title: Diurnal variation and short-term pre-analytical stability of serum soluble α-klotho in healthy volunteers: a pilot study.
abstract: OBJECTIVE
  To investigate the diurnal variability and pre-analytical stability of soluble α-klotho in serum.
  
  
  BACKGROUND
  Recent evidence suggests that the cleaved extracellular domain of the α-klotho receptor, soluble α-klotho, affects phosphate homeostasis, ion channel regulation and antifibrotic/antioxidant pathways. However, soluble α-klotho measurements have yielded inconsistent results when related to renal function, markers of mineral metabolism and patient outcomes. Pre-analytical factors such as biological variation and analyte stability may affect the interpretation of soluble α-klotho results but are yet to be formally assessed.
  
  
  METHODS
  Clotted blood samples were collected from 10 healthy adult volunteers at three time-points during the day to assess diurnal change. Additional samples were collected and allowed to stand at room temperature for 30, 60 and 120 min, prior to centrifugation and analysis to evaluate analyte stability. Serum soluble α-klotho was measured using a validated commercial enzyme-linked immunosorbent assay.
  
  
  RESULTS
  Delayed processing of samples had no significant effect on serum soluble α-klotho concentrations over a 2-h period. Serum soluble α-klotho concentrations remained stable over morning, midday and afternoon time-points in this pilot study.
  
  
  CONCLUSIONS
  Serum soluble α-klotho demonstrates short-term pre-analytical stability and minimal diurnal variability in this pilot study. Larger studies are warranted to confirm these findings.
authors.affiliation: Department of Nephrology, The Royal Melbourne Hospital (RMH), Parkville, Australia Department of Medicine (RMH), The University of Melbourne, Melbourne, Australia Jean.Tan@mh.org.au.
authors.forename: Sven-Jean
authors.initials: SJ
authors.lastname: Tan
authors.affiliation: Department of Nephrology, The Royal Melbourne Hospital (RMH), Parkville, Australia.
authors.forename: Edward R
authors.initials: ER
authors.lastname: Smith
authors.affiliation: Department of Nephrology, The Royal Melbourne Hospital (RMH), Parkville, Australia Department of Medicine (RMH), The University of Melbourne, Melbourne, Australia.
authors.forename: Tim D
authors.initials: TD
authors.lastname: Hewitson
authors.affiliation: Department of Nephrology, The Royal Melbourne Hospital (RMH), Parkville, Australia Department of Medicine (RMH), The University of Melbourne, Melbourne, Australia.
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Holt
authors.affiliation: Department of Nephrology, The Royal Melbourne Hospital (RMH), Parkville, Australia Department of Medicine (RMH), The University of Melbourne, Melbourne, Australia.
authors.forename: Nigel D
authors.initials: ND
authors.lastname: Toussaint
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood*; D002940:Circadian Rhythm; D004797:Enzyme-Linked Immunosorbent Assay; D005966:Glucuronidase / Q000097:blood* / Q000737:chemistry*; D064368:Healthy Volunteers; D006801:Humans; D000090265:Klotho Proteins; D008297:Male; D010865:Pilot Projects; D013048:Specimen Handling
chemical_list: D015415:Biomarkers; D005966:Glucuronidase; D000090265:Klotho Proteins
keywords: ELISA; soluble klotho; stability; variability