Comparison of Three different techniques used for Measurement of Na+ & K+ in Human plasma

Abstract

A descriptive, cross sectional study conducted in Sudan, Khartoum State during the period of May to August 2007. Analytical and statistical methods were applied to compare results of Eppendrof flame photometer, IL-543 digital flame photometer and ion selective electrode, for measurement of sodium and potassium and assess the difference that can be found, also to check the accuracy and precision of the instruments. Blood samples from a total of 55 apparently healthy adult males (volunteers) were taken randomly, and specimens (plasma) were analyzed for sodium and potassium concentrations by three different instruments. The results were statistically analyzed. Results showed that the mean concentrations of sodium were 138±3.7 for the IL-543 digital flame photometer, 140±2.9 for the ion selective electrode and 136±3.6 for the Eppendrof flame photometer. And the mean concentrations of potassium were 3.7±0.3 for the IL-543 digital flame photometer, 3.9±0.4 for the ion selective electrode and 3.7±0.3 for the Eppendrof flame photometer. In considering the IL-543 as the reference method, the data obtained by ANOVA test showed that, there was a significant difference between IL- 543 and ion selective electrode for the mean concentrations of plasma sodium where the p value was 0.008, as well as, the significant difference between the IL-543 and Eppendrof flame photometer where the p value was 0.001. Also there was a high significant difference between the ISE and Eppendrof were p value was 0.00. Also ANOVA test showed that, there was a significant difference between IL-543 and ISE for the mean concentrations of plasma potassium, where the p value was 0.01, as well as, the highly significant difference between ISE and Eppendrof flame photometer, where the p value was 0.001. The test also showed that there was no significant difference between the IL-543 and Eppendrof flame photometer for plasma potassium where p value was 1.000. This study concluded that there was a difference in results obtained by the three different instruments, which can be attributed to variation in plasma water, residual liquid junctions, binding of ions to protein or any other ligand or interference from other ions when using ISE, on the other hand source of error in using Eppendrof flame photometer due to fluctuations in the light sources. Further studies should be conducted for more accuracy and precision of any new introduced instrument.