The Correlation between Infection Probability Score and Procalcitonin in Emergency Department Patients

ABSTRACT

PURPOSE: Procalcitonin is a well-established biochemical marker for bacterial infection. We conducted this study to analyze the correlation between procalcitonin and Infection Probability Score (IPS), a recently introduced scoring system to predict bacterial infection in intensive care unit patients. The cutoff value of IPS corresponding to procalcitonin cutoff values was determined for procalcitonin-guided antibiotic therapy in emergency department (ED) patients. METHODS: A retrospective observation study was conducted on adult ED patients who simultaneously underwent an IPS-required blood test and procalcitonin treatment from January 1, 2012 to June 30, 2012. Based on their diagnosis at discharge, patients were grouped into a lower respiratory infection group or an "other" diagnosis group. The correlation between IPS and procalcitonin was analyzed by correlation and linear regression analysis. The IPS value corresponded to 0.25 ng/mL procalcitonin (in the lower respiratory infection group) and 0.5 ng/mL (in the other diagnosis group) as inferred by ROC curve analysis. A total of 722 cases (lower respiratory infection group 258, other diagnosis group 464) were included in the final analysis. RESULTS: In correlation analysis, the IPS showed a significant correlation with procalcitonin level in both groups (r=0.26, p or =0.25 microg/L in the lower respiratory infection group (area under curve 0.783 [95% CI, 0.724-0.841], sensitivity 77.8%, specificity 72.3%). Also, IPS 14 could predict procalcitonin> or =0.5 microg/L in the other diagnosis group (area under curve 0.764 [95% CI, 0.717-0.810], sensitivity 70.1%, specificity 74.2%). CONCLUSION: The IPS had a significant correlation with procalcitonin level and IPS> or =14 corresponded to the procalcitonin cut-off value to predict bacterial infection in ED patients. Thus, IPS> or =14 may be used to predict bacterial infection and can guide early anti-microbial therapy in ED patients when procalcitonin is not readily available.