The effect of rapid screening for methicillin-resistant Staphylococcus aureus (MRSA) on the identification and earlier isolation of MRSA-positive patients.
OBJECTIVE
(1) To determine whether rapid screening with polymerase chain reaction (PCR) assays leads to the earlier isolation of patients at risk for methicillin-resistant Staphylococcus aureus (MRSA) colonization, (2) to assess compliance with routine MRSA screening protocols, (3) to confirm the diagnostic accuracy of the Xpert MRSA real-time PCR assay (Cepheid) by comparison with culture, and (4) to compare turnaround times for PCR assay results with those for culture results.


METHODS
Before-and-after study conducted in a 700-bed acute tertiary care referral hospital. Study periods were (1) a 5-week period before PCR testing began, (2) a 10-week period when the PCR assay was used, and (3) a 5-week period after PCR testing was discontinued.


RESULTS
Among 489 at-risk patients, MRSA was isolated from 20 (33%) of 60 patients during period 1, 77 (22%) of 349 patients during period 2, and 18 (23%) of 80 patients during period 3. Twenty-two (27%) of 82 at-risk patients were not screened during period 1, compared with 40 (10%) of 389 at-risk patients not screened during period 2 (P < .001). More MRSA-positive patients were preemptively isolated during periods 1 and 3 compared with period 2 (34 [24%] of 140 vs 28 [8%] of 389; P < .001); however, more MRSA-positive patients were isolated after notification of MRSA-positive results during period 2 (47 [13%] of 349) compared with periods 1 and 3 (2 [1%] of 140; P < .001). The sensitivity, specificity, positive predictive value, and negative predictive value of the PCR assay were 95%, 97%, 82%, and 99%, respectively. The mean turnaround time from receipt of specimens in the laboratory to PCR assay result was 2.6 hours.


CONCLUSIONS
Rapid screening with the Xpert MRSA PCR assay facilitated compliance with screening policies and the earlier isolation of MRSA-positive patients. Discrepant results confirm that PCR testing should be used as a screening tool rather than as a diagnostic tool.
Creamer
Eilish
E
Department of Clinical Microbiology, Education and Research Centre, Royal College of Surgeons, Ireland. eilishcreamer@rcsi.ie
Dolan
Anthony
A
Sherlock
Orla
O
Thomas
Toney
T
Walsh
John
J
Moore
Joan
J
Smyth
Edmond
E
O'Neill
Eoghan
E
Shore
Anna
A
Sullivan
Derek
D
Rossney
Angela S
AS
Cunney
Robert
R
Coleman
David
D
Humphreys
Hilary
H
D000362:Agar; D015373:Bacterial Typing Techniques; D001431:Bacteriological Techniques; D002863:Chromogenic Compounds; D003470:Culture Media; D019983:Guideline Adherence; D006801:Humans; D008403:Mass Screening / Q000379:methods*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D008826:Microbial Sensitivity Tests / Q000379:methods; D016133:Polymerase Chain Reaction / Q000379:methods*; D011237:Predictive Value of Tests; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000382:microbiology*; D013997:Time Factors
D002863:Chromogenic Compounds; D003470:Culture Media; D000362:Agar