title: Effect of long-term storage of urine samples on measurement of kidney injury molecule 1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL).
abstract: BACKGROUND
  Levels of urinary biomarkers, such as kidney injury molecule 1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL), can determine the risk of renal damage and predict the outcome of multiple kidney diseases, including transplant rejection. Studies of urinary biomarkers frequently use urine that has been stored frozen before analysis without taking into account the potential of biomarker degradation during storage.
  
  
  METHODS
  Observational study.
  
  
  METHODS
  39 kidney transplant patients visiting an outpatient clinic.
  
  
  METHODS
  Urine storage conditions (4°C and -80°C with or without protease inhibitors) and centrifugation after thawing of samples.
  
  
  RESULTS
  Urinary concentrations of NGAL and KIM-1.
  
  
  METHODS
  NGAL and KIM-1 were measured with commercially available enzyme-linked immunosorbent assay kits.
  
  
  RESULTS
  Urinary NGAL and KIM-1 concentrations were stable in urine up to 48 hours when stored at 4°C and up to 6 months when stored at -80°C, independent of the addition of protease inhibitors. A centrifugation step prior to biomarker measurement did not change urinary biomarker concentrations of urine stored at -80°C.
  
  
  CONCLUSIONS
  Only KIM-1 and NGAL were measured, which possibly limits the relevance of the findings when making determinations about other urinary biomarkers.
  
  
  CONCLUSIONS
  This study recommends that urine samples collected for the assessment of KIM-1 or NGAL are immediately cooled to 4°C and subsequently frozen at -80°C within 2 days. At -80°C, both KIM-1 and NGAL concentrations are stable for at least 6 months.
authors.affiliation: Department of Nephrology, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands.
authors.forename: Mathijs
authors.initials: M
authors.lastname: van de Vrie
authors.affiliation: Department of Nephrology, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands.
authors.forename: Jeroen K
authors.initials: JK
authors.lastname: Deegens
authors.affiliation: Department of Nephrology, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands.
authors.forename: Johan
authors.initials: J
authors.lastname: van der Vlag
authors.affiliation: Department of Nephrology, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands. Electronic address: l.hilbrands@nier.umcn.nl.
authors.forename: Luuk B
authors.initials: LB
authors.lastname: Hilbrands
mesh_terms: D058186:Acute Kidney Injury / Q000175:diagnosis / Q000652:urine*; D000209:Acute-Phase Proteins / Q000652:urine*; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005615:Freezing; D000072596:Hepatitis A Virus Cellular Receptor 1; D006801:Humans; D000071068:Lipocalin-2; D054834:Lipocalins / Q000652:urine*; D008297:Male; D008562:Membrane Glycoproteins / Q000652:urine*; D008875:Middle Aged; D011446:Prospective Studies; D011518:Proto-Oncogene Proteins / Q000652:urine*; D011991:Receptors, Virus; D013048:Specimen Handling; D013997:Time Factors; D059349:Urine Specimen Collection / Q000379:methods
chemical_list: D000209:Acute-Phase Proteins; C491143:HAVCR1 protein, human; D000072596:Hepatitis A Virus Cellular Receptor 1; C489506:LCN2 protein, human; D000071068:Lipocalin-2; D054834:Lipocalins; D008562:Membrane Glycoproteins; D011518:Proto-Oncogene Proteins; D011991:Receptors, Virus
keywords: Kidney injury molecule 1 (KIM-1); neutrophil gelatinase-associated lipocalin (NGAL); urinary biomarkers; urine storage