Discontinuation of contact precautions for methicillin-resistant staphylococcus aureus: a randomized controlled trial comparing passive and active screening with culture and polymerase chain reaction

Abstract

Background: There have been no randomized controlled trials comparing active and passive screening for documenting clearance of colonization with methicillin-resistant Staphylococcus aureus (MRSA). We compared the efficacy of active and passive screening using both culture and commercial polymerase chain reaction (PCR) for documentation of MRSA clearance and discontinuation of MRSA contact precautions (CPs).

Methods: Inpatients with a history of MRSA infection or colonization enrolled between December 2010 and September 2011 were randomized to either passive (nonintervention arm; n = 202; observation with local standard of care) or active screening (intervention arm; n = 405; study staff screened using culture and commercial PCR). The primary outcome was discontinuation of CPs by trial arm based on 3 negative cultures. In the intervention arm, sensitivity, specificity, and positive and negative predictive values of the first PCR were compared to cultures.

Results: CPs were discontinued significantly more often (rate ratio [RR], 4.1; 95% confidence interval [CI], 2.3%-7.1%) in the intervention arm, including in an intent-to-screen analysis (RR, 2.6; 95% CI, 1.5%-4.7%). The first PCR, compared to 3 cultures, detected MRSA with a sensitivity of 93.9% (95% CI, 85.4%-97.6%), a specificity of 92.0% (95% CI, 85.9%-95.6%), a positive predictive value of 86.1% (95% CI, 75.9%-93.1%), and a negative predictive value of 96.6% (95% CI, 91.6%-99.1%).

Conclusions: Compared to passive screening using culture methods, active screening resulted in discontinuation of MRSA CPs at a significantly higher frequency. Active screening with a single PCR would significantly increase the completion of the screening process. Clinical Trials Registration. NCT01234831.

Keywords: MRSA; clinical trial; contact precautions; infection control; isolation.

Figures

Figure 1.

Patient flow diagram. aOnly patients with a history of methicillin-resistant Staphylococcus aureus (MRSA) >90 days at time of admission were assessed for eligibility. bSubjects were assigned to the nonintervention arm and intervention arm in a sequential 1:2 fashion in the order of admission, which was assumed to be random. cOf 202 subjects randomized to the nonintervention arm, 4 were excluded because they were found to be ineligible after enrollment (admission cancelled [n = 2]; found to be MRSA negative based on prior cultures [n = 1]; or determined to have methicillin-susceptible S. aureus, not MRSA [n = 1]). Of 261 randomized to the intervention arm, 2 were excluded because they were found to be ineligible after enrollment (prior enrollment [n = 1]; or found to be MRSA negative based on prior cultures [n = 1]). Abbreviations: CA, chromogenic agar (culture); MRSA, methicillin-resistant Staphylococcus aureus; PCR, polymerase chain reaction.

Figure 2.

Negative predictive value of a first polymerase chain reaction result across a range of methicillin-resistant Staphylococcus aureus prevalence. Abbreviations: MRSA, methicillin-resistant Staphylococcus aureus; NPV, negative predictive value.