Comparing C-reactive protein, procalcitonin, and interleukin-6 for the diagnosis of bacterial infection in adult atraumatic patients in a medical center emergency department

Introduction

Procalcitonin (PCT) has been proposed as a marker of sepsis in the critically ill patients. Its level is related to the severity of sepsis. We investigated the value of PCT, comparing with C-reactive protein (CRP) and interleukin (IL)-6, in the detection of infection in the emergency department (ED).

Methods

Ninety adult atraumatic patients admitted through the ED of a tertiary university hospital in June 2001 were consecutively enrolled. Forty-five were infected, and 31 were not infected. The serum levels of CRP (mg/l), PCT (ng/ml) and IL-6 (pg/ml) were compared between the infected and noninfected groups of patients. Mann-Whitney U test and chi-square test were employed to compare independent and group data, and the receiver operating characteristics (ROC) curve and the respective areas under the curve were calculated.

Results

The best cut-off level for CRP, PCT and IL-6, identified using Youden's Index, was 60 mg/l, 0.6 ng/ml and 24 pg/ml, respectively. Compared with CRP and IL-6, PCT had a comparable sensitivity, a lower specificity, and a lower area under the ROC curve. Bacteremic patients had higher PCT and IL-6 concentrations than those without bacteremia, but similar CRP concentrations. PCT and IL-6 levels were particularly high in septic shock patients.

Conclusions

PCT is not a better marker of infection than CRP and IL-6 in the adult ED patients, but it is a useful marker of the severity of infection.

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