Analytical evaluation of direct bicarbonate measurement with the new gem premier chemstat in hemodialysis patients

Abstract

GEM Premier ChemSTAT is a whole-blood analyzer designed for providing a rapid basic metabolic panel, inclusive of creatinine and blood urea nitrogen, with the unique characteristic of providing measured bicarbonate (HCO₃^–) levels. The aim of this work was to evaluate the clinical performance of HCO₃^– assessment with this analyser in a real-life hemodialysis setting. Imprecision was calculated at different HCO₃^– levels, along with assay comparison with Gem Premier 4000 analysers. GEM Premier ChemSTAT displayed an imprecision and a bias (in comparison to GEM Premier 4000) for HCO₃^– of 0.4% and 37.3% at 20.8 mmol/L, 1.2% and 25.6% at 16.4 mmol/L, and 2.1% and 11.6% at 11.5 mmol/L, respectively, using three levels of HCO₃^– quality control sample ChemSTAT System Evaluator. At direct comparison with the GEM Premier 4000 in the hemodialysis setting, Bland–Altman analysis of HCO₃^– levels evidenced a bias (µ) of −4.9 (95% CI, −5.2 to −4.7) mmol/L. Such difference was attenuated by recalculating the GEM ChemSTAT expected HCO₃^– values from pH and pCO₂ using the Henderson Hasselbach equation, µ=–0.07 (95%CI, −0.19 to 0.05) mmol/L (p = .24). In conclusion, our results show a remarkable difference between the HCO₃^– values reported by GEM ChemSTAT or GEM 4000. New reference values for GEM ChemSTAT HCO₃^– shall hence be defined according to our findings. We suggest that further investigation and a re-evaluation of the reference range should be made before extending the clinical use of this device.

Keywords:

• Performance
• measure error
• bed-side analysis
• potentiometry

Acknowledgments

We would like to thank all the staff, nurses and patients of the IFCA Nephrology and Dialysis Unit, the laboratory staff and outpatients service nurses and patients.

Disclosure statement

No potential conflict of interest was reported by the author(s).