Methods: : A cohort of patients was identified by cross-matching internal physician and laboratory billing data from the past 10 years at IU hospitals in the Indianapolis area for pneumonia. An initial pool of 550 patients were identified. Patients less than 25 years of age were eligible. Patients were excluded if they had medical conditions such as Cystic Fibrosis, Chronic Lung Disease, or cavitary pneumonia seondary to IV drug use. Chart review identified a total of 28 patients that met diagnostic criteria for pneumonia, had culture data and had a MRSA PCR nasal swab performed during treatment.
Results: In the cohort, 5 patients had positive MRSA nasal swab and positive cultures for MRSA. Two patients had positive MRSA swab with negative cultures. Twenty one patients had negative MRSA nasal swabs and cultures without MRSA growth. No patients were identified with a negative MRSA nasal swab that grew MRSA in cultures. In this population the MRSA nasal swab had a sensitivity of 100%, specificity of 91%, positive predictive valve of 71%, and a negative predictive value of 100%. The patients with negative MRSA swab and negative cultures, 66% were treated with vancomycin. If MRSA nasal PCR was used to guide treatment, 71% of the patients with a negative nasal swab had potential to discontinue MRSA empiric antibiotics sooner.
Conclusion:The MRSA PCR nasal swab has a high negative predictive valve in this pediatric population of inpatients treated for HAP/CAP. This is consistent with results from adult studies. The high negative predictive valve makes the MRSA PCR nasal swab a potential tool as a rapid diagnostic test to guide empiric antibiotic therapy.