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How accurate are blood glucose meters?

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BY T'ARA SMITH (BEYOND TYPE 2)
Article originally published on Beyond Type 2

We know blood glucose meters are pretty necessary for managing Type 2 diabetes. How else can we track our blood sugar? Going to the doctor every three months or so certainly isn’t the way, though it’s how we get updates on our A1c. Blood glucose meters are used to monitor our progress on a daily basis, too and serve as our primary reference to being able to analyze our blood glucose data. With that said, it’s easy to assume your readings are accurate. But that also means blood glucose meter accuracy is critical.

Importance of Accurate Meters

Blood glucose meter accuracy is important for several reasons:

  • Improved reliability in your data and trust in your current diabetes management plan.
  • Helps you understand and/or anticipate potential lab results when going for your A1c checkup.
  • Lets you know what impacts your blood sugar:
    • Did that glass of wine last night have a significant impact?
    • Did you experience a spike or drop in blood sugar after that amazing Zumba class?
    • Is there a connection between your stress and blood sugar?
  • Accurate meters are able to detect episodes of hypo- or hyperglycemia.
  • Can help with decision-making surrounding medication dosages.

8 Factors that Affect Blood Glucose Meter Accuracy

Although you should follow the instructions provided with your meter, with this guide, you’ll learn what impacts the validity of it and tips to ensure you’re getting the most accurate result possible. An array of things can impact your readings, from the temperature to the testing location, as well as:

Meter Calibration, Quality, and Coding

In order to trust the data your meter is providing you, make sure you’re getting a quality meter. We discuss this more below, but manufacturers must meet certain standards to be considered accurate. If you’re unsure about the quality of the meter, check for the latest updates and versions by the maker.

When you first set up your meter, follow the directions included with it. The calibration process can vary per manufacturer and meter. Finally, your meter will need to match a calibration code with the number on the test strip vial. Some meters are the exception to this. For example, with an Accu-Chek meter, there’s no need to code it, so you have fewer steps in glucose testing.

Test Strip Quality and Compatibility

This is a major one. If you can, use the test strips of the same brand as your meter. Some third-party products are compatible with branded meters, but not always. Using an incompatible test strip can cause inaccurate or error readings; different manufacturers have their own processes for developing their test strips. Test strips also come with expiration dates – don’t use strips beyond the expiration date. Lastly, beware of using test strips that are unauthorized for sale or that were previously owned.

Standards and Quality Control

The Food and Drug Administration (FDA) sets standards for manufacturers who produce blood glucose meters in the United States and the International Organization for Standardization develops and publishes standards on a global scale. A position statement published in January 2019 compared the standards for blood glucose meter accuracy set by these two organizations. Let’s a take a look at the standards for the home-use of these devices:

  • FDA: Readings are 95 percent accurate within 15 percent for all readings within the “usable” blood glucose range and 99 percent accurate within 20 percent for all readings within that usable range. The term “usable” in this case means the range of blood glucose values where the meter has proven to be accurate.
  • ISO: Readings are 95 percent accurate within 15 percent of blood glucose equal to or above 100 mg/dl and are 95 percent accurate within 15 mg/dl for readings under 100 mg/dl.

Manufacturers, themselves, also have quality control protocols and standards. For example, Accu-Chek’s strict manufacturing processes ensure their products meet uncompromising standards of quality.

  • The company’s quality control process tests over 60,000 test strips for consistent accuracy.1
  • For every lot of their test strips, which contain millions of strips, at least 1 out of every 128 vials is tested for consistency of performance. Vials are then tested a second time with blood at various glucose levels to reflect a real-world environment.
  • Investigations and additional testing are conducted if a test strip sample displays a reading outside of specific ranges.

Another example is Accu-Chek’s advanced 10/10 accuracy rule, which was used for the Accu-Chek Guide system2. 95 percent of measured glucose results should fall within 10 mg/dl of a lab reference value for blood glucose concentrations below 100 mg/dl and 10 percent for blood glucose concentrations equal to or above 100 mg/dl. A 2017 summary of the Blood Glucose Surveillance Program by the Diabetes Technology Society revealed the Accu-Chek Aviva Plus and Accu-Chek SmartView platforms were two of the six devices, out of a total of 18 surveyed devices, that met accuracy standards.

Cleanliness of Your Hands and Testing site

Dirt, food, grease, or any other kind of residue at or around your testing site can skew your readings. Wash your hands prior to testing your blood sugar and clean the area around your finger before doing so. Make sure your testing site is dry as to not dilute the blood before taking your reading.

Testing Technique and Site

Make sure you’re following the directions of your meter. Traditionally, fingertips are the primary place to test your blood sugar. Alternative testing sites such as on the palm, upper arm, forearm, thigh, and calf are used, typically in clinical settings, instead of fingers due to the many nerve endings on fingers, including the pain from testing and the resulting calloused fingers. But, it isn’t advised to use an alternate site unless you have a device that’s designed for it. However, using an alternate site may not always produce accurate results, especially if your blood sugar is rising or falling fast. Research shows that glucose readings differ depending on if you get your blood sample from the capillaries in your fingers or another part of your body.

Another note about the technique – make sure you have enough blood in your test strip. Having too little blood will cause an error or false reading. You can adjust the settings on your lancet to make sure you’re drawing enough blood. Finally, make sure you’re fully inserting the test strip into your meter.

Temperature/Environment

Avoid having your testing supplies in extreme heat or cold conditions. If you’re the type to leave your supplies in your car, avoid doing so if they’ll be left in extreme temperatures. High altitude can also affect your meter’s readings. Be sure to store your meter according to the maker’s instructions.

Hematocrit

Your hematocrit represents the number of red blood cells in your blood. If you suffer from anemiaor dehydration, your results may not be as accurate as one who has a normal blood cell level count. Check with your provider on how to ensure you’ll get accurate readings.

Medication

Drugs like acetaminophen, dopamine, ascorbic acid (vitamin C), and mannitol can significantly affect the accuracy of some glucose meters. Acetaminophen and ascorbic acid can result in readings that show false lower readings. People with diabetes who are on dialysis, specifically peritoneal dialysis to treat kidney failure, are at risk for false higher readings due to a component that turns into maltose. As a result, the meter can confuse maltose for glucose.

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1Data on file. Based on average weekly strip production of approximately 80M and includes a combination of testing test strips for accuracy and precision standards.

2Data on file. [10/10 accuracy: 95% of measured glucose results shall fall within ±10 mg/dL of lab reference value for blood glucose concentrations <100 mg/dL and within 10% for blood glucose concentrations ≥100 mg/dL.]

Disclaimer: This content was published in partnership with Roche, the makers of Accu-Chek products, a Founding Partner of Beyond Type 2.

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