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Healthcare Worker Hand Size Can Impact Bacterial Load, Product Effectiveness

Posted in Articles, Hand Hygiene

By Kelly M. Pyrek

Researchers are advising healthcare professionals to consider the size of their hands when it comes to using alcohol-based hand sanitizer, to ensure adequate coverage by the product. In their study of whether the volume of alcohol-based handrub (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 HCWs' 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 seconds, and then, held up to dry for 3 minutes. After the first contamination procedure, baseline bacterial recovery was obtained using the fingertip 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 World Health Organization (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 4 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 HCWs 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 powerful 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 HCW 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 HCWs with very large hands. We can imagine, in the future, HCWs having their hands measured in their first admission to a health-care 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 HCW 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 antimicrobial 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 HCW hand hygiene compliance is that which is promulgated by the World Health Organization, 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."

Pittet recommends that hospitals everywhere consider participating in the “Hand Sanitizing Relay” activity promoted this year by the World Health Organization to celebrate the 10th anniversary of the “Clean Care is Safer Care” campaign. "The Hand Sanitizing Relay” consisted in having as many HCWs as possible performing a sequential chain of hand hygiene actions according to the 'How to Handrub' technique recommended by the WHO," Pittet says. "HCWs were encouraged to train and practice with their colleagues the WHO 6 step-technique to be able to perform it perfectly during the event, as the gestures were supervised and validated by infection control practitioners. A total of 133 hospitals in 43 countries across all WHO regions registered and completed a relay. More than 15,000 enthusiastic HCWs reported to have participated. (see Feedback from hospitals identified the Hand Sanitizing Relay as an excellent opportunity for team building and reinforcement of team spirit between both infection control practitioners and other HCWs in hospitals. The event was perceived as an excellent informal way to teach, train and raise awareness on the quality of hand hygiene procedures, and to possibly further promote compliance with the WHO My 5 Moments for Hand Hygiene concept. (See AJIC 2015, 43:295-297)."

Reference: Bellissimo-Rodrigues F, Soule H, Gayet-Ageron A, Martin Y and Pittet D.  Should Alcohol-Based Handrub Use Be Customized to Healthcare Workers’ Hand Size? Infection Control & Hospital Epidemiology. December 2015, pp 1-3. DOI: 10.1017/ice.2015.271, Published online Nov. 24, 2015.


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