Many people with diabetes routinely use glucometers to measure their blood glucose concentration and make decisions on the basis of these results to help manage the disease. Glucometers are also used in veterinary medicine to monitor blood glucose levels in cats and dogs with diabetes or other conditions, and veterinarians similarly use that information to guide diagnostic and treatment decisions.

Glucometers are popular because they work quickly and require only a small drop of blood to produce a reading, but they are not as accurate as some other methods. “It's widely known that glucometer readings come with a degree of inaccuracy, and until now we've just lived with it,” said Rebecka Hess (University of Pennsylvania School of Veterinary Medicine, Philadelphia) in a press release. Biochemical analyzers, for example, produce more accurate results but are slower and more expensive to operate and require larger amounts of blood.

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Hess and her colleagues noted some concern among veterinary clinicians that the inaccuracy of glucometer readings might affect the quality of clinical decisions based on these readings. They considered that the inaccuracy of glucometers might be due in part to the fact that glucometers obtain readings from whole blood rather than plasma (whole blood without red and white blood cells) or serum (whole blood without red and white blood cells or clotting factors), both of which can be obtained by spinning whole blood in a centrifuge. To test this idea, they carried out a study comparing glucometer readings obtained from whole blood, plasma and serum with the serum glucose concentration measured by a biochemical analyzer as the 'gold standard.'

They obtained 96 blood samples from 80 dogs and 90 blood samples from 65 cats that were being treated at their institution's veterinary hospital and took aliquots of whole blood, plasma and serum from each sample. They measured glucose concentration in each aliquot using a glucometer and in serum aliquots using a biochemical analyzer. They found that glucometer readings obtained from plasma or serum—but not whole blood—correlated well with the concentration measured by a biochemical analyzer (J. Am. Vet. Med. Assoc. 246, 1327–1333; 2015). The results indicate that obtaining glucometer readings from plasma or serum rather than whole blood might enable veterinarians to make better diagnostic and treatment decisions, and practices at the authors' institution's veterinary hospital have been changed accordingly. Additional studies are needed to assess whether the results hold true—and might therefore have implications for glucose monitoring—in people.