Comparing Point-of-Care and Central Laboratory Electrolyte Testing
Author Information
Author(s): Chacko Binila Peter, John V Patole, Shalom Fleming Jude J, Selvakumar Ratnasamy
Primary Institution: Christian Medical College & Hospital, Vellore, India
Hypothesis
Is there agreement between whole blood electrolytes measured by a point-of-care device and serum electrolytes measured using indirect ion-selective electrodes?
Conclusion
Clinicians should be aware of the differences between whole blood and serum electrolytes, especially when urgent samples are tested at point of care.
Supporting Evidence
- The mean sodium value was significantly different between whole blood and serum samples.
- The agreement for potassium values ≥3.0 mmol/L was good, but poor for values <3.0 mmol/L.
- A correction factor for sodium and potassium was estimated to minimize differences.
Takeaway
This study shows that tests done at the bedside for electrolytes can give different results than those done in the lab, so doctors need to be careful when making decisions based on these tests.
Methodology
Electrolytes were analyzed in 44 paired samples from critically ill patients using both point-of-care and central laboratory methods.
Potential Biases
Differences in sample type and analysis methods could introduce bias.
Limitations
The sample size was small and there were very few sodium values in the hypernatremic and hyponatremic ranges.
Participant Demographics
Critically ill patients in a medical ICU.
Statistical Information
P-Value
<0.001
Confidence Interval
95% LOA −8.78 to 0.65 for sodium; 95% LOA −0.72 to 0.13 for potassium
Statistical Significance
p<0.001
Digital Object Identifier (DOI)
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