Effects of volume and periodicity on blood cultures

Abstract

Blood specimens collected for culture by using the high-volume resin-based BACTEC system over an 18-month period at the Seattle Veterans Administration Center were examined in this study. Of 7,783 cultures obtained, 624 were classified as true positives. Patients'in this group had between 20 and 60 ml of blood drawn per culture and separated into 10-ml aliquots for incubation. Analysis of the results stratified by cultured volume and time interval between specimen collection accorded yield advantage to culture volume at the maximal amounts tested. No advantage was observed with any particular interval of collection. Increasing cultured volume from 20 to 40 ml increased yield by 19%o. Increasing cultured volume from 40 to 60 ml increased yield by an additional 10lo. The same effect was seen whether cultures were drawn simultaneously or serially within 24 h. These observations support other reports demonstrating increased yield with increased cultured blood volume. However, they demonstrate increases in yield at volumes much higher than previously considered. In conclusion, this study demonstrates that high-volume blood cultures drawn serially or simultaneously return the best yields.

Unique blood culture for diagnosis of bloodstream infections in emergency departments: a prospective multicentre study

“…This notion is based on many studies of patients with bacteraemia [4,[8][9][10][11][12]. Li et al demonstrated that increasing cultured volume from 20 to 40 mL increased yield by 19% [9]. Collecting only one BC should be discouraged because it results in an inadequate volume of cultured blood and therefore lacks sufficient sensitivity for detecting BSI [6].…”

Update on detection of bacteremia and fungemia.

“…Since bacteria are rapidly cleared from blood and since fever spikes follow bacteremic episodes by 30 to 90 min, the best opportunity for recovering pathogenic microorganisms should be as soon after the fever spike as possible. Interestingly, in the only published systematic study of which we are aware, Li et al (97) showed that there was no difference in organism recovery between multiple blood cultures drawn simultaneously and those drawn serially over a 24-h period. Nonetheless, since blood cultures should be collected before antimicrobial agents are given and since newer blood culture systems can detect microbial growth within a few hours, it makes more sense to draw blood cultures simultaneously rather than serially.…”

Identifying and Classifying Bloodstream Infections Among Hemodialysis Patients

“…This can be complicated for some freestanding dialysis centers that must send blood cultures out to sometimes distant laboratories. Third, blood cultures can yield false-negative results, especially if done after antimicrobials have been started or if inadequate volumes of blood are sampled (8,9). Blood cultures may also not detect some important pathogens (e.g., Legionella pneumophila) or results may be delayed when certain pathogens are involved (e.g., invasive fungal infections) (10).…”

“…To increase yield and to assist with interpretation, multiple culture sets should generally be obtained, but the recommended time interval between cultures varies. One study evaluated the timing of serial cultures and found no obvious difference in yield between cultures collected at the same time, 10 minutes to 2 hours apart, or 2 hours to 24 hours apart (9). CLSI recommends that blood cultures be drawn simultaneously or over a short interval (16).…”

“…The concentration of organisms in the blood during a BSI is generally thought to be relatively low, in the range of <1-10 CFUs/ml, so obtaining adequate blood volumes for culture is paramount to improving detection (24). Li et al (9) found that an increase from 20 ml cultured to 40 ml increased the yield of the cultures by 19%, while adding 20 ml drawn within 24 hours after 40 ml increased the yield an additional 10%. In another study, the yield IDENTIFYING AND CLASSIFYING BLOODSTREAM INFECTIONS beyond that found when 10 ml was drawn for culture, increased 29.8% for 20 ml, 47.2% for 30 ml, and 57.9% for 40 ml (20).…”