Febrile Patient Blood Sample Protocol

Patient samples were handled as described in our previous study[12 (link)]. Briefly, blood samples were collected to lithium-heparin tubes from adult febrile patients (age range 53–91, median age 76 years) coming to the outpatient emergency clinic of Peijas Hospital, Helsinki University Hospital (Vantaa, Finland). Blood cultures were taken based on clinical suspicion of a serious infection both from the later confirmed cases and from the febrile controls on the same grounds. An approval for the study was received from the Ethics Committee of Medical Sciences (HUS 169/13/01/2014) and a written informed consent was obtained from all subjects at the time of plasma sample collection. Blood culturing was performed by using BacT/ALERT® FA Plus and BacT/ALERT® FN Plus blood culture bottles (BioMerieux, Durham, NC, USA) and BacT ALERT 3D incubator (BioMerieux). Identification of bacteria in positive blood cultures was done by Vitek MS MALDI-TOF instrument (bioMerieux). For proteomic analyses blood samples (3–5 ml) were adjusted to room temperature for 15 min. Subsequently, plasma was separated by centrifugation (1200xg) for 10 minutes at room temperature. Plasma samples were stored at -70°C until tested at the same time.