Predictive values of methicillin-resistant Staphylococcus aureus nasal swabs for pneumonia in burn ICU patients.

Introduction/objective: This retrospective cohort study aimed to determine the sensitivity, specificity, and positive (PPV) and negative predictive values (NPV) of MRSA nasal swabs for pneumonia in burn-injured intensive care unit (ICU) patients.

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 occurrences of pneumonia across 136 patients. MRSA nasal swabs had an overall sensitivity of 39 %, specificity of 98.7 %, PPV of 84.2 %, and 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.