Reducing Blood Culture Contamination Rates in the ED

False-positive blood culture results caused by skin contaminants and inadequate aseptic techniques remain a significant concern for U.S. hospitals and health care providers. Blood culture contamination rates in the San Joaquin General Hospital ED fluctuated monthly and often exceeded the recommended threshold of less than 3%.

The primary aim of this quality improvement project was to implement an evidence-based intervention to reduce blood culture contamination rates in the ED. Secondary goals were to measure compliance with the initiative and add to the body of knowledge on the financial costs associated with blood culture contamination.

A new protocol for collecting blood cultures was introduced in the hospital's ED from March 1 to April 30, 2025. This protocol involved using a sterile diversion tube (the Z-tube) to collect the initial blood specimen before proceeding with the blood cultures. To ensure compliance, nurses were instructed to send the diversion tube along with the culture bottles to the microbiology laboratory. Blood culture sets obtained using a Z-tube were designated as the diversion group, and those without as the non-diversion group. Compliance was tracked, and a cost analysis was performed to calculate the additional expenses associated with contaminated blood cultures.

Of the 1,904 blood cultures collected during the intervention period, the diversion group included 1,242 (65.2%) blood culture sets and the non-diversion group, 662 (34.8%). Blood culture contamination rates decreased by 85%, from 2.7% (18 of 662 blood culture sets) in the non-diversion group to 0.4% (five of 1,242 blood culture sets) in the diversion group. Additionally, contamination was 86% lower in the diversion group than in the historical control group, the two months preceding the intervention period (0.4% versus 2.9% [56 of 1,931 blood culture sets]). During the intervention period, Z-tube compliance was 65.8%, which was tracked by the number of Z-tubes sent to the laboratory. Our analysis found that the average additional cost for patients with contaminated blood cultures was $10,921 per patient.

Using a sterile diversion tube was associated with a decrease in the blood culture contamination rate in hospitalized patients, suggesting this is an effective way for hospitals to decrease contamination rates, leading to better patient outcomes and reduced health care costs.