Comparison between white blood cell count, procalcitonin and C reactive protein as diagnostic and prognostic biomarkers of infection or sepsis in patients presenting to the emergency department

Background: Procalcitonin (PCT) is currently the most studied infection biomarker and its blood levels seem to mirror the severity of illness and outcome. PCT is widely used together with other biomarkers, such as white blood cells (WBC) count and C reactive protein (CRP), in order to guide antibiotic therapy. This study aimed to verify the diagnostic and prognostic power of WBC, CRP and PCT in patients with suspected infection in emergency department (ED). Methods: A total of 513 patients presenting to the ED with signs/symptoms of local infections or sepsis were enrolled. APACHEII score and in-hospital death were recorded. Patients were subdivided into quartiles by age, and the biomarkers were measured at baseline. Receiver operating characteristics (ROC) curves for evaluating diagnostic and prognostic role of PCT, CRP and WBC were calculated for each variable alone and combined. Results: When compared each other for PCT, CRP, and WBC there was no significant difference between the four subgroups. A direct correlation between PCT and WBC was found in the II, III, and IV quartiles (the highest correlation, r = 0.34, p < 0.0003). PCT alone or when combined with WBC showed the best diagnostic and prognostic power at ROC analysis. Conclusions: Our data demonstrate that WBC, but more CRP and PCT are reliable diagnostic and prognostic biomarkers, when considered in combination and with severity clinical score. PCT confirms its stronger usefulness as a diagnostic marker of sepsis. A multi-diagnostic tools approach is fundamental to perform a correct and rapid diagnosis of infection and sepsis in ED.