Electrolytes play an extremely important role in the human body by generating electric potential via cell membranes, maintaining ionic balance in cells and taking part in metabolic processes. The deficiency of any of body electrolytes can cause severe health disorders. Therefore it is extremely important in clinical practice to reliably measure electrolyte concentrations in the human blood. The use of industrially produced syringes for blood sampling may introduce pre-analytical errors in the measurement of ionized species. Berkel & Scharnhorst (2011) compared several syringes from different manufacturers with regard to the interference with analysis of blood electrolytes.
Since the sample for electrolyte analysis is drawn from blood vessels, it is important to ensure that blood does not coagulate. This is achieved by treating the blood syringe by heparin. Heparin is a naturally occurring anticoagulant that belongs to highly sulphated family of carbohydrate polymers. However heparin binds positively charged species (such as sodium, potassium, calcium ions) thus introducing negative bias in measurement of blood electrolytes levels (Dimeski et al., 2010). To avoid above mentioned problem syringe manufacturing companies started to produce syringes with electrolyte balanced heparin. In order to evaluate the possible bias on blood electrolyte measurements, non-heparinised syringes together with commercially available heparin blood syringes from three different companies were used to sample the blood from healthy donors. After that the blood samples were analysed for ionised species levels. The results showed that sodium and calcium levels in blood sampled from two out of three syringes types were significantly lower than those obtained from non-heparinised syringes. In contrast the calcium concentration in the blood from Radiometer syringe was not statistically different from the control syringe. However, the sodium concentration was slightly lower, being significantly different.
The use of electrolyte balanced heparin syringes was shown to introduce a significant negative bias in the measurement of positively charged ions. This bias exceeded total allowable error for measured ions that can lead to clinical errors. The syringe from only one company out of three tested did not introduce negative bias in the calcium concentration, but there was significant decrease in sodium concentration. Observed results suggest that there is a difference in the production process of heparin treated syringes among manufacturers. Therefore there is a strong need to improve the production technology of electrolyte balanced heparin syringes to ensure reliable and trustful analytical results.
Berkel, M & Scharnhorst, V. Electrolyte-balanced heparin in blood gas syringes can introduce a significant bias in the measurement of positively charged electrolytes. (2011). Clin Chem Lab Med, 49, 2, 249–252.
Dimeski, G, Badrick, T & St John, A. (2010). Ion selective electrodes (ISEs) and interferences – a review. Clin Chim Acta, 411, 309–17.
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