Flame Photometer and Direct Ion-Selective Electrode on Serum Sodium and Potassium Concentration.
The study aimed to compare the [Na.sub.+] and [K.sub.+] serum levels of the blood samples using flame photometry and ion-selective electrode methods. The study was conducted using the descriptive and comparative design. By random sampling, the values of the 180 test samples were extracted from the Chemistry Clinical logbook. The mean values and paired t-test were used to treat the data gathered. The mean value of [Na.sub.+] serum of the 180 blood samples using flame photometry and ISE are 136.96 (SD = 6.21) and 138.32 (SD = 6.21) respectively. The potassium mean values are 3.77 (SD = 0.83) for the flame photometry and 3.84 (SD=0.86) for the ISE. The t-values resulted to p-values, which are lesser than 0.05, indicating that there is a significant difference between the electrolyte values of both sodium and potassium using the flame photometer and ion-selective electrodes. The ion-selective electrode outweighs the flame photometer in determining the electrolytes particularly sodium and potassium in serum.
Keywords: Flame photometer, ion-selective electrode, serum electrolytes
It is an undeniable fact that the selection of appropriate equipment is essential to carry out laboratory function. Technological advances in instrumentation can accomplish quality measurements and examinations. There is value in examining the development of instrumentation for clinical laboratory because one can integrate those developments with current trends in medicine to arrive at a better projection of how to manage laboratory changes. The performance level of the clinical laboratory is expected to improve each year. As expected in electrolyte determinations, speed and accuracy are the foremost concern in selecting an instrument.
The rapid changes in technology places the laboratory medicine practitioner in a constant query as to which of these new methods would be of relevance to practice. The old methods have been there for a long time and have gained the confidence of the laboratories. To shift to a new method with an entirely different technology requires thorough study and investigation. One needs to establish precision and accuracy of the new procedure before a decision can be arrived at. Since the decision to shift to a new technology carries with it capital expenditure, the laboratory manager likewise needs to come up with a justification to the hospital administration for the purchase of the new machine. This justification entails establishing the fact that the new method has far greater advantages than the existing method. Above all the new method should greatly improve laboratory management. It is the laboratory's function to perform the test as accurately and as speedily as possible and to see that the results are properly and correctly entered into the system for delivery to the physician.
Experience in clinical chemistry of direct reading ion-selective electrode analyzers for the measurement of sodium and potassium concentrations has shown that the results obtained on any specimen may vary significantly from one instrument to another. This study proposed that instruments should be standardized to report Na+ and [K.sub.+] concentrations to agree with the findings using the flame photometry.
Electrolytes which are free ions in body fluids are important in the maintenance of many body functions including electrical neutrality, regulation of membrane potentials, and acid-base homeostasis. The most frequently used methods to measure [Na.sub.+] and [K.sub.+] in the clinical laboratory is emission photometry and ion-specific potentiometer electrodes (Henry, 1991). Ion-selective electrodes have been incorporated into many automated systems, which determine the activity of sodium and potassium that is the number of atoms that act as true ions in a defined volume of water. [Na.sub.+] and [K.sub.+] both being alkali metals are easily excited in a low-temperature flame photometry which determines the number of atoms in a defined volume of solution (Bangert and Marshall, 2004).
Technology in the field of serum electrolyte determination is continuously advancing. There has been claimed that [Na.sub.+] and [K.sub.+] obtained with ion-selective electrodes in undiluted whole blood or serum should be multiplied by an appropriate factor to have the same values as the substance concentrations tested using the flame photometer (Worth, 1985). In this study, undiluted serum samples were directly tested in ISE while 0.2 ml. of serum samples after dilution preparations were subjected to flame photometry tests. These two methods are the most frequent means of measuring sodium ([Na.sub.+]) and potassium ([K.sub.+]) in clinical laboratory. Although the use of electrodes has become increasingly popular, photometry remains the standard technique.
Under most circumstances, ISE according to Henry (1991) give values approximately 1% to 3% higher than those from flame-emission instruments. This difference may result from the physiochemical properties of the two analytical techniques because Ion-selective electrodes are not affected, to the same extent, by variations in plasma water from increased protein or lipid content (Burtis, 2008).
OBJECTIVES OF THE STUDY
This study aimed to compare the [Na.sub.+] and [K.sub.+] serum levels of the blood samples using flame photometry and ion-selective electrode methods. Specifically the study would like to answer the following inquiries: 1) What is the serum mean value of [Na.sub.+] and [K.sub.+] using flame photometer and ion-selective electrode (ISE)? 2) Is there significant difference between the two mean values of sodium and potassium? 3) What recommendations can be formulated to enhance the laboratory management?
The study was conducted using the descriptive and comparative design. About 326 fresh serum from in and out patients of a tertiary hospital requiring [Na.sub.+] and [K.sub.+] determinations during the 3 month period was used as the population of the study. Each serum was subjected to both flame photometer and ISE. The results were recorded in the designated logbook. One hundred and eighty (180) serum samples were used in the study from a population at margin error of 0.05 using the Slovin's formula. By random sampling, the values of the 180 test samples were extracted from the Chemistry Clinical logbook. The mean values and paired t-test were used to treat the data gathered.
RESULTS AND DISCUSSION
The mean value of [Na.sub.+] serum of the 180 blood samples using flame photometry and ISE are 136.96 (SD = 6.21) and 138.32 (SD = 6.21) respectively. For potassium serum mean values, an average electrolyte values of 3.77 (SD = 0.83) for the flame photometry and 3.84 (SD=0.86) for the ISE. For the sodium serum electrolyte, there is a difference of 1.36 in the mean values between the flame photometer and ISE. This difference was tested at 0.05 level of significance. It was found out that the computed value for the t-test is 4.24 with a p-value of 0.000. Since the p value is lesser than 0.05, there is significant difference between the mean values of electrolytes utilizing the two methods. The mean values for [K.sub.+] serum differ by 0.07. The computed t value is 2.69 with a p value of 0.008. Since the p value is very much lesser than 0.05, this implies that there is significant difference between the [K.sub.+] serum levels comparing the flame photometer and ISE.
The mean values of [Na.sub.+] and [K.sub.+] differed significantly when using flame photometry and ISE. The difference may result when other factors such as plasma water content, variations in ionic strength and lipid and protein content can be detected by the ISE but not detected by flame photometer.
The use of ion-selective electrode (ISE) is recommended for the following reasons: It measures ionic activity hence it is specific. It gives speedy results of electrolyte since the turnaround time is only 1 minute for both sodium and potassium. The collection of specimen is not a hassle since less volume is required. The analysis will be free from contamination since it will test undiluted samples.
Bangert, S. K. and Marshall, S.
2004 Clinical Chemistry. (5th Ed.). United Kingdom. Elsevier Limited.
Burtis, C. A. and Ashwood, E. R.
2008 Tietz Fundamentals of Clinical Chemistry. (6th Ed.). U.S.A. Saunders Company.
Henry, John Bernard.
1991 Clinical Diagnosis and Management by Laboratory Methods. Philadelphia: W.B. Saunders Company.
1985 A Comparison of the Measurement of Sodium and Potassium by Flame Photometry and Ion-Selective Electrode. Annals of Clinical Biochemistry: An International Journal of Biochemistry in Medicine, 22(4), 343-350.
EMMALYN B. CUTAMORA
ORCID No. 0000-0002-2799-0150
ASONITA J. PARMISANA
ORCID No. 0000-0002-3663-1256
Cebu Doctors' University
Cebu City, Philippines
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|Author:||Cutamora, Emmalyn B.; Parmisana, Asonita J.|
|Publication:||Asian Journal of Health|
|Date:||Jan 1, 2015|
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