Tamara van Donge

Chapter 7 128 Determining and establishing (gestational) age-dependent Scr reference ranges early in neonatal life could support the clinical evaluation of kidney function, especially when considering extremely low birth weight neonates (ELBW, ≤1000 g). Aims of this study were (i) to characterize the dynamics of Scr and associated creatinine clearance during the first six weeks of life by the development of a mathematical model, (ii) to identify and quantify factors influencing Scr and kidney function in this specific population, and (iii) to derive age-dependent Scr reference ranges to facilitate monitoring and evaluation of kidney function in ELBW neonates. Methods Study population and clinical characteristics Data for this retrospective study is based on longitudinal Scr data of neonates admitted to the neonatal intensive care unit (NICU) of the University Hospitals Leuven. The study population used for model development has been previously described and includes all neonates admitted to the NICU of the University Hospitals Leuven between July 2007 and August 2011 whose Scr concentrations were available. 11 For the current analysis, all Scr concentrations during the first six weeks of life (extended to all available Scr data in the first 42 days after birth instead of the more narrow time windows in the initial paper) 3 were retrieved from these ELBW neonates (≤ 1000 g). In addition, all clinical data (demographic characteristics and information on co-medication) were retrieved from medical files, verified and complemented. Detailed information on the perinatal characteristics (i.e. 21% of women were diagnosed with pre-eclampsia, 33% of ELBW neonates were small for gestational age, median duration of ventilation was 8 days, and median days until full enteral feeding was 34 days) can be found in the initial paper, published in this journal. 3 Clinical data, such as GA, birth weight, current weight, sex, length, mode of delivery (MOD), ibuprofen treatment (IBU), treatment with inotropic agents (as disease severity marker), maternal betamethasone treatment, neonatal death and Scr concentrations from birth through six weeks of life were retrieved. Patients were excluded if there was no information on GA and/or MOD, or if they were not classified as ELBW. An external evaluation analysis was performed based on an additional dataset of a retrospective study to explore postnatal albuminemia trends. This dataset includes all neonates admitted to the NICU of the University Hospitals Leuven between June 2015 and March 2017 whose albuminemia data were available. For the external evaluation dataset, ELBW cases were selected and Scr measurements were extended to the first six weeks of life for the current study. Ethical approval of the current study covered the additional