Blood Glucose Meters 2014
Will meters be more accurate? And getting the most from what you have
Accuracy. It’s the No. 1 thing readers shopping for a meter ask about. The fact is, home-use meters aren’t perfect, but they’re much more accurate than they used to be.
There was a time when meters’ results varied wildly depending on the user’s testing technique, says David Marrero, PhD, the American Diabetes Association’s president-elect for health care and education and J.O. Ritchey professor of medicine and director of the Diabetes Translational Research Center at Indiana University School of Medicine. If you didn’t follow instructions exactly, the values you saw could be significantly wrong. Meters with calibration codes were an answer to this problem. Most meters no longer require coding, but user technique still plays a role.
Many people want their meters to have laboratory-level accuracy, which is understandable. But to do so, says Marrero, meters would have to have much more complicated technology, which could get exceptionally expensive. When it comes to health outcomes, experts agree that accuracy at every blood glucose level is less important than accuracy at levels for which a wrong number is most likely to cause a clinical error. Those are results that might encourage you to make a possibly harmful decision about not treating hypoglycemia (low blood glucose) or dosing too much insulin for what appears to be high blood glucose.
Current FDA Standards
The Food and Drug Administration (FDA) has accuracy requirements for all meters marketed in the United States. The FDA’s requirements allow for a range of readings.
For results at or above 75 mg/dl: 95 percent of meter test results must be within plus or minus 20 percent of the actual blood glucose level. Example: An actual blood glucose result of 180 mg/dl could potentially show on a meter as any value from 144 mg/dl to 216 mg/dl and meet the standard.
For results below 75 mg/dl: 95 percent of test results must be within plus or minus 15 points of the actual blood glucose level. Example: An actual blood glucose result of 70 mg/dl could potentially show on a meter as any value from 55 mg/dl to 85 mg/dl and meet the standard.
Those might seem like wide ranges, but Robert Ratner, MD, FACP, FACE, the American Diabetes Association’s chief scientific and medical officer, says those ranges are generally safe and reasonable. “[This level of] accuracy is sufficient for reliable clinical decision making and therapy,” Ratner says. Simply put, if a meter meets the FDA’s current standards, it is likely to give a reading close enough to the actual blood glucose level that users would treat any number in the range in a similar way. The range is accurate enough for you to decide if and how you will treat yourself.
Take, for instance, the first example listed above. Whether your blood glucose level is 144, 180, or 216, you are likely to decide that is a little high. For the majority of people with diabetes—who do not use insulin—the only immediate way to lower that high is exercise. Otherwise, it’s just one number—but a pattern of highs at the same time of day may indicate the need to make changes in medication, food, and/or exercise.
For people who use rapid-acting insulin, some might consider a correction dose. It’s smart to be cautious in response to a meter reading. “If I can’t explain [a high] away through behavior … I’m going to make a modest correction. I’m not going to take myself from 280 to 100,” says Marrero, who has type 1 diabetes.
To protect meter users, manufacturers are required to report adverse events during meter use, which may include injuries, quality problems, and problems after switching from one device to another. The FDA tracks the reports and decides whether to investigate adverse events. Routinely, the FDA receives 25,000 to 30,000 reports annually about blood glucose meters, says Courtney Lias, director of the FDA’s Division of Chemistry and Toxicology Devices. These include malfunctions not likely to result in injuries all the way to serious injury and death (which is rare).
Post-market surveillance (that is, checking the accuracy of meters once they reach consumers) currently is done on a voluntary basis and, frankly, some companies invest more in quality checks than do others. Some manufacturers have voluntarily recalled products that did not meet accuracy standards. Others were compelled to do so by the FDA.
The FDA models its accuracy guidelines on the ones set by the International Organization for Standardization (ISO), the group that defines standards for products around the world.
New ISO Standards
In 2013, the ISO announced it plans to implement new blood glucose meter standards at an undetermined time in the future. For high blood glucose levels, the ISO proposes a narrower range. For both high and low levels, more readings (out of 100) must fall into the acceptable range. Specifically:
For results at or above 75 mg/dl: 99 percent of meter test results must be within plus or minus 15 percent of the actual blood glucose level. Example: An actual blood glucose result of 180 mg/dl could potentially show on a meter as any value from 153 mg/dl to 207 mg/dl and meet the standard.
For results below 75 mg/dl: 99 percent of test results must be within plus or minus 15 points of the actual blood glucose level. This is the same range as the current FDA standard, but more results (99 percent versus 95 percent) must land within the range.
On the ISO’s website, Alan Cariski, MD, who is project leader for ISO 15197 (its blood glucose meter accuracy project), says, “More accurate glucose measurements will help patients to better regulate their diabetes through more informed treatment decisions that may affect, for example, dietary intake and medication dose, especially insulin.”
So far, the FDA has not indicated that it would update its accuracy requirements along with the ISO. At a September 2013 meeting of the Diabetes Technology Society (DTS), a nonprofit organization committed to promoting science and technology to fight diabetes, researchers found that a few of the meters on the U.S. market today would not meet the new ISO standard. Guido Freckmann, MD, a researcher at the University of Ulm in Germany, noted at the meeting that in his research, “unbranded” meters and strips and store brands were more likely to fail the new ISO standards.
Now, don’t rush to throw your store-brand meter out the window. But do know that technology—and the standards it is held to—continues to evolve.
The Future of Accuracy
At the same DTS meeting, a few independent researchers suggested that the society, with the cooperation of the FDA, manufacturers, and independent labs, do more after-market testing. All meters on the U.S. market met the standards when the FDA originally cleared the devices and strips for sale, but there is no consistent program to monitor their performance once the products are in the marketplace.
Accuracy can change if quality assurance isn’t rigorously maintained by the manufacturer. Distributors and retailers have to protect strips and meters in transit and on store shelves, too. And users can affect accuracy when they, for example, put dirty or damp fingers into a vial of strips or store strips in a hot car. Some researchers and advocacy groups such as Strip Safely have raised questions about the FDA’s inspection of overseas manufacturing plants and the agency’s enforcement of standards and punishments for companies that fail to maintain standards.
The purpose of the proposed DTS Blood Glucose Monitor Surveillance Program, says David Klonoff, MD, a clinical professor of endocrinology at the Diabetes Center of the University of California–San Francisco who presented the proposal, is to provide an independent assessment of whether FDA-cleared meters continue to perform to standards. The data could help the FDA to decide if meters should be taken off the market.
The proposal would make the DTS a watchdog for consumers. However, the meeting reached no consensus on if or when the surveillance program would begin. It’s unclear what’s next for the proposal. At the meeting, the FDA’s Lias seemed a little skeptical of the proposal but noted that after-market testing is extremely important. “It doesn’t matter how good you were when you manufactured those lots to get approval,” she said. “What matters is the lots you put out two years down the line, three years down the line, four years down the line.”
Maximize Your Meter
Some factors that contribute to accuracy are in your control. Consider these tips:
Wash your hands. If you’ve been handling food or drinks or using some lotions, you can affect the meter reading. Wash your hands with soap and dry them completely before every finger prick, if possible.
Test, then test again. If your reading comes up contrary to what you expected, and you can’t explain the reading based on your experience (food intake, exercise, stress, illness, etc.), test near the same site again. Make sure to saturate the test strip completely—too little blood can throw off the reading. If the two numbers vary greatly, Marrero suggests testing a third time. And know this: Marrero says one of your hands will always test at a higher number than the other. It won’t be by a lot, but it will always be true.
Take care of your strips. Mishandled test strips lead to errors. A 2005 study at East Carolina University found that once a vial of test strips was opened, it kept the longest in a refrigerated setting (35 to 50 days) and went bad most quickly in direct light and humidity (three to 14 days). So don’t risk it; those suckers are expensive! Keep your test strips out of direct sunlight, away from moisture, and at room temperature or cooler (but not freezing). A pocket, wallet, or car is no place for a test strip to live.
Use control solution. Control solution is a liquid with a known amount of glucose. When you run a check with a drop of control solution instead of blood, you can make sure the meter and vial of strips are performing together as they should. Squeeze a drop of solution on your clean hand and touch the strip to it. Most meters come with control solution; ask your pharmacist to order more as necessary.