Emergency room crowding associated with increased rate of blood culture contamination


Intravenous literature: Halverson, S., Malani, P.N., Newton, D.W., Habicht, A., Vander Have, K. and Younger, J.G. (2013) Impact of Hourly Emergency Department Patient Volume on Blood Culture Contamination and Diagnostic Yield. Journal of Clinical Microbiology. March 20th. .


Background: Emergency departments (EDs) are an important diagnostic site for outpatients with potentially serious infections. EDs frequently experience high patient volumes, and crowding has been shown to negatively impact the delivery of early care for serious infections such as pneumonia. Here we hypothesized that another important part of early care of infectious diseases, the rate of blood culture contamination and accurate detection of pathogens, would be sensitive to ED operational stress, as proper collection requires fastidious attention to technique and timing.

Methods: We related all blood cultures collected over one year and their rates of recovery of likely contaminants and likely pathogens to the number of patients being cared for in the ED at the time of sample collection. Likely pathogens and contaminants were classified through combined microbiological and manual chart review criteria. Zero-inflated Poisson regression was used to relate crowding to culture results.

Results: Cultures were obtained in 7,586 patients over 82,521 adult and pediatric patient visits. The unadjusted rates of recovering a likely pathogen or contaminant were 8.0% and 3.7%, respectively. Periods of increased crowding (3rd and 4th quartiles of hourly occupancy) were significantly associated (p<0.01) with increased rates of contamination (relative risk 1.23 compared to least busy quartile). Cultures collected during busy times also reduced the likelihood of recovering a likely pathogen (relative risk 0.93 compared to least busy quartile).

Conclusions: ED crowding was associated with degraded performance of blood culture, both increasing the rate of contamination and decreasing the diagnostic yield.

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