Letters to the Editor A Quality Control Comment Concerning Routine Blood Cultures
Received August 15, 1975; accepted for publication September 12, 1975. Keywords: Blood culture collection; Quality control in microbiology.
416
sampling system) is necessary even though it may be less desirable. 3 T h e use of a syringe is more liable to contamination from room air, and multiple samples delivered from a syringe may all be contaminated, whereas multiple samples from a transfer set will be more likely to yield contaminants (if present) in the initial bottles but no contaminants in the last bottles filled. 3. We recommend that the 50 ml. blood culture vacuum bottles be manufactured to draw 3 - 5 ml. when used with a transfertubing closed-system set. WILLIAM SUEOKA, IRWIN SCHOEN,
M.D.
M.D.
Department of Pathology Los Robles Hospital 215 W. Janss Road Thousand Oaks, California 91360 References 1. Bartlett RC, Ellner PD, Washington I I J A: Blood cultures, Cumitech 1, American Society for Microbiology. Edited by J C Sherris. Washington, D.C., October 1974 2. Isenberg HD, Washington JA II, Balows A, et al: Collection, handling, and processing of specimens, Manual of Clinical Microbiology. Second edition. Edited by EH Lennette, EH Spaulding, J P Truant. Washington D.C., American Society for Microbiology, 1974, p p 5 9 - 8 8 3. Lee S, Schoen I, Malkin A: Comparison of use of alcohol with that of iodine for skin antisepsis in obtaining blood cultures. Am J Clin Pathol 47:646-648, 1967 4. Washington J A II: Subject Review, Blood cultures, principles and techniques. Mayo Clin Proc 50:91-98, 1975
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To the Editor: — 1. Blood culture sample size is ideally determined by the amount of blood culture medium to be used. T h e recommended ratio of blood sample to medium is 1:10 to 1.-20.1-2-4 For 50 ml. of the medium, according to the above ratios, the blood sample size should be between 2.5 and 5.0 ml. 2. Some currently available commercial blood culture bottles or tubes provide instructions for blood collection that are apparently inappropriate considering the above recommendations. For example, a supplier with a bottle that contains 50 ml. of medium states on the bottle label and package that 3 ml. or more of blood should be obtained, delivered to the bottle, and that as much as 10 ml. of blood may be cultured. However, this bit of information is in error; the instructions should indicate a maximum of 5 ml. of blood be cultured, as is stated on an advertisement flyer by the company describing the same product. Since the bottle has a vacuum sufficient to draw as much as 14 ml. of blood and there is no indicator on the bottle as to the maximum allowable level to be drawn, the use of a transfer tubing set (a closed sampling system) may result in a significant overdraw into the blood culture bottle. T o avoid this, a syringe transfer (an open
Received August 15, 1975; accepted for publication September 12, 1975. Keywords: Blood culture collection; Quality control in microbiology.
416
sampling system) is necessary even though it may be less desirable. 3 T h e use of a syringe is more liable to contamination from room air, and multiple samples delivered from a syringe may all be contaminated, whereas multiple samples from a transfer set will be more likely to yield contaminants (if present) in the initial bottles but no contaminants in the last bottles filled. 3. We recommend that the 50 ml. blood culture vacuum bottles be manufactured to draw 3 - 5 ml. when used with a transfertubing closed-system set. WILLIAM SUEOKA, IRWIN SCHOEN,
M.D.
M.D.
Department of Pathology Los Robles Hospital 215 W. Janss Road Thousand Oaks, California 91360 References 1. Bartlett RC, Ellner PD, Washington I I J A: Blood cultures, Cumitech 1, American Society for Microbiology. Edited by J C Sherris. Washington, D.C., October 1974 2. Isenberg HD, Washington JA II, Balows A, et al: Collection, handling, and processing of specimens, Manual of Clinical Microbiology. Second edition. Edited by EH Lennette, EH Spaulding, J P Truant. Washington D.C., American Society for Microbiology, 1974, p p 5 9 - 8 8 3. Lee S, Schoen I, Malkin A: Comparison of use of alcohol with that of iodine for skin antisepsis in obtaining blood cultures. Am J Clin Pathol 47:646-648, 1967 4. Washington J A II: Subject Review, Blood cultures, principles and techniques. Mayo Clin Proc 50:91-98, 1975
Downloaded from http://ajcp.oxfordjournals.org/ by guest on June 5, 2016
To the Editor: — 1. Blood culture sample size is ideally determined by the amount of blood culture medium to be used. T h e recommended ratio of blood sample to medium is 1:10 to 1.-20.1-2-4 For 50 ml. of the medium, according to the above ratios, the blood sample size should be between 2.5 and 5.0 ml. 2. Some currently available commercial blood culture bottles or tubes provide instructions for blood collection that are apparently inappropriate considering the above recommendations. For example, a supplier with a bottle that contains 50 ml. of medium states on the bottle label and package that 3 ml. or more of blood should be obtained, delivered to the bottle, and that as much as 10 ml. of blood may be cultured. However, this bit of information is in error; the instructions should indicate a maximum of 5 ml. of blood be cultured, as is stated on an advertisement flyer by the company describing the same product. Since the bottle has a vacuum sufficient to draw as much as 14 ml. of blood and there is no indicator on the bottle as to the maximum allowable level to be drawn, the use of a transfer tubing set (a closed sampling system) may result in a significant overdraw into the blood culture bottle. T o avoid this, a syringe transfer (an open
