DETECTION OF BACTEREMIA IN ADULTS - CONSEQUENCES OF CULTURING AN INADEQUATE VOLUME OF BLOOD

The yield of blood cultures depends on the volume of blood cultured. W e recently discovered that 15% of blood-culture specimens from adults in our hospital were being collected in 3.5-mL pediatric tubes and tha t another 5%, drawn in 10-mL adult tubes, contained less than 5 mL of blood. A comparison of 829 matched pairs of standard-volume (mean, 8.7 mL) and low-volume (mean, 2.7 mL) blood cultures showed that standard -volume cultures had a substantially higher detection rate for bloodst ream infection than did low-volume cultures (92% compared with 69%; di fference, 23% [95% CI, 9% to 37%]; P < 0.001). Our data, together with an analysis of previous studies, show that the yield of blood culture s in adults increases approximately 3% per millilitre of blood culture d. A survey of 158 U.S. clinical microbiology laboratory directors in the American Society of Clinical Pathologists showed that only 20% of 71 responding laboratories record the volume of blood submitted for cu lture and that the practice of culturing suboptimal volumes of blood f rom adults is widespread. Clinical laboratories should routinely monit or the volume of blood cultured as a quality-assurance measure. Blood- culture specimens from adults should not be drawn using small pediatri c tubes.