Diabetes: Choosing and Using Your Glucose Meter (cont.)

Feelings about Fingersticks. Surprisingly, most of the participants stated that fingerstick discomfort was not a big concern - even with children: "At first, fingersticks were a real problem, but now it doesn't bother her."

Most participants stated that discomfort was an issue when they first started to use the meter; this was especially true for children, but that the discomfort grew less important after a few weeks or months of use.

However, one participant of a "fragile" child with diabetes stated: "We test 8 to 10 times a day. He was losing sensitivity in his fingertips [from the frequent fingersticks]. We prefer the meter that allows testing in alternative sites."

Use of Test Solution. Most users did not use test solution often. Some never used it. They stated that the solution was difficult to use because it expired in a month, it was difficult to order, and they were not convinced that it helped.

Important Features. Users discussed and rated aspects of meters such as accuracy, ease-of-use, cost of the meter, cost of test strips, size, whether it was recommended by a friend etc. The most important consideration in this group was accuracy. This was followed by "ease of use" and then affordability.

New Technologies: Alternative Site Testing

Some glucose meters allow testing blood from alternative sites, such as the upper arm, forearm, base of the thumb, and thigh.

Sampling blood from alternative sites may be desirable, but it may have some limitations. Blood in the fingertips show changes in glucose levels more quickly than blood in other parts of the body. This means that alternative site test results may be different from fingertip test results not because of the meter's ability to test accurately, but because the actual glucose concentration can be different. FDA believes that further research is needed to better understand these differences in test values and their possible impact on the health of people with diabetes.

Glucose concentrations change rapidly after a meal, insulin or exercise. Glucose levels at the alternative site appear to change more slowly than in the fingertips. Because of this concern, FDA has now requested that manufacturers either show their device is not affected by differences between alternative site and fingertip blood samples during times of rapidly changing glucose, or alert users about possible different values at these times.

Recommended labeling precautions include these statements:

  • Alternative site results may be different than the fingertip when glucose levels are changing rapidly (e.g. after a meal, taking insulin or during or after exercise).
  • Do not test at an alternative site, but use samples taken from the fingertip, if
    • you think your blood sugar is low,
    • you are not aware of symptoms when you become hypoglycemic, or
    • the site results do not agree with the way you feel.

In October, 2001, FDA held a public meeting to discuss the types of information and labeling needed for glucose measuring devices if the blood sample is taken from alternative sites rather than the fingertip. Presenters included manufacturers of blood glucose meters, healthcare providers, people with diabetes, and parents of children with diabetes.

Minimally Invasive and Non-Invasive Glucose Meters

Researchers are exploring new technologies for glucose testing that avoid fingersticks. One of these is based on near-infrared spectroscopy for measurement of glucose. Essentially, this amounts to measuring glucose by shining a beam of light on the skin. It is painless. There are increasing numbers of reports in the scientific literature on the challenges, strengths, and weaknesses of this and other new approaches to testing glucose without fingersticks.

FDA has approved one "minimally invasive" meter and one "non-invasive" glucose meter. Neither of these should replace standard glucose testing. They are used to obtain additional glucose values between fingerstick tests. Both devices require daily calibration using standard fingerstick glucose measurements and both remain the subject of continuing studies to find how they are best used as tools for diabetes management.

  • MiniMed Continuous Glucose Monitoring System. The MiniMed system consists of a small plastic catheter (very small tube) inserted just under the skin. The catheter collects small amounts of liquid that is passed through a "biosensor" to measure the amount of glucose present.

Minimed is intended for occasional use and to discover trends in glucose levels during the day. It does not give you readings for individual tests and therefore you can't use it for typical day-to-day monitoring. The device collects measurements over a 72-hour period and then must be downloaded by the patient or healthcare provider. Understanding trends over time might help patients know the best time to do their standard fingerstick tests. You need a prescription to buy MiniMed.

  • Cygnus GlucoWatch Biographer. GlucoWatch is worn on the arm like a wristwatch. It pulls tiny amounts of fluid from the skin and measures the glucose in the fluid without puncturing the skin. The device requires 3 hours to warm up after it is put on. After this, it can provide up to 3 glucose measurements per hour for 12 hours. Unlike the MiniMed device, the GlucoWatch displays results that can be read by the wearer, although like the MiniMed device, these readings are not meant to be used as replacements for fingerstick-based tests. The results are meant to show trends and patterns in glucose levels rather than report any one result alone. It is useful for detecting and evaluating episodes of hyperglycemia and hypoglycemia. However, you must confirm its results with a standard glucose meter before you take corrective action. You need a prescription to buy GlucoWatch.

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