Performance of enzymatic creatinine methods in the pediatric concentration range

Creatinine is a widely used clinical biomarker in adult and pediatric patients to estimate kidney function and glomerular filtration rate. There are however few recent studies that have addressed method performance in the creatinine range relevant for children. This study aimed to describe measurement performance in the pediatric concentration range by comparing commonly used enzymatic methods on four platforms: Abbott Alinity, Radiometer ABL800, Roche Cobas and Siemens Atellica, to the reference method isotope dilution mass spectrometry (IDMS). A secondary aim was to compare the Roche enzymatic methods by using dilutions of control sera issued by the Nordic Association of Clinical Chemistry. We found varying accuracy of the creatinine methods in the low concentration range. The relative difference between platforms, in an investigated range below 75 µmol/L, decreased as creatinine concentration increased. Using an absolute factor to correct for method bias as recommended by one of the manufacturers could hamper measurement trueness in the low concentration range. The in vitro diagnostic industry and stakeholders should strive towards creatinine measurement agreeability. Attention to the pediatric concentration range is needed when correcting for method bias.