title: Citric/citrate buffer: an effective antiglycolytic agent.
abstract: BACKGROUND
  In order to minimize the influence of glycolysis on diabetes mellitus (DM) diagnostic tests, we have compared the behavior of citric/citrate, fluoride additives and gel-serum with plasma-heparin under careful preanalytical conditions. Subsequently, we compared the effectiveness of both fluoride and citric additives at different pre-centrifugation times. Finally, the influence of citric/citrate collection tube on diagnostic tests results was evaluated.
  
  
  METHODS
  The first study of 80 voluntary patients assessed the glucose bias of citric/citrate, fluoride additive tubes and gel-serum tubes versus plasma-heparin tubes at several medical decision cut-offs (MDC). The second study performed with 72 volunteers evaluated additives, simulating transport times to the laboratory and centrifugation delay periods. Final evaluation compares the proportion of positive tests in total tests carried out in two different periods.
  
  
  RESULTS
  When citric/citrate (n=79) and fluoride tubes (n=60) were compared with plasma-heparin under controlled preanalytical conditions, both met the bias specification for plasma glucose (±1.8%) at seven MDC. On the contrary, serum samples (n=15) did not meet it at five MDC. In the second study, differences in glucose values at distinct pre-centrifugation times were not statistically significant for citric/citrate tubes, but significant for fluoride tubes and also for comparison of fluoride and citric/citrate tubes. Hemolysis in fluoride tubes was higher. Citric/citrate tube implementation in our laboratory caused an increase in positive diagnostic tests that were only statistically significant for gestational diabetes mellitus (GDM) screening.
  
  
  CONCLUSIONS
  Citric/citrate additive tube is equivalent to plasma-heparin avoiding glycolysis completely and immediately under careful preanalytical conditions even with a 3-h delay in plasma separation. According to used MDC we have not statistically significantly increased the diagnoses of DM cases.
authors.forename: Isabel García
authors.initials: IG
authors.lastname: del Pino
authors.forename: Ignacio
authors.initials: I
authors.lastname: Constanso
authors.forename: Luis Vázquez
authors.initials: LV
authors.lastname: Mourín
authors.forename: Carmela Barbuzano
authors.initials: CB
authors.lastname: Safont
authors.forename: Pastora Rodríguez
authors.initials: PR
authors.lastname: Vázquez
mesh_terms: D000328:Adult; D000925:Anticoagulants / Q000737:chemistry; D001773:Blood Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D001786:Blood Glucose / Q000032:analysis; D001800:Blood Specimen Collection / Q000295:instrumentation / Q000379:methods; D002021:Buffers; D002498:Centrifugation; D019343:Citric Acid / Q000737:chemistry / Q000494:pharmacology*; D016640:Diabetes, Gestational / Q000097:blood* / Q000175:diagnosis* / Q000473:pathology; D005260:Female; D006019:Glycolysis / Q000187:drug effects*; D006461:Hemolysis; D006493:Heparin / Q000737:chemistry; D006801:Humans; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D012969:Sodium Fluoride / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000925:Anticoagulants; D001786:Blood Glucose; D002021:Buffers; D019343:Citric Acid; D012969:Sodium Fluoride; D006493:Heparin