Blood Samples
BLOOD
Blood samples were collected in ethylenediaminetetraacetic acid (EDTA) tubes upon PICU admission (day 0 or 1) and on days 3 and 5 if patients were still participating in the study by that time. The blood samples were processed for plasma collection by centrifugation, after which they were stored at −80°C. Plasma concentrations of CCK, PYY, leptin, glucagon, and I-FABP2 were assessed with enzyme-linked immunosorbent assays (ELISA) according to the manufacturer’s protocol (CCK: Cloud-Cone Corp. CEA802Ca; PYY: Cloud-Cone Corp. CEB067Hu; leptin: Mediagnost ELISA for leptin E07; glucagon: Mercodia 10-1271-01; I-FABP2: BioVendor RD191246200R). Citrulline concentrations were assessed using liquid chromatography-mass spectrometry. The assays were measured in batches sorted by day. For results below the measuring range (limit of quantitation, LOQ), the values for I-FABP2 concentrations were extrapolated using the calibration curve. For the other biomarkers, the values were estimated using LOQ/√2.