Tamara van Donge

Chapter 10 196 Table 1: Kidney function and injury markers and their characteristics. Biomarker Features Molecular weight Sample medium Specific kidney localization Refs Beta 2-micrglobulin Component of MHC class I 11 kDa Serum Glomerulus 3, 36 Urine Tubules Beta-trace protein Expressed in brain, retina and kidneys 23-29 kDa Serum Glomerulus 3, 37 Urine Tubules Cystatin C Expressed in all tissues and body fluids 13.3 kDa Serum Glomerulus 3, 34 Urine Tubules NGAL Expressed mainly in neutrophils, as well in kidney, prostate and respiratory tracts 22-25 kDa Serum Glomerulus 38 Urine Tubules KIM-1 Expressed on surface of tubular epithelial cells 85 kDa Serum Glomerulus 34 Urine Tubules Uromodulin Produced in kidney (thick ascending limb) 105 kDa Serum Distal tubule 10, 39 Urine Distal tubule The majority of pediatric studies focused on the comparison of kidney function and injury markers between critically ill patients or between patients with kidney diseases and their control subgroups. 16-18,21,22 Since other disease conditions influence the kidney function, these control groups cannot be viewed as true controls for establishing a reference or normative interval. 2 Consequently, there is a paucity of data on age-dependency of serum kidney function and injury markers in the healthy pediatric population. The establishment of age-dependent reference intervals for kidney function and injury markers in a healthy pediatric population is important because it will allow earlier detection of kidney injury in pediatric patients who are ill and/or treated with nephrotoxic drugs. 23 Therefore, it is necessary to examine whether these markers have different values with advancing age, since that will help establish reference intervals for different pediatric age groups that are currently lacking. The aim of this study was to establish age-dependent reference intervals in a healthy pediatric population for a set of kidney function and injury markers (BTP, B2M, CYSC, KIM-1, NGAL and URO) that are currently not part of routine clinical care, as well as two markers (SCR and albumin) that are commonly used clinically. Additionally, the relationship between these markers and demographic characteristics such as weight and/or sex was investigated.