Methicillin-resistant Staphylococcus aureus (MRSA) remains a leading cause of healthcare-associated infections (HAIs)1 and is associated with higher morbidity and mortality rates, longer hospital stays, and greater costs than methicillin-susceptible S. aureus.2 To address the MRSA problem, growing numbers of U.S. hospitals are incorporating MRSA surveillance as part of their measures to control HAIs. The experience of institutions that have led the way since the early 2000s has shed some light on what factors play a key role in a successful MRSA surveillance program.3 This data is prompting a second look at current strategies to determine how they can be improved to realize the full potential of MRSA surveillance in reducing infection and avoiding associated costs.
By definition, MRSA surveillance means testing patients for the presence of MRSA (colonization). Colonized patients are not infected but are carrying MRSA as part of their normal flora and may be at risk for infection under certain conditions, such as following surgery or when immunocompromised. Surveillance encompasses universal screening for all admissions or targeted screening for specific patient groups (e.g., those deemed at higher risk). The trend toward surveillance testing, whether targeted or universal, is fueled by increasing evidence of the effectiveness of such programs in lowering MRSA infection rates,4 declining reimbursement for complications related to HAIs,5 and the continuing focus by hospitals on quality improvement.
The definition of success
In today’s environment of cost containment and resource constraints, a successful MRSA surveillance program must go beyond reducing infection and address cost issues—being cost-neutral or better, in part because MRSA screening is generally not reimbursed. Each institution must assess potential program benefits not only in terms of patient care and quality improvement, but also in cost avoidance achieved through reduction of infection, in order to justify the investment. Indeed, studies have shown that successful surveillance programs can pay for themselves through fewer ICU days and shorter hospital stays.6 While estimates vary depending on facility and geography, the average length and cost of hospital stays for MRSA infections are more than double those of all other stays.7
Thus, reducing MRSA infection can potentially meet the dual objective of improving patient care and enhancing financial performance, and is the overarching goal in designing and planning a surveillance program.
Assessing the impact of test methodology factors
The preponderance of studies demonstrates the effectiveness of MRSA surveillance as measured by reduction in infection. But a few studies also highlight the critical role of two specific methodology factors in helping to reduce MRSA infection.5,8,9,10
The first factor is sensitivity. The test methodology needs to be sufficiently sensitive to identify the majority of colonized patients so that they can be managed to decrease the risk of infection and isolated to prevent spread of the pathogen. False negatives can result in an increase in infections when colonized patients develop MRSA infections or spread MRSA to other patients, many of whom are already at risk due to their status.
The second factor is turnaround time (TAT). Published data suggests that a time-to-results of less than one day is necessary for MRSA reduction in the acute care setting.8 One study that demonstrated a 50% reduction in the number of MRSA infections identified the combination of universal surveillance and a TAT of less than one day as key to its success.5
Culture vs. molecular
Culture is a well-established methodology and is used by many labs for MRSA surveillance, in part because it is perceived as inexpensive. However, laboratories may want to consider the impact of culture’s lower sensitivity and longer time-to-results in light of overall program effectiveness. Lower sensitivity can translate into missed opportunities to manage colonized patients, and longer time-to-results can mean delayed intervention, both of which can decrease the effectiveness of the surveillance program in reducing infection. To achieve a level of sensitivity equivalent to molecular methods using culture, it is necessary to perform an additional enrichment step, which further delays availability of results.
Batch vs. stat
The relatively fast laboratory testing turnaround time for molecular methods for MRSA testing (about 1 1/2 to 2 hours) can help support prompt intervention efforts. But hospitals can also choose between batch and stat processing, and the choice carries with it some potential process and cost implications.
Some institutions prefer a stat method, in which tests are run on demand and individual results are typically delivered within two hours. One obvious benefit of this approach is that it provides the opportunity for near-immediate intervention. On the flip side, it can be associated with significantly higher reagent costs per test. In light of the price premium, hospitals may want to evaluate whether it is feasible to provide rapid response to every incidence of a patient who tests positive for MRSA colonization with the hospital’s current infrastructure and processes. Having a test result within two hours after collecting the patient sample may not equate to immediate intervention, and a time-to-results of less than one day (such as batch processing offers), which may be significantly less costly, has been shown to be effective in reducing MRSA infection.8 Another consideration is the investment that may be needed to put in place a rapid response mechanism to justify stat testing for MRSA surveillance.
Depending on infection control and operational needs, batch mode may potentially offer a more cost-effective process. One available instrument that offers batch processing, for example, can accommodate batch sizes up to 30 samples, with a typical TAT (from collection to availability of results) of four to eight hours.
Understanding cost
These examples of how the test methodology can impact the process and effectiveness of MRSA surveillance programs illustrate that the issue of program cost really has several dimensions. First, there are operating costs related to the surveillance measures themselves. These include both direct expenses (instruments, reagents, supplies, and subtle factors like reagent waste) and indirect costs (labor, including operator hands-on and training time, activities related to maintenance and reliability issues, and manual review and logging of results).
Second, and perhaps even more important, are the costs—or savings—associated with the program impact in the areas of patient care and quality improvement. One critical financial impact to consider is the potential for cost avoidance that could be achieved through a reduction of infection, which on its own could theoretically justify the investment.
This second area is where factors like test performance (sensitivity and specificity) and turnaround time especially come into play. For example, false negatives from a test methodology that is not sufficiently sensitive can result in a lost opportunity to take preventive measures and manage a colonized patient. Conversely, false positives can lead to unnecessary isolation. Similarly, a delay in availability of test results may mean a delay in taking proper action. In this context, it is important to note that the concept of captured isolation days, defined as “days during which a patient colonized or infected with MRSA [is] placed in isolation,” has been shown to be a predictor of the success of a surveillance program, with captured isolation days of 80% or greater being associated with success.8
Assessing the financial impact
In addition, a prospective financial analysis of MRSA surveillance testing requires an adjustment in thinking from the paradigm of diagnostic testing (focusing on patient management) to surveillance testing (addressing broader hospital and health system issues). Assessing and quantifying the impact of surveillance on infection control is critical in determining the surveillance strategy that makes the most sense for an institution. This includes the consideration of situation-dependent, interrelated variables, such as prevalence, transmission rates and infection rates.
The ultimate decision concerning what is best for any institution should balance the needs of three areas: hospital administration, infection control, and the laboratory. It should also assess the financial impact of a MRSA surveillance program using different approaches (e.g., molecular vs. culture, targeted or universal screening) while taking into account the unique characteristics of the institution (e.g., hospital type, location, size and MRSA prevalence). The most salient financial impact analysis factors are summarized in Figure 1.
Figure 1.
A MRSA surveillance financial impact analysis should include an assessment of the key variables and assumptions.
Making it happen
MRSA surveillance is a long-term endeavor—a marathon vs. a sprint—that constantly evolves as hospitals grow and new policies are enacted. One key ingredient for success is close collaboration between infection control staff, who have day-to-day contact with clinicians and patients and are responsible for prevention, and the laboratory, which is responsible for delivering accurate test results in a timely and cost-effective manner.
Clearly, the importance of reducing MRSA infection and the potential benefits in quality and financial outcome call for a step-by-step process and a team approach to assessing MRSA surveillance needs, identifying the solutions, getting institution-wide buy-in, and implementing the right program for the institution.
John McCune, MT(ASCP), MS HRP, is group marketing manager for microbiology and genomics and oncology at Roche Diagnostics in Indianapolis.
References
- Hidron AI, Edwards JR, Patel J, et al. Antimicrobial-resistant pathogens associated with healthcare-associated infections: annual summary of data reported to the National Healthcare Safety Network at the Centers for Disease Control and Prevention, 2006-2007. Infect Control Hosp Epidemiol. 2008;29:996-1011.
- Gopal Rao G, Michalczyk P, Nayeem N, Walker G, Wigmore L. Prevalence and risk factors for meticillin-resistant Staphylococcus aureus in adult emergency admissions a case for screening all patients? University Hospital Lewisham, London, UK. J Hosp Infect. 2007 May;66(1):15-21.
- Robicsek A, Beaumont JL, Paule SM, et al. Universal surveillance for methicillin-resistant Staphylococcus aureus in affiliated hospitals. Ann Intern Med. 2008;148:409-418.
- Jain R, Kralovic SM, Evans ME, et al. Veterans affairs initiative to prevent methicillin-resistant Staphylococcus aureus infections. N Engl J Med. 2011;364:1419-1430.
- http://www.cms.gov/HospitalAcqCond/06_Hospital-Acquired_Conditions.asp#TopOfPage. Accessed December 13, 2011.
- Peterson LR, Hacek DM, Robicsek A. Case Study: a MRSA intervention at Evanston Northwestern Healthcare. J Qual Patient Saf. December 2007;33:732-738.
- Eixhauser A, Steiner C. Statistical Brief #35. Healthcare Cost and Utilization Project (HCUP). July 2007. Agency for Healthcare Research and Quality. Rockville, MD. http://www.hcup-us.ahrq.gov/reports/statbriefs/sb35.jsp.Accessed December 13, 2011.
- Peterson LR, Diekama DJ. To screen or not to screen for methicillin-resistant Staphylococcus aureus. J Clin Microbiol. 2010;48:683-689.
- Peterson LR, Karchmer T, Tenover FC. Letter to Editor: Transmission of resistant bacteria in intensive care. N Engl J Med. 2011;365:761-762.
- Evans ME, Kralovic SM, Jain R. Author/Editor Response: Transmission of resistant bacteria in intensive care. N Engl J Med. 2011;365:765.
