IntroductionFaecal calprotectin (FC) is a routinely used marker for identifying and monitoring children with inflammatory bowel disease (IBD). This non-invasive test is useful for screening children with gastrointestinal symptoms to avoid unnecessary invasive procedures. In this study, we validated for the first time the performance of a fully automated particle-enhanced turbidimetric immunoassay (PETIA) on the VITROS® 5600 analyzer for measurement of FC in symptomatic children and adolescents.Materials and methodsFor performance validation of the PETIA (fCAL® turbo, Bühlmann Laboratories, Switzerland) on the VITROS® 5600 analyzer (Ortho Clinical Diagnostics, USA) limit of quantitation (LoQ), linearity, precision data and calibration curve stability were defined. Additionally, 95 faecal samples were measured using the PETIA, an enzyme-linked immunosorbent assay (ELISA; fCAL®, Bühlmann Laboratories, Switzerland) and a semi-quantitative lateral flow assay (Quantum Blue Reader®, Bühlmann Laboratories, Switzerland) for agreement evaluation.ResultsThe LoQ for calprotectin using PETIA on the VITROS® 5600 analyzer was 21 µg/g. The linearity range was 20 - 2100 µg/g and the precision study showed a total coefficient of variation (CV) between 2.3% and 8.9%. The calibration curve was stable for 4 weeks. Using the clinical samples quantifiable by PETIA, ELISA and the semi-quantitative lateral flow assay, Passing-Bablok regression analysis and Bland-Altman plots showed good agreement.ConclusionsDue to good performance characteristics and agreement with established methods, the fully automated PETIA on the routine chemistry analyzer VITROS® 5600 is a new analytical option for the rapid determination of FC.

Objective This study describes a modified 4-hour peritoneal equilibration test (PET) for analyzing peritoneal transport characteristics of proteins with different molecular weights and predicting daily peritoneal protein losses in children on chronic peritoneal dialysis (PD). Design Cross-sectional study. Setting A single regional pediatric dialysis unit in a teaching hospital. Patients 9 stable pediatric dialysis patients; 4 were on continuous ambulatory PD, 5 were on continuous cycling PD. Main Outcome Measures Serum and dialysate concentrations of IgG, albumin, β2-microglobulin, and transferrin were determined during a PET. Changes in dialysate-to-plasma (D/P) ratios were determined hourly. Agreement between PET-derived and measured daily peritoneal protein losses was examined. Results The D/P ratio decreased with increased molecular radius ( p < 0.0001). Many children had low plasma levels of IgG, albumin, and transferrin, but elevated levels of β2-microglobulin. The D/P ratio increased linearly during the PET for all measured proteins, regardless of molecular weight. There was close correlation between 4-hour PET protein losses and 24-hour losses during routine PD. Conclusions Proteins are lost through the peritoneum according to their size, demonstrating linear transport kinetics during a 4-hour PET. The PET-derived data predicted daily protein losses in children on chronic PD. This approach might help to eliminate inaccuracies due to incomplete dialysate collection.

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