Direct Ion-selective Electrode Method Research Articles

Pseudohypobicarbonatemia Associated with Profound Hypertriglyceridemia

A case is presented of falsely low serum bicarbonate levels with normal arterial blood gas bicarbonate levels in a patient with high triglyceride (TG) levels. This false phenomenon is explained by the presence of high triglyceride levels. Most laboratories use an enzymatic/photometric or indirect ion-selective electrode method to measure bicarbonate. Hyperlipidemia interferes with photometric analysis due to its light scattering effect. An ABG analyser employs a direct ion-selective electrode method that is free from the errors of a photometric analyser. Currently, several methods are available to eliminate the interference of lipemia and allow accurate measurement of biological quantities. The clinical laboratory must establish a protocol for handling lipemic samples according to the biological quantity to be tested.

Sweat Rate, Sweat Sodium Losses, and Body Composition in Professional Male Soccer Players in Southwest Colombia.

Background and Objective: Dehydration and hyperhydration impact athletes' performance. Exploring the fluid balance concerning body composition might help estimate individual hydration requirements. This area of research, particularly regarding sodium losses, has been relatively understudied. We evaluated the sweat rate (SR), sweat sodium losses, and their relationship with body composition in professional soccer players in Cali, Colombia. Materials and Methods: Thirty-two male players, aged 24.3 (±5.2) years, from the Colombian main soccer league, underwent high-intensity training at 32 °C (with a relative humidity of 79%). The outcome variables included SR, calculated using weight loss and fluid intake; forearm sweat sodium concentration (FSCC), measured through the direct ion-selective electrode method; and estimated the predicted whole sweat sodium loss (PWSSL) in mmol. Predictor variables (body mass, fat, and muscle masses) were estimated using the Deborah Kerr anthropometry method. The association between predictors and outcomes was assessed using linear regression. Results: The mean FSCC, PWSSL, and SR were 26.7 ± 11.3 mmol/L, 43 ± 15.9 mmol/L, and 1.7 ± 0.5 L/h, respectively. Body mass positively predicted FSCC in unadjusted and age/fat-mass-adjusted models [Beta 1.28, 95% confidence interval (CI) 0.39-2.18, p = 0.006], and continued related to FSCC after adjustment for muscle mass with marginal significance [Beta 0.85, 95% CI -0.02 to 1.73, p = 0.056]. Muscle mass was associated with the PWSSL in unadjusted and age/fat-mass-adjusted models [Beta 2.42, 95% CI 0.58-4.26, p = 0.012] and sustained an association with marginal statistical significance after adjustment for body mass [Beta 1.86, 95% CI -0.35 to 4.09, p = 0.097]. Conclusions: Under hot tropical weather conditions, FSCC was relatively low among the players. Body mass was better associated with the FSSC, and muscle mass better related to the PWSSL. Body and muscle masses could be regarded as potential factors to be explored in the estimation of individual sodium needs. However, further studies are required to validate and contrast our findings.

Comparing the effect of Hypoalbuminemia on Sodium measured by Indirect versus Direct Ion Selective Electrode Method

Objective: To evaluate the effect of low serum Albumin levels on serum sodium measurement when analyzed by the indirect Ion Selective Electrode (ISE) method and to compare the results with the direct Ion selective electrode (ISE) method.
 Study Design: Cross-sectional study
 Place and Duration of Study: Department of Chemical Pathology, Armed Forces Institute of Pathology, Rawalpindi Pakistan, from Jan to Mar 2021.
 Methodology: Patients of either gender, aged 18 to 70 years, who were admitted to the Intensive Care Unit of Combined Military Hospital, Rawalpindi, were selected. A total of 200 blood samples were collected in a gel tube. Serum samples were analyzed for albumin and sodium within two hours of sample collection. Sodium levels were measured concurrently by both direct and indirect ISE methods. The difference in results between these two techniques was studied.
 Results: Hypoalbuminemia was detected in 176(88%) patients, while 24(12%) had normal albumin levels. In Hypoalbuminemic patients, serum sodium measurements were higher using the indirect ISE method(134.07±5.55) compared to the direct ISE method (130.95±6.04); the difference between the two techniques was statistically significant (p-value <0.001).Pearson correlation coefficient (r-value = -0.86, p-value <0.001) revealed a symmetrical increase in differences between the two methods as the albumin level decreased.
 Conclusion: In Hypoalbuminemic patients, the indirect ISE method gave falsely raised results of serum sodium. In such patients, serum sodium measurement by the Direct ISE method offers more accurate and consistent electrolyte results.

Effect of Hypoproteinemia on Electrolyte Measurement by Direct and Indirect Ion Selective Electrode Methods.

Objective The aim of this study was to see the effect of hypoproteinemia on electrolyte measurement by two different techniques, that is, direct ion selective electrode (ISE) and indirect ISE. Material and Method It was an observational study in which 90 serum samples with normal protein content (Group-1) were subjected to sodium (Na + ) and potassium (K + ) measurements by direct and indirect ISE methods. In the same way, 90 serum samples with total protein < 5 g/dL (Group-2) were subjected to Na + and K + measurements by direct and indirect ISE methods. Result In samples from Group-1 patients, average Na + was 138.1 ± 4.764 mmol/L by direct ISE method and 139.3 ± 3.887 mmol/L by indirect ISE method while average K + was 4.41 ± 0.644 mmol/L by direct ISE method and 4.40 ± 0.592 mmol/L by indirect ISE method. There was no statistically significant difference in Na + and K + values measured by different methods. In samples from Group-2 patients, measured value of Na + by direct ISE and indirect ISE was 134.57 ± 5.520 mmol/L and 138.64 ± 5.401 mmol/L, respectively. Difference between these two values was statistically significant with p -value of < 0.0001, but direct ISE and indirect ISE measured values of K + was 4.146 ± 0.9639 mmol/L and 4.186 ± 0.8989, respectively, with no significant difference. Conclusion Direct and indirect ISE methods are not comparable and showing significantly different results for Na + in case of hypoproteinemia. So, it is recommended that setups like intensive care unit or emergency department, where electrolyte values have significant treatment outcome, should follow direct ISE method and should compare its previous result with the same method. Both the methods should not be used interchangeably.

Quantitative susceptibility mapping and 23 Na imaging-based in vitro characterization of blood clotting kinetics.

Blood clotting is a fundamental biochemical process in post-hemorrhagic hemostasis. Although the varying appearance of coagulating blood in T1 - and T2 -weighted images is widely used to qualitatively determine bleeding age, the technique permits only a rough discrimination of coagulation stages, and it remains difficult to distinguish acute and chronic hemorrhagic stages because of low T1 - and T2 -weighted signal intensities in both instances. To investigate new biomedical parameters for magnetic resonance imaging-based characterization of blood clotting kinetics, sodium imaging and quantitative susceptibility mapping (QSM) were compared with conventional T1 - and T2 -weighted imaging, as well as with biochemical hemolysis parameters. For this purpose, a blood-filled spherical agar phantom was investigated daily for 14days, as well as after 24days at 7T after initial preparation with fresh blood. T1 - and T2 -weighted sequences, a three-dimensional (3D) gradient echo sequence and a density-adapted 3D radial projection reconstruction pulse sequence for 23 Na imaging were applied. For hemolysis estimations, free hemoglobin and free potassium concentrations were measured photometrically and with the direct ion-selective electrode method, respectively, in separate heparinized whole-blood samples along the same timeline. Initial mean susceptibility was low (0.154±0.020ppm) and increased steadily during the course of coagulation to reach up to 0.570±0.165ppm. The highest total sodium (NaT) values (1.02±0.06 arbitrary units) in the clot were observed initially, dropped to 0.69±0.13 arbitrary units after oneday and increased again to initial values. Compartmentalized sodium (NaS) showed a similar signal evolution, and the NaS/NaT ratio steadily increased over clot evolution. QSM depicts clot evolution in vitro as a process associated with hemoglobin accumulation and transformation, and enables the differentiation of the acute and chronic coagulation stages. Sodium imaging visualizes clotting independent of susceptibility and seems to correspond to clot integrity. A combination of QSM and sodium imaging may enhance the characterization of hemorrhage.

A Study on Effect of Lipemia on Electrolyte Measurement by Direct Ion selective Electrode Method

Background: Lipemia affects electrolyte concentration obtained by indirect ion selective electrode (ISE) method, but the specific influence on measurements by direct ion selective electrode method is yet to be clearly understood. A study was designed in this backdrop to assess possible role of escalating concentration of lipemia on electrolyte measurement by direct ISE. Methods: Samples were collected from selected subjects in a hospital setting. A predesigned pretested format was used for recording the data from each subject. Serum sample was divided into 5 aliquots. Except for one, in the rest four, intralipid was added in escalating concentration to induce lipemia. The 5 sub-samples were tested for electrolytes and lipid concentration in parallel by two different direct ion-selective electrode methods, namely VITROS250 & HDC-Lyte. Electrolytes like sodium & potassium concentration was measured by both, while the first one also measured triglyceride concentration. Result: Results from two instruments were compared and data were also analsyed in subgroups of standard clinical classification for sodium concentration. Considering 0-350 mg% of triglyceride as the reference, electrolytes concentration mostly decreased over increasing lipemia. Beyond triglyceride concentration of 650mg%, this decline in electrolytes concentration was statistically significantly for samples in all subgroups. In majority of samples, electrolyte values obtained from two instruments were comparable. Beyond triglyceride concentration of 1550 mg%, the sodium concentration obtained from two instruments varied significantly. Conclusion: A correction factor may be used for the amendment of this interference property of lipemic serum samples for the major electrolytes i.e., sodium and potassium.

Reference Intervals of Serum Sodium, Potassium, and Chlorine in Chinese Han Population and Comparison of Two ISE Methods.

Currently there are no reference intervals (RIs) of sodium (Na), potassium (K), and chlorine (Cl) on Chinese population. Two kinds of ion-selective electrode (ISE) methods were commonly used to determine K, Na, and Cl levels in China, the difference between these two methods needs to be evaluated. A total of 4,524 healthy participants (1,916 males and 2,608 females) between 20-79 years old from six cities in China were selected by strict criteria. Serum K, Na, and CL were tested on Roche Modular analyzers in six assigned laboratories. According to EP-9A2, using Roche Modular analyzer (indirect ISE) as comparative method, Olympus AU 5400 analyzer (indirect ISE) and Johnson&Johnson Fusion 5.1 analyzer (direct ISE) were evaluated. In Chinese population, the RIs for K, Na, and CL are 3.6-5.2, 136-146, and 99-110 mmol/l, respectively. Compared to the Roche indirect ISE method, Johnson direct ISE method showed a positive bias; and Olympus indirect ISE method just showed a very slight bias. The RIs of K, Na, and Cl of Han Chinese healthy adult population were found to be smaller than those provided by the manufacturer. By a criteria of biological variations for CV, the differences of Na and K between Roche analyzer and Johnson analyzer were not acceptable for clinical application, while the differences of Na, K, and Cl between Roche and Olympus analyzers were acceptable for clinical application.

Case study : spurious elevation of sodium levels : peer reviewed case study

In hospitalized patients, plasma sodium disturbances remain common and can be associated with significant mortality and morbidity if not diagnosed and treated. A hypoproteinaemic, critically ill patient with discrepant blood gas analyzer and central laboratory analyzer sodium values presented as a case of possible spurious elevation of sodium or pseudohypernatraemia. The indirect ion selective electrode method yielded a persistently higher sodium value than the direct ion selective electrode method. A statistically significant difference between the sodium measured with the direct ISE and indirect ISE method was noted. The differences could not be explained by analytical variation alone, in most of the samples.

Are your hands clean enough for point-of-care electrolyte analysis?

SummaryAimTo investigate clinically significant analytical interference in point-of-care electrolyte analysis caused by contamination of blood specimens with hand disinfectant.MethodsSix different hand hygiene products were added separately to heparinised blood samples in varying amounts as contaminant. The contaminated samples were analysed by three different blood gas and electrolyte analysers for assessing interference on measured whole blood sodium and potassium concentrations.ResultsThere were significant analytical interferences caused by hand hygiene product contamination that varied depending on the combination of disinfectant and analyser. Small amounts of Microshield Antibacterial Hand Gel contamination caused large increases in measured sodium concentration. Such effect was much greater compared with the other five products tested, and started to occur at much lower levels of contamination. There was a trend towards lower sodium results in blood samples contaminated with Hexol Antiseptic Lotion (Hexol), the hand hygiene product that we used initially. Apart from AiE Hand Sanitizer, all the other hand disinfectants, especially Hexol, significantly elevated the measured potassium concentration, particularly when a direct ion-selective electrode method was used for measurement.ConclusionHand disinfectant products can significantly interfere with blood electrolyte analysis. Proper precautions must be taken against contamination since the resultant errors can adversely affect the clinical management of patients.

Discrepancies Between Sodium Concentrations Measured by the Kodak Ektachem 700 and by Dilutional and Direct Ion-Selective Electrode Analyzers

We have identified rare (approximately 0.2% of all samples), but clinically significant, discrepancies between serum or plasma sodium concentrations measured with the Kodak Ektachem 700's direct ion-selective electrode (ISE) method and concentrations measured with two other analyzers: the Beckman Synchron CX3's dilutional ISE instrument and the Radiometer KNA2 instrument for sodium-potassium analysis by the direct ISE method. The differences do not appear to be related to any previously identified sources of discrepancy, such as variations in triglycerides, bicarbonate, total protein, albumin, or gamma-globulin, the presence of paraproteins, or interference by benzalkonium chloride from heparinized catheters. They occurred despite the use of Gen 04 reference fluid on the Ektachem. We could not identify any drug or family of drugs that the patients had taken in common and that might influence the results. Until this problem is resolved, Ektachem users should be aware of the potential for discrepancies of > 6 mmol/L in measurements of sodium concentrations.

Centrifugal ion-selective electrode system for potassium in whole blood

We describe a novel ion-selective electrode (ISE) system that can be used in the Abbott Vision analyzer. A reusable sensor pack and a disposable test pack have been miniaturized to approximately the size and weight of a conventional Vision test pack, thus eliminating the need for a separate ISE module. The sensor pack contains a fluid path, battery-powered electronics, and screw-in electrodes. The test pack contains separate chambers and fluid channels for a blood specimen and two aqueous calibrators. During a run, plasma is separated from blood cells and is moved sequentially, along with the two calibrators, into and out of the sensor pack by centrifugal force. Each run includes checks for electromechanical integrity, fluid contamination, calibration slope and intercept, and specimen hemolysis. The system operates with CVs of less than 2% and gives results that correlate well with those by flame photometry and direct ISE methods. Either skin-puncture or venipuncture whole blood can be assayed, as well as serum or plasma.

Errors due to heparin in the estimation of plasma sodium and potassium concentrations

The effect of adding sodium heparin (5000 U/ml and 1000 U/ml) to whole blood on the concentrations of plasma sodium and potassium was examined. When the analysis was done by flame photometry both preparations of heparin caused an increase in plasma sodium concentration. If the analysis was done by a direct ion selective electrode method the 5000 U/ml heparin caused a decrease and the 1000 U/ml caused an increase in plasma sodium concentration. Plasma potassium concentration decreased when 1000 U/ml heparin was added irrespective of the method of analysis. It is recommended that sodium heparin should not be used in samples taken for estimation of sodium and potassium.

Ion Selective Method for the Determination of Nitrite in Smoked Fish

In a direct ion selective electrode method for determining nitrite in smoked fish, the nitrite extracted from the sample is converted to nitrous acid with a measured addition of an acid buffer. The released nitrous acid is measured by a nitrogen oxide electrode. A known addition procedure is used to accurately measure the amount of nitrite in solution and the nitrite concentration is determined directly from Gran's plot paper. Recoveries of nitrite from spiked smoked chub samples ranged from 94.0 to 100.0% with an average of 96.7 and a relative standard deviation of +/-1.9% at the 100 ppm level. Results from the ion selective method were comparable with those from the official first action AOAC method 24.037-24.038.