[Evaluation of enzymatic methods for the determination of plasma sodium and potassium using the Hitachi 747 analytic system].

In the hospital clinical laboratory, plasma potassium and sodium are usually determined by using a flame photometer or ion-selective electrodes, for which special equipment is required. The new enzymatic methods of sodium and potassium can be used as a routine chemical method. We evaluated the new enzymatic methods for the determination of sodium and potassium in human plasma on the Hitachi 747. The sodium and potassium assay kits were purchased from Boehringer Mannheim, Germany. Precision studies were performed using three levels of pool plasma. The coefficients of variation (CV) of sodium and potassium determination were less than 1.0% and less than 2.2% by intraassay and interassay respectively. The recoveries of the assigned values of the ten control sera were 97-102%. Comparisons with results either from flame photometry and from ion-selective electrodes showed no clinically relevant differences for 100 patient samples. Performance of the enzymatic methods for Na+ and K+ is clinically comparable to flame photometry or ion-selective electrodes in the routine clinical chemistry laboratory.