(480) Methicillin-Resistant Staphylococcus aureus Nasal Screening in Critically Ill Transplant Patients

Introduction: MRSA polymerase chain reaction (PCR) tests are minimally invasive and provide rapid results to assist in selection of targeted antibiotic therapy. While previous studies have validated the predictive values of MRSA PCR in a critically ill patient population, there is limited data evaluating solid organ transplant (SOT) recipients.

Methods: The primary objective was to evaluate the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR), and negative likelihood ratio (NLR) of the MRSA nasal PCR in predicting MRSA in a clinical culture. This was a single-center, retrospective cohort study of adult SOT patients admitted to the ICU from 7/1/13-10/1/22. Patients were included if they received a MRSA nasal PCR within 24 hours of or during ICU admission, at least 72 hours after transplant, and had at least one clinical culture within 48h before or 14 days after MRSA nasal PCR collection. Patients were excluded if they received anti-MRSA surgical prophylaxis immediately post-transplant. Descriptive statistics were used to summarize demographics and clinical characteristics. Wilcoxon rank-sum tests or Kruskal-Wallis tests were used to compare continuous variables. Fisher exact tests or chi-squared tests were used to compare categorical variables.

Results: A total of 67 nasal PCRs and 318 associated clinical cultures from 59 patients met inclusion criteria. The most common site of primary transplant were liver (27%), lung (25.4%), and kidney (23.7%). The specificity of the nasal PCR was 0.98 (95% CI 0.91-1.00) and the NPV was 0.94 (95% CI 0.85-0.98). The NLR was 0.68. The sensitivity of the MRSA nasal PCR was 0.33, 95% CI 0.1-0.7). Because of the low number of positive MRSA nasal PCR and clinical cultures, the PPV and PLR could not be assessed.

Conclusions: Given the high NPV of MRSA nasal PCR reported by our study and by other literature, this remains a useful tool for clinical decision making and de-escalating anti-MRSA therapy. Here we report exploratory findings that would need to be confirmed by studies with a larger patient cohort. Our study was limited by our small sample size, and more information is needed to better understand the PPV and likelihood ratios in this population.