title: Monitoring renal function in children with Fabry disease: comparisons of measured and creatinine-based estimated glomerular filtration rate.
abstract: BACKGROUND
  Studies on renal function in children with Fabry disease have mainly been done using estimated creatinine-based glomerular filtration rate (GFR). The aim of this study was to compare estimated creatinine-based GFR (eGFR) with measured GFR (mGFR) in children with Fabry disease and normal renal function.
  
  
  METHODS
  Eighty-two examinations were done in 42 children (24 boys, 18 girls) with Fabry disease from three different centres. The mean age was 12.3 years. GFR was measured with iohexol, Cr(51)-EDTA or iothalamate, and the mean mGFR was 108 ml/min/1.73 m(2).
  
  
  RESULTS
  The widely used original Schwartz formula (1976) overestimated GFR substantially by 50.6 ml/min/1.73 m(2) with a very low accuracy, whereas the new abbreviated Schwartz formula (2009) showed relatively good performances with a mean GFR overestimation of 5.3 ml/min/1.73 m(2) and 79% of the eGFR calculated within 20% of mGFR, thus being only slightly superior to the Counahan-Barratt formula. However, less than half of the eGFR calculated by the new abbreviated Schwartz equation were within 10% of the mGFR. When repeated measurements were performed, mGFR showed less variation than eGFR.
  
  
  CONCLUSIONS
  The new abbreviated Schwartz formula should replace the original Schwartz formula in the routine follow-up of children with Fabry disease. The current creatinine-based GFR formulas are all hampered by low accuracy in the 'creatinine-blind' GFR range, and early progressive disease may be missed. Supplemental mGFR is, therefore, recommended in patients where changes in GFR have potential impact on important treatment regimens. Cystatin C-based GFR formulas remain to be validated in Fabry children.
authors.affiliation: Renal Research Group, Institute of Medicine, University of Bergen, Bergen, Norway. camilla.tondel@med.uib.no
authors.forename: Camilla
authors.initials: C
authors.lastname: Tøndel
authors.forename: Uma
authors.initials: U
authors.lastname: Ramaswami
authors.forename: Kristin Moberg
authors.initials: KM
authors.lastname: Aakre
authors.forename: Frits
authors.initials: F
authors.lastname: Wijburg
authors.forename: Machtelt
authors.initials: M
authors.lastname: Bouwman
authors.forename: Einar
authors.initials: E
authors.lastname: Svarstad
mesh_terms: D000293:Adolescent; D015992:Body Mass Index; D002648:Child; D003404:Creatinine / Q000097:blood*; D056947:Enzyme Replacement Therapy; D000795:Fabry Disease / Q000503:physiopathology* / Q000628:therapy; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male
chemical_list: D003404:Creatinine