	Low	Direct
Jonsson^24 2013	Acute	Yes	Weak	Medium	Direct
Kan^40 2013	Acute	Yes	N/A	N/A	Extrapolation
Khatami^34 2017	Acute	No	Weak	Low	Direct
Medrano^12 2014	Acute	Yes	Weak	Medium	Direct
Townes^41 2016	Outpatient	No	Weak	Low	Direct
Uppal^20 2014	Acute	No	Weak	Medium	Direct
Harris^22 2013	LTC	Yes	Weak	Low	Direct
Overall			Weak	Medium	Direct

^ARating the quality of the overall body of available evidence for specific recommendations was conducted using the Public Health Agency of Canada Critical Appraisal Toolkit (CAT). Moralejo D, Ogunremi T, Dunn K. Critical Appraisal Toolkit (CAT) for assessing multiple types of evidence. Can Commun Dis Rep. 2017;43(9):176-81. https://doi.org/10.14745/ccdr.v43i09a02

Table 2d. Tuberculosis (TB) exposures due to premature discontinuation of airborne precautions

Research Question: Have premature discontinuation of airborne precautions in patients or residents been linked to TB exposures in healthcare or long-term care facilities? This body of evidence informs Chapter 14 recommendations on identifying individuals with respiratory TB in the healthcare setting
Study	Setting	Trans- mission	Study Design	Quality	Directness	Critical Appraisal Results^A
Holden^18 2018	Acute	Yes	Weak	Low	Extrapolation	Study Number: Three epidemiological investigations report premature discontinuation of airborne precautions linked to exposure. Study Quality: Study quality between the two studies reporting primary evidence was low to medium. Consistency of Results: Both studies report premature discontinuation of airborne precautions. In one instance, airborne precautions were discontinued before sputum analysis. In the other, airborne precautions were removed from a still-infectious patient who completed 14 days of effective therapy but remained symptomatic. Directness: One study provides direct evidence of missing smear negative sputum. The other study provides extrapolated evidence that suggests sputum smear positivity was not considered when airborne precautions were removed, as the only consideration for discontinuation was completion of treatment. Generalizability: Overall, this evidence is generalizable to Canadian hospital and long-term care settings. Strength of Body of Evidence: Weak
Jonsson^24 2013	Acute	Yes	Weak	Medium	Direct
Kan^40 2013	Acute	Yes	N/A	N/A	Extrapolation
Overall			Weak	Low	Extrapolation

^ARating the quality of the overall body of available evidence for specific recommendations was conducted using the Public Health Agency of Canada Critical Appraisal Toolkit (CAT). Moralejo D, Ogunremi T, Dunn K. Critical Appraisal Toolkit (CAT) for assessing multiple types of evidence. Can Commun Dis Rep. 2017;43(9):176-81. https://doi.org/10.14745/ccdr.v43i09a02

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