Blood cultures: towards zero false positives

Abstract

he culture of micro-organisms from blood is an essential laboratory test for the diagnosis of bacteraemia. Early positive results provide valuable diagnostic information on which appropriate antimicrobial therapy can be initiated. Like any tests, however, false-positive blood culture results can limit the utility of this important tool. These false-positive results arise due to contamination. Reports from NHS trusts and equipment suppliers suggest these contamination rates could be as high as 10 % ( Department of Health (DH), 2007) . A variety of strategies have been investigated and employed to decrease contamination rates. This article describes the utility of a variety of approaches to reduce the number of false-positive percutaneous blood cultures specifi cally in the adult population. Abstract Tat RUTGERS UNIV on April 13, 2015 bji.sagepub.com Downloaded from

Taxa de contaminação de testes hematológicos e seus fatores determinantes

“…(1)(2)(3)8,16) Regarding the number of needles used, no significant results were obtained. According to the reviewed bibliography, the single-needle with pre-attached holder (Vacutainer®) is considered to increase the inoculation sterility of the tubes and reduce the risk for professionals.…”

“…Most professionals reported to occasionally obtain samples from venous catheters, despite the protocol emphasizing that blood should not be extracted from intravenous catheters under any circumstances, as corroborated by other studies, (6) unless in the case of suspected bacteremia associated with a microorganism present in the intravenous device, (1,3,6,18) and always in the case of a patient with a complicated venous access.…”

“…(2) Regarding the amount of blood extracted by tube, with at least 10 ml, between 90 and 95% of microorganisms are obtained, although the current recommendations are 20 ml per tube. (1,2,7) Our hypothesis is that contamination of blood cultures in a hospital is higher than we thought, and that it happens in the emergency service in particular, where rushing in carrying out diagnostic tests and taking medical decisions presumably hinders the following of established protocols at the same time that it increases the percentage of mistakes, and therefore also increases the percentage of infected cultures.…”

“…It is a diagnostic tool used to isolate, detect and identify the microorganisms present in the blood, for further observation of their susceptibility in order to choose the appropriate treatment. (1)(2)(3) Contamination of blood cultures is a frequent problem in any hospital. A blood culture is considered to be contaminated if the presence of the following microorganisms is observed in 50% of all blood culture kits extracted in a day from a patient: S. coagulase-negative, alpha-hemolytic Streptococcus, Micrococcus species, Propionibacterium species, Corynebacterium species and Bacillus species.…”

Practical Steps to Lower Blood Culture Contamination Rates in the Emergency Department

“…Delays in identifying causative pathogens can result in overly conservative antibiotic treatment, potentially putting patients at risk for more serious illness, or, conversely, for treatment when no infection is present. 1,[3][4][5] In a study by Souvenir et al,5 half of patients with a false-positive blood culture result were treated with antibiotics, 10% of patients with significant bacteremia were treated with inappropriate agents, and vancomycin was misused in 34% of patients. These improper treatments cost an additional $1000 per patient (1998 dollars).…”