Citation Information :
Role of correction factor in minimizing errors while calculating electrolyte values between Blood–gas analyzer and laboratory autoanalyzer: A comparative study. Indian J Crit Care Med 2018; 22 (1):34-39.
Aims: Electrolytes are charged elements that play important functions in the body. They are measured by both arterial blood–gas (ABG) analyzers and autoanalyzers (AA). In this study, we tried to find out the correction factor for sodium and potassium to establish the concordance between ABG and AA values.
Materials and Methods: We prospectively studied 100 samples of patients, and for validation of the result, we applied our result on 30 patients later. 1.5 ml of blood collected in the 2.0 ml syringe preflushed with heparin and analyzed using blood–gas analyzer (ABG). Another sample was sent, to central laboratory, where serum Na+ and K+ concentrations were analyzed. Means, standard deviations, and coefficients of variation with Karl Pearson\'s correlation coefficients were found out. Deming regression analysis was performed and Bland–Altman plots were also constructed.
Results: The mean sodium and potassium were 130.27 ± 7.85 mmol/L and 3.542 ± 0.76 mmol/L using ABG and 139.28 ± 7.89 mmol/L and 4.196 ± 0.72 mmol/L using AA. Concordance between ABG and AA is done by adding the correction factor: for sodium, correction factor is 9.01, standard error = 1.113, class interval = 6.815–11.205; and for potassium (K+), correction factor is 0.654, standard error = 0.1047, class interval = 0.4475–0.8605.
Conclusion: The instrument type and calibration methods differ in different hospitals, so it is important that each center conducts an in-hospital study to know the correction factor before installation of an ABG, and the factor should be used accordingly to minimize all errors.
Hoekstra M, Vogelzang M, Drost JT, Janse M, Loef BG, van der Horst IC, et al. Implementation and evaluation of a nurse-centered computerized potassium regulation protocol in the Intensive Care Unit – A before and after analysis. BMC Med Inform Decis Mak 2010;10:5.
Murray MJ, James M. American Society of Critical Care Anesthesiologists. Philadelphia, PA: Lippincott Williams & Wilkins; 2002. p. 168-9.
Cox CJ. Acute care testing. Blood gases and electrolytes at the point of care. Clin Lab Med 2001;21:321-35.
Scott MG, LeGrys VA, Klutts JS. Electrolytes and blood gases. In: Burtis DE, Ashwood ER, Bruns DE, editors. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 4th ed. St. Louis, MO: Elsevier; 2006. p. 983-1018.
D'Orazio P, Miller WG, Myers GL, Doumas BT, Eckfeldt JH, Evans SA, et al. Standardization of Sodium and Potassium Ion-Selective Electrode Systems to the Flame Photometric Reference Method: Approved Standard. C29-A2. 2nd ed., Vol. 20. CLSI; 2000. p. 1-22.
Ladenson JH. Direct potentiometric measurement of sodium and potassium in whole blood. Clin Chem 1977;23:1912-6.
Budak YU, Huysal K, Polat M. Use of a blood gas analyzer and a laboratory autoanalyzer in routine practice to measure electrolytes in intensive care unit patients. BMC Anesthesiol 2012;12:17.
Chacko B, Peter JV, Patole S, Fleming JJ, Selvakumar R. Authors' reply. Indian J Crit Care Med 2011;15:196-7.
Burtis C, Bruns D, editors. Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics. 7th ed. Philadelphia PA: Saunders; 2014.
Statland BE, Brzys K. Evaluating STAT testing alternatives by calculating annual laboratory costs. Chest 1990;97:198S-203S.
King RI, Mackay RJ, Florkowski CM, Lynn AM. Electrolytes in sick neonates – Which sodium is the right answer? Arch Dis Child Fetal Neonatal Ed 2013;98:F74-6.
Magny E, Beaudeux JL, Launay JM. Point care testing in blood gas and electrolyte analysis: Examples of implementation and cost analysis. Ann Biol Clin (Paris) 2003;61:344-51.
Morimatsu H, Rocktäschel J, Bellomo R, Uchino S, Goldsmith D, Gutteridge G, et al. Comparison of point-of-care versus central laboratory measurement of electrolyte concentrations on calculations of the anion gap and the strong ion difference. Anesthesiology 2003;98:1077-84.
Scott MG, LeGrys VA, Klufts JC. Electrolytes and blood gases. In: Burtis CA, Ashwood E, Bruns DE, editors. Tietz Textbook of Clinical Chemistry. 4th ed., Ch. 27. Missouri USA: Elsevier; 2006. p. 985.
Sakyi A, Laing E, Ephraim R, Asibey O, Sadique O. Evaluation of analytical errors in a clinical chemistry laboratory: A 3 year experience. Ann Med Health Sci Res 2015;5:8-12.
Flegar-Mestrić Z, Perkov S. Comparability of point-of-care whole-blood electrolyte and substrate testing using a stat profile critical care xpress analyzer and standard laboratory methods. Clin Chem Lab Med 2006;44:898-903.
Story DA, Morimatsu H, Egi M, Bellomo R. The effect of albumin concentration on plasma sodium and chloride measurements in critically ill patients. Anesth Analg 2007;104:893-7.
Chow E, Fox N, Gama R. Effect of low serum total protein on sodium and potassium measurement by ion-selective electrodes in critically ill patients. Br J Biomed Sci 2008;65:128-31.
Jacobs E, Ancy JJ, Smith M. Multi site performance evaluation of pH, bood gas, electrolyte, glucose and lactate determinations with the GEM Premier 3000 critical care analyser. Point Care 2002;1:135-44.
van Berkel M, Scharnhorst V. Electrolyte-balanced heparin in blood gas syringes can introduce a significant bias in the measurement of positively charged electrolytes. Clin Chem Lab Med 2011;49:249-52.
Yilmaz S, Uysal HB, Avcil M, Yilmaz M, Daǧlı B, Bakış M, et al. Comparison of different methods for measurement of electrolytes in patients admitted to the Intensive Care Unit. Saudi Med J 2016;37:262-7.
Rouse C. Theoretical reasons for sodium measurement error - POCT specialist -C29-A2 ISBN 1–56238–410–4 ISSN 0273–3099.