MRSA nasal screening predictive values assessment in patients with osteomyelitis.

Objective and design: The purpose of this study was to evaluate the diagnostic value of methicillin-resistant Staphylococcus aureus (MRSA) nasal screening utilizing polymerase chain reaction (PCR) assays in patients with osteomyelitis.

Setting: A multisite, retrospective adult chart review from March 2021 to June 2022 was conducted, with no interventions performed. Patients treated with anti-MRSA therapy for osteomyelitis, MRSA nares PCR collected within 48 hours of antibiotic initiation, and related cultures were evaluated.

Patients: Adults with associated cultures were assessed for concordance with MRSA nares PCR screening results. The primary outcome was the diagnostic value of MRSA nares PCR assay screening for predicting MRSA osteomyelitis. An assessment of sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) was performed. Key secondary outcomes included length of hospital stay and duration of anti-MRSA therapy.

Results: One hundred seven patients with MRSA nares PCR sensitivities were included in this assessment. The PPV and NPV were determined to be 25% CI (10.08-49.79%) and 94.7% CI (91.29-96.87%), respectively. Median and interquartile range durations of anti-MRSA therapy were decreased in the MRSA PCR negative group at 5 (3-8) versus 6.5 (6-9.75) days (p = 0.03752).

Conclusion: This research showed a high NPV (94.7%) and a low PPV (25%) that aligned with other studies evaluating MRSA nares PCR utilization in osteomyelitis. Additionally, despite no active intervention on the results, early de-escalation of inappropriate antibiotic therapy was observed.