Comparison of enzymic method and ion-selective electrode method in detection of serum potassium and sodium

Objective: To compare enzymic method and ion-selective electrodes(ISE) in detection of serum potassium(K⁺) and sodium(Na⁺).Methods: Fixed-value serum as the control samples,fifty clinical samples were collected at random and levels of K⁺ and Na⁺ in these samples were tested by the two methods.Results: CV of serum levels of K⁺ and Na⁺ by enzymic method was less than 1.98% in the same day and less than 2.26% in different days.The linearity was satisfied with the clinical requirement.There was a positive correlation between the two methods in measurement of serum levels of K⁺ and Na⁺.The contamination rate of enzymic method was 0.66% to 1.15% and that of the ISE was 1.15% to 2.32%.Conclusions: The enzymic method and the ISE can be used alternately,and the enzymic method is more convenient,precise and there are good repetitiveness and correlation.Moreover,the enzymic method to test the level of K⁺ and Na⁺ in serum could be used in automatic biochemical analysator because of less consumption of serum.