- of-care procalcitonin ( PCT ) and clinical performances in an unselected population as compared

Procalcitonin (PCT) is well established as a biomarker that reflects the presence and severity of local and systemic bacterial infections, i.e. sepsis [1] and as valuable tool to guide antibiotic treatment [2, 3] allowing to tailor antibiotic treatment and to reduce antibiotic resistance [4]. PCT is widely used as a rule-out test for sepsis and it is frequently requested by primary care doctors facilitating a clinician decision. Several studies have shown that specific treatment should ideally be initiated within 4 h and no later than 8 h after diagnosis [5, 6]. Hence, the establishment of a point-of-care (POC) for the determination of the PCT could be of great interest reducing the time to diagnosis for patients with suspected sepsis. To date, only Thermo Fisher has developed a POC (called BRAHMS PCT direct) for fast PCT measurement [7]. In recent times, Radiometer launched a POC test for PCT adapted for emergency situations with a low functional sensitivity. Here, we report the analytical performances of the Radiometer AQT90 FLEX® PCT assay (Neuilly-Plaisance, France) and we evaluate the concordance with Elecsys BRAHMS PCT on Cobas8000/e602© (Roche, Meylan, France) and BRAHMS PCT Kryptor Compact Plus© results from central laboratory considered as reference method. AQT90 FLEX® PCT immunoassay on a AQT90 Flex® instrument is a one-step sandwich immunofluorometric assay. All reagents and the antibodies were manufactured by Radiometer. The minimum sample volume is 2 mL. EDTA or lithium heparinized whole blood or plasma samples are appropriate. Results were obtained within 18 min with an analytic measuring range up to 100 ng/ mL. The 95th percentile claimed by the manufacturer was < 0.12 ng/mL for whole blood and 0.087 ng/mL for plasma. BRAHMS PCT assay is based on the TRACE on Kryptor Compact Plus© instrument (ThermoScientific, BRAHMS AG, Hennigsdorf, Germany) using anti-calcitonin polyclonal antibody conjugated with europium cryptate and anti-katacalcin monoclonal antibody conjugated with XL665. Results were obtained within 19 min. The 95th percentile claimed by the manufacturer was < 0.064 ng/mL. The Elecsys BRAHMS PCT© assay on Cobas8000/e602© was an automated sandwich immunoassay based on ECLIA technology with results obtained within 18 min. Reagents, calibrators and controls were provided by ThermoFisher. This test is based on two anti-PCT monoclonal antibodies. The matrix recommended by the manufacturer was EDTA, dry or lithium heparinized tubes. The 95th percentile claimed by the manufacturer was < 0.046 ng/mL. Evaluation of the analytical performance was assessed following the CLSI EP5, CLSI EP06A and CLSI EP17 guidelines [8–10]. A plasma pool with PCT concentration of 7.3 ng/mL was used to test the linearity and was *Corresponding author: Jean Paul Cristol, Department of Biochemistry, Centre Ressources Biologiques de Montpellier, University Hospital of Montpellier, Montpellier, France, Fax: +33 4 67 33 83 93, E-mail: jp-cristol@chu-montpellier.fr; and PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214. 34295 Montpellier cédex 5, France Anne Marie Dupuy and Quentin Chevrier: Department of Biochemistry, Centre Ressources Biologiques de Montpellier, University Hospital of Montpellier, Montpellier, France Yan Olejnik: LaboSud OCBiologie, Montpellier, France Anne Sophie Bargnoux and Stéphanie Badiou: Department of Biochemistry, Centre Ressources Biologiques de Montpellier, University Hospital of Montpellier, Montpellier, France; and PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214. 34295 Montpellier cédex 5, France