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Journal of Clinical Microbiology, September 2007, p. 2765-2769, Vol. 45, No. 9
0095-1137/07/$08.00+0     doi:10.1128/JCM.00140-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Is the Volume of Blood Cultured Still a Significant Factor in the Diagnosis of Bloodstream Infections?

Division of Clinical Microbiology and Infectious Diseases, Hospital General Universitario "Gregorio Marañón," Universidad Complutense, Madrid, Spain,¹ Division of Infectious Diseases, Hospital Juan Canalejo, La Coruña, Spain²

Received 19 January 2007/ Returned for modification 28 February 2007/ Accepted 4 June 2007

"The higher the volume of blood cultured the higher the yield of blood cultures" has been a well-accepted dictum since J. A. Washington II performed his classic work. This rule has not been questioned in the era of highly automated blood culture machines, nor has it been correlated with clinical variables. Our objective in this study was to complete a prospective analysis of the relationship between blood volume, the yield of blood cultures, and the severity of clinical conditions in adult patients with suspected bloodstream infections (BSI). During a 6-month period, random samples of blood cultures were weighed to determine the volume of injected blood (weight/density). Overall, 298 patients with significant BSI and 303 patients with sepsis and negative blood cultures were studied. The mean volume of blood cultured in patients with BSI (30.03 ± 14.96 ml [mean ± standard deviation]) was lower than in patients without BSI (32.98 ± 15.22 ml [P = 0.017]), and more episodes of bacteremia were detected with <20 ml (58.9%) than with >40 ml (40.2%) of blood cultured (P = 0.022). When patients were stratified according to the severity of their underlying condition, patients with BSI had higher APACHE II scores, and higher APACHE II scores were related to lower sample volumes (P < 0.001). A multivariate analysis showed that in the group of patients with APACHE II scores of 18, higher volumes yielded higher rates of bacteremia (odds ratio, 1.04 per ml of blood; 95% confidence interval, 1.001 to 1.08). We conclude that the higher yield of blood cultures inoculated with lower volumes of blood reflects the conditions of the population cultured. Washington's dictum holds true today in the era of automated blood culture machines.

Published ahead of print on 13 June 2007.

This article has been cited by other articles:

• Sergentanis, T. N., Mariolis, A., Bouza, E., Sousa, D. (2008). Volume of Blood Cultured and APACHE II Score: an Intriguing Diptych for Diagnosis of Bloodstream Infections?. J. Clin. Microbiol. 46: 2828-2828 [Full Text]  
• Nicola, F. G., Weinstein, M. P., Lee, A., Reller, L. B., Mirrett, S. (2008). Assessing How Many Blood Cultures Are Needed for Detecting Bloodstream Infections. J. Clin. Microbiol. 46: 1155-1156 [Full Text]