By Kelly M. Pyrek
If having limited resources at your healthcare institution is forcing you to choose one key infection control-related intervention -- either hand hygiene or environmental hygiene -- to get the most return on investment, what would you select? Researchers have developed a model that can help infection preventionists, healthcare epidemiologists and administrators determine which strategies have a better pay-off from a patient safety perspective and can help guide resource-allocation decisions.
As Barnes, et al. (2014) acknowledge, "Hospitalized patients are at risk for acquiring MDROs primarily from the hands of transiently colonized healthcare workers or indirectly from contaminated environmental surfaces. Hand hygiene has long been considered the central tenet of infection prevention aimed at limiting the spread of MDROs as well as susceptible pathogens. More recently, potential pathogens have been found to contaminate the near-patient environment, and environmental contamination has been linked to transmission from one patient to another. Infection prevention strategies to improve hand hygiene compliance and environmental cleaning in the healthcare setting are aimed at reducing this risk of transmission. However, despite knowledge of the importance of these strategies, compliance is notoriously poor … Significant efforts and resources are required to improve compliance in either of these areas, as they both rely on sustained change of behaviors among healthcare personnel. When healthcare facilities are investing limited resources in infection prevention strategies, it would be useful to know which strategy is likely to have the greater impact on preventing transmission; however, the relative impact of each of these strategies is unknown."
Sean Barnes, PhD, assistant professor of operations management in the Robert H. Smith School of Business at the University of Maryland, College Park, and Kerri Thom, MD, MS, associate professor of epidemiology and public health at the University of Maryland School of Medicine, and their colleagues developed an agent-based model of patient-to-patient transmission—via the hands of transiently colonized healthcare workers and incompletely terminally cleaned rooms—in a 20-patient intensive care unit. Their mathematical model was used to investigate the relative impact of each factor on the transmission of Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus, and vancomycin-resistant enterococci.
Barnes, et al. (2014) simulated 175 parameter-based scenarios and compared the effects of hand hygiene and environmental cleaning on rates of multidrug-resistant organism acquisition. They report that for all organisms, increases in hand hygiene compliance outperformed equal increases in thoroughness of terminal cleaning. The researchers explain that from the baseline measurement, a 21 improvement in terminal cleaning compared with hand hygiene was required to match an equal reduction in acquisition rates -- meaning that a 20 percent improvement in terminal cleaning was required to match the reduction in acquisition due to a 10 percent improvement in hand hygiene compliance.
When describing the purpose of their study, Thom notes, "We tried to be very practical. If we were in an ideal world and had all the monetary resources, time and staff available, we would give 100 percent in both hand hygiene and environmental hygiene. But we know that is not the reality, and that there are immense demands on healthcare personnel. Even a well-staffed and resourced hospital still must figure out how it is going to allocate its infection prevention-related efforts and resources. The unfortunate reality is that we can't give 100 percent in both areas all the time, and sometimes we have to make a choice. That's what this paper was about -- to see if there is more bang for your buck in one area than the other -- not to say that one is more important than the other." Thom continues, "What I found comforting was to know that even though hand hygiene had the greatest impact in our model, if you are just looking at it in an isolated way, both strategies are important, especially depending upon the scenario. I think we focus so much effort on hand hygiene because we all know and understand how critical it is, but to see in a mathematical way that environmental hygiene also has an important role, was nice."
Barnes, Thom and their colleagues used agent-based modeling to simulate the interactions between patients, healthcare workers (nurses and physicians) and the healthcare environment. As parameters, they modeled hand hygiene efficacy to be 83 percent on the basis of prior studies, used terminal cleaning only because there is more available data to support its use in practice and its effectiveness in reducing MDRO transmission, and used an average hospital ICU as the setting. Hand hygiene compliance and thoroughness of terminal cleaning were the experimental variables. Baseline levels for hand hygiene compliance depend on healthcare worker type and whether the hand hygiene opportunity occurred on entry to the patient room or on exit. The researchers established baseline rates for hand hygiene compliance of nurses at 70 percent and 85 percent on entry and exit, respectively, and at 57 percent and 67 percent on entry and exit for physicians, respectively, on the basis of observed data from a sample hospital. The baseline level for thoroughness of terminal cleaning was established at 40 percent. The researchers explain that they varied these figures in increments of 10 percent relative to their respective baseline levels.
"We modeled two moments of hand hygiene opportunities, on entry and exit, so the healthcare worker faces a compliance opportunity, expressed as a certain percentage," explains Barnes. "So if they wash their hands they will remove bacteria for the time being, and if they don't, they will carry it to each subsequent patient and potentially have a chance of transmitting it to them. It was the process for each organism that we modeled -- Acinetobacter, MRSA and VRE."
Thom adds, "We picked Staph aureus and Enterococci because they were the most common drug-resistant organisms that all hospitals will encounter. We were interested to see if any of the Gram-negatives had any different behavior, so we focused on Acinetobacter for a variety of reasons. We anticipate it probably behaves like many of the other persistent Gram-negatives."
For MDR A. baumannii, the researchers say that hand hygiene compliance was varied from baseline to reflect 10 percent and 20 percent improvements and 10 percent and 20 percent decreases in compliance. Thoroughness of terminal cleaning was varied from 30 percent to 90 percent in 10 percent increments. They found that increases in hand hygiene compliance (equally across nurses and physicians, entry and exit) outperform equal improvements in terminal cleaning. These results also show that acquisition rates would increase substantially more if hand hygiene compliance fell 10 percent or 20 percent than it would if cleaning thoroughness fell from its baseline level. As the researchers note, "We found that the relative reduction in acquisitions would be even larger from lower baseline levels of hand hygiene compliance, whereas the effect of cleaning thoroughness is generally linear and constant."
"The literature has found, generally, that hand hygiene has always shown some kind of diminishing returns -- once you get to the higher levels of hand hygiene, that same amount of improvement in hand hygiene will have a smaller effect, at least in the models, on reducing pathogen acquisition," Barnes says. "So environmental cleaning being linear and constant was a point that we tried to emphasize a bit in our paper. When the levels of hand hygiene are higher, we still saw some benefit in improving cleaning processes. Even though it doesn't have the same magnitude in effect at the lower levels, there was some benefit in trying to improve cleaning even if your hand hygiene levels are high. The linear trend in cleaning was an interesting finding."
The authors note in their paper that a limitation of the model is its focus on terminal cleaning after patient discharge and not daily cleaning when the room is occupied. They say that "A greater relative impact of environmental cleaning on MDRO transmission (compared with hand hygiene) might be seen if hospitals were to improve the thoroughness of both terminal and daily cleaning."
"We focused on terminal cleaning because the bottom line is, if you look in the literature thus far, terminal cleaning has been the absolute minimum expectation," Thom explains. "Most of the available data on environmental cleanliness in hospitals is on based on terminal cleaning, so we didn't have a lot of data on how effective daily cleaning is. We also wanted to create as simple a message as possible without making things too complicated. I think daily cleaning is important, but it was harder for us to understand the full dynamics of what a typical hospital's daily cleaning compliance looks like. So we went with what the literature is determining as the basic minimum."
"When you look at the patient length of stay (LOS) in our model, the median LOS was two days," Barnes says. "So, relative to the effect of terminal cleaning, daily cleaning in this model probably would have had more of a marginal effect. I think it would help but the terminal cleaning between patients was the trigger -- if you were a patient admitted to a room after a patient who was colonized, then you are at an increased risk. Daily cleaning probably would have had less of an effect on such a short LOS."
The researchers also compared the individual strategies of improving hand hygiene or terminal cleaning with mixed strategies that improve some combination of each and show that the strategy of improving only hand hygiene compliance outperforms any mixed strategies as long as the total percent improvements are equal (comparing a 20 percent improvement in hand hygiene compliance to a mixed strategy of plus-10 percent hand hygiene compliance and plus-10 percent terminal cleaning). In addition, the model showed that the strategy of improving hand hygiene compliance by 20 percent outperforms the mixed strategy of improving hand hygiene compliance by 10 percent and terminal cleaning thoroughness by 20 percent.
For MRSA and VRE, on average, Barnes, et al. (2014) report that "The same 21 ratio held when we compared the effects of these two factors on reducing acquisition rates. Hand hygiene compliance outperformed terminal cleaning by more than two-fold at the less thorough cleaning levels but less than that at higher levels. As in the first scenario, the strategy of improving hand hygiene compliance by 20 percent outperformed the mixed strategy of improving hand hygiene compliance by 10 percent and terminal cleaning by 10 percent. However, the mixed strategies in this scenario perform significantly better than for A. baumannii, where there was little benefit of improving hand hygiene once cleaning thoroughness reached levels of plus-20 percent or higher. This trend suggests that, for organisms with low environmental risk, some effort to improve hand hygiene compliance should accompany any strategy to improve terminal cleaning. The only exception to this trend in mixed strategies is the case where terminal cleaning is improved by approximately 50 percent or higher. In this case, the acquisition rate reduction is better than that of any mixed strategy, and it is substantially better than the maximum hand hygiene improvement of plus-20 percent."
Barnes, et al. (2014) acknowledge that their model creates an opportunity for hospitals to continue to evaluate their processes and the resulting ROI. They note, "It is unclear whether these findings suggest favoring investment in hand hygiene compliance over improving environmental cleaning. For each of the organisms modeled, a benefit was seen for each increment of improvement in terminal cleaning, consistent with the clinical studies on which our modeling was based, that environmental hygiene plays an important role in the prevention of MDRO acquisition and possible infection. This effect may be most pronounced in scenarios that include an MDRO with a significant environmental risk (e.g., the high-risk MDR A. baumannii), which suggests that if improvements in terminal cleaning thoroughness above 30 percent can be achieved, a strategy focusing solely on environmental cleaning may be of greater benefit. The literature suggests that thoroughness of terminal cleaning is 40 percent on average, and studies have shown that specific interventions may enhance cleaning to 78 percent to 88 percent."
The researchers add, "For facilities with low baseline levels of compliance of both hand hygiene and environmental cleaning, the question may then be which strategy is easiest to employ. This is dependent on facility characteristics, personnel, and whether improvement in terminal cleaning are easier to achieve than improvement in hand hygiene compliance. If terminal cleaning is more easily improved (as may be the case in many settings), then improving thoroughness may be the more effective strategy."
According to Thom, "This may not come from the data but most people would agree that we can't work in a silo in infection prevention and need to use multiple modalities to prevent infections. What I think we can take from this data is maybe a bit of common sense -- if we know that we have more than 90 percent hand hygiene compliance that has been ongoing for a while, I think this tells you it's probably OK to focus elsewhere and put more emphasis on environmental cleaning because we will probably get more bang for our buck in that area. Facilities must consider their own data and determine where they are on the spectrum."
The authors acknowledge that the modeling results would likely change if different parameters were used, since some factors vary widely across different institutions. They add, "In particular, the admission prevalence of MDROs and baseline values for hand hygiene and thoroughness of terminal cleaning are also likely to vary. We varied these parameters in the sensitivity analyses so that our results would be applicable to most facilities, and we have offered some considerations for facilities that may be operating outside our parameter ranges. In addition, facilities could adapt and individualize our model by incorporating their own parameters."
Thom says infection preventionists can plug their data into the model. "The data you would need would be to understand how often your healthcare providers are washing their hands when they are supposed to, and how well healthcare personnel are complying with terminal cleaning at your institution," Thom says. "Infection preventionists or hospital epidemiologists can crunch those numbers, but the question goes back to whether or not they have those resources to actually do it. Do they really have the number of people they need out there performing the observations and collecting that data? I don't think it's a matter of can they do it -- there are plenty of smart people at every facility that can collect data -- but do they have the resources to get it done?"
Adds Barnes, "It comes down to how well they can determine the plus-10 percent on these interventions. We don't know how much effort needs to be put into these improvement programs to actually raise hand hygiene 10 percent or environmental cleaning 10 percent -- that would be a little harder to quantify. Facilities should know their baselines and see where they fall in the continuum established by our models. For example, if you have low hand hygiene compliance and low cleaning levels, I think the results would suggest that focusing on hand hygiene is a better way to go. But if you have high hand hygiene and low cleaning levels, then I think we have shown that even if hand hygiene is at a high level, you can see pretty good improvement by focusing on cleaning at that point."
He continues, "If you have the resources, improve both types of interventions. But if you don't, there are multiple modeling papers showing that hand hygiene will have the largest effect -- that seems to be the metric time and time again. In the literature people have gone back and forth about that, but from the model we developed, hand hygiene is where you are going to get the most benefit if you are starting out at a lower compliance level."
In the end, the study found that "hand hygiene should remain a priority for infection control programs, but environmental cleaning can have significant benefit for hospitals or individual hospital units that have either high hand hygiene compliance levels or low terminal cleaning thoroughness." The researchers add, "In the setting of unlimited time and resources, healthcare facilities may choose to invest heavily in multiple strategies aimed at reducing transmission. However, resources are often limited, and efforts must be invested in one strategy over another. In addition to available resources, institutions need to consider MDRO prevalence, baseline compliance rates with infection prevention strategies, and personnel buy-in. Our model may assist facility leadership in determining the best strategy for their site. In general, a strategy that includes improvements in hand hygiene is likely to be beneficial; however, environmental cleaning also plays an important role in the prevention of transmission. In our modeling, improvements in hand hygiene were more efficient than comparable improvements in terminal cleaning; however, a strategy of improving some combination of both factors predicted the greatest reduction in MDRO acquisition and may be the most effective approach to minimizing transmission."
Thom says infection preventionists can make a big difference in raising compliance rates and should continue to encourage healthcare personnel to improve both hand hygiene and environmental hygiene to reduce transmission of resistant bacteria. "We know that in many institutions, IPs are under-resourced and can take models like ours back to the C-suite to help make the case about what kind of impacts various interventions can have -- it isn't so much they have to choose one or the other, but they need additional resources to be able to tackle both when it's appropriate." Thom continues, "Hopefully, if we are all doing our jobs, we are already focusing on the most cost-effective infection prevention strategies, the ones that have the biggest impact on patient safety. So we should already be in the position where we are able to be driven by both imperatives. The reality of hospital finance being what it is, however, we need to work with the people who are making the fiscal decisions who are very influential in allocating our resources, refocusing them on how much we are actually saving by preventing infections. Even if we have to put a little investment upfront, as we know we must in any type of prevention, we are saving money on the back end -- and saving lives."
Reference: Barnes SL, Morgan DJ, Harris AD, Carling PC and Thom KA. Preventing the Transmission of Multidrug-Resistant Organisms: Modeling the Relative Importance of Hand Hygiene and Environmental Cleaning Interventions. Infect Control Hosp Epidemiol. 2014 Sep;35(9):1156-62.