Proposal for standardizing direct-reading biosensors for blood glucose

Area of Science:

• Clinical Chemistry
• Biosensor Technology
• Analytical Chemistry

Background:

• Direct-reading glucose biosensors measure molality, differing from concentration-based methods.
• Aqueous calibration can lead to higher glucose readings in blood and plasma compared to routine methods.
• This discrepancy is theoretically explained by the ratio of water concentrations between calibrator and sample.

Purpose of the Study:

• To confirm the theoretical explanation for higher glucose readings from direct-reading biosensors.
• To evaluate the accuracy of direct-reading glucose biosensor measurements against routine methods.
• To propose a method for standardizing glucose reporting to avoid confusion.

Main Methods:

• Glucose levels were measured in 14 blood and 40 plasma samples using the Chiron Model 860 direct-reading glucose sensor.
• Measurements were compared with results from a routine method (ESAT 6660; Eppendorf).
• Chiron sensor results were converted using assumed water concentrations for blood (0.84 kg/L) and plasma (0.93 kg/L) relative to the calibrator's water concentration (0.99 kg/L).

Main Results:

• Conversion of direct-reading glucose biosensor results using water content ratios achieved agreement with the routine method.
• Individual conversion based on hematocrit in whole blood samples was less accurate.
• The study confirmed that molality measurement by direct-reading biosensors leads to higher results than concentration-based methods.

Conclusions:

• Standardizing the reporting of whole-blood glucose results as equivalent plasma concentrations is proposed to reduce confusion.
• This standardization can be conveniently achieved using a reference material like NIST SRM 965.
• Accurate glucose measurement and reporting are crucial for clinical decision-making.