Electrolyte measurement by clinicians

The development of automated techniques for the measurement of electrolytes using ion-selective electrode technology has resulted in the availability of such machines for use by clinicians. A study is described which compares values obtained for plasma sodium and potassium by interested clinicians using a Beckman Electrolyte 2 analyser, with results obtained by laboratory staff using a Beckman E2A autoanalyser. A total of 14 estimations each for sodium and potassium were made on 96 samples of venous blood from patients on an intensive care unit. Comparisons were made using the coefficient of variation and analysis of variance (ANOVA). Seventy-three percent of observations of sodium and 87% of observations of potassium made by clinicians lie within 2 mmol l-1 and 0.2 mmol l-1 respectively, of observations made by laboratory staff. Observations outside these ranges are examined. The authors conclude that the results obtained by interested clinicians lie well within acceptable limits for medical usefulness, that inappropriate therapy based on such results is unlikely, and that such estimations would appear to be safe and acceptably accurate.