Blood glucose monitoring
From Wikipedia, the free encyclopedia
Blood glucose monitoring is a way of testing how much glucose is in the blood (glycemia).
This is important in the care of diabetes mellitus. Most persons with Type 2 diabetes need to test at least once per day (usually before breakfast) to assess the effectiveness of their diet and exercise for controlling their blood glucose levels. Many persons with Type 2 are using an oral medication to combat their insulin resistance, and must test their blood glucose before and after breakfast to assess the effectiveness of their dosage. All persons who need to inject insulin, both for Type 1 diabetes and Type 2, need also to test their blood sugar more often (3 to 10 times per day) to assess the effectiveness of their prior insulin dose and to calculate their next insulin dose.
Improved technology for measuring blood glucose is rapidly changing the standards of care for all diabetic persons. There are several methods of blood glucose testing currently available.
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[edit] Chemical Test Strips
Chemical test strips are a low cost method for monitoring blood glucose. A fairly large drop of blood, usually taken from the fingertip, is placed on a chemically prepared strip, called a blood glucose testing strip. The strip chemistry will cause it to change color according to the amount of glucose is in the blood. One can tell if their level of blood glucose is low, high, or normal by comparing the color on the end of the strip to a color chart that is printed on the side of the test strip container.
These are suitable for persons who are occasionally monitoring their blood glucose level (prediabetic or type 2) and are not using insulin.
The Betachek Diabetes Test Strips
Pamphlet for Use of Chemical Test Strips
[edit] Blood Glucose Meters
A blood glucose meter is an electronic device for measuring the blood glucose level. A relatively small drop of blood is placed on a disposable test strip which interfaces with a digital meter. Within several seconds, the level of blood glucose will be shown on the digital display.
While more expensive, blood glucose meters seem a breakthrough in diabetes self care. As the drops of blood needed for the meter become smaller, the pain associated with testing is reduced and the compliance of diabetic persons to their testing regimens is improved. However, the cost of test strips is more painful than the finger poke if the user does not have good medical insurance. Although the cost of using blood glucose meters seems high, it is believed to be a cost benefit relative to the avoided medical costs of the complications of diabetes.
A recent and welcome advance is the use of small blood drops for blood glucose testing from other places than the finger tips. This alternate site testing uses the same test strips and meter, is practically pain free, and gives the real estate on the finger tips a needed break if they become sore.
[edit] Glucose Meter Companies and Products
- FreeStyle Flash, FreeStyle, Precision Xtra
- Contour, Breeze, DEX2, Elite, Elite XL
- OneTouch UltraSmart, OneTouch Ultra2, OneTouch Ultra, OneTouch UltraMini, InDuo, FastTake, Profile (no longer sold in the US), Basic, SureStep
- Accu-Chek Aviva, Accu-Chek Active, Accu-Chek Compact Plus, Accu-Chek Compact, Accu-Chek Complete
[edit] Continuous Blood Glucose Monitoring
A continuous blood glucose monitor measures blood glucose levels on a continuous basis (every few minutes). A typical system consists of:
- a disposable glucose sensor placed just under the skin, which is worn for a few days until replacement,
- a link from the sensor to a non-implanted transmitter which communicates to a meter,
- an electronic meter worn like a pager (or insulin pump) that displays blood glucose levels on a practically continuous manner, as well as monitors rising and falling trends in glycemic excursions.
Continuous blood glucose monitors do not directly measure glucose levels in the blood, but measure the glucose level of interstitial fluid. This results in two disadvantages as compared to traditional blood glucose monitoring. First, using current technology, continuous systems must be calibrated with a traditional blood glucose measurement; therefore, continuous systems do not yet fully replace "fingerstick" measurements. Second, glucose levels in interstitial fluid are temporally behind blood glucose values. For both of these reasons, patients are typically advised to take traditional fingerstick measurements at least twice a day (for calibration) and whenever symptoms of a high or low blood glucose level (hyperglycemia and hypoglycemia, respectively) are felt.
An additional financial disadvantage of continuous blood glucose monitoring is that systems are not typically covered by health insurance in the United States. This is exacerbated by the fact that disposable sensors must be frequently replaced (sensors by Dexcom and Minimed have been FDA approved for 3-day use, though many patients wear sensors for much longer) and the meters likewise have finite lifetimes (less than 2 years and as little as 6 months).
In spite of these limitations, continuous glucose monitoring offers many advantages, particularly for individuals with type 1 diabetes mellitus. Continuous monitoring allows the patient and his or her medical provider(s) to see how a patient's blood glucose level reacts to insulin, exercise, food, and other factors. The additional data can be useful for setting correct insulin dosing ratios for food intake and correction of hyperglycemia. Monitoring during periods when blood glucose levels are not typically checked (e.g. overnight) can help to identify problems in insulin dosing (such as basal levels for insulin pump users or long-acting insulin levels for patients taking injections). Monitors may also be equipped with alarms to alert patients of hyperglycemia or hypoglycemia so that a patient can take corrective action(s) even in cases where they do not feel symptoms of either condition.
Some current and future continuous glucose monitoring products include:
- The Freestyle Navigator (not yet FDA approved)
- Minimed Paradigm (insulin pump plus continuous sensor)
- The Guardian
- Dexcom STS
- GlucoDay S
- The Animas GlucoWatch
See this summary by a diabetes support group for a review of CBGM products, performance, and features.
Technology being demonstrated for continuous glucose monitoring is promising in the development of a closed-loop system connecting real-time automatic control of an insulin pump based on immediate blood glucose data from the sensor. One important goal is to develop an algorithm for automatic control, by which the system would function as an artificial pancreas.
[edit] Glucose sensing bio-implants
Longer term solutions to continuous monitoring, not yet available but under development, use a long-lasting bio-implant. These systems promise to ease the burden of blood glucose monitoring for their users, but at the trade off of a minor surgical implantation of the sensor that lasts from one year to more than five years depending on the product selected.
Products under development include:
- The SMSI Glucose Sensor
- The Animas Glucose Sensor
- Implanted Glucose Bio-sensor
- The Dexcom LTS (long term system)
[edit] Non-Invasive Technologies
Some new technologies to monitor blood glucose levels will not require access to blood to read the glucose level. Non-invasive technologies include near IR detection, ultrasound and dielectric spectroscopy. These will free the person with diabetes from finger sticks to supply the drop of blood for blood glucose analysis.
Most of the non-invasive methods under development are continuous glucose monitoring methods and offer the advantage of providing additional information to the subject between the conventional finger stick, blood glucose measurements and over time periods where no finger stick measurements are available (i.e. while the subject is sleeping).
Products under development include:
- Fovioptics retinal glucose analyzer
- Inlight Solutions, NIR glucose sensor
- NIR Diagnostics, NIR glucose sensor
- Sinsys Medical GTS
- Sontra ultrasonic Symphony Diabetes management system
- Solianis Monitoring AG
