BERLIN, Germany — New evidence suggests that in patients at risk for methicillin-resistant Staphylococcus aureus (MRSA), polymerase chain reaction (PCR) screening followed by isolation reduces the frequency of hospital-acquired infections and is cost-effective.

The practice remains controversial, but investigators presenting here at the 23rd European Congress of Clinical Microbiology and Infectious Diseases showed that the approach is effective.

"We were skeptical before the study about whether or not this relatively expensive test would be cost-effective, but in our view it is," presenter Michael Walter, MD, from the Institute of Laboratory Medicine and Pathobiochemistry, Charité, in Berlin, Germany, told Medscape Medical News.

Using a 2-phase interventional study in a 550-bed emergency hospital, researchers screened all newly admitted patients determined to be at high-risk for MRSA.

During phase 1, 11.6% of the 10,434 patients were screened using a microbiology assay. MRSA-positive patients were placed in contact isolation after the lab result was received (mean, 62.8 ± 15.7 hours).

During phase 2, 11.5% of 10,472 patients were screened using both rapid real-time PCR (Xpert MRSA, Cepheid) and microbiology assays. Patients were placed in contact isolation if their preliminary PCR test was positive.

The number of admitted MRSA cases in phase 1 and 2 were approximately the same (2.1 vs 1.96 per 100 patients). There were slightly more hospital MRSA days in phase 1 than in phase 2 (50.9 vs 45.5 per 1000 patient-days), and slightly more MRSA cases per 1000 patient-days (2.42 vs 2.25).

Transmission Dramatically Reduced

In phase 1, the reduction in MRSA infection and colonization rates was more dramatic. Infections fell from 0.20 to 0.10 per 1000 patient days (< .05), and colonizations fell from 0.66 to 0.35 per 1000 patient days (= .01).

In 4 consecutive 6-month periods after the study, infections and colonizations remained at the lower rates or dropped even further.

To determine the cost-effectiveness of the measure, the researchers compared every patient with a nosocomial infection with 3 patients with the same initial diagnosis, and calculated the costs. They estimated that the PCR system saves the hospital €200,000 to €300,000 each year.

"The difference between the 2 phases was that immediate contact isolation at the time of admission was only possible in phase 2 because the microbiology results were not available for 2 or 3 days," Dr. Walter explained.

One step that the researchers took to reduce costs was to pool patient samples in the PCR analysis. That is not recommended in the instrument's instructions, but the researchers felt comfortable doing it because all samples were also being tested with the standard microbiology technique.

"It was a very good study," Sven Schimanski, MD, from Central Hospital in Bayreuth, Germany, who attended the talk, told Medscape Medical News. "One issue is that it is safe. You know you will not increase MRSA rates by switching to PCR."

The cost-effectiveness of the PCR test will vary, depending on the reimbursement system that the hospital operates under, Dr. Schimanski pointed out, because costs for MRSA treatment and isolation might be reimbursable. "But the basic point is that PCR is not more expensive. It saves some money," he added.

This study was not funded. Dr. Walter has disclosed no relevant financial relationships. Dr. Schimanski served on Cepheid's Speakers Symposium in 2011.

23rd European Congress of Clinical Microbiology and Infectious Diseases (ECCMID): Abstract O122. Presented April 27, 2013.

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