C-178. Performance Comparison of Low-Volume and High-Volume Blood Culture Systems: A Retrospective Study

S. A. Wahab, L. L. Hallagan, D. R. Lodge-Rigal;
Bloomington Hosp., Bloomington, IN.

Background: Balancing the conventional wisdom that “8 to 10 mL of blood are needed for the detection of septicemia” with the CAP requirement (CAP Checklist # GEN.40500) to minimize the amount of blood drawn, we decided to look at the performance of two growth detection (Blood Culture) systems, requiring high volume (Bactec-9000 series)and low volume (VersaTREK) of blood. Method: In the early part of 2006 we replaced Bactec-9240 (BT) with the VersaTREK (VT) instrument. For BT we were using aerobic, anaerobic and pediatric media with resins, which required 8 to 10 mL of blood per bottle. For VT we use 40 mL aerobic and anaerobic bottles, with a maximum specimen capacity of 5 mL. VT media (Redox 1 and 2) do not contain resins (as in BT) or activated charcoal (as in Bac/T Alert). Because the 40 mL VT bottles required less blood, we had a very favorable response from patients and employees. We decided to compare the performance of both systems in a retrospective study of one year data for each system (BT for 2005 and VT for 2006). We looked at the total number of blood cultures, percent positivity, contamination rate, average number of cultures/ patient, average volume of blood/ bottle and average time to detection of growth of some common organisms. Results: Total number of cultures: BT=8,369; VT=8,177. Average number of blood cultures/ patient: BT=2; VT=2. Average volume of blood/ bottle: BT=8 mL; VT=4 mL. Positivity rate: BT=10.7%; VT=8.5%. Contamination rate: BT=2.6%; VT=2.0%. We also realized a reduction in time to detection of positives. Conclusion: In the light of our experience, we conclude that VersaTREK is a viable alternative to the high-volume blood culture instruments, reducing the amount of blood required without compromising patient-care.