An Evaluation of  Blood Culture Contamination Analyzed by Collection Route and Initial Specimen Diversion ​

Background Obtaining blood cultures at IV insertion is common practice, but is probably associated with greater contamination. Whether use of first-aliquot-diversion (diversion) reduces contamination in this context is not clear. Objective To assess the effect of diversion on contamination and true-positive rates of blood cultures obtained from venipuncture vs. peripheral IV insertion. Methods Blood cultures were obtained from venipuncture or peripheral IV and diversion used according to clinician preference. Patient demographics, culture source, diversion use, and culture outcomes were recorded. Contamination and true bacteremia rates were compared for venipuncture vs peripheral IV, and according to use of diversion. Results Amongst 1156 blood cultures, 35 (3%) grew a contaminant including 24/557 (4.3%) IV vs 11/599 (1.8%) venipuncture cultures (p = 0.016). Diversion did not alter the contamination rate [Diversion: 24/890, 3% vs 11/266, 4% non-diversion, p = 0.2]. On multivariate analysis of contamination only IV culture source was significant (OR 2.5; 95% CI 1.2–5.1; p = 0.014) after adjusting for age and use of diversion