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Croat Med J. 2012 Feb 15;53(1):30-9.

Predictors of positive blood cultures in critically ill patients: a retrospective evaluation.

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Intensive Care Unit, Ospedale Regionale Bellinzona e Valli, Bellinzona, Switzerland.



To identify predictors of bacteremia in critically ill patients, to evaluate the impact of blood cultures on the outcome, and to define conditions for breakthrough bacteremia despite concurrent antibiotic treatment.


A descriptive retrospective study was performed over a two-year period (2007-2008) in the medico-surgical Intensive Care Unit (ICU) of the San Giovanni Hospital in Bellinzona, Switzerland.


Forty-five out of 231 patients (19.5%) had positive blood cultures. Predictors of positive blood cultures were elevated procalcitonin levels (>2 µg/L, P<0.001), higher severity scores (Simplified Acute Physiology Score II>43, P=0.014; Sequential Organ Failure Assessment >4.0, P<0.001), and liver failure (P=0.028). Patients with bacteremia had longer hospital stays (31 vs 21 days, P=0.058), but their mortality was not different from patients without bacteremia. Fever (t>38.5°C) only showed a trend toward a higher rate of blood culture positivity (P=0.053). The rate of positive blood cultures was not affected by concurrent antibiotic therapy.


The prediction of positive blood culture results still remains a very difficult task. In our analysis, blood cultures were positive in 20% of ICU patients whose blood was cultured, and positive findings increased with elevated procalcitonin levels, liver failure, and higher severity scores. Blood cultures drawn >4 days after the start of antibiotic therapy and >5 days after surgery could detect pathogens responsible for a new infection complication.

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