Personal protective equipment for preventing highly infectious diseases due to exposure to contaminated body fluids in healthcare staff
In epidemics of highly infectious diseases, such as Ebola, severe acute respiratory syndrome (SARS), or coronavirus (COVID‐19), healthcare workers (HCW) are at much greater risk of infection than the general population, due to their contact with patients' contaminated body fluids. Personal protective equipment (PPE) can reduce the risk by covering exposed body parts. It is unclear which type of PPE protects best, what is the best way to put PPE on (i.e. donning) or to remove PPE (i.e. doffing), and how to train HCWs to use PPE as instructed.
To evaluate which type of full‐body PPE and which method of donning or doffing PPE have the least risk of contamination or infection for HCW, and which training methods increase compliance with PPE protocols.
We searched CENTRAL, MEDLINE, Embase and CINAHL to 20 March 2020.
We included all controlled studies that evaluated the effect of full‐body PPE used by HCW exposed to highly infectious diseases, on the risk of infection, contamination, or noncompliance with protocols. We also included studies that compared the effect of various ways of donning or doffing PPE, and the effects of training on the same outcomes.
Data collection and analysis
Two review authors independently selected studies, extracted data and assessed the risk of bias in included trials. We conducted random‐effects meta‐analyses were appropriate.
Earlier versions of this review were published in 2016 and 2019. In this update, we included 24 studies with 2278 participants, of which 14 were randomised controlled trials (RCT), one was a quasi‐RCT and nine had a non‐randomised design.
Eight studies compared types of PPE. Six studies evaluated adapted PPE. Eight studies compared donning and doffing processes and three studies evaluated types of training. Eighteen studies used simulated exposure with fluorescent markers or harmless microbes. In simulation studies, median contamination rates were 25% for the intervention and 67% for the control groups.
Evidence for all outcomes is of very low certainty unless otherwise stated because it is based on one or two studies, the indirectness of the evidence in simulation studies and because of risk of bias.
Types of PPE
The use of a powered, air‐purifying respirator with coverall may protect against the risk of contamination better than a N95 mask and gown (risk ratio (RR) 0.27, 95% confidence interval (CI) 0.17 to 0.43) but was more difficult to don (non‐compliance: RR 7.5, 95% CI 1.81 to 31.1). In one RCT (59 participants) coveralls were more difficult to doff than isolation gowns (very low‐certainty evidence). Gowns may protect better against contamination than aprons (small patches: mean difference (MD) −10.28, 95% CI −14.77 to −5.79). PPE made of more breathable material may lead to a similar number of spots on the trunk (MD 1.60, 95% CI −0.15 to 3.35) compared to more water‐repellent material but may have greater user satisfaction (MD −0.46, 95% CI −0.84 to −0.08, scale of 1 to 5). According to three studies that tested more recently introduced full‐body PPE ensembles, there may be no difference in contamination.
Modified PPE versus standard PPE
The following modifications to PPE design may lead to less contamination compared to standard PPE: sealed gown and glove combination (RR 0.27, 95% CI 0.09 to 0.78), a better fitting gown around the neck, wrists and hands (RR 0.08, 95% CI 0.01 to 0.55), a better cover of the gown‐wrist interface (RR 0.45, 95% CI 0.26 to 0.78, low‐certainty evidence), added tabs to grab to facilitate doffing of masks (RR 0.33, 95% CI 0.14 to 0.80) or gloves (RR 0.22, 95% CI 0.15 to 0.31).
Donning and doffing
Using Centers for Disease Control and Prevention (CDC) recommendations for doffing may lead to less contamination compared to no guidance (small patches: MD −5.44, 95% CI −7.43 to −3.45). One‐step removal of gloves and gown may lead to less bacterial contamination (RR 0.20, 95% CI 0.05 to 0.77) but not to less fluorescent contamination (RR 0.98, 95% CI 0.75 to 1.28) than separate removal. Double‐gloving may lead to less viral or bacterial contamination compared to single gloving (RR 0.34, 95% CI 0.17 to 0.66) but not to less fluorescent contamination (RR 0.98, 95% CI 0.75 to 1.28). Additional spoken instruction may lead to fewer errors in doffing (MD −0.9, 95% CI −1.4 to −0.4) and to fewer contamination spots (MD −5, 95% CI −8.08 to −1.92). Extra sanitation of gloves before doffing with quaternary ammonium or bleach may decrease contamination, but not alcohol‐based hand rub.
The use of additional computer simulation may lead to fewer errors in doffing (MD −1.2, 95% CI −1.6 to −0.7). A video lecture on donning PPE may lead to better skills scores (MD 30.70, 95% CI 20.14 to 41.26) than a traditional lecture. Face‐to‐face instruction may reduce noncompliance with doffing guidance more (odds ratio 0.45, 95% CI 0.21 to 0.98) than providing folders or videos only.
We found low‐ to very low‐certainty evidence that covering more parts of the body leads to better protection but usually comes at the cost of more difficult donning or doffing and less user comfort. More breathable types of PPE may lead to similar contamination but may have greater user satisfaction. Modifications to PPE design, such as tabs to grab, may decrease the risk of contamination. For donning and doffing procedures, following CDC doffing guidance, a one‐step glove and gown removal, double‐gloving, spoken instructions during doffing, and using glove disinfection may reduce contamination and increase compliance. Face‐to‐face training in PPE use may reduce errors more than folder‐based training.
We still need RCTs of training with long‐term follow‐up. We need simulation studies with more participants to find out which combinations of PPE and which doffing procedure protects best. Consensus on simulation of exposure and assessment of outcome is urgently needed. We also need more real‐life evidence. Therefore, the use of PPE of HCW exposed to highly infectious diseases should be registered and the HCW should be prospectively followed for their risk of infection.
Jos H Verbeek, Blair Rajamaki, Sharea Ijaz, Riitta Sauni, Elaine Toomey, Bronagh Blackwood, Christina Tikka, Jani H Ruotsalainen, F Selcen Kilinc Balci
Plain language summary
Protective clothes and equipment for healthcare workers to prevent them catching coronavirus and other highly infectious diseases
Healthcare workers treating patients with infections such as coronavirus (COVID‐19) are at risk of infection themselves. Healthcare workers use personal protective equipment (PPE) to shield themselves from droplets from coughs, sneezes or other body fluids from infected patients and contaminated surfaces that might infect them. PPE may include aprons, gowns or coveralls (a one‐piece suit), gloves, masks and breathing equipment (respirators), and goggles. PPE must be put on correctly; it may be uncomfortable to wear, and healthcare workers may contaminate themselves when they remove it. Some PPE has been adapted, for example, by adding tabs to grab to make it easier to remove. Guidance on the correct procedure for putting on and removing PPE is available from organisations such as the Centers for Disease Control and Prevention (CDC) in the USA.
This is the 2020 update of a review first published in 2016 and previously updated in 2019.
What did we want to find out?
We wanted to know:
what type of PPE or combination of PPE gives healthcare workers the best protection;
whether modifying PPE for easier removal is effective;
whether following guidance on removing PPE reduced contamination;
whether training reduced contamination.
What did we find?
We found 24 relevant studies with 2278 participants that evaluated types of PPE, modified PPE, procedures for putting on and removing PPE, and types of training. Eighteen of the studies did not assess healthcare workers who were treating infected patients but simulated the effect of exposure to infection using fluorescent markers or harmless viruses or bacteria. Most of the studies were small, and only one or two studies addressed each of our questions.
Types of PPE
Covering more of the body leads to better protection. However, as this is usually associated with increased difficulty in putting on and removing PPE, and the PPE is less comfortable. Coveralls are the most difficult PPE to remove but may offer the best protection, followed by long gowns, gowns and aprons. Respirators worn with coveralls may protect better than a mask worn with a gown, but are more difficult to put on. More breathable types of PPE may lead to similar levels of contamination but be more comfortable. Contamination was common in half the studies despite improved PPE.
Gowns that have gloves attached at the cuff, so that gloves and gown are removed together and cover the wrist area, and gowns that are modified to fit tightly at the neck may reduce contamination. Also, adding tabs to gloves and face masks may lead to less contamination. However, one study did not find fewer errors in putting on or removing modified gowns.
Guidance on PPE use
Following CDC guidance for apron or gown removal, or any instructions for removing PPE compared to an individual’s own preferences may reduce self‐contamination. Removing gown and gloves in one step, using two pairs of gloves, and cleaning gloves with bleach or disinfectant (but not alcohol) may also reduce contamination.
Face‐to‐face training, computer simulation and video training led to fewer errors in PPE removal than training delivered as written material only or a traditional lecture.
Certainty of the evidence
Our certainty (confidence) in the evidence is limited because the studies simulated infection (i.e. it was not real), and they had a small number of participants.
What do we still need to find out?
There were no studies that investigated goggles or face shields. We are unclear about the best way to remove PPE after use and the best type of training in the long term.
Hospitals need to organise more studies, and researchers need to agree on the best way to simulate exposure to a virus.
In future, simulation studies need to have at least 60 participants each, and use exposure to a harmless virus to assess which type and combination of PPE is most protective.
It would be helpful if hospitals could register and record the type of PPE used by their workers to provide urgently needed, real‐life information.
This review includes evidence published up to 20 March 2020.
Jos H Verbeek, Blair Rajamaki, Sharea Ijaz, Riitta Sauni, Elaine Toomey, Bronagh Blackwood, Christina Tikka, Jani H Ruotsalainen, F Selcen Kilinc Balci
Implications for practice
In addition to other infection control measures, consistent use of full‐body personal protective equipment (PPE) can diminish the risk of infection for healthcare workers (HCW). EN (European) and ISO (international) standards for protective clothing and fabric permeability for viruses are helpful to determine which PPE should technically protect sufficiently against highly infectious diseases. However, the risk of contamination depends on more than just these technical factors. In simulation studies, contamination happened in almost all intervention and control arms but seemed to be less in more recent studies.
For choosing between PPE types, there is very low‐certainty evidence, based on single‐exposure simulation studies. Covering more parts of the body leads to better protection but usually comes at the cost of more difficult donning (putting on) or doffing (taking off) and user comfort, and may therefore even lead to more contamination. A powered, air‐purifying respirator (PAPR) with a hood may protect better than an N95 mask with a gown but is more difficult to don.Coveralls may be more difficult to doff. A more breathable fabric may still lead to similar levels of contamination protection to less breathable fabric, and may be preferred by users.
For changes to PPE, there is low‐ to very low‐certainty evidence that adding tabs to gloves or masks or closer fit of gowns at the neck or the wrist may decrease contamination, even though one study could not show a decrease in donning or doffing errors.
For different procedures of donning and doffing, there is very low‐certainty evidence that double gloves, as part of PPE and following Centers for Disease Control and Prevention (CDC) guidelines, and providing users with help or spoken instructions during donning and doffing may reduce the risk of contamination. Extra disinfection of gloves with bleach or quaternary ammonium may decrease hand contamination but not alcohol‐based hand rub.
For various training procedures there is very low‐certainty evidence that more active training (including video or computer simulation or spoken instructions) may increase compliance with instructions compared to passive training (lectures or no added instructions). No studies compared methods to retain PPE skills needed for proper donning and doffing in the long term.
The certainty of the evidence is low to very low for all comparisons because conclusions are based on one or two small studies and a high or unclear risk of bias in studies, indirectness of evidence, and small numbers of participants. This means that we are uncertain about the estimates of effects and it is therefore possible that the true effects may be substantially different from the ones reported in this review.
Implications for research
We concur with the World Health Organization (WHO) that there is a need to carry out a re‐evaluation of how PPE is standardised, designed, and tested (WHO 2018). What is missing is a harmonised set of PPE standards and a unified design for PPE to be used when taking care of patients with highly infectious diseases. This holds for PPE as used for preventing contact transmission as well as other ways of transmission. There is, for example, no unified technical standard for isolation gowns. There is also a need for a more transparent and uniform labelling of infection control measures, such as droplet precautions, and the protection level of PPE for HCW. We believe that this is an important prerequisite for the universal implementation of infection control measures for HCW.
Simulation studies are a feasible and relatively simple way to compare different types of PPE and to find out which protects best against contamination. It is a prerequisite for a reliable answer that methods of simulation studies are standardised in terms of exposure and outcome measurement. We recommend developing a core outcome set (COS) in this field that would provide critical outcomes measures to enable better comparisons and synthesis across trials. Viral marker bacteriophage MS2 seems to be the most sensitive marker and we would advocate using this. Studies should have sufficient power. A sample size of 62 would be needed to be able to detect a relatively large risk ratio of 0.5 with a large control group rate of contamination of 0.7, assuming α = 0.05 and β = 0.80. In addition, it would help evidence synthesis if study authors would better adhere to the appropriate reporting guidelines (Cheng 2016).
To find out how PPE behaves under real exposure, we need prospective follow‐up of HCW involved in the treatment of patients with highly infectious diseases, with careful registration of PPE, donning and doffing and risk of infection. Here, the effect sizes would be smaller and thus the sample size should be bigger than 60.
In addition, case‐control studies comparing PPE use among infected HCW and matched healthy controls, using rigorous collection of exposure data, can provide information about the effects of PPE on the risk of infection. The sample sizes should be much bigger than the current case studies because we would like to detect small but important differences in effect between various combinations of PPE such as gowns versus coveralls. There is a need for collaboration between organisations serving epidemic areas to carry out this important research in circumstances with limited resources, and during the throes of an outbreak.
We also need more randomised controlled studies of the effects of one type of training versus another, to find out which training works best, especially at long‐term follow‐up of one year or more. Here also, the effect size seems to be quite large and thus a sample size of around 60 seems to provide adequate power.