When it comes to testing blood glucose levels, glucose meters have the advantage of being fast and requiring only a small drop of blood; however, they are not as accurate as some other methods of measuring blood glucose. But don’t count them out yet: In a new study, researchers from the University of Pennsylvania School of Veterinary Medicine have found a way of obtaining more accurate measurements from glucose meters by using blood plasma or serum rather than whole blood, as reported by the university. “Correlation between glucose concentrations in serum, plasma, and whole blood measured by a point-of-care glucometer and serum glucose concentration measured by an automated biochemical analyzer for canine and feline blood samples” was reported in the Journal of the American Veterinary Medical Association in June. The findings have already resulted in changes in practice at Penn Vet’s Ryan Hospital and may inspire an investigation into whether the same should hold true for human patients who rely on glucose meters to monitor their blood glucose levels. University of Pennsylvania’s School of Veterinary Medicine Rebecka Hess (right) senior author on the work and a professor of internal medicine at Penn Vet. Koranda A. Wallace, formerly a lecturer in the Department of Pathobiology, collaborated with Hess and other authors on the work. “It’s a simple study, but it has changed the way we do things,” said Rebecka Hess, senior author on the work and a professor of internal medicine at Penn Vet. Hess collaborated on the work with fellow Penn Vet scientists Barbara S. Tauk, the study’s lead author and a clinical studies resident; Kenneth J. Drobatz, director of emergency services and chief of critical care; and Koranda A. Wallace, formerly a lecturer in the Department of Pathobiology. “It’s widely known that glucose meter readings come with a degree of inaccuracy, and until now we’ve just lived with it,” Hess said. To find a better way of maintaining the glucose meter's conveniences while improving its accuracy, the Penn team assessed cats and dogs treated at Ryan Hospital. With their owners’ consent, animals that were going to have blood drawn for another purpose were enrolled in the study. The researchers obtained 96 blood samples from 80 dogs and 90 blood samples from 65 cats. Normally, glucose meters are used to measure glucose on whole blood, but the researchers wanted to try measuring glucose on blood plasma and blood serum as well. Blood plasma is what’s left of blood after removing the red and white blood cells; blood serum is what’s left of blood plasma after also removing clotting factors. Both can be obtained by spinning whole blood in a centrifuge for a few minutes. The researchers tested each sample in both the glucose meter and, as a control, a biochemical analyzer. The biochemical analyzer takes about five minutes to render a reading, requires more blood and is more expensive to operate than a glucose meter, but its measurement of blood glucose from serum is considered the gold standard of accuracy. The Penn researchers found that testing either blood plasma or blood serum in the glucose meter gave results that were nearly the same as those given by the biochemical analyzer and were more accurate than whole blood. As they wrote in the abstract for their article: “For both canine and feline samples, glucose concentrations in serum and plasma measured by the POCG were more strongly correlated with the serum glucose concentration measured by the biochemical analyzer (ρc, 0.98 for both canine serum and plasma; ρc, 0.99 for both feline serum and plasma) than was that in whole blood (ρc, 0.62 for canine samples; ρc, 0.90 for feline samples). The mean difference between the glucose concentrations determined by the biochemical analyzer and the POCG in serum, plasma, and whole blood was 0.4, 0.3, and 31 mg/dL, respectively, for canine samples and 7, 6, and 32 mg/dL, respectively, for feline samples.” “The plasma and serum results were very tightly clumped with the results from the gold standard machine,” Drobatz said. “That gives us a lot of confidence in this method.” Drobatz said that using a glucose meter is preferable to a biochemical analyzer in many cases in the emergency room, when results are needed quickly or when only a very small amount of blood can be obtained in hypoglycemic puppies and kittens. “The analyzer requires 2 milliliters of blood while the glucose meter only needs 0.6 milliliters,” he said. “That can be meaningful to a small animal or an animal who is already anemic.” On the power of these results, Ryan Hospital changed its practices to use blood plasma or sera rather than whole blood when measuring blood glucose with a glucose meter.
