Methods: We reviewed the charts of patients ages 0 to18 years with positive blood cultures at our institution from February 2012 to January 2014. Subjects were excluded if cultures were obtained at other institutions, they were not admitted to hospital, or had organisms not validated on MALDI TOF. The pre-intervention group (PG) had cultures collected from February 2012 to January 2013 with pathogen identification (ID) done using conventional methods. The intervention group (IG) had cultures collected from February 2013 to January 2014 and had initial pathogen ID with MALDI-TOF. The primary outcome, time to optimal therapy was defined as time from obtaining the culture to stopping empiric therapy or switching to new therapy. Time to event data was analyzed using quantile regression for the difference in medians.
Results:1072 cultures met inclusion criteria and 329 included in the final analysis (PG n=148, IG n=93). PG and IG patients were similar for baseline characteristics except for the number without comorbidities (IG=22, PG=11, p=0.004). Median time to species ID was 17 hours (IQR 13-23) in the IG and 47 hours (IQR 37-56) in the PG (p<0.05). Time to optimal therapy was 16h (IQR 3-55) in the IG vs 24 h (IQR 2-60) in the PG (not significant). Length of stay (days) did not differ between groups (IG=32.6, PG=41.2, p=0.309).
Conclusion: Species level ID is faster with MALDI TOF in the diagnosis of bloodstream infections. However, it does not appear to allow for faster initiation of targeted antimicrobials and cessation of redundant therapy. MALDI TOF does not affect length of stay in patients with bloodstream infections. Further study is needed to determine how best to utilize rapid identification methods to optimize prescribing of antimicrobials.
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