The Prognostic Role of Serum Procalcitonin for Adult Patients with Acute Diarrhea in the Emergency Department

<b>Background.</b> Acute diarrhea is one of the leading causes of Emergency Department (ED) access. The search for the causative pathogen cannot be routinely performed since conventional methods, like stool cultures, are time-consuming, requiring days for growth and delaying diagnosis and the start of therapy. In this large sample retrospective study, we evaluated the prognostic role of serum procalcitonin (PCT) for adult patients with acute diarrhea in the ED. <b>Methods.</b> In a retrospective, mono-centric study, we enrolled all patients visiting our ED complaining of acute diarrhea and then hospitalized over five years. Final diagnosis of an infective (including bacterial) diarrhea, any other infection, and a bloodstream infection (BSI) was collected by clinical records, according to the International Disease Classification 10th edition. Procalcitonin determination was obtained upon request of the ED physician at the admission visit based on patient evaluation and clinical judgment. <b>Results.</b> Of a total of 1910 patients, early PCT values (cut-off of 0.5 ng/mL) did not show a significant predictive value for infective diarrhea (OR 0.554 [0.395-0.778]), nor for bacterial diarrhea (OR 0.596 [0.405-0.875]). Conversely, PCT levels at ED admission showed a significant predictive value for a final diagnosis of any infection (OR 1.793 [1.362-2.362]) and, above all, of bloodstream infection (BSI) (OR 6.694 [4.869-9.202]). <b>Conclusions.</b> Our data suggest that in ED, where the complexity and heterogeneity of patients are very high, indiscriminate PCT-guided management of patients with diarrhea is not indicated. Conversely, in patients with diarrhea but also clinical suspicion of BSI, PCT determination remains a useful instrument, possibly improving clinical management.