Enzyme Chemistry: GOx vs. GDH

The choice of enzyme in diabetic test strips—Glucose Oxidase (GOx) versus Glucose Dehydrogenase (GDH)—represents a trade-off between specificity and environmental stability.

GOx is the traditional standard, offering high specificity for glucose with no cross-reactivity to other sugars. However, it is susceptible to the "Oxygen Effect," where variations in blood oxygen levels (e.g., in COPD patients or at high altitudes) can skew results.

GDH enzymes solve the oxygen problem, allowing for accurate testing in venous and arterial blood. However, early iterations using the PQQ cofactor (GDH-PQQ) caused fatal errors by cross-reacting with non-glucose sugars like maltose (common in dialysis patients). This led to a massive industry shift toward GDH-FAD, which combines the oxygen-independence of GDH with the glucose-specificity of GOx, effectively mitigating the risks associated with both oxygen tension and maltose interference.