Blood collection procedures influence contamination rates in blood culture: a prospective study.

BACKGROUND: Blood culture contamination is a significant adverse event. The aim of this project was to evaluate the efficacy of a strict blood collection procedure in reducing the blood culture contamination rate.

METHODS: A prospectively controlled study was performed in two different medical areas in Peking Union Medical College Hospital (PUMCH) for 16 months (from May 2006 to September 2007). In test group, a strict blood collection procedure was carried out by trained nurses with the veinpuncture sites were scrupulously disinfected with 2.5% tincture of iodine plus 70% alcohol. In control group, commonly used procedure in PUMCH was performed with 0.45% chlorhexidine acetate plus 0.2% iodine. Blood culture positive results for 4 target organisms (Coagulase-negative staphylococci, Propionibacterium acnes, Corynebacterium species and Bacillus species) were further assessed by physicians from infectious department to determine whether a sample was true positive (pathogen) or false positive (contamination).

RESULTS: Total 9321 blood culture collections were analyzed. The blood culture contamination rate in test group was significantly lower than that in control group (5/3177 (0.16%) vs. 77/6144 (1.25%); χ(2) = 13.382, P < 0.001). The most common contaminant was Coagulase-negative staphylococcus (76.83%). The average cultural time during which contaminated samples became positive was longer than that for true pathogen samples (42.0 hours vs. 13.9 hours, P = 0.041).

CONCLUSION: Using a strict blood collection procedure can significantly reduce blood culture contamination rate.