Variations in sample pH and pO2 affect ExacTech meter glucose measurements

Area of Science:

• Clinical Chemistry
• Medical Devices
• Biomedical Engineering

Background:

• Accurate blood glucose monitoring is crucial for patient management.
• Several portable blood glucose meters are available for point-of-care testing.
• The performance of these devices can be influenced by physiological factors like blood pH and oxygen levels.

Purpose of the Study:

• To evaluate the impact of varying sample pH and partial pressure of oxygen (pO2) on the accuracy of five blood glucose meters.
• Specifically assess the performance of Accutrend, ExacTech Companion, Glucometer II, One Touch II, and Refloflux II under different physiological conditions.

Main Methods:

• Venous blood samples were tonometered to create samples with a pH range of 6.54-7.73 while maintaining consistent pO2 and pCO2.
• Further samples were prepared with a pO2 range of 2.0-33.6 kPa, keeping pH and pCO2 constant.
• Deviations in glucose measurements were recorded against reference values at pH 7.40 and specific pO2 levels.

Main Results:

• The ExacTech Companion demonstrated >15% deviation below pH 6.95 and above pH 7.85.
• ExacTech glucose readings deviated by >15% below pO2 of 5.8 kPa and above 22.9 kPa.
• Accutrend and One Touch II meters required larger pO2 changes (42 kPa and 45 kPa, respectively) to exhibit similar error margins.

Conclusions:

• The ExacTech Companion exhibits significant inaccuracies in glucose measurements under conditions of severe acidosis or hypoxia.
• The Accutrend and One Touch II meters show greater stability across a wider range of pO2 variations.
• Clinical interpretation of ExacTech Companion glucose readings requires caution in patients with critically altered blood gas parameters.