BIOCHEMISTRY OF GLUCOSE MEASUREMENTS
In 1964, Ernie Adams invented Dextrostix, a paper strip that developed varying shades of color proportional to the glucose concentration. In 1970, Anton Clemens developed the first glucometer, the Ames Reflectance Meter (ARM), to detect reflected light from a Dextrostix. The ARM weighed 3 lb and cost $650.1
Modern glucometers analyze whole blood using both an enzymatic reaction and a detector. The enzyme is packaged in a dehydrated state contained in a disposable strip. The glucose in the patient’s blood rehydrates and reacts with enzymes in the strip to produce a detectable product.1
The gold standard for measuring glucose is isotope dilution mass spectrometry; however, this is not commonly performed in clinical laboratories. The accuracy of glucometers is most commonly assessed by comparing the glucometer result to a venous plasma sample collected at the same time and analyzed by a clinical laboratory using multi-analyte automated instrumentation.1
The two main types of commercially available glucometers are the glucose oxidase (GO) and glucose dehydrogenase (GDH) systems. The GO meters utilize the GO enzyme to catalyze the oxidation of glucose into gluconic acid. The oxidation reaction produces electrons that generate current proportional to the glucose level in the test sample.1-3
With GDH glucometers, several different enzymes can catalyze glucose oxidation, including nicotinamide adenine dinucleotide (GDH-NAD), flavin adenine dinucleotide (GDH-FAD), pyrroloquinoline quinone (GDH-PQQ), or mutant glucose dehydrogenase PQQ (Mut Q-GDH).2,4,5
Measurement of glucose using the hexokinase enzyme is considered more accurate than both the GO and GDH systems and is commonly used in clinical laboratories. However, the cost of this system is more than that of the commercially available glucometers, and thus it is not widely available.2
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