Mayo Clinic Sustains Reduced Blood Culture Contamination in the Laboratory

By Kelley Luedke • March 27, 2017

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A recent article in MedicalLab Management, authored by Mayo Clinic staff, discusses how to sustain reduced blood-culture contamination. According to the article, blood-culture contamination remains a problematic cause of false positives and diagnostic errors for many clinical laboratories.

According to the College of American Pathologists (CAP), a blood culture is considered contaminated if one or more of the following organisms are identified in only one culture of a series of specimens in a 24-hour period:

• Coagulase-negative Staphylococcus species
• Propionibacterium acnes
• Micrococcus species
• Alpha-hemolytic viridans group streptococci
• Corynebacterium species (diphtheroids)
• Bacillus species

Further, CAP has established a blood-culture contamination rate threshold of 3% for corrective action.

However, laboratory leadership at Mayo Clinic Health System–Franciscan Healthcare (MCHS-FH) in La Crosse, Wisconsin, felt the lab could, and should, establish a more stringent threshold than 3% after accounting for the cost-of-poor-quality (COPQ) impacts on patients.

Laboratory leadership observed the practices of senior phlebotomists who had produced no contaminated cultures during a set observation period, and implemented those techniques, coupled with best practices found in literature, as the standard operating procedures for phlebotomy. Exemplary staffers also were asked to help train coworkers on contamination countermeasures that included:

• Ensuring the collection site is sterile by performing a friction scrub of 30 to 60 seconds to expose underlying bacteria to the antiseptic that follows.
• After the friction scrub, apply antiseptic in a 2- to 3-inch concentric circle from collection site outward.
• Let the site air dry for at least 30 seconds (no waving of the hand or excessive movement to expedite the drying process).
• No re-palpation or touching of the cleansed site to re-find a vein (surgical gloves are not sterile, and fingertip sanitation is not advised).
• Establish and be certain of the draw site before cleaning.
• Require venipuncture and avoid line draws.

Contamination rates fell significantly. In 2014, the laboratory had a total of 93 contaminated blood cultures out of 5,784 collected, equaling a contamination rate of 1.6%. Over the course of 2015, there were a total of 79 contaminated cultures out of 5,863 collected, further reducing the contamination rate down to 1.3%. (Anything below 1% is considered improbable due to uncontrollable factors such as transient bacteremia.)

Read the full article to learn more.

Authors include:

• Dana Sorenson, Operations Supervisor of the Mayo Clinic Health System–Franciscan Healthcare Laboratory.
• Heidi Miksanek, Senior Systems Engineer in the Department of Laboratory Medicine and Pathology at Mayo Clinic in Rochester, Minnesota.
• Matthew Tradewell, CT(ASCP), Operations Administrator overseeing cardiology, emergency medicine, hospital medicine, and diagnostics at Mayo Clinic Health System–Franciscan Healthcare in La Crosse, Wisconsin.
• Kristin Hagen, Supervisor of the Microbiology Laboratory at Mayo Clinic Health System–Franciscan Healthcare, in La Crosse, Wisconsin.
• Christophe Bahn, freelance writer for Mayo Medical Laboratories, specializing in clinical research and discovery.

Kelley Luedke

Kelley Luedke is a Marketing Channel Manager at Mayo Clinic Laboratories. She is the principle editor and writer of Insights and leads social media and direct marketing strategy. Kelley has worked at Mayo Clinic since 2013. Outside of work, you can find Kelley running, traveling, playing with her kitty, and exploring new foods.