LB-17. Discontinuation of Contact Precautions for Patients with a History of Methicillin-Resistant Staphylococcus aureus: A Randomized Trial Comparing Passive Culture-based Screening to Active Surveillance with PCR and Culture
Session: Poster Abstract Session: Late Breaker Posters
Saturday, October 22, 2011
Room: Poster Hall B1


Guidelines do not address when Contact Precautions (CP) should be discontinued for patients with history of MRSA. Identification of patients who are no longer colonized has implications for patient care and resource allocation.


We randomized eligible patients to standard passive screening with CHROMagar (“CA”, BD Diagnostics) vs. active screening with both CA & molecular methods (“PCR”, GeneXpert MRSA, Cepheid). Subjects were adult inpatients admitted 12/6/10-6/30/2011. Three anterior nares swabs were obtained on consecutive days from consenting subjects.

Outcomes were: series completion and colonization clearance by arm; for the active arm only: sensitivity, specificity and negative predictive value (NPV) of the first PCR compared to 3 negative CAs.


467 subjects were randomized (2:1) to the active and passive arms. Enrollment, protocol completion frequencies, and MRSA prevalences (given screening completion) were:  Passive arm: 152/155 (98.7%) ; 15/155 (9.7%); and 13.3% (95% CI 3.7-37.9); Active arm: 207/312 (66.3%); 154/207 (74.4%); 35.1% (95% CI 28.0-42.9).

Active arm subjects were 7.8 times (95% CI 4.7-12.5) more likely to have completed the series and 3.1 times (95% CI 1.7-5.4) more likely to have CP discontinued based on CAs.   

Among active-arm subjects completing the series, first PCR sensitivity was 94.4%, specificity was 91.0%, NPV was 96.8%, compared to 3 CA.  Among active-arm subjects who did not receive antibiotics prior to sampling (n=87), sensitivity, specificity and NPV were not statistically different.  NPV ranged from 95.0-99.9% across a range of MRSA prevalences.  

Table 1. PCR Performance

Sensitivity % (95% CI)

Specificity % (95% CI)

NPV % (95% CI)

Subjects completing series (n= 154)

94.4 (84.9-98.1)

91.1 (83.8-95.2)

96.8 (99.1-99.3)

Subjects completing series, no antibiotics (n=87)

98.1 (89.9-99.7)

85.7 (70.6-93.7)

96.8 (83.3-99.9)


Compared to passive screening, active screening substantially improved documented clearance of MRSA colonization and led to a significant increase in the frequency of CP removal. A single negative PCR has a high sensitivity, good specificity, and acceptable NPV and should be considered a new, more effective, approach for removal of CP.

Subject Category: N. Hospital-acquired and surgical infections, infection control, and health outcomes including general public health and health services research

Erica S. Shenoy, MD, PhD1,2,3, JiYeon Kim, MD, MPH4, Eric Rosenberg, MD4, Hang Lee, PhD5, Jessica Cotter, MPH2, Rochelle Walensky, MD, MPH, FIDSA1,6 and David Hooper, MD1,3,7, (1)Medicine, Div Infectious Diseases, Massachusetts General Hospital, Boston, MA, (2)Infection Control Unit, Massachusetts General Hospital, Boston, MA, (3)Medicine, Harvard Medical School, Boston, MA, (4)Pathology, Massachusetts General Hospital, Boston, MA, (5)Biostatistics, Massachusetts General Hospital, Boston, MA, (6)Harvard Medical School, Boston, MA, (7)Massachusetts General Hospital, Boston, MA


E. S. Shenoy, None

J. Kim, None

E. Rosenberg, None

H. Lee, None

J. Cotter, None

R. Walensky, None

D. Hooper, None

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