For MRSA detection, nasal screening alone may be insufficient

PHILADELPHIA – Conducting nasal screening alone to identify patients with methicillin-resistant Staphylococcus aureus may lead to some missed diagnoses, according to results of a study presented at the 109th General Meeting of the American Society for Microbiology, held here this week.

The results of the study, conducted by Choong Park, PhD, and Deborah Hixon, both from Inova Fairfax Hospital in Falls Church, Va., indicated that adding throat screening as a second test for MRSA helped to identify 12.3% more patients with MRSA.

The researchers screened all patients that were treated in intensive care units at their hospital between June and October 2008. Swabs from throat and both anterior nares were collected from 2,669 patients.

The overall prevalence rate of MRSA was 8.2% (220 patients). One hundred nineteen patients (4.4%) tested positive for MRSA from nasal and throat screening. But 74 patients (2.8%) tested positive for MRSA in the nasal screening alone and 27 patients (1%) tested positive for MRSA in the throat screening alone.

The researchers said these findings were important because if the nasal screening had been the only method of testing for MRSA, the 27 patients whose MRSA was detected by the throat screening alone would have remained undiagnosed.

“The results of this study show that nasal screening alone may be insufficient,” the researchers wrote. “The addition of throat screening increased the detection of positive MRSA by 12.3%.”

Park and Hixon also noted that the cost-effectiveness of using both methods of detection would be “difficult to assess” and that additional screening methods should also be analyzed. – by Jay Lewis

For more information:

Park C. C-050. Presented at: The 109th General Meeting of the American Society for Microbiology. May 17-21, 2009. Philadelphia.