Can we reduce the number of MRSA screening site swabs in elective orthopedic patients?

Deep infection after routine elective orthopedic procedures can be catastrophic, leading to further surgery, loss of limb, disability, and risk of mortality. Ring-fencing elective orthopedic ward has been shown to significantly reduce the incidence of all postoperative infections especially with methicillin-resistant Staphylococcus aureus (MRSA). Our hospital's current MRSA screening is a four-site MRSA swabs.

This study evaluates the possibility of reducing the number of MRSA swab sites as part of a quality improvement project.

Patients on the waiting list for elective orthopedic procedure in our trust who had an MRSA-positive swab from either four sites were analyzed over the time period from January 2012 to December 2014. Those without swabs from all four areas (nose, throat, axilla, and groin) were excluded. Positive swabs of different regions were recorded and compared.

There were 138 MRSA-positive patients, giving an incidence of 31 per 10,000 screen/year over that time period. Some patients ( n = 31, 22.5%) had a positive swab in more than one site. The positive sites were as follows: nose (69.60%, n = 96), groin (26.10%, n = 36), throat (25.30%, n = 35), and axilla (8.70%, n = 12). In our cohort, we would miss a significant proportion of positive patients if we change it to a two swab screening policy (26.8% for nose and axilla combination; 18.10% for nose and groin combination; and 15.20% for nose and throat). However, we would only miss 2.2% of cases for a nose, groin, and throat three-swab policy. There were also 11 instances, where a previously negative site become positive in the next swab.

A three-swab combination of nasal, throat, and groin swabs improves pickup rate of MRSA significantly compared to a two-swab policy and misses only 2.2% compared to a four-swab policy. Axilla swabbing does not make a significant difference to the results. Based on this study, the policy has now been changed from a four-swab to three-swab screening in our trust. This has now been audited four times and they were all negative. This has helped to reduce cost in terms of staff time and resources. We would not recommend screening only the previous positive site for the next repeat screening swabs as there is an 8% chance of missing MRSA carrier status.