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106 - Solitary blood cultures and blood culture contamination rates as preanalytic quality indicators of blood culture practice

Autor(s): A. Camporese

Issue: RIMeL - IJLaM, Vol. 3, N. 2, 2007 (MAF Servizi srl ed.)

Page(s): 106-112

Background. Previous studies have shown that acquiring at least 2 sets of blood samples instead of just 1 set represents better performance when attempting to diagnose sepsis. Infact, the likelihood that a blood culture specimen container will capture the presence of bacteria in the blood of a septic patient increases with the number of blood samples collected during the patient’s febrile episode. Contaminated blood cultures may cause results to be misinterpreted, create unnecessary work for the laboratory, and increase costs. Our objective was to determine wether the frequency with which solitary blood culture samples obtained from adult inpatients and outpatients were submitted to our laboratory or the rate of contaminated blood cultures, as preanalytic quality indicators of blood culture practice. Methods. In our study we have investigated all blood culture samples collected from inpatients and outpatients (which came not only from community strictly, but also from nursing homes and residential home care centers) in the past 3 years (2003-2005). During the 3 years study period we measured: 1) the number of blood culture sets obtained from adult (15 years or older) inpatients and outpatients and rates of solitary blood cultures; 2) the contamination rates, expressed by the number of organisms isolated that are more often considered contaminants, like coagulase negatives staphylococci (CoNEG), the most commonly isolated contaminants from blood cultures. We did not evaluate the consequences of solitary blood cultures and contamination on clinical outcomes. Results. During the study period, we examined a total of 6.437 adult patients with suspected sepsis (5.479 inpatients and 858 outpatients). Solitary blood cultures were 927 (rate 14,4%). During the year 2005 we obtained an increasing rate of solitary blood cultures (16,1% versus 13,3% in 2004 and 13,4% in 2003). Solitary blood cultures increased expecially in hospital setting, where the rate raised from 11,1% (year 2003) to 15,1% (year 2005) and where CoNEG increased likewise from 4,7% to 5,4%. Conclusions. Solitary blood culture and contamination rates can represent good preanalytic quality indicators of blood culture practice and a good method to evaluate sepsis diagnostic appropriateness. Our data showed that solitary blood culture and contamination rates increased along the late 3 years, expecially in hospital setting. The results obtained will provide benchmark for quality assessment and an opportunity to initiate specific corrective actions and continuous, specific quality improvement programs. Measure of solitary blood culture and contamination rates will be monitored routinely for the next years as a part of total quality control programs. Key words: solitary blood cultures, contamination, preanalytic quality.

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