PBM Module 4a Evidence-tabel

Evidence table for systematic review of RCTs and observational studies (intervention studies)

Study reference

Study characteristics

Patient characteristics

Intervention (I)

Comparison / control (C)


Outcome measures and effect size


Bartoszko, 2020

SR and meta-analysis of RCTs
Literature search up to March/2020
A: Loeb, 2009
B: MacIntyre, 2011
C: MacIntyre, 2013
D: Radonovich, 2019

Study design: RCT

Setting and Country:
A: Emergency departments, medical units and pediatric units, Canada
B: Emergency departments and respiratory wards, China
C: Emergency departments and respiratory wards, China
D: primary care facilities, dental clinics, adult and pediatric clinics, dialysis units, urgent care facilities and emergency departments, and emergency transport services, USA

Source of funding and conflicts of interest:
Study conducted without financial support
Conflicts of interest not reported

Inclusion criteria SR:
Design: RCT including cluster randomized trials; Intervention: medical masks compared with N95 respirators
Population: healthcare workers
Outcome: viral respiratory infection laboratory confirmed by PCR, serology, or viral culture, laboratory confirmed coronavirus infection, laboratory-confirmed influenza infection, influenza-like illness, clinical respiratory illness, or workplace absenteeism

Exclusion criteria SR:
Not reported

4 studies included

Important patient characteristics at baseline:

A: 446 patients
B: 1441
C: 1669
D: 2862

Time period
A: 2008-2009 influenza season
B: December 2008 – January 2009
C: December 2009 – February 2010
D: 2011-12 – 2014-15

% of healthcare workers that undertook high risk procedures
A: Not reported
B: 33%
C: 73%
D: 60%

Groups comparable at baseline?
No information available

Describe intervention:
A: Medical mask
B: Medical mask
C: Medical mask
D: Medical mask

Describe control:
A: N95
B: N95
C: N95
D: N95

End-point of follow-up:
A: 2008-2009 influenza season
B: December 2008 – January 2009
C: December 2009 – February 2010
D: 2011-12 – 2014-15

For how many participants were no complete outcome data available?
A: not reported
B: not reported
C: not reported
D: not reported

1.laboratory-confirmed viral respiratory infection

Effect measure: OR [95% CI]:
A: 0.97 [0.65; 1.45]
B: 1.96 [0.68; 5.65]
C:1.29 [0.61; 2.70]
D: 1.05 [0.87; 1.26]

Pooled effect (random effects model):
OR 1.06 [95% CI 0.90 to 1.25] favoring N95
Heterogeneity (I²): 0%
RR 1.04 (95% CI 0.92-1.17)

2. laboratory‐confirmed coronavirus infection
A: seasonal coronavirus (OC43, HKU1, 229E, NL63) tested for by PCR
medical masks: 4.3% (9/212)
N95: 5.7% (12/210) (P = .49).

3. Laboratory‐confirmed influenza infection

Effect measure: OR [95% CI]:
A: 1.03 [0.66; 1.61]
B: 2.92 [0.48; 17.59]
C: 0.64 [0.07; 6.15]
D: 0.87 [0.64; 1.18]

Pooled effect (random effects model): OR 0.94 [95% CI 0.73 to 1.20] favoring medical mask
Heterogeneity (I²): 0%
RR 0.95 (95% CI 0.76-1.18)

4. influenza‐like illness
Effect measure: OR [95% CI]:
A: 4.56 [0.97; 21.36]
B: 1.94 [0.27; 13.85]
C: 0.77 [0.15; 3.96]
D: 1.24 [0.87; 1.78]

Pooled effect (random effects model):OR 1.31 [95% CI 0.94 to 1.85] favoring N95
Heterogeneity (I²): 5%
RR 1.33 (95% CI 0.89-1.98)

5. clinical respiratory illness
Effect measure: OR [95% CI]:
B: 1.78 [0.91; 3.49]
C: 1.99 [1.36; 2.92]
D: 1.10 [0.93; 1.30]

Pooled effect (random effects model): OR 1.49 [95% CI 0.98 to 2.28] favoring N95
Heterogeneity (I²): 78%
RR 1.42 (95% CI: 0.90-2.25)

6. workplace absenteeism
A: Medical mask: 19.8% (42/212)
N95: 18.6% (39/210)
This difference was not statistically significant P = .75

The authors report the OR, The RRs are calculated by ourselves.

The authors state they used a random effects model for all outcome measures. However, when calculating the pooled effect using the data from the systematic review it seems that the authors used a fixed effects model for the outcome Influenza-Like Illness

Loeb, 2022

Type of study:
Randomized open label controlled trial

Setting and country: Canada, Israel, Pakistan, and Egypt

Funding and conflicts of interest:
Funding was received from the Canadian Institutes of Health Research, World Health Organization, and Juravinski Research Institute.

The authors declared no conflicts of interest

Inclusion criteria:
Health care workers who provided direct care to patients with suspected or confirmed COVID-19 in specialized COVID-19 units and in emergency departments, medical units, pediatric units, and long-term care facilities

Exclusion criteria:
did not have a valid fit test within the past 24 months or could not pass a fit test, had 1 or more high-risk comorbidities for COVID-19 (hypertension, cardiac disease, pulmonary disease, chronic kidney disease, diabetes, chronic liver disease, actively treated cancer, or immunosuppression due to illness or medications), had a previous laboratory-confirmed clinical diagnosis of COVID-19 at the time of enrollment, or had received 1 or more doses of a COVID-19 vaccine with greater than 50% efficacy for the circulating strain (for example, mRNA or vector-based COVID-19 vaccine against the original SARS-CoV-2 strain)

N total at baseline:
Medical mask: 500
N95 respirator: 509

Important prognostic factors:
Mean age
Medical mask: 34.6±10.2
N95: 24.9±10.9

Medical mask:72.6% F
N.95: 66.7% F

Groups comparable at baseline?

Describe intervention (treatment/procedure/test):

ASTM International certified medical masks

Describe control (treatment/procedure/test):

fit-tested National Institute for Occupational Safety and Health–approved N95 respirator

Length of follow-up:
10 weeks

N =2
1 ineligible based on inclusion criteria
1 withdrew before follow-up

N 2
1 ineligible based on inclusion criteria
1 withdrew before follow-up

Incomplete outcome data: No incomplete outcome data

Outcome measures and effect size (include 95%CI and p-value if available):

Laboratory confirmed COVID-19
Medical mask:
52/497 (10.5%)
47/507 (9.4%)
HR = 1.14 (95% CI 0.77 to 1.69).

The authors conclude that among health care workers who provided routine care to patients with COVID-19, the overall estimates rule out a doubling in hazard of PCR–confirmed COVID-19 for medical masks when compared with HRs of RT-PCR–confirmed COVID-19 for N95 respirators. The subgroup results varied by country, and the overall estimates may not be applicable to individual countries because of treatment effect heterogeneity.