title: Glucose is stable during prolonged storage in un-centrifuged Greiner tubes with liquid citrate buffer, but not in serum and NaF/KOx tubes.
abstract: BACKGROUND
  Delayed sample processing can affect accurate glucose measurement. Our aim was to investigate the stability of glucose in samples collected in serum, sodium fluoride/potassium oxalate (NaF/KOx) and Glucomedics tubes processed according to different controlled pre-centrifugation delays (up to 180 min after venipuncture) in order to simulate prolonged sample transport between venipuncture and centrifugation.
  
  
  METHODS
  Samples were collected from healthy volunteers (n=80) into either serum or NaF/KOx and Glucomedics tubes. Glucose concentration was measured in samples centrifuged immediately after venipuncture and compared with tubes processed with a delay of 60, 120 and 180 min prior to centrifugation. Differences between baseline and respective delayed centrifugation glucose value for each tube type were tested using the paired t-test. Mean bias calculated for each tube type and delay protocol was compared to recommended quality specifications for glucose (2.2%).
  
  
  RESULTS
  Glucose concentrations measured in all three delayed tube types were lower in comparison to respective baseline glucose concentrations measured in immediately processed tube (p<0.001). The highest decrease in glucose was observed in serum tubes in all specified time points (p<0.001), while glucose was most stable in Glucomedics tubes (p<0.001). The decrease in glucose observed for serum and NaF/KOx tubes was clinically significant at all specified time points while the bias for Glucomedics tubes did not exceed the criteria even with a centrifugation delay of 180 min.
  
  
  CONCLUSIONS
  Glucose stability in un-centrifuged Glucomedics tubes is much superior to serum and NaF/KOx tubes. Glucomedics tubes can be left un-centrifuged for up to 3 h without affecting glucose concentration.
authors.forename: Gordana
authors.initials: G
authors.lastname: Juricic
authors.forename: Ana
authors.initials: A
authors.lastname: Bakliza
authors.forename: Andrea
authors.initials: A
authors.lastname: Saracevic
authors.forename: Lara Milevoj
authors.initials: LM
authors.lastname: Kopcinovic
authors.forename: Sanja
authors.initials: S
authors.lastname: Dobrijevic
authors.forename: Sandra
authors.initials: S
authors.lastname: Drmic
authors.forename: Ana-Maria
authors.initials: AM
authors.lastname: Simundic
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000737:chemistry* / Q000378:metabolism; D001800:Blood Specimen Collection / Q000295:instrumentation* / Q000379:methods* / Q000592:standards*; D002951:Citrates / Q000737:chemistry* / Q000592:standards; D006801:Humans; D008875:Middle Aged; D019815:Oxalic Acid / Q000737:chemistry; D044967:Serum / Q000737:chemistry*; D012969:Sodium Fluoride / Q000737:chemistry
chemical_list: D001786:Blood Glucose; D002951:Citrates; D012969:Sodium Fluoride; D019815:Oxalic Acid