MRSA Testing on Hospital Admission: Universal or Selective Screening?
Today's Seattle Times provides a multi-part, if anecdotally ridden, expose of the MRSA scourge in Washington state (HT to the WSJ Health Blog). As in other states, the number of inpatients with the resistant bug has shot up dramatically during the last 10 years.
Measures to prevent and control MRSA infection in Washington hospitals, particularly in surgical patients, include prescreening for the bacterium. However, universal screening for MRSA is impractical at most hospitals, because of added costs and the extra work load imposed on already overtaxed personnel. Some hospitals, the Times reports, use selective screening programs, often inconsistently. One Washington hospital only screens for MRSA in elective-surgery patients; another only screens ICU patients; and another still only screens premature infants.
In this month's issue of the Journal of the American College of Surgeons, Swiss investigators report a more judicious model for screening hospital patients to prevent the nosocomial spread of MRSA. In their prospective study of more than 13,000 patients admitted for surgery, 3 independent factors correlated with MRSA carriage: recent antibiotic treatment, history of hospitalization within the last year, and age older than 75 years.
|
MRSA Risk Factor |
Adjusted Odds Ratio |
P Value |
|
Recent antibiotic treatment |
4.5 |
.001 |
|
History of hospitalization within last 12 months |
2.7 |
.03 |
|
Age >75 y |
1.9 |
.048 |
The investigators then calculated a score, from 0 to 9, to assess the probability of previously unknown MRSA. Two points were given for age older than 75 years; 3 for previous hospitalization; and 4 for recent antibiotic treatment.
|
Score |
Probability of MRSA Carriage |
|
<2 |
5% |
|
2-6 |
11% |
|
≥7 |
34% |
Screening patients with all 3 risk factors would have identified approximately 40%-50% of MRSA carriers, according to the investigators. Notably, most MRSA-positive patients (64%) had not been previously identified as MRSA carriers, and their status would have been missed without testing on admission. While not perfect, this model allows for discriminatory MRSA screening in presurgical inpatients, when universal surveillance is not feasible.
MRSA = methicillin-resistant Staphylococcus aureus.
Scanning electron photomicrograph of MRSA from the CDC (magnification 9560x).
