Purpose: We aimed to determine whether serum procalcitonin (PCT) values could help in identifying flu in patient admitted to the emergency department (ED) with influenza-like illness (ILI) during influenza A(H1N1)2009 pandemic.
Methods: An observational retrospective cohort study was performed in a referral ED for emerging infectious diseases. All patients tested for influenza A(H1N1)2009 by Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) and procalcitonin between June 2009 and January 2010 were analyzed. PCT was studied for its negative predictive value of bacterial infection. Patients PCT-/RT-PCR + were considered as true positive.
Results: On the 80 patients included, 16 were positive for influenza A(H1N1)2009 RT-PCR, all but one of them had low PCT concentrations. Conversely, 19 (30%) of the 64 patients with negative RT-PCR had elevated PCT concentrations. For a PCT threshold <0.25 μg/L, sensitivity was 0.94, specificity 0.30, positive predictive value 0.25 and negative predictive value 0.95 for the diagnosis of flu.
Conclusion: In the context of an influenza pandemic, serum PCT measurement may be useful for clinical decisions in the ED as most of RT-PCR confirmed patients have low PCT values. Patients with PCT above 0.25 μg/L are unlikely to have a unique diagnosis of flu.
Keywords: Procalcitonin; antibiotic; emergency department; flu; influenza.