Artefactual reduction in plasma total carbon dioxide concentration in children.
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.
Williams
Andrew J
AJ
Department of Clinical Immunology, Royal Prince Alfred Hospital, Camperdown, Australia. awilliams@immu.rpa.cs.nsw.gov.au
Norris
Lisa
L
Coakley
John C
JC
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
D002245:Carbon Dioxide