Specimens from multiple body sites are needed to accurately test for MRSA
Research Activities, December 2009, No. 352
When it comes to accurately diagnosing methicillin-resistant Staphylococcus aureus (MRSA) colonization, taking swab samples from the nose may not be enough. According to a new study, samples from at least two sites on the body need to be obtained in order to achieve a sensitivity of more than 90 percent for MRSA colonization.
At the Center for Education and Research on Therapeutics (CERT) at the University of Pennsylvania School of Medicine, researchers identified 56 individuals who had swab samples positive for MRSA. Swab specimens were taken from the nose, under the arm, throat, groin, and perineum. Immediately after these were taken, either the patient or the parent (for pediatric patients) took swab samples from the same body sites. For both provider- and patient-collected samples, the nose was the most common site where MRSA was present, followed by the throat. However, nearly a quarter of individuals would not have been identified as having MRSA if the nose had not been sampled. Likewise, 5 percent of cases would have been missed if samples were not obtained from the throat. Swab samples from the groin and perineum tested positive for probable community-acquired MRSA significantly more often (75 percent) than they did for hospital-acquired MRSA (33 percent).
The researchers found strong agreement between the findings for patient-collected samples and provider-collected samples. As such, patient-collected sampling may be a way to improve the efficiency of community-based surveillance and research.
This study was funded in part by a grant from the Agency for Healthcare Research and Quality (HS10399) to the University of Pennsylvania School of Medicine CERT. For more information on the CERTs program, please visit http://www.certs.hhs.gov.
See "Surveillance cultures for detection of methicillin-resistant Staphylococcus aureus: Diagnostic yield of anatomic sites and comparison of provider- and patient-collected samples," by Ebbing Lautenbach, M.D., M.P.H., M.S.C.E., Irving Nachamkin, Dr.P.H., M.P.H., Baofeng Hu, M.D., and others, in the April 2009 Infection Control and Hospital Epidemiology 30(4), pp. 380-382.