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BLOOD GLUCOSE MONITORS

BGM’s

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Introduction An estimated 135 million people worldwide —

18.2 million in the United States — have diabetes mellitus:

a disease in which the pancreas secretes an inadequate supply of insulin.

When blood glucose concentration is high, insulin lowers glucose levels from the extracellular form of glucose

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Introduction When insulin production is deficient or absent,

extracellular glucose concentrations in the blood rise unchecked to above-normal levels; this condition is called hyperglycemia.

Hyperglycemia is potentially fatal and can also lead to severe damage to the heart, kidneys, eyes, blood vessels, and nerves.

The normal fasting glucose concentration is between 70 and 110 mg/dL in blood serum or plasma

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Purpose of BGM’s

BGMs measure blood glucose concentration using areagent strip, cartridge, or cuvette and a drop

of capillary blood from a finger puncture.

Health professionals and individuals with diabetes use these battery-powered monitors to manage diabetes and to test for transient high or low blood glucose

levels (e.g., during surgery).

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Principles of operation

Currently available BGMs use optical or electromechanical methods to measure glucose levels.

With optical systems, the blood sample is exposed to a semipermeable membrane covering the reagent pad, which is coated with an enzyme (e.g., glucose oxidase, glucose dehydrogenase, hexokinase).

The reaction causes a significant color change in an indicator or dye; the intensity of this change is directly proportional to the amount of glucose in the blood sample.

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Reflectance photometry BGMs Most portable BGMs with optical detection use

reflectance photometry to measure the amount of light (which is produced by an LED (light-emitting diode [LED]) reflected from a reagent-impregnated test pad that has reacted with a drop of blood.

Once the reagent pad is inserted, light from the LED strikes its surface and is reflected to the photodiode, which measures the light’s intensity and converts its energy to electrical signals

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Principles of operation These signals are amplified, digitized, analyzed by a

microprocessor, and converted by the unit’s programming to the corresponding glucose concentration for display on the readout, expressed in mmol/L of blood.

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Electrochemical BGMs Electrochemical BGMs use an electrode sensor to

measure the current that is produced when glucose oxidase, glucose dehydrogenase, or hexokinase converts glucose to gluconic acid when blood is applied to a test strip.

The resulting current is directly proportional to the amount of glucose in the sample.

These automatic devices require no reaction timing or reagent-strip wiping.