A study comparing values of serum sodium estimated by colorimetric kit method with those obtained by direct and indirect ion selective electrode methods

Introduction: Electrolyte abnormalities are known to cause significant morbidity and mortality, when it is not detected. Dyselectrolytemias are usually treatable. Hyponatremia is a common manifestation encountered in the elderly. The rural health care facilities may not have well equipped laboratories. Therefore, this study intended to look for the possibility of establishing a screening technique that can help detect hyponatremia in such centres. Materials and Methods: Serum sodium levels were estimated in 120 samples using direct, indirect ISE and colorimeter. Statistical analysis was done using SPSS version 17, NCSS 11 and MINITAB 18 software. A p value< 0> Results: A simple linear regression analysis was done and a regression equation was derived for sodium levels while comparing between the instruments. The Bland Altman analysis gave an agreement limit of 95% between the instruments which is well within the CLIA suggested target value of ±4 mmol/L in the hyponatremic and normonatremic range. Conclusion: The derived regression equation calculates a predicted value for direct and Indirect ISE using the values obtained on the colorimeter making it comparable on all the three instruments in the hyponatremic and normonatremic ranges. The colorimetric method can be used as a cost effective screening technique to identify the hyponatremic elderly for whom a tertiary hospital may not be accessible, thus facilitating early intervention.