Tuesday, August 21, 2018

Blood cultures volume

Q: What is the optimal volume for each blood culture in adults? 

A) 5 mL 
B) 10 mL 
C) 20 mL 
D) 30 mL 
E) It does not depend on volume

Answer: C

The optimal volume for each blood culture in adults is 20 mL with 10 mL for an aerobic bottle and 10 mL for an anaerobic bottle, each.

Ideally three blood culture sets are recommended with first two blood cultures, drawn with separate venipunctures. The third blood culture set should be drawn four to six hours later.

The take home message of this question is to understand that low quantity of blood volume may hamper the results of blood culture (choice E).



1. . Miller JM, Binnicker MJ, Campbell S, et al. A Guide to Utilization of the Microbiology Laboratory for Diagnosis of Infectious Diseases: 2018 Update by the Infectious Diseases Society of America and the American Society for Microbiology. Clin Infect Dis 2018. 

2.  Ilstrup DM, Washington JA 2nd. The importance of volume of blood cultured in the detection of bacteremia and fungemia. Diagn Microbiol Infect Dis 1983; 1:107. 

3. Mermel LA, Maki DG. Detection of bacteremia in adults: consequences of culturing an inadequate volume of blood. Ann Intern Med 1993; 119:270.

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