Julie Refardt1,2, Clara Odilia Sailer1,2, Irina Chifu3, Bettina Winzeler1,2, Ingeborg Schnyder1,2, Martin Fassnacht3,4, Wiebke Fenske5,6, Mirjam Christ-Crain1,2. 1. Departments of Endocrinology, Diabetology and Metabolism, University Hospital Basel, Basel, Switzerland. 2. Department of Clinical Research, University of Basel, Basel, Switzerland. 3. Division of Endocrinology and Diabetes, Department of Internal Medicine I, University Hospital, University of Würzburg, Würzburg, Germany. 4. Central Laboratory, University Hospital Würzburg, Würzburg, Germany. 5. Department of Endocrinology and Nephrology, University of Leipzig, Leipzig, Germany. 6. Leipzig University Medical Center, IFB AdiposityDiseases, Leipzig, Germany.
Abstract
BACKGROUND: Diagnosis and treatment of dysnatremia is challenging and further complicated by the pitfalls of different sodium measurement methods. Routinely used sodium measurements are the indirect (plasma/serum) and direct (whole blood) ion-selective electrode (ISE) method, showing discrepant results especially in the setting of acute illness. Few clinicians are aware of the differences between the methods in clinically stable patients or healthy volunteers. METHODS: Data of 140 patients and 91 healthy volunteers undergoing osmotic stimulation with hypertonic saline infusion were analyzed. Sodium levels were measured simultaneously by indirect and direct ISE method before and at different time points during osmotic stimulation up to a sodium threshold of ≥150 mmol/L. The primary outcome was the difference in sodium levels between the indirect and direct ISE method. RESULTS: 878 sodium measurements were analyzed. Mean (s.d.) sodium levels ranged from 141 mmol/L (2.9) to 151 mmol/L (2.1) by the indirect ISE compared to 140 mmol/L (3) to 149 mmol/L (2.8) by the direct ISE method. The interclass correlation coefficient between the two methods was 0.844 (95% CI: 0.823-0.863). On average, measurements by the indirect ISE were 1.9 mmol/L (95% CI limits: -3.2 to 6.9) higher than those by the direct ISE method (P < 0.001). The tendency of the indirect ISE method resulting in higher levels increased with increasing sodium levels. CONCLUSION: Intra-individual sodium levels differ significantly between the indirect and direct ISE method also in the absence of acute illness. It is therefore crucial to adhere to the same method in critical situations to avoid false decisions due to measurement differences.
BACKGROUND: Diagnosis and treatment of dysnatremia is challenging and further complicated by the pitfalls of different sodium measurement methods. Routinely used sodium measurements are the indirect (plasma/serum) and direct (whole blood) ion-selective electrode (ISE) method, showing discrepant results especially in the setting of acute illness. Few clinicians are aware of the differences between the methods in clinically stable patients or healthy volunteers. METHODS: Data of 140 patients and 91 healthy volunteers undergoing osmotic stimulation with hypertonic saline infusion were analyzed. Sodium levels were measured simultaneously by indirect and direct ISE method before and at different time points during osmotic stimulation up to a sodium threshold of ≥150 mmol/L. The primary outcome was the difference in sodium levels between the indirect and direct ISE method. RESULTS: 878 sodium measurements were analyzed. Mean (s.d.) sodium levels ranged from 141 mmol/L (2.9) to 151 mmol/L (2.1) by the indirect ISE compared to 140 mmol/L (3) to 149 mmol/L (2.8) by the direct ISE method. The interclass correlation coefficient between the two methods was 0.844 (95% CI: 0.823-0.863). On average, measurements by the indirect ISE were 1.9 mmol/L (95% CI limits: -3.2 to 6.9) higher than those by the direct ISE method (P < 0.001). The tendency of the indirect ISE method resulting in higher levels increased with increasing sodium levels. CONCLUSION: Intra-individual sodium levels differ significantly between the indirect and direct ISE method also in the absence of acute illness. It is therefore crucial to adhere to the same method in critical situations to avoid false decisions due to measurement differences.
Authors: Muhammad Fahad Arshad; Ahmed Iqbal; James Weeks; Ines Fonseca; Alia Munir; William Bennet Journal: Endocr Connect Date: 2022-05-23 Impact factor: 3.221
Authors: Chloe C A Grim; Fabian Termorshuizen; Robert J Bosman; Olaf L Cremer; Arend Jan Meinders; Maarten W N Nijsten; Peter Pickkers; Angelique M E de Man; Marcus J Schultz; Peter van Vliet; Joachim D Weigel; Hendrik J F Helmerhorst; Nicolette F de Keizer; Evert de Jonge Journal: Crit Care Med Date: 2021-12-01 Impact factor: 7.598