Vol. 14 •Issue 4
• Page 55
Read That Meter!
Getting the Most Out of Blood Glucose Monitoring
By Jane Jeffrie Seley, NP, CDE, and Andrea Zaldivar, NP, CDE
It is well known that tight glucose control can markedly reduce the microvascular complications of diabetes. Home blood glucose monitoring (BGM) has become a cornerstone of glucose control and the overall management of diabetes.
The American Diabetes Association (ADA) recommends a general A1C goal of less than 7%. This level correlates with a mean plasma glucose of 170 mg/dL. BGM allows patients to determine blood glucose levels and make treatment adjustments to facilitate achievement of the recommended mean plasma glucose.
Barriers to Monitoring
Research shows that the majority of patients with diabetes do not monitor their blood glucose on a regular basis. Common barriers include cost of supplies, poor understanding of benefits, lack of training or skill, sampling discomfort and lack of time to perform the test.1
BGM is now quicker and simpler and requires a much smaller blood sample than in years past. So in addition to educating patients about the ease and sophistication of today's monitors, we must motivate them to regularly monitor their blood glucose levels by stressing the benefits of BGM and how this simple testing can positively and powerfully affect their personal diabetes treatment plan. To help patients understand that they can achieve accurate and useful results without difficulty, we recommend demonstrating BGM and practicing the procedure with patients during office visits.
Glycemic Targets
The ADA recommends that, in general adults with diabetes should achieve preprandial glucose levels between 90 mg/dL and 130 mg/dL, peak postprandial rises that do not exceed 180 mg/dL, and A1C of less than 7%.1 The ADA now recommends that individual patients achieve an A1C of close to normal (<6%), as long as they do not experience significant hypoglycemia.2
The American Association of Clinical Endocrinologists (AACE) recommends a preprandial level of less than 110 mg/dL, a 2-hour postprandial blood glucose of less than 140 mg/dL, and an A1C of less than 6.5%.3 We recommend focusing on the ADA's general target first. Once achieved, the patient can continue to work toward the goals set by the ADA and AACE.
Choosing a Meter
A variety of features should be considered when choosing a meter. Generally, the fewer steps required to perform BGM, the lower the rate of user error. Meters that require cleaning impose an unnecessary source of error and should be avoided.
Meter size is important if the patient checks blood sugar outside the home. If frequent testing is needed, portability is also important. The patient may not want to carry equipment that does not readily fit in a purse or briefcase.
Blood sample size is an issue as well, since smaller samples are associated with the least discomfort. A meter that requires a small sample (as little as 0.3 microliters) is particularly appropriate for frequent testers.
The time from sampling to result can range from 5 to 50 seconds. A young, active patient might insist on a quick result, whereas a homebound elderly patient would not consider a fast reading as important as an easy-open lid on the test strip vial.
Test strips are packed in vials or foil wrappers, depending on the meter. Some patients like foil-wrapped strips because they are individually wrapped and easier to carry. Other patients have difficulty opening the foil wrapper and handling the strip. Try the equipment with the patient to determine whether he or she is able to correctly perform the necessary steps.
Another meter feature worth considering is memory and download capability. At the very least, patients should choose a meter that tags each result with the date and time and stores at least 150 tests. This is helpful when patients neglect to record values in a log book.
Depending on the meter, charts and graphs may be available on the meter display screen or by download to a computer. This method of reviewing data can be valuable for identifying patterns of hypo- and hyperglycemia.
Other features to consider for some patients are altitude, temperature and hematocrit ranges.4
A comparison chart of available blood glucose meters was published in Diabetes Health magazine and is posted at http://www.diabeteshealth.com/media/pdfs/MeterReferenceGuide-July-2005.pdf.5
Frequency of Testing
BGM requires significant time, money and effort. Determine testing frequency recommendations by asking the patient the total number of times per day he or she is willing to do it. Once you establish the patient's willingness, you can decide which times would provide the most valuable information.
Preprandial testing is important if a patient is taking a variable dose of insulin or a rapid-acting insulin secretogogue based on blood glucose level. Postprandial testing is important at least some of the time to learn whether the medication and the amount of carbohydrate in the meal are balanced. If the A1C level is high and the daily blood glucose tests are not, the patient is not testing at the right times.
Patients often continue to test at the same time day after day, even when their result is in the target range and no immediate medication changes are made based on the result. This pattern of monitoring is unnecessary. It is better to check at different times, such as before and 2 hours after a single meal, and to vary which meal the testing surrounds.6 You can't effectively evaluate a high postprandial glucose if you don't know what the preprandial glucose was.
Common Errors
Although it is a critical component of diabetes management, BGM remains a time consuming and somewhat painful task. Once a patient has made the commitment to perform BGM, all efforts should be made to assure that the results he or she obtains are accurate.
Even patients with good intentions frequently commit errors while performing BGM. Errors often lead to inaccurate results and may affect treatment decisions and overall diabetes control.7
Some of the more common sources of errors are putting insufficient blood on the test strip, not calibrating or coding the meter correctly, and using strips that are expired or ruined.5 In addition, meters with low battery strength may give erroneous results.
BGM errors can be reduced. To increase the likelihood of producing a sufficient blood sample, advise patients to wash their hands in warm water to stimulate blood flow or to hang their hands in a dependent position before performing BGM.6 Patients using a monitor for the first time should carefully review the calibration and coding directions provided with the meter. All patients should check strip expiration dates and protect strips from overexposure to heat or moisture.8
Patients who perform BGM should be confident that the results they obtain are correct. When uncertainty arises, patients should know how to check the meter or call the manufacturer's customer service department. The number is printed or affixed to each meter, and most help desks are staffed 24 hours a day.
What the Numbers Tell Us
The appropriate frequency of BGM is usually dictated by the prescribed treatment, overall diabetes control status, patient preference and hypoglycemia risk.7,9
A patient may check his or her blood glucose anywhere from once a day to more than four times a day.6 Each blood glucose result provides valuable information for patient and provider.
Review blood glucose records to identify any patterns. This allows treatment decisions to be made based on trends rather than single values. When assessing for blood glucose patterns, note whether blood glucose levels are consistently outside the target range at a particular time of day. This may indicate a need to adjust medications or evaluate carbohydrate intake at a specific meal.6
Are all blood glucose results higher than they should be? This usually suggests a need for drastic change in treatment. Patients who were managed adequately in the past with lifestyle modifications alone may now require pharmacologic therapy.
Consistently elevated glucose levels may indicate a need to switch from an oral medication to insulin therapy. Patients already on insulin may need a change in basal insulin dose.6
Lastly, when a sudden conversion to overall elevated blood glucose levels is documented, consider the possibility of underlying illness or infection.8
The evaluation of blood glucose results for patterns or trends is not the sole responsibility of health care providers. Encourage patients to write their blood glucose results in a log book or to use a computer software program to track results.7 Software programs are provided by many meter manufacturers. Urge patients to play detective and document why they believe numbers are outside the target range. Was there a change in medication, food intake or activity level?7 Blood glucose monitoring can also assist patients in immediately confirming and appropriately treating hypoglycemia symptoms.8
Putting It Into Practice
Blood glucose monitoring is an important tool for evaluating the efficacy of a diabetes treatment regimen. With that in mind, test times should coincide with types of treatment, treatment changes, how well controlled the blood glucose is, and the frequency of hypoglycemia. Special circumstances such as hypoglycemic unawareness, illness, intermittent use of steroids and pregnancy require adjustment in testing times.9 To continue to motivate patients to monitor blood glucose, review, evaluate and adjust frequency, testing times and test results on an ongoing basis.
References
1. Goldstein DE, et al. Tests of glycemia in diabetes. Diabetes Care. 2004;27(7):1761-1773.
2. American Diabetes Association. Clinical practice recommendations 2006. Summary of revisions for the 2006 clinical practice recommendations. Diabetes Care. 2006;29(suppl 1):53.
3. American Association of Clinical Endocrinologists and the American College of Endocrinology. Medical guidelines for the management of diabetes mellitus: the AACE system of intensive diabetes self-management — 2002 update. Endocrine Practice. 2002;8(Suppl 1):40-82.
4. Ervin KR, Kiser EJ. Issues and implications in the selection of blood glucose monitoring technologies. Diabetes Technology & Therapeutics. 1999;1(1):3-11.
5. Your complete blood glucose meter reference guide from Diabetes Health. Diabetes Health. 2005;July:40-43.
6. Childs BP, Cypress M, Spollett G, eds. Complete Nurse's Guide to Diabetes Care. Alexandria, Va.: American Diabetes Association; 2005: 59-73.
7. Beaser RS, ed. Joslin's Diabetes Desk Book. Boston, Mass.: Joslin Diabetes Center; 2003: 46-54.
8. Franz MJ, ed. A CORE Curriculum for Diabetes Education: Diabetes Management Therapies. 5th ed. Chicago, Ill.: American Association of Diabetes Educators; 2003: 154-264.
9. Bergenstal RM, Gavin JR, on behalf of the Global Consensus Conference on Glucose Monitoring Panel. The role of self-monitoring of blood glucose in the care of people with diabetes: report of a global consensus conference. American Journal of Medicine. 2005;118(9A):1S-6S.
Jane Jeffrie Seley is a gerontological nurse practitioner and certified diabetes educator who specializes in diabetes at New York Weill Cornell Medical Center in New York City.
Andrea Zaldivar is an adult nurse practitioner and certified diabetes educator who is clinical director of the North General Diagnostic and Treatment Center in New York City.
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