title: Artefactual reduction in plasma total carbon dioxide concentration in children.
abstract: METHODS
  The effect on plasma total carbon dioxide (ctCO2) of collecting a small volume of blood into a large tube was investigated. In a 7-month-old infant presenting with diarrhoea the initial ctCO2 was low when 0.3 mL of sample was received in a 4-mL tube. To investigate this further blood samples were obtained from three volunteers on five occasions and various volumes were placed in a 4 mL container and analysed after varying intervals.
  
  
  RESULTS
  When the sample volume was less than 2 mL there was a significant decrease in ctCO2. A 42% decrease was seen in the tube containing 0.3 mL after 4 h.
  
  
  CONCLUSIONS
  We recommend that when a small volume of sample is collected it should be placed in a smaller tube with minimal air space.
authors.affiliation: Department of Clinical Immunology, Royal Prince Alfred Hospital, Camperdown, Australia. awilliams@immu.rpa.cs.nsw.gov.au
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Williams
authors.forename: Lisa
authors.initials: L
authors.lastname: Norris
authors.forename: John C
authors.initials: JC
authors.lastname: Coakley
mesh_terms: D016477:Artifacts; D001800:Blood Specimen Collection / Q000379:methods*; D002245:Carbon Dioxide / Q000097:blood*; D005260:Female; D006801:Humans; D007223:Infant; D011786:Quality Control; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide