The American Diabetes Association has found that diabetics whose blood sugar levels are kept under tight control have fewer complications. Diabetes test strips enable diabetics to monitor their blood sugar levels at home. This allows patients to adjust their diet and insulin doses when needed. Logs of blood glucose readings also give physicians a picture of a patient's blood sugar fluctuations.
Reagents in Test Strips
Glucose test strips are made of plastic. The end of the strip is coated with enzymes, either glucose oxidase or glucose dehydrogenase. A drop of blood, usually taken from a prick in the finger, is placed on the reagent end of the strip. The enzyme chemically reacts with the glucose in the blood, and the strength of the reaction depends on the glucose concentration. The strip is then placed into a meter that reads and then displays the blood sugar concentration. There are two different types of meters: a reflectance photometer and an amperometric system.
Reflectance Photometers
Reflectance photometers rely on light to measure the glucose concentration. The chemical reaction between glucose in the blood and glucose oxidase produces hydrogen peroxide. The hydrogen peroxide reacts with a dye on the test strip. The intensity of the color change is proportional to the amount of glucose in the blood. When the test strip is inserted into the meter, the meter shines light on the test strip. The meter electronically measures the intensity of the color change to give the glucose concentration.
Reflective hexokinase meters also measure blood glucose concentration based on the intensity of a color change. Rather than using the glucose oxidase/perioxidase reaction, the reagents on the strip react with the glucose to form glucose-6-phosphate. This in turn reacts with a dye, and the meter measures the intensity of the color change.
Amperometric Systems
In amperometric systems, an electric current is used to measure blood glucose concentration. The glucose in the blood turns either to gluconic acid or gluconolactone, depending on the type of reagent used on the strip. This chemical reaction produces electrons. When the strip is placed in the meter, the test meter sends an electric current through the sample. The amount of electric current the test strip can transmit is related to the amount of glucose in the blood. This amount of current is calculated to a blood glucose reading that the meter displays on the screen.
Visual Glucose Strips
For people who test their blood only occasionally, reagents strips that are visually read are an option. Visually read test strips rely on the same color-change reaction that reflectance photometers use. The color of the strip is compared to the key on the side of the package to give an estimate of blood sugar concentration. Since visually read strips are not as accurate as those used in glucose meters, most physicians prefer that their patients use glucose meters.
