Evaluation of methicillin-resistant Staphylococcus aureus nasal swab screening at a large comprehensive cancer center

The aim of this study is to determine the predictive values of MRSA swab screenings in patients with cancer.

This is a retrospective cohort observational study of adult patients admitted to The University of Texas MD Anderson Cancer Center between January 2019 and October 2022. Data collected from patients with documented MRSA nasal swab screenings and clinical cultures taken within 7 days were collected. The first documented MRSA swab screening and culture results from unique patients were included for analysis to calculate sensitivity, specificity, positive predictive value, and NPV.

A total of 6475 patients with MRSA nasal swab cultures had 13129 clinical cultures from different anatomical sites. Of the patients included, 57% had a solid tumor and 37% had a hematological malignancy, with 82% of patients receiving an anti-MRSA antibiotic prior to MRSA nasal swab. There were 167 documented positive MRSA cultures, most commonly from a wound (41.3%) or respiratory source (24%). Overall sensitivity and specificity for all culture sites were 50.9% and 98.4%, respectively, with an overall NPV of 99.4%. The NPV was 99.8% for bloodstream infections, 98.5% for respiratory infections, 92.6% for wound infections, and greater than 99% for other culture sites.

The specificity and negative predictive value of MRSA swab screenings in patients with cancer was high overall and consistent with the literature in immunocompetent patients. These results may aid in antimicrobial stewardship activities that can help guide the discontinuation of empiric antibiotics in patients with cancer.