14.1.11—Glucose test strips and biosensors

A glucose test strip uses immobilised enzymes to convert glucose into a colour signal, while a blood-glucose biosensor converts an enzyme reaction into an electrical signal. The signal is interpreted as an estimate of glucose concentration within the method’s calibrated range.

Urine test-strip method:

1. Immerse the enzyme-containing pad in the urine sample for the specified short time.
2. If glucose is present, glucose oxidase produces hydrogen peroxide; peroxidase uses it in a second reaction that forms a coloured product.
3. Compare the pad colour with the supplied colour chart: darker colour corresponds to a higher glucose concentration in the chart range.
4. Treat the result as a urine-glucose indication, not a direct current blood-glucose reading.

Blood biosensor method:

1. A partially permeable membrane allows small molecules from the blood sample to reach immobilised glucose oxidase on the recognition layer.
2. Glucose oxidation produces hydrogen peroxide, whose electron transfer at an electrode creates a current.
3. Electron flow is related to glucose concentration; the processor converts the amplified signal into a digital reading.

Use the stated sample volume or immersion, timing and calibration/colour chart consistently; compare with appropriate controls or a known reference when the method provides them. Read only within the validated range and do not infer more precision than the colour scale or sensor supports.

Enzyme specificity makes the test selective for glucose. A urine strip indicates whether glucose was present in the urine and reflects earlier renal-threshold conditions; it does not show the current blood-glucose concentration. This card covers signal generation and reading, not insulin/glucagon feedback or a medical diagnosis.