Comparison of the point-of-care blood gas analyzer versus the laboratory auto-analyzer for the measurement of electrolytes
Open accessAbstract
BACKGROUND: Electrolyte values are measured both by arterial blood gas (ABG) analyzers and central laboratory auto-analyzers (AA), but a significant time gap exists between the availability of both these results, with the ABG giving faster results than the AA. The authors hypothesized that there is no difference between the results obtained after measurement of electrolytes by the blood gas and auto-analyzers. METHODS: After approval by the ethics committee, an observational cohort study was conducted in which 200 paired venous and arterial samples from patients admitted to the Medical Intensive Care Unit (ICU) of Apollo Hospital, Hyderabad, India, were analyzed for electrolytes on the ABG machine and the AA. Analyses were done on the ABL555 blood gas analyzer and the Dade Dimension RxL Max, both located in the central laboratory. Statistical analyses were performed using paired Student's t test. RESULTS: A total of 200 paired samples were analyzed. The mean ABG sodium value was 131.28 (SD 7.33), and the mean AA sodium value was 136.45 (SD 6.50) (p < 0.001). The mean ABG potassium value was 3.74 (SD 1.92), and the mean AA potassium value was 3.896 (SD 1.848) (p = 0.2679). CONCLUSION: Based on the above analysis, the authors found no significant difference between the potassium values measured by the blood gas machine and the auto-analyzer. However, the difference between the measured sodium was found to be significant. We therefore conclude that critical decisions can be made by trusting the potassium values obtained from the arterial blood gas analysis.
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Whole-blood POCT analyzers tend to report slightly elevated potassium levels compared to serum-based laboratory systems due to differences in sample handling and electrode sensitivity.
“This minor overestimation bias is consistent with earlier work by Chhapola et al. [3] and Jain et al. [4], who observed that whole-blood POCT analyzers tend to report slightly elevated K⁺ levels compared to serum-based lab systems due to differences in sample handling and electrode sensitivity.”
From Reliability of Point-of-Care Venous Blood Gas Testing for Potassium and Sodium Compared to Central Laboratory Results in Emergency Patients: A Clinical Audit (2025) · cites this paper as Jain et al. [4]
The Results report the opposite direction: mean potassium was 3.7 mmol/l on the blood gas analyzer versus 3.9 mmol/l on the laboratory auto-analyzer, and 71.5% of blood gas readings were lower. The Introduction describes differences in sample type and electrode technology, but does not attribute an upward potassium bias to them. The paper’s conclusion says the potassium measurements did not differ significantly. (LLM, conf=0.90)
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Experimental — accuracy not yet measuredMultiple factors contribute to discrepancies between POCT and laboratory values: variation in sample matrix, pre-analytical handling, device calibration intervals, and analytical methodology.
“Multiple factors contribute to discrepancies between POCT and laboratory values: variation in sample matrix (whole blood vs. serum/plasma), pre-analytical handling, device calibration intervals, and analytical methodology [4,5].”
From Reliability of Point-of-Care Venous Blood Gas Testing for Potassium and Sodium Compared to Central Laboratory Results in Emergency Patients: A Clinical Audit (2025) · cites this paper as [4]
The Introduction (Table 1; page not provided) contrasts whole blood with serum, direct with indirect electrode methods, and different sample dilutions; it also explains how heparin dilution can lower measured electrolyte values. Materials and methods (page not provided) describes sample handling and says both analyzers were calibrated before each measurement cycle. It does not identify variation in device calibration intervals as a cause of discrepancies. (LLM, conf=0.88)
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Research works printed but not linked: 15
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Allardet-Servent, J., Lebsir, M., Dubroca, C., Fabrigoule, M., Jordana, S., Signouret, T., Castanier, M., Thomas, G., Soundaravelou, R., Lepidi, A., et al. (2017) · PLOS ONE · doi:10.1371/journal.pone.0169593 · Cited by 64 · see citing works
Lasfer, C., Lahib, A., Soliman, K., & Gouda, S. (2025) · Cureus · doi:10.7759/cureus.89106
“This minor overestimation bias is consistent with earlier work by Chhapola et al. [3] and Jain et al. [4], who observed that whole-blood POCT analyzers tend to report slightly elevated K ⁺ levels compared to serum-based lab systems due to differences in sample handling and electrode sensitivity.”
- Authors
- Jain, A., Subhan, I., & Joshi, M.
- Affiliations
- Mayo Clinic (US)
- Apollo Hospitals (IN)
- Corresponding author
- Jain, Anunaya
- Venue
- International Journal of Emergency Medicine
- Published
- 2009-02-24
- Volume
- 2
- Issue
- 2
- Pages
- 117-120
- ISSN
- 1865-1372 (ISSN-L)
- 1865-1380
- PMC
- PMC2700230
- OpenAlex
- W2051694322
- Cited by
- 108
- References
- 0
- Citations by year
- 2026: 3 · 2025: 9 · 2024: 10 · 2023: 6 · 2022: 11 · 2021: 7 · 2020: 4 · 2019: 8 · 2018: 7 · 2017: 4 · 2016: 8 · 2015: 8 · 2014: 10 · 2013: 4 · 2012: 5
- FWCI
- 1.99
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- Locations
- International Journal of Emergency Medicine (publishedVersion, cc-by-nc)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Health Sciences › Medicine › Physiology › Clinical Laboratory Practices and Quality Control
- Health Sciences › Medicine › Pulmonary and Respiratory Medicine › Electrolyte and hormonal disorders
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Clinical Biochemistry › Bacterial Identification and Susceptibility Testing
- Keywords
- electrolyte measurement, sodium, potassium, arterial blood gases, venous blood samples, intensive care, intensive care unit, method comparison
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