title: Inversion of lithium heparin gel tubes after centrifugation is a significant source of bias in clinical chemistry testing.
abstract: BACKGROUND
  This study was planned to establish whether random orientation of gel tubes after centrifugation may impair sample quality.
  
  
  METHODS
  Eight gel tubes were collected from 17 volunteers: 2 Becton Dickinson (BD) serum tubes, 2 Terumo serum tubes, 2 BD lithium heparin tubes and 2 Terumo lithium heparin tubes. One patient's tube for each category was kept in a vertical, closure-up position for 90 min ("upright"), whereas paired tubes underwent bottom-up inversion every 15 min, for 90 min ("inverted"). Immediately after this period of time, 14 clinical chemistry analytes, serum indices and complete blood count were then assessed in all tubes.
  
  
  RESULTS
  Significant increases were found for phosphate and lipaemic index in all inverted tubes, along with AST, calcium, cholesterol, LDH, potassium, hemolysis index, leukocytes, erythrocytes and platelets limited to lithium heparin tubes. The desirable quality specifications were exceeded for AST, LDH, and potassium in inverted lithium heparin tubes. Residual leukocytes, erythrocytes, platelets and cellular debris were also significantly increased in inverted lithium heparin tubes.
  
  
  CONCLUSIONS
  Lithium heparin gel tubes should be maintained in a vertical, closure-up position after centrifugation.
authors.affiliation: Laboratory of Clinical Chemistry and Hematology, Academic Hospital of Parma, Parma, Italy. Electronic address: glippi@ao.pr.it.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Lippi
authors.affiliation: Laboratory of Clinical Biochemistry, Department of Life and Reproduction Sciences, University of Verona, Verona, Italy.
authors.forename: Gian Luca
authors.initials: GL
authors.lastname: Salvagno
authors.affiliation: Laboratory of Clinical Biochemistry, Department of Life and Reproduction Sciences, University of Verona, Verona, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Danese
authors.affiliation: Laboratory of Clinical Biochemistry, Department of Life and Reproduction Sciences, University of Verona, Verona, Italy; Post-Graduate Program of Pharmaceutical Sciences, Department of Medical Pathology Federal University of Parana, Curitiba, Parana, Brazil.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Lima-Oliveira
authors.affiliation: Laboratory of Clinical Biochemistry, Department of Life and Reproduction Sciences, University of Verona, Verona, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Brocco
authors.affiliation: Laboratory of Clinical Biochemistry, Department of Life and Reproduction Sciences, University of Verona, Verona, Italy; Post-Graduate Program of Pharmaceutical Sciences, Department of Medical Pathology Federal University of Parana, Curitiba, Parana, Brazil.
authors.forename: Gian Cesare
authors.initials: GC
authors.lastname: Guidi
mesh_terms: D000328:Adult; D016477:Artifacts; D001774:Blood Chemical Analysis / Q000295:instrumentation*; D002498:Centrifugation / Q000295:instrumentation*; D005260:Female; D005782:Gels; D006493:Heparin; D006801:Humans; D008094:Lithium; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D005782:Gels; D006493:Heparin; D008094:Lithium
keywords: Blood collection; Gel tubes; Lithium heparin; Preanalytical variability; Serum