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Open Access Short Report

Establishing reference intervals for electrolytes in newborns and infants using direct ISE analyzer

Mulugeta Melkie1*, Mahilet Yigeremu2, Paulos Nigussie3, Tilahun Teka2 and Samuel Kinde2

Author Affiliations

1 Department of Medical Laboratory Science, Arbaminch University, Arbaminch, Ethiopia

2 Faculty of Medicine, Addis Ababa University, Addis Ababa, Ethiopia

3 Ethiopian Health and Nutrition Research Institute, Addis Ababa, Ethiopia

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BMC Research Notes 2013, 6:199  doi:10.1186/1756-0500-6-199

Published: 20 May 2013



To generate clinically applicable reference intervals (RIs) for commonly requested electrolytes in Ethiopian newborns and infants that can help in early detection, close monitoring and correction of electrolyte abnormalities. Cord blood (from newborns, n = 60) and venous blood samples (from infants, n = 57) were collected and analyzed using direct ISE analyzer, AVL (9181). MedCalc® software was applied to determine the robust upper and lower end points covering 95% of the reference values of each electrolyte with respective 90% CIs.


This is an extension report of our recent study; and hence is resulted from the same data source. The level of Na+ and K+ showed difference in newborns and infants even though combined RIs were suggested by the Haris and Boyd rule as 126–143 mmol/l and 4.0-7.9 mmol/l respectively. However, Cl- values failed to show such a difference and thus a combined RI was determined to be 100–111 mmol/l. Almost all maternal, neonatal and infantile factors were not able to affect the values of the electrolytes.


Combined RIs are suggested for the interpretation of electrolyte values in newborns and infants without taking the effect of maternal, neonatal and infantile factors into account. Since the RIs were different from previously reported values, it will be appropriate to apply such RIs for the interpretation of electrolyte values in Ethiopian pediatric population.

Reference intervals; Electrolytes; Robust method; Newborns; Infants; Cord blood; Direct ISE