title: Effectiveness of citrate buffer-fluoride mixture in Terumo tubes as an inhibitor of in vitro glycolysis.
abstract: BACKGROUND
  Glycolysis affects glucose determination in vitro. The placement of sample tubes in ice-water slurry with plasma separation within 30 minutes is recommended, or alternatively the use of a glycolysis inhibitor. The aim of our two-steps study was to evaluate which Terumo tube is best for glucose determination in routine clinical setting.
  
  
  METHODS
  In the first study, blood from 100 volunteers was collected into lithium heparin (LH), NaF/Na heparin (FH) and NaF/citrate buffer/Na2EDTA (FC-Mixture) tubes. LH sample was treated as recommended and considered as reference, while FH and FC-Mixture samples were aliquoted, maintained at room temperature (RT) for 1, 2 and 4 hours; centrifuged and plasma analysed in triplicate. In the second study, samples from 375 volunteers were collected in LH, FH and FC-Mixture tubes and held at RT before centrifugation from 10 to 340 minutes, depending on each laboratory practice. Samples were analysed in one analytical run.
  
  
  RESULTS
  In the first study, FH glucose concentrations were 5.15 ± 0.66 mmol/L, 5.05 ± 0.65 mmol/L and 5.00 ± 0.65 mmol/L (P < 0.001) in tubes stored at RT for 1, 2 and 4 hours, respectively. Mean biases in all time points exceeded the analytical goal for desirable bias based on biological variation criteria. FC-Mixture glucose concentrations were 5.48 ± 0.65 mmol/L, 5.46 ± 0.6 mmol/L and 5.46 ± 0.64 mmol/L in tubes stored at RT for 1, 2 and 4 hours, respectively. Mean biases for FC-Mixture glucose in all time points reached optimal analytical goals. In the second study, the biases for LH and FH glucose compared to reference FC-Mixture glucose exceeded the preset analytical goals, regardless of the blood collection to centrifugation time interval.
  
  
  CONCLUSIONS
  FC-mixture tubes glucose concentrations were preserved up to 4h storage at RT. We confirmed that NaF alone does not allow immediate glycolysis inhibition in real life pre-centrifugation storage conditions (up to 340 minutes). FC-Mixture should be used exclusively for glucose determination in laboratories unable to implement the recommended blood samples' treatment.
authors.affiliation: Clinical Chemistry Laboratory, Spedali Civili of Brescia, Brescia, Italy.
authors.forename: Graziella
authors.initials: G
authors.lastname: Bonetti
authors.affiliation: Clinical Chemistry and Haematology Laboratory, St. Bortolo Hospital, Vicenza, Italy.
authors.forename: Mariarosa
authors.initials: M
authors.lastname: Carta
authors.affiliation: Clinical Biochemistry Section, University of Verona, Verona, Italy.
authors.forename: Martina
authors.initials: M
authors.lastname: Montagnana
authors.affiliation: Clinical Laboratory, AOUI Verona, Verona, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Lo Cascio
authors.affiliation: Scientific Direction, Italian National Research Center on Aging (INRCA), Ancona, Italy.
authors.forename: Anna Rita
authors.initials: AR
authors.lastname: Bonfigli
authors.affiliation: Department of Physiopathology and Transplantation, University of Milano, Milano, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Mosca
authors.affiliation: Experimental Models in Clinical Pathology, INRCA-IRCCS National Institute, Ancona, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Testa
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000737:chemistry / Q000494:pharmacology; D001786:Blood Glucose / Q000032:analysis* / Q000378:metabolism; D001800:Blood Specimen Collection / Q000295:instrumentation* / Q000379:methods; D002021:Buffers; D002498:Centrifugation; D002951:Citrates / Q000737:chemistry / Q000494:pharmacology*; D004492:Edetic Acid / Q000737:chemistry / Q000494:pharmacology; D005260:Female; D005459:Fluorides / Q000737:chemistry / Q000494:pharmacology*; D006019:Glycolysis / Q000187:drug effects*; D006493:Heparin / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D008094:Lithium / Q000737:chemistry / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013696:Temperature; D013997:Time Factors; D055815:Young Adult
chemical_list: D000925:Anticoagulants; D001786:Blood Glucose; D002021:Buffers; D002951:Citrates; D006493:Heparin; D008094:Lithium; D004492:Edetic Acid; D005459:Fluorides
keywords: citrate acidification; glucose; pre-analytical phase; sodium fluoride; stability