All calculations were performed with SPSS v. 21 (IBM; Armonk, NY) using an a priori alpha level of 0.05, such that all results yielding P < 0.05 were deemed statistically significant.
Results
Of the 561 patient records reviewed, 319 patients were included and 242 patients were excluded. Reasons for exclusion included 65 patients admitted for a duration of 48 hours or less or discharged from the emergency department; 61 patients having another infection requiring anti-MRSA therapy; 60 patients not having a diagnosis of a LRTI or not receiving anti-MRSA therapy; 52 patients having received anti-MRSA therapy within 30 days prior to admission; and 4 patients treated outside of the specified date range.
Of the 319 patients included, 155 (48.6%) were in the MRSA PCR group and 164 (51.4%) were in the group that did not undergo MRSA PCR (Table 1). Of the 155 patients with a MRSA PCR ordered, the test was utilized appropriately in 94 (60.6%) patients and inappropriately in 61 (39.4%) patients (Table 2). In the MRSA PCR group, 135 patients had a negative result on PCR assay, with 133 of those patients having negative respiratory cultures, resulting in a NPV of 98.5%. Differences in baseline characteristics between the MRSA PCR and no MRSA PCR groups were observed. The patients in the MRSA PCR group appeared to be significantly more ill than those in the no MRSA PCR group, as indicated by statistically significant differences in intensive care unit (ICU) admissions (P = 0.001), positive chest radiographs (P = 0.034), sepsis at time of anti-MRSA initiation (P = 0.013), pulmonary consults placed (P = 0.003), and carbapenem usage (P = 0.047).
In the subgroup analysis comparing appropriate and inappropriate utilization within the MRSA PCR group, the inappropriate utilization group had significantly higher numbers of infectious diseases consults placed, patients with hospital-acquired pneumonia, and patients with community-acquired pneumonia with risk factors.
Outcomes
Median anti-MRSA DOT in the MRSA PCR group was shorter than DOT in the no MRSA PCR group, but this difference did not reach statistical significance (1.68 [IQR, 0.80-2.74] vs 1.86 days [IQR, 0.56-3.33], P = 0.458; Table 3). LOS in the MRSA PCR group was longer than in the no MRSA PCR group (6.0 [IQR, 4.0-10.0] vs 5.0 [IQR, 3.0-7.0] days, P = 0.001). There was no difference in 30-day readmissions that were related to the previous visit or incidence of AKI between groups.
