Initial Specimen Diversion Device (ISDD) Prevents Blood Culture Contamination

Background:  Contamination of blood cultures and resultant false-positive results is common and causes unnecessary antibiotic therapy, additional laboratory testing, and excess healthcare costs.  Skin microbes that are not eradicated by antiseptics result in contamination at the time of phlebotomy. This study tested the effectiveness of a device designed to limit blood culture contamination through diversion and sequestration of the initial 1.5-2.0 mL of blood.

Methods: Single center, prospective, open-label, controlled trial, conducted from Nov 2014 - Oct 2015, of an initial specimen diversion device (SteriPath, Magnolia) (ISDD) in adults in an emergency department.  Select subjects granting consent had paired blood cultures performed by trained phlebotomists via peripheral venipuncture (one culture was obtained using standard laboratory procedures (SLP), the other using ISDD).  Blood cultures were monitored and microbes were characterized using routine institutional clinical microbiology protocols. A standard definition of contamination was employed.  McNemar’s test was used to compare proportions of contaminated and true positive blood cultures.  Fisher’s exact test was used to examine the association between phlebotomists and contamination rate.  

Results: 971 subjects were enrolled resulting in 904 nonduplicative patients with 1808 blood cultures. 96/1808 (5.3%) blood cultures yielded microbial growth with 79/1808 (4.4%) regarded as true infections and 18/1808 (1%) contaminants.  The ISDD was associated with less blood culture contamination compared to SLP: (2/904 (0.22%) vs 16/904 (1.78%), P=0.001).  There was no association between phlebotomist and contamination using SLP (P=0.31) or ISDD (P=0.62).  Sensitivity was not compromised: true bacteremia was noted in 65/904 (7.2%) with ISDD and 69/904 (7.6%) with SLP, P=0.41.

Conclusion: Use of the ISDD resulted in a significant reduction in contamination of blood cultures, without an impact on sensitivity, in adult patients in an emergency department setting.  A reduction in blood culture contamination may decrease unnecessary antimicrobial usage, result in cost savings, and improved patient outcomes.