Detection kinetics for positive blood culture bottles by using the VITAL automated system

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Abstract
The VITAL system principle is based on homogeneous fluorescence technology. During an 11-month period, a total of 19,706 blood cultures from adult patients hospitalized in various establishments of the Montpellier Teaching Hospital were collected in VITAL bottles, of which 1,939 were declared positive. Only 204 bottles (1.04%) were false positives. The 1,735 true-positive bottles were collected from 130 patients. The final visual control permitted the detection of 10 falsely negative bottles (0.05%), of which 5 contained clinically significant microorganisms from four patients. The kinetics of detection for all microorganisms showed that 66.6% were detected within 24 h, 83.1% within 48 h, 95.5% within 120 h, and 100% within 150 h. No clinical episode would have been missed had a 5-day protocol been used instead of a 7-day protocol. Among the positive bottles, 65.7% were detected by the SLOPE algorithm, 20.1% by the DELTA algorithm, and 14.2% by the THRESHOLD algorithm. This retrospective study of our results shows that a 5-day protocol is sufficient for the detection of septic episodes using the VITAL system.