Electrolyte-balanced heparin in blood gas syringes can introduce a significant bias in the measurement of positively charged electrolytes

M. Berkel, van, V. Scharnhorst

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BACKGROUND: Heparin binds positively charged electrolytes. In blood gas syringes, electrolyte-balanced heparin is used to prevent a negative bias in electrolyte concentrations. The potential pre-analytical errors introduced by blood gas syringes are largely unknown. Here, we evaluate electrolyte concentrations in non-anticoagulated blood compared with concentrations measured in electrolyte-balanced blood gas syringes. METHODS: Venous blood was collected into plain tubes. Ionized calcium, potassium, sodium and hydrogen ions were analyzed directly using a blood gas analyzer and the remaining blood was collected into different blood gas syringes in random order: Preset (Becton Dickinson), Monovette (Sarstedt) and Pico 50-2 (Radiometer). RESULTS: Ionized calcium and sodium concentrations were significantly lower in blood collected in Becton Dickinson and Sarstedt syringes compared to non-heparinized (NH) blood. The mean bias exceeded biological variation-based total allowable error, which in most cases leads to clinically misleading individual results. In contrast, ionized calcium concentrations in blood collected in Pico 50-2 syringes were identical to values obtained from NH blood. Sodium showed a minor, yet statistically significant, bias. CONCLUSIONS: Despite the fact that blood gas syringes now contain electrolyte-balanced heparin, one should be aware of the fact that these syringes can introduce pre-analytical bias in electrolyte concentrations. The extent of the bias differs between syringes.
Original languageEnglish
Pages (from-to)249-252
JournalClinical Chemistry and Laboratory Medicine
Issue number2
Publication statusPublished - 2011


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