Annals of clinical biochemistry
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Ann. Clin. Biochem. · Nov 2006
Comparative StudySodium measurement: effects of differing sampling and analytical methods.
It is recommended that children receiving intravenous fluids should have frequent biochemical monitoring, in some situations 4-6 hourly. Small changes in sodium must be detected, requiring very high precision from sodium analyses. Some children are monitored using venous blood analysed by indirect ion-selective electrode (ISE) interchangeably with capillary blood analysed by direct ISE. Our aim was to determine whether variability in sample collection together with variability in sodium measurement would lead to results which were unacceptable in the clinical setting. ⋯ Venous plasma using indirect ISE and capillary blood with direct ISE cannot be used interchangeably to detect small changes in plasma sodium concentrations. To avoid misinterpretation of results when monitoring sodium over short time periods, the use of single methods of sampling and analysis must be strongly encouraged.