We assessed whether the GFR marker cystatin C can be measured reliably in capillary blood samples in children with renal disease. Cystatin C was measured in venous and capillary blood samples obtained simultaneously from 48 children, and GFR was estimated using the Filler equation. Estimated GFR based on capillary cystatin C concentrations was higher than the venous cystatin C based GFR. The limits of agreement between estimated GFR based on capillary and venous measurements exceeded +/-20% at the upper reference concentration, which hampers the clinical usefulness of capillary sampling.
(c) 2009 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.