513 Predictive Values of MRSA Nasal Swabs for Pneumonia in Burn ICU Patients

Abstract Introduction Sepsis in burn-injured patients remains a leading cause of mortality in those who survive initial resuscitation. Methicillin-resistant Staphylococcus aureus (MRSA) is a common causative pathogen for pneumonia in burn-injured patients. Studies evaluating the predictive value of MRSA nasal swabs for pneumonia have largely excluded the burn-injured population. Methods Patients 18 years or older admitted to the Burn ICU at a tertiary medical center from 2016 to 2021 were included if they had any burns, a pneumonia ICD-10 code, an MRSA nasal swab obtained during admission, and any respiratory cultures associated with at least five consecutive days of antibiotics. Results There were 267 instances of pneumonia across 136 patients included. MRSA nasal swabs had an overall sensitivity of 39%, specificity of 98.7%, positive predictive value (PPV) of 84.2%, and negative predictive value (NPV) of 89.9%. MRSA nasal swabs obtained less than seven days from antibiotic initiation had a specificity of 98.6% and NPV of 98.6%; meanwhile, swabs obtained at least seven days from antibiotic initiation had a specificity of 98.7% and NPV of 86.4%. Conclusions The high specificity and NPV indicate that negative MRSA nasal swabs obtained less than seven days from antibiotic initiation may be used to de-escalate anti-MRSA antibiotics in clinically stable burn-injured patients with suspicion of pneumonia. The decrease in NPV suggests that it may be beneficial to obtain a repeat swab periodically or upon suspicion of pneumonia. Applicability of Research to Practice This study is the first to measure the sensitivity, specificity, PPV, and NPV of the MRSA PCR nasal swab in a cohort comprised only of patients admitted to a burn intensive care unit. The findings support the use of the MRSA nasal swab as a tool to aid in the decision to initiate or de-escalate anti-MRSA antimicrobials for pneumonia.