The agreement of point-of-care and standard laboratory electrolyte and glucose analysis in critically ill patients in a sub-Saharan tertiary teaching hospital

Abstract

Background: The critically ill patient undergoes rapid changes in the internal milieu requiring quick intervention. Point of care testing has been shown to be valuable in the early diagnosis and management of such patients.

Objective: This study determined the agreement between I-STAT Abbot point of care testing with standard laboratory testing in the analysis of electrolytes and glucose concentrations in critically ill patients.

Methods: The study was performed in a Sub-Saharan Tertiary Teaching Hospital in critically ill patients. Electrolyte and glucose analysis were measured with ISTAT Abbot Analyzer unit with parallel blood specimens (n=30) tested in the laboratory on an ion-selective electrode, SFRI analyzer ISE 6000.

Results: There was no significant difference in mean sodium, potassium, chloride and glucose between I-STAT POCT and standard laboratory measurements. The agreement between POCT and laboratory glucose was good p_c = 0.967, mean difference of 0.79 and 95% limit of agreement from -3.83 to +5.107 mmol/L, p = 0.733. Bicarbonate was moderate (p_c) = 0.637, mean difference of 1.95 and 95% limit of agreement from -4.294 to +0.394 mmol/L, p = 0.101. There was moderate agreement for sodium (p_c) = 0.32, mean difference of 5.8 and 95% limit of agreement from -0.378 to +11.98 mmol/L, p = 0.064. Agreement for potassium was moderate (p_c) = 0.439, mean difference of 0.15 and limit of agreement from -0.401 to +0.701 mmol/L, p = 0.588. There was, however, a significant difference in mean chloride, and BUN values; chloride (p_c) = 0.0796, mean difference of 13.8 and 95%  limit of agreement from -7.55 to + 20.015 mmol/L. Blood urea nitrogen (p_c) = 0.064, mean difference of 18.55 and 95% limit of agreement from -30.126 to +6.974 mmol/L.

Conclusion: The mean sodium, potassium, glucose and bicarbonate were comparable with moderate to good agreement between I-STAT POCT and ISE 6000 Analyzer. Though, the mean BUN and chloride levels between the analytical methods differ significantly.

Keywords: Point of care testing, Bland and Altman, concordance, electrolytes, ICU