title: Discarding the initial aliquot of blood does not reduce contamination rates in intravenous-catheter-drawn blood cultures.
abstract: Although venipuncture is the preferred method for obtaining blood cultures, specimens often are obtained from intravenous catheters (IVC). For IVC-drawn blood cultures, some authorities recommend discarding the initial 5 to 10 ml of blood to reduce contamination and remove potential inhibitory substances. To determine whether this practice reduced contamination rates (CR), we assessed the results of IVC-drawn blood cultures for adults. Thirty milliliters of blood was obtained aseptically. The first 10 ml, rather than being discarded, was inoculated into an aerobic culture vial. Using a second sterile syringe, 20 ml of blood was obtained and inoculated in 10-ml aliquots to aerobic and anaerobic culture vials. Positive cultures were evaluated to assess clinical significance (true versus contaminant). Out of 653 IVC-drawn blood culture pairs, both vials were contaminated in 38 pairs (5.8%); only the "discard" vial was contaminated in 33 (5.1%); and only the "standard" vial was contaminated in 31 (4.7%). Overall CR were 10.9% for the discard vial versus 10.5% for the standard vial (P = 0.90). We conclude that discarding an initial aliquot of blood when obtaining blood cultures from IVCs does not reduce CR.
authors.affiliation: Division of Infectious Diseases, Allergy & Immunology, Robert Wood Johnson Medical School, New Brunswick, NJ 08901-0019, USA.
authors.forename: Sukrut
authors.initials: S
authors.lastname: Dwivedi
authors.forename: Rohit
authors.initials: R
authors.lastname: Bhalla
authors.forename: Donald R
authors.initials: DR
authors.lastname: Hoover
authors.forename: Melvin P
authors.initials: MP
authors.lastname: Weinstein
mesh_terms: D016470:Bacteremia / Q000175:diagnosis*; D001769:Blood / Q000382:microbiology*; D001800:Blood Specimen Collection / Q000379:methods*; D002404:Catheterization; D003951:Diagnostic Errors / Q000706:statistics & numerical data*; D006801:Humans; D018962:Phlebotomy