January 16, 2011

Portable Blood Sugar Monitors Inaccurate For Some

A new study said that portable meters used to gauge blood sugar levels in pregnant women with diabetes gave readings that differed from lab tests by up to 16 percent.

Researchers say that this kind of inaccuracy is concerning because small differences in blood sugar during pregnancy can have potentially serious consequences for the mother and baby.

However, Dr. David Sacks, who heads the clinical chemistry lab at the National Institutes of Health, told Reuters that women should pay more attention to getting the readings right.

People who have diabetes often rely on the devices as convenient indicators of when to take insulin and how much they need.

"They're very small, you can put them in your pocket," Sacks, who was not involved in the new work, told Reuters. "You can prick your finger and get the result immediately. But the meters have never been as accurate as blood that's drawn in central labs."

Dr. Nimalie Perera of the Royal Prince Alfred Hospital in Sydney, Australia compared the readings from 102 women to a more precise lab test in order to see how accurate the devices really are.

The women all had diabetes and came to a prenatal clinic for nurses to measure their blood sugar levels.  Nurses drew blood with a finger prick on each patient by using six different glucose meters.

According to findings published in Diabetes Care, the most accurate model, Stat-Strip, was off from the lab result by an average of 6 percent.  Optium Xceed was the least accurate by almost 16 percent. 

The U.S. Food and Drug Administration (FDA) has approved all the devices that are marketed for medical conditions in the U.S.

Sacks told Reuters that the FDA has been trying to improve standards to increase the accuracy of blood glucose meters.

Abbott Diabetes Care makes three of the glucose meters that were tested.

"All of Abbott's blood glucose monitoring systems meet the current international standard for blood glucose meter accuracy," Adrienne Turner, a spokesperson for the company, wrote in an e-mail to Reuters Health.

"The accuracy of its medical products is one of Abbott's main priorities and we will continue to meet current and future regulatory and industry standards for blood glucose meter accuracy."

U.S. and Australian standards committees recommend that glucose meters should give results within 20 percent of laboratory tests.  However, researchers say that they may not be good enough, especially for pregnant women with diabetes.

Diabetes can lead to a higher risk of miscarriage or a more difficult birth and heavier newborns.  Dr. Boyd Metzger, who studies diabetes in pregnancy at Northwestern University, said that because of that, the goal is "to bring the blood glucose levels of (pregnant women) with diabetes as close to normal as can be achieved."

However, he added, "that's led to a lot of dependence on self-monitoring."

Meters also store the readings so doctors are able to keep track of patients' diabetes every time they go in for an appointment.

If the measurements are inaccurate, women may give themselves doses of insulin that are higher or lower than what they should be receiving, or doctors may not have the most accurate information to counsel and treat their patients.

Metzger, who was not involved in the current study, said that using the devices is not straightforward either.

"We give them a meter and teach them how to do it and then try to use that information (from the meter) right away," he told Reuters. "There's a significant learning curve for ... this kind of technology."

Sacks said the new study might underestimate the problems with glucose meters, because trained nurses performed all the readings.

Women may also be hesitant to redo a measurement even if they worry it could be wrong. 

Sacks said that despite the inaccuracies, the meters are still the best tool there is to manage diabetes on a day-to-day basis.

"What pregnant women should do is follow the directions very, very carefully," he said. "Make sure that the technique is as good as can be."

And if something seems off "they should repeat the test," he advised.


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