Journal List > Ann Clin Microbiol > v.19(3) > 1078560

So, Choi, Lee, So, Chung, Kim, Choi, and Lee: Effects of Blood Volume Monitoring on the Rate of Positive Blood Cultures from the Emergency Room

Abstract

Background

Blood cultures are essential in diagnosing and treating sepsis. There are several factors that affect the diagnostic yield of blood cultures such as the number of blood sampling episodes, the incubation period, the type and volume of culture media, and the amount of blood drawn. This study aimed to elucidate whether monitoring the volume of blood drawn with an educational intervention could affect the diagnostic quality of blood cultures.

Methods

We implemented quality monitoring for the blood volume drawn during blood culture testing for adults in an emergency room. We instructed the nurses in the emergency room to draw the optimal amount of blood and to reduce the number of blood culture sets from three to two. We analyzed and compared the amount of blood drawn, the rate of positive blood cultures, the contamination rate, and time to positivity (TTP) between 908 patients pre-in-tervention and 921 patients post-intervention.

Results

The amount of blood drawn increased from 0.7±0.3 mL per bottle (pre-intervention) to 6.5±1.7 mL per bottle (post-intervention) (P<0.0001). The rate of positive blood culture post-intervention (12.14%) was higher than that pre-intervention (6.65%) (P<0.0001). The contamination rate post-intervention (1.82%) was also significantly greater than that pre-intervention (0.60%) (P<0.0001). Except for anaerobes, there was no significant difference in the distribution of microorganisms between the pre- and post-intervention periods. The TTP for anaerobe bottles post-inter-vention was significantly shorter than that of pre-in-tervention (16.1±16.3 versus 18.6±18.3 h).

Conclusion

This study suggests that continuing education about adequate blood volume and aseptic techniques is needed to increase the rate of positive blood cultures and reduce the contamination rate of blood cultures.

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Fig. 1.
Blood volumes in aerobic bottles submitted for blood culture during pre- and post-intervention periods. Error bars represent the standard deviation. *Comparison between pre- and post-intervention.
acm-19-70f1.tif
Table 1.
Analysis of the blood culture volumes submitted from each department prior to intervention (January-March 2016)
Department Mean±SD (mL) N
Emergency 0.7±0.3 2,630
Hematology 1.3±0.8 928
Neurological Surgery 2.7±1.5 453
Pulmonology 3.1±1.8 413
Nephrology 3.0±1.8 205
Gastroenterology 2.0±1.4 170
Cardiology 2.9±1.8 141
Hepatobiliary Surgery 2.3±1.5 58
Oncology 2.7±1.5 54
Neurology 2.7±2.1 39
Neurology ICU 3.5±1.9 39
Transplantation Surgery 2.8±1.7 38
Orthopedic Surgery 2.3±1.6 37
Thoracic and Cardiovascular Surgery 2.5±1.7 32
Infectious Disease 2.1±1.3 31
Breast and Thyroid Surgery 1.9±1.2 28
Urology 2.7±1.5 27
All groups 2.4±1.5 5,481

Departments that submitted fewer than 25 blood culture sets from January-March 2016 are not shown in the table.

Table 2.
Comparison of the true positive rate and contamination rate in bottles submitted for blood culture pre- and post-intervention
Period Total No. of blood culture sets No. (%) of
Positive culture sets Contaminant culture sets True positive culture sets
Pre-intervention 2,813 187 (6.65) 17 (0.60) 170 (6.04)
Post-intervention 1,928 234 (12.14) 35 (1.82) 199 (10.32)
Table 3.
Comparison of the time to positivity (TTP) values between pre- and post-intervention
Parameter Aerobic bottles Anaerobic bottles
Parameter Pre-intervention Post-intervention P-value* Pre-intervention Post-intervention P-value*
TTP of total positive (h) 18.8±15.2 22.7±22.3 0.5283 18.6±18.3 16.1±16.3 0.0370
TTP of contaminant (h) 43.5±22.4 32.8±22.5 0.0487 60.8±36.4 49.7±36.7 0.5283

*Calculated by the Mann-Whitney test.

Table 4.
Distribution of microorganisms isolated from blood culture-positive patients pre- and post-intervention
Microorganisms No. of patients with positive results (%) P-value
Pre-intervention Post-intervention
Escherichia coli 31 (36) 60 (38) 0.656
Coagulase-negative Staphylococcus spp. (CoNS) 10 (12) 28 (18) 0.197
Klebsiella spp. 9 (10) 18 (12) 0.800
Streptococcus spp. 5 (6) 11 (7) 0.711
Staphylococcus aureus 9 (10) 8 (5) 0.121
Enterococcus spp. 0 (0) 4 (3) 0.135
Other Enterobacteriaceae 3 (3) 10 (6) 0.336
Anaerobes 8 (9) 3 (2) 0.009
Candida spp. 1 (1) 1 (1) 0.669
Pseudomonas aeruginosa 3 (3) 1 (1) 0.100
Others 7 (8) 12 (8) 0.902
Total 86 (100) 156 (100)  
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