939-P: Dynamic Interference Testing Results with the Libre 2 Continuous Glucose Monitoring Device

Background: Sensors for continuous glucose monitoring (CGM) are increasingly used by people with type 1 and type 2 diabetes. However, the reaction of the glucose oxidase-based sensor technologies to potentially interfering nutritional, endogenous, or pharmaceutical substances is barely understood. We have developed an in-vitro test method for continuous and dynamic CGM interference testing and explored the sensitivity of the Libre 2 sensor to a panel of 68 individual substances.

Method: In each interference experiment, three sensors were exposed to substance gradients from zero to supra-physiological concentrations generated by HPLC-pumps at a fixed glucose concentration of 200 mg/dL. YSI Stat 2300 Plus was used as the glucose reference method. Interference was assumed if the CGM sensors showed a mean bias of more than ±10% from baseline with a tested substance at any given substance concentration.

Results: Interference was seen with the following substances: xylose (difference from baseline: +178%), galactose (+134%), mannose (+130%), hydroxyurea (+84%), ascorbic acid (+48%), dithiothreitol (+46%), methyldopa (+16%), ibuprofen (+14%), red wine (+12%), N-acetyl-cysteine (+11%), icodextrin (+10%), while no interference was seen with the other substances. Suspected sensor fouling, in that the needle sensors subsequently ceased to operate after exposure to a substance, was not observed with Libre 2.

Conclusions: Our standardized dynamic interference testing protocol identified several nutritional and pharmacological substances that substantially influenced the Libre 2 signal. Clinical trials are now necessary to investigate, whether our findings are of relevance for routine care.