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The Significance of Self-Monitoring of Blood Glucose
It is imperative that people with both type 1 and type 2 diabetes melli-tus (DM) have good glycemic control, which can be attained with appropriate drug and nondrug treatment and self-monitoring of blood glucose (SMBG). The benefit of such glycemic control has been proven in rigorous trials, including the Diabetes Control and Complications Trial (DCCT)(1)in patients with type 1 and the United Kingdom Prospective Diabetes Study (UKPDS)(2)in patients with type 2 diabetes. Tight glycemic control reduces microvascular complications?such as neuropathy, retinopathy, and nephro-pathy?by as much as 25%.(1,2)Therefore, the American Diabetes Association recommends SMBG as a vital component in the management of patients with both type 1 and type 2 DM.(3)Because people with DM encounter pharmacists more than any other health care provider for prescription refills, these professionals are in an optimal position to educate patients about the benefits of SMBG. Pharmacists can also help patients select the most appropriate blood glucose meter and provide instruction on proper testing techniques. In order for pharmacists to provide this valuable service to people with DM, it is important for them to know how to choose the best meter, based on the available meter technologies and features.
Blood Glucose Meter Technologies
The 2 basic technologies employed in home blood glucose meters are reflectance photometry and biosensor (electrochemical) technology.(3-6)Color reflectance photometry is first-generation blood glucose meter technology. Biosensor technology is newer, second-generation technology.(4,7)Although the type of technology is one factor that contributes to the overall performance of blood glucose meters, other factors to be considered are the performance of both the operator and the test strips.(6)In color reflectance photometry, an enzyme catalyzes oxidation of the blood glucose within the test strip. Oxidized glucose reacts with chroma-gen, which is an iron, to produce a color change. This color change is proportional to the amount of glucose in the blood, and a numerical value is generated. Adequate lighting and appropriate environmental factors (eg, temperature, humidity, altitude) are necessary for accurate results to be obtained.(4-6)Also, the optic area of reflectance photometry meters should be cleaned periodically with a cotton swab that has been moistened with water, so that the meter will produce accurate readings.(6)
In biosensor technology, the blood also undergoes oxidation, but this reaction is slightly different. An electrical charge is created, and this charge is directly proportional to the blood glucose content. The charge generated represents the concentration of glucose in the blood sample, and a numerical value is displayed.(4,5)Amperometry and coulometry are the 2 types of biosensor (electrochemical) blood glucose testing methods. Amperometric technology measures only a small percentage of the glucose and uses a multiplier to convert this to a numerical value. Therefore, blood glucose readings may be affected by environmental temperature, hemat-ocrit, medications, and other factors. Also, small samples may result in inaccurate readings because of a weak signal being generated.(5)
Coulometry is a relatively new technology in the realm of blood glucose monitoring. Coulometry converts all the glucose in a blood sample into an electrical current and is not affected by other medications or conditions the patient may have. Coulometry allows the patient to use the smallest sample size of any available technology.(8)
Factors Affecting Blood Glucose Readings
There are several factors to consider when evaluating the results of a blood glucose measurement. Ensuring that the person using the meter is doing so correctly can minimize most of these factors. The simplest way is to observe the patient as he or she performs a blood glucose test and to provide constructive feedback as needed.
1. Preparing the meter: It is important for the patient to know how to calibrate and turn on the meter and prepare all the supplies needed for the test. Strips should be opened only when the patient is ready for the test. Otherwise, they should be stored in a closed vial or unopened foil wrapper at room temperature. The meter should be correctly coded to match the test strips being used. The code number is usually found on the test strip packaging.
2. Obtaining the blood sample: The patient should be instructed to wash his or her hands with soap and warm water. Discuss appropriate lancing device technique, including use of a new lancet for each test, and where to obtain the sample. Remember that squeezing the finger may cause hemolysis and/or skin-cell dilution, resulting in a diluted sample and falsely low glucose readings.
3. Applying blood to the test strip: The patient should be instructed on where to apply the blood sample (top or side of strip) and whether the test strip requires a hanging drop of blood or has capillary suction to collect the sample. It is also important to review how the patient can verify adequate sample application and whether reapplication is appropriate if inadequate blood volume is applied initially.
4. Interpreting and recording SMBG results: The patient should be educated on how to interpret different blood glucose readings. Be sure to include target glucose values (post-prandial vs fasting) in whole blood or plasma equivalents relative to the meter being used. Discuss signs and symptoms of hypoglycemia and hyperglycemia and the appropriate steps for treating each. The patient should be instructed to record glucose readings, date, time, last meal, and events, and to share these results with his or her health care provider(s).
5. Disposal: The patient should be instructed on sharps disposal.
What?s New in SMBG? A Look at Alternate-Site Testing
In the past several years, alternate-site testing has received attention, and many blood glucose meter manufacturers have obtained FDA approval for alternate-site testing (Table).(8-28)Also, some manufacturers have developed meters marketed specifically as alternate-site testing devices. These devices eliminate painful finger sticks by allowing the users instead to lance their arms or thighs to obtain blood samples.
The FreeStyle blood glucose monitoring system, manufactured by Therasense, has been available since June 2000. It uses coulometric technology to measure blood glucose and requires the smallest blood sample of any of the SMBG devices available on the market?only 0.3 microliters. The FreeStyle lancing device can be used to lance the upper arm, thigh, calf, or anywhere on the hand. In using the device, the patient rubs the test surface until it gets warm, then lances the area. The patient places the test strip against the blood sample, and the blood is drawn into the strip via capillary suction. The test result is displayed within 15 seconds.(8)
Abbott?s Sof-Tact meter is a combination meter that contains the test strip and lancing device within the meter?s casing. The user simply places the device on the upper arm, thigh, or palm and holds it in place while the meter obtains the blood sample, places it on the test strip, and displays the blood glucose reading within seconds. The display is backlit to make nighttime testing easy for the user.
Accu-Chek?s Active, Bayer?s DEX2 Glucometer, and LifeScan?s One Touch Ultra blood glucose meters offer multiple-site testing at the finger, arm, thigh, calf, and hand. The user lances the site and then places the strip on the blood supply. The sample is drawn into the strip by capillary suction, and test results appear on the meter display. Also available from LifeScan is the InDuo, a combination product that contains an Ultra meter and a Novo-Nordisk insulin delivery system. A ?noninvasive? laser-lancing device, the personal Lasette Plus by Cell Robotics, uses a beam of light, rather than the traditional steel lancet, to pierce skin. It features 16 different power settings and may be used with any glucose meter. It should be used, however, only for patients over 5 years old and may not be affordable for all patients.(10)
Choosing the Right Meter
With the numerous blood glucose meters on the market, selecting the appropriate meter for a particular patient can be overwhelming. Most meters are comparable in performance, but they do vary with regard to plasma versus whole blood calibration, testing site, meter size and shape, test time, sample size, memory capacity, software compatibility, complexity, and test strips. When selecting a meter, the following patient and meter characteristics should be considered.
The pharmacist should recommend a meter with a large digital display and easy sample collection (preferably large strips) for patients who have poor vision. The Accu-Chek Advantage meter, when combined with the Accu-Chek Voicemate and Comfort Curve test strips, is an appropriate selection for visually impaired patients. The Voicemate attaches to the meter and provides audible prompts to facilitate the testing process. The Comfort Curve test strips have a rounded groove that accommodates the shape of the finger to ensure more accuracy in blood sample placement. One Touch meters can be combined with Digi-Voice Deluxe, Touch-n-Talk, or Voice Touch Pro devices, which provide audible prompts to guide the user through the testing process.
Arthritis or Poor Manual Dexterity
For patients who have arthritis or problems with dexterity, manipulation of both the meter and the test strips can be an issue. Easy-to-use meters with a small sample size and test strips that do not require excessive manipulation should be recommended to make the testing process as easy as possible. The Accu-Chek Advantage, Assure, One Touch SureStep, Sof-Tact, and Supreme are good meters to be considered for these patients.
Children and/or Adults with Type 1 DM
Considerations for children with diabetes are appearance, portability, and small sample size. The Accu-Chek Advantage, DEX2 Glucometer, One Touch Ultra, and Precision QID are good choices. Children and adults with type 1 DM may benefit from monitors that record insulin doses, meals, snacks, and events. The Accu-Chek Complete and One Touch Profile are 2 examples of such devices. The Precision Xtra also is a good choice because it features ketone strips for early detection of ketosis. Additionally, the Accu-Chek Compact, One Touch InDuo, and Sof-Tact meters provide convenient all-in-one testing.
Concurrent Disease States or Medications
People with sickle-cell disease, end-stage renal disease, or other conditions that alter hemoglobin/hemat-ocrit (dehydration, anemia) should be advised to use a meter that is not affected by variations in hematocrit. The Precision QID and Precision Xtra employ 3-electrode technology to minimize interference from medications and/or hematocrit levels. The FreeStyle meter?s coulometric technology also reduces the potential for such interference. Those people who take warfarin or other anticoagulant medications should use a meter that requires a small sample so as to minimize the depth of puncture required to obtain a blood sample. Some of the meters that require the smallest sample sizes are the Glucometer meters, the Precision meters, and the One Touch Ultra.
For the active person with DM, portable meters include the Accu-Chek Advantage, CheckMate Plus, One Touch Ultra, Glucometer Elite, DEX2 Glucometer, Precision QID, and the combination meters.
Most glucose meters have compatible software for patients who are interested in downloading test results for the purpose of reviewing blood glucose trend or graph information. Software may be downloaded free of charge on most manufacturers? Web sites or may be purchased for use on personal computers and personal digital assistants. Downloaded data may be sent via e-mail to the patients? physician(s) and may be compiled into useful charts and/or diagrams.
When people with DM monitor their blood glucose regularly, they are taking responsibility and playing an active role in their own health and well-being. SMBG allows patients to identify episodes of hypo- and hyper-glycemia as well as their daily responses to food and medications. With guidance from health care professionals, patients can use this information to adjust their diet, exercise, or medication regimen in order to minimize adverse diabetes-related outcomes and complications.
It is the duty of pharmacists to ensure that every person with diabetes understands the great importance of SMBG. It also is important for each person with DM to have a meter that he or she is able to use properly. Pharmacists can work to expand their pharmaceutical care services by helping people with diabetes pick the right blood glucose meter and understand the importance of self-monitoring of blood glucose for all people with diabetes.
For a list of references, send a stamped, self-addressed envelope to: References Department, Attn. D. Campagnola, Pharmacy Times, 241 Forsgate Drive, Jamesburg, NJ 08831; or send an e-mail request to: firstname.lastname@example.org.