Hand Hygiene Science Asking New Questions About Product Volume and Hand Coverage

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By Kelly M. Pyrek

As hand hygiene-related science advances, we gain a better understanding of how handwashing contributes to infection prevention. There are unresolved issues, some of which continue to spark debate and new research, and investigators are attempting to answer some of the lingering questions relating to technique, hand size, product volume, and how all these factors impact hand-cleansing efficacy.

For example, Pires, et al. (2017) asserts that the optimal hand-hygiene gesture "remains poorly defined" and sought to evaluate the influence of hand-rubbing duration on the reduction of bacterial counts on the hands of healthcare personnel. The researchers conducted an experimental study in which hand-rubbing was performed for 10, 15, 20, 30, 45, or 60 seconds, according to the World Health Organization (WHO) technique using 3 mL of alcohol-based handrub. Hand contamination with E. coli ATCC 10536 was followed by hand-rubbing and sampling. The researchers looked at the effect on the subject, adjusted for hand size and gender, and analyzed the reduction in bacterial counts after each hand-rubbing action. In addition, hand-rubbing durations of 15 and 30 seconds were compared to assert non-inferiority (0.6 log10). In total, 32 healthcare workers performed 123 trials, and the researchers found that all durations of hand-rubbing led to significant reductions in bacterial counts. However, reductions achieved after 10, 15, or 20 seconds of hand-rubbing were not significantly different from those obtained after 30 seconds. The average bacterial reduction after 15 seconds of hand-rubbing was 0.11 log10 lower than after 30 seconds, demonstrating non-inferiority. The investigators concluded that hand-rubbing for 15 seconds was not inferior to 30 seconds in reducing bacterial counts on hands under the described experimental conditions. There was no gain in reducing bacterial counts from hand-rubbing longer than 30 seconds, and they add that further studies are needed to assess the clinical significance of their findings.

Kampf (2017), in reply to the research conducted by Pires, et al. (2017), confirms that although the researchers did not look at the coverage of both hands after 15 or 30 seconds with a fluorescent dye, "the data nevertheless suggest that once the handrub is fairly distributed to both hands within 15 seconds, further rubbing does not add to the overall efficacy of 60 percent isopropanol." Kampf brings up the issue of the sufficiency of 3 mL, pointing to research by Girard, et al. (2012) that indicated that, based on data from France, the use of 3 mL is regarded by 99.8 percent of healthcare personnel  as sufficient for complete hand coverage. Both Kampf, et al. (2010) and Macinga, et al. (2014) found that by and large, the application of 3 mL keeps hands moist for more than 30 seconds. However, as Kampf (2017) explains, "The other side of this correlation is that a healthcare worker will require a volume between 1.7 and 2.1 mL depending on the type of handrub if hands are to remain moist for 30 seconds. If the setting used by Pires, et al. with 3 mL per application for a 15-second duration were transferred into clinical practice, hands would still be moist after 15 seconds and would need to dry during the next 15 to 45 seconds before further patient-care activities. What would a healthcare worker be able to do during the drying time?"

Kampf (2017) acknowledges that making hand hygiene easier for healthcare workers can boost compliance but is concerned about product volumes: "If hands are rubbed until dry and shorter application times are desired, smaller volumes per application will be needed on average size hands, (e.g., 1.5 or 2 mL). A volume of 1.5 mL is considered sufficient for hand coverage by 95.8 percent of healthcare workers, and a volume of 2 mL is considered sufficient by 98.5 percent. A volume of ~2 mL would also be acceptable to users. Average-sized hands are dry after ~30 seconds. But based on efficacy data obtained with European Standard EN 1500, these volumes usually fail the EN 1500 efficacy requirement with mean log10 reductions between 3.05 and 4.03." As Kampf continues, "Healthcare workers will certainly welcome shorter but equally effective hand disinfection. Recommending a smaller volume, however, should be assured from various viewpoints. This new volume should ensure coverage of both hands; this technique should be easy to perform and be effective on small and large hands. Coverage of hands can quite easily be measured with a fluorescent dye. At the same time, the simplicity of the rub-in technique can be evaluated. These measurements could provide the basis for testing the efficacy of such a change (e.g., according to EN 1500)."

Hand size and its impact on cleansing efficacy with alcohol-based hand sanitizer (ABHR) has been addressed by researchers. In their study of whether the volume of ABHR used by healthcare workers affects the residual bacterial concentration on their hands according to hand size, Bellissimo-Rodrigues and colleagues (2015) found that bacterial reduction was significantly lower for large hands compared with small hands, which suggests a need for customizing the volume of alcohol-based handrub for the most effective hand hygiene. It's an aspect of hand hygiene that many individuals may not have considered until now, according to study co-author Didier Pittet, MD, MS, of the University of Geneva Hospitals and faculty of medicine in Geneva, Switzerland; who says that this is a new topic that has not been fully explored by research.

As the researchers acknowledge, "Over the past 20 years, ABHRs have become the preferential tool for hand hygiene in healthcare settings because of their high antimicrobial efficacy, tolerability, and accessibility. There is common sense and microbiologic evidence that the volume of ABHR used should be large enough to cover the whole surface area of both hands, but there is no consensus on how much is the minimum necessary, and whether healthcare worker (HCW) hand size influences it."

The researchers conducted their laboratory-based experimental study at the University of Geneva Hospitals by recruiting 15 HCWs from the infection control program who had extensive training and expertise in hand hygiene. Two senior infection control experts calculated and classified their hand-surface area as small (=375 cm2), medium (376–424 cm2), or large (=425 cm2). Four participants had small hands, six had medium hands, and five had large hands. The healthcare workers' hands were contaminated with the reference strain Escherichia coli ATCC 10536 to obtain a homogeneous bacterial suspension containing from 2.0 ×108 to 2.0 ×109 colony-forming units/mL.

As Bellissimo-Rodrigues, et al. (2015) explain, prior to each contamination procedure, participants were asked to wash their hands with 5mL of plain soap for 1 minute. Hands were contaminated artificially by inserting them into the bacterial suspension up to the mid-carpals for 5 sec-onds, and then, held up to dry for 3 minutes. After the first contamination procedure, baseline bacterial recovery was obtained using the finger-tip method. As a next step, participants washed their hands, re-contaminated them in the same way as before, and undertook a hand friction action with no ABHR using the WHO-recommended sequence for hand hygiene. Following the process above, a second baseline recovery of bacteria was performed."

After these measurements were taken, study participants applied the reference EN 1500 ABHR (2-propanol 60 percent) varying every 0.5 mL from 0.5 to 3 mL. HCWs with large hands were investigated further with the application of 4, 5, and 6mL of ABHR. At each application stage, the ABHR test volume was dispensed into the dominant hand of the HCW, and then the recommended WHO sequence was followed for 30 seconds. After each action, the surviving bacteria were recovered from the participant’s dominant hand. At the end of the experiment, HCWs were asked to wash their hands with a 2 percent chlorhexidine handwash for 2 minutes. Each sample was studied in a minimum of four different dilutions to accurately estimate bacterial counts. After dilution, 1-mL samples were distributed in tryptic soy agar plates within 30 minutes of recovery and incubated. Bacterial colony-forming units were counted by visual inspection of each plate, adjusted for the corresponding dilution factor, and converted to log10. For each HCW and volume of ABHR applied, a log10 reduction was calculated.

The researchers found that overall, the average level of contamination of hands at baseline was 6.2 (0.58) log10 and there was no difference between the hand size categories. The mean reduction of bacterial count was 0.28 log10 for each additional increase of 0.5 mL of ABHR (95% CI, 0.20–0.36, P <.001). They also report that bacterial reduction was inversely and significantly associated with hand surface area (-0.003 [95% CI, -0.006 to -0.0005], P = .019).

Bellissimo-Rodrigues, et al. (2015) say their study demonstrates a strong relationship between the reduction of bacterial count on hands and the amount of ABHR used for hand hygiene, taking into account the hand-surface area, emphasizing, "It is a matter of concern that healthcare workers with large hands could not achieve a minimum of 2 log10 reduction of bacteria on their hands by the application of 3mL of ABHR, the volume recommended by most manufacturers. That concern gets greater when we realize that the mean application volume of ABHR in clinical practice may be lower than 1 mL.10."

"We are currently trying building a model to answer that very important question but, so far, we don’t have any definitive answer to provide," says Bellissimo-Rodrigues.

The researchers add, "Our results are significant: under the strict experimental conditions of our study design, even one of the most power-ful ABHR available, applied under controlled conditions by trained, supervised experts, did not reach the expected bacterial reduction when the volume applied was not adapted to the hand size, a parameter yet unrecognized in daily clinical practice."

There is a concern that busy hospitals may not take healthcare worker hand sizes into consideration when instructing about proper hand hygiene and the appropriate amount of product needed to kill bacteria.

"This is an issue which clearly needs further research in clinical practice but, so far, we can state that no volume fits all hand sizes and this is already a very important change," Bellissimo-Rodrigues says. "Certainly the 3mL rule is inappropriate, since 3mL seems to be too much for HCWs with small hands and not enough for healthcare workers with very large hands. We can imagine, in the future, healthcare workers having their hands measured in their first admission to a healthcare facility, and then setting up the amount necessary of ABHR for him/her to handrub and clean his/her hands. It is not a measure that should be taken on a daily basis, because it’s not going to change. We can also imagine, in the future, automatic customized dispensers that communicate with the healthcare worker identification badge and dispense a personalized amount of ABHR."

The researchers state that "there is a need to move the issue further forward by improving the quality of hand hygiene technique and anti-microbial efficacy, considering the evidence that a poorly performed hand hygiene action is less effective and may compromise patient safety."

Among the best strategies to boost healthcare worker hand hygiene compliance is that which is promulgated by the WHO, according to Pittet: "We are very confident that the WHO Multimodal Strategy for Improving Hand Hygiene Practices is universally effective, since it has been tested in different scenarios and in many different countries (from high to low-income) with a large variety of cultural background. Recently, a systematic review has been published on that issue by the British Medical Journal (See BMJ 2015 Jul 28;351:h3728). A tool has been developed and issued by WHO in 2009, the Hand Hygiene Self-Assessment Framework (HHSAF, see This is a scoring system that allows each hospital to monitor the level of progress the institution can demonstrate from one year to the next, in its capacity to promote hand hygiene procedures. WHO is currently inviting healthcare facilities worldwide to monitor their capacity to promote good practices: I strongly encourage each institution to participate."

Kampf (2017) asserts that, "It may be time to review some parameters of current efficacy testing standards. Hand size currently has no place in EN 1500. Why not have three subgroups of subjects with small, medium, and large hands, respectively.  Each participant would initially have to determine how much volume is necessary to keep both hands wet (e.g., for 20 or 30 seconds), resulting in a specific test volume per subject and application time. This volume would later be used for efficacy testing against the reference procedure. A second parameter for review may be the type of contamination in EN 1500. Having half of the hands in an E. coli broth is associated with a high organic load on both hands. If the broth contained a black dye, hands would probably be classified as “visibly soiled” and should be washed instead of treated with a handrub (WHO, 2009). A different type of contamination with a high inoculum but a substantially lower amount of organic load may better resemble clinical practice (Macinga, et al. 2011); it may even show that 2 mL of a handrub is very effective."


Technique is also receiving attention from researchers, who debate whether current instruction should be modified. For example, Reilly, et al. (2016) found that the six-step hand-hygiene technique recommended by the WHO is superior to a three-step method suggested by the Centers for Disease Control and Prevention (CDC) in reducing bacteria on healthcare workers’ hands.

"Hand hygiene is regarded as the most important intervention to reduce HAIs, but there is limited evidence on which technique is most effective,” says Jacqui Reilly, PhD, lead author of the study and professor of infection prevention and control at Glasgow Caledonian University in Scotland.  “This study provides a foundation for effective best practices to implement on the frontlines of healthcare.”

During the randomized controlled trial in an urban, acute-care teaching hospital, researchers observed 42 physicians and 78 nurses completing handwashing using an alcohol-based handrub after delivering patient care. The six-step technique was determined to be microbiologically more effective for reducing the median bacterial count (3.28 to 2.58) compared to the three-step method (3.08 to 2.88). However, using the six-step method required 25 percent more time to complete (42.50 seconds vs. 35 seconds).

“One of the interesting incidental findings was that compliance with the six-step technique was lacking. Only 65 percent of providers completed the entire hand hygiene process despite participants having instructions on the technique in front of them and having their technique observed. This warrants further investigation for this particular technique and how compliance rates can be improved,” says Reilly. The re-searchers recommend authors of international guidance should consider this evidence when making official recommendations on best practices in hand hygiene.

Some researchers are suggesting that the WHO recommendations be modified to emphasize cleansing fingertips first, citing evidence that there is a direct relationship between the bacterial burden on healthcare workers' hands and the likelihood of cross-transmission. Bellissimo-Rodrigues and Pires, et al. (2017) conducted a laboratory-based study involving pairs of healthcare personnel. The hands of a healthcare worker (transmitter) were contaminated with E. coli ATCC 10536 before holding hands with another healthcare worker (host) for 1 minute. Meanwhile, the unheld hand of the transmitter was sampled. Afterward, the host’s held hand was also sampled. Each experiment consisted of 4 trials with increasing concentrations of E. coli (103–106 colony-forming units [cfu]/mL). The primary outcome was the likelihood of transmission of at least 1 cfu from transmitter to host.  In total, six healthcare personnel performed 30 experiments and 120 trials. According to the researchers, the bacterial counts recovered from host hands were directly associated with the bacterial counts on transmitter hands (P<.001). The probability of cross-transmission was 8.22 higher when transmitter hand bacterial count was >1 and =3 log10 cfu compared to =1 log10. When transmitter contamination was <1 log10 cfu, no cross-transmission was detected.

Pires and Bellissimo-Rodrigues, et al. (2017) assert that because hands are implicated in the cross-transmission of microbial pathogens and fingertips are the crux of the problem, that a hand-rubbing technique with a fingertips-first emphasis showed greater efficacy than the standard technique in reducing fingertip contamination, potentially improving hand hygiene-action quality. The researchers aimed to evaluate whether modifying the sequence of the WHO “How to Handrub” standard technique to clean the fingertips first would impact the microbiological efficacy of the procedure, in controlled laboratory conditions. Among the 16 participants who were part of the study, four had small (25.0 per-cent), six had (37.5 percent) medium-sized hands and six (37.5%) large-sized hands; 10 (62.5 percent) were women. At baseline, the mean bacterial log10 count in HCWs hands was 6.18 (±SD 0.86). It fell to 3.51 (±1.45) after the WHO standard technique application, and to 2.74 (±1.28) after the application of the WHO fingertips-first technique (p<0.001). After adjustment for the hand size category and gender, the mean reduction of bacterial count on healthcare workers' hands was 0.77 log10 higher following the application of the WHO fingertips-first technique com-pared to the application of the WHO standard technique (p=0.002). As the researchers emphasized, "Starting the WHO handrub sequence by the fingertips decontamination led to greater microbiological efficacy when compared to the WHO standard technique. Our findings deserve further validation in clinical practice, but could potentially enhance patient safety in the healthcare setting."


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