036 - Quality Assurance of blood culture
Autor(s): A. Conti, R. De Rosa
Issue: RIMeL - IJLaM, Vol. 4, N. 3-S1, 2008 (MAF Servizi srl ed.)
Page(s): 36-44
Blood culture is a microbiologic test used to check for the presence of bacteria in the bloodstream. Blood is collected through sterile vials containing anticoagulated nutritive media; these are then incubated in thermostatic ovens. Isolation of microorganisms by blood culture is the essential pre-requisite to get a diagnosis of bacteriemia, infectious endocarditis and many other infectious diseases associated with the clinical picture of fever of unknown origin. Diagnostic efficiency and clinical significance of the test are strictly dependent from many variables in methodology, logistics, interpretation. The pre-analytical steps are of paramount importance, as long as a reliable colture system, solid laboratory procedures and expertise and a sound and effective communication protocol. Interfering factors in bacterial isolation are: a) timing of the blood drawing, also in relation to the current use of antibiotics (type and pharmacological characteristics); b) antiseptic technique of the skin before blood drawing; c) number of blood culture set for each event; d) sampling errors (blood volume), e) dilution factor by the medium; f) drug neutralisation substances, such as active charcoal or resins; g) test conditions (temperature, oxygen pressure and length of incubation); h) possible blind sub-cultures. Moreover, the influence of exogen contamination increases potential risks for incorrect interpretation of false positive/negative results and affects the therapeutic turn around time. Laboratory physicians must take full responsibility for the optimal clinical use of this test, sharing with their clinical colleagues both information and consistent medical decisions. A powerful aid to this hard task will be garanted by an intelligent approach mediated by Information Technology