2021 Volume 70 Issue 4 Pages 754-759
The blood culture positivity rate is affected by blood sample volume, and the American Society for Microbiology guidelines (CUMITECH) recommends 20–30 mL of blood for a single sample. The optimal blood sample volume for aerobic and anaerobic culture vials used with the BD BactecTM FX system is 8–10 mL (the measurable blood sampling volume ranges from 3 to 10 mL). If one set comprises one aerobic culture vial and one anaerobic culture vial, the CUMITECH recommendation may not be met when using only one set of vials or a single blood sample volume in the measurable range. We analyzed 3,841 sets of blood culture vials submitted during a 2-year period between July 2014 and June 2016 for variations in the positivity rate with changes in blood culture and blood drawn volumes using laboratory results from our hospital. We observed a significant decrease in the positivity rate with blood volumes of 4.0 mL or less in anaerobic culture vials, suggesting that false negatives may occur with insufficient blood volumes in the measurable range.