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Screening patients to prevent their infections
Decolonizing staph carriers could save millions
While the contentious debate over active surveillance cultures (ASC) threatens to shed more heat than light on health care epidemiology, there is a less controversial screening approach that could prevent many post-surgical infections and save hospitals millions of dollars in the process: pre-admission screening (PAT).
Rapid pre-admission testing for nasal carriage of Staphylococcus aureus among elective surgical patients followed by decolonization of carriers could result in an average annual cost savings of some $519 million for U.S. hospitals, according to a study recently presented in Baltimore at the 2007 Society for Healthcare Epidemiology of America (SHEA) conference.1 The idea is prevent surgical patients from later seeding their own infections by eliminating S. aureus colonization prior to the procedure. The ASC approach is essentially identifying and isolating the one to prevent subsequent infections in the many. A PAT approach — which could be a complement to ASC or as a stand-alone program — attempts to improve the outcome of a single patient who may not even be admitted to the hospital.
"In general, the goals of active surveillance cultures are to identify people who are colonized with an organism, with the expectation that you can put them in isolation to help prevent transmission," says Gary Noskin, MD, lead author of the study and a health care epidemiologist at Northwestern Memorial Hospital in Chicago. "The goal of pre-admission testing is actually the prevention of infection in that individual patient. Depending on the surgery, they may not even be in the hospital. With pre-admission testing, you would be able to perform this in the outpatient setting. So if a patient is scheduled to have a bypass surgery in two weeks, you swab them to see if they have [staph] and then try to intervene before they are even in the hospital."
Noskin and colleagues analyzed data from the 2003 Nationwide Inpatient Sample and published literature. Primary input variables related to Staph aureus included costs, prevalence of carriage, sensitivity and specificity of the rapid screening tests, and efficacy of nasal Staph aureus colonization suppression and cost data. In 2003, there were an estimated 7.1 million elective surgical admissions in U.S. hospitals; the mean cost of screening for staph was estimated at $215 million, while the cost of colonization infection was $201 million. However the study projected prevented infections as a result of PAT would result in the $519 million savings range. "Sensitivity analysis results indicated a 77% probability that there would be cost savings to U.S. hospitals as a result of PAT and subsequent colonization projection," they concluded.
Mupirocin reduces colonization
In a previously published study, which used mupirocin to decolonize patients with nasal carriage of S. aureus prior to surgery, researchers found that that approach reduced the infection risk to a colonized patient by about 50%. Overall, 4% of colonized patients who received mupirocin had nosocomial S. aureus infections, as compared with 7.7% of those who received placebo.
Prophylactic intranasal application of mupirocin did not significantly reduce the rate of S. aureus surgical-site infections overall, but it did significantly decrease the rate of all nosocomial S. aureus infections among the patients who were S. aureus carriers, they concluded.2 "We conclude that mupirocin therapy is safe, has a protective effect among nasal carriers of S. aureus, and is a reasonable adjuvant agent to prevent such infections in carriers after surgery," the authors noted.
Indeed, in an age of patient empowerment from increasingly public infection prevention education, it could be argued that the patient going in for surgery would be well served to ask to be screened and decolonized if needed.
"We do that as well for some of our surgical subspecialties, particularly cardiac surgery," says Leonard Mermel, MD, a health care epidemiologist at Rhode Island Hospital in Providence. "We do it in a more spotty fashion in neurosurgery and in orthopedics, where we will screen not just for MRSA but for Staph aureus carriage. If it's an elective procedure, particularly [involving] some implanted hardware, we will try to decolonize them prior to the procedure. We currently do 'all comers' for certain procedures, but if that were too costly you could target certain populations."
Which patient groups are more likely to be staph carriers? Mermel provided some insight into that question in another study presented at SHEA. He found that patients in long-term elder care and HIV-infected outpatients appear to be high-risk groups of MRSA. In the prospective, multicenter trial, clinical nasal swabs were collected from various patient groups at 11 U.S. sites, including inpatients screened for MRSA through active surveillance, inpatients and outpatients requiring hemodialysis, inpatients and outpatients with HIV-infection, pre-op cardiac surgery patients and patients admitted from long-term elder care. Among patients at facilities that did not regularly screen for MRSA, prevalence of MRSA was highest in patients admitted from long-term care (18%) and HIV-infected outpatients (17%), suggesting these patient populations are at especially high risk of MRSA carriage. Such patients would be likely candidates for PAT screening prior to elective surgery, but what about the implications for ASC?
"One obvious implication — for places such as our hospital that are doing active surveillance — do you include such [patient] groups among those that are screened upon admission?" he asked. "For those institutions that are screening selected high-risk populations to minimize costs in the microbiology lab, these [patient] groups might be [considered for] screening on admission to the hospital or if they are admitted to an ICU."