chapter 2 of management of Type 2 diabetes

[Guest guest]

Diagnosis_and_Management_of_Type_2_DiabetesSteve V. Edelman, MD

R. Henry, MD

Self-Monitoring of Blood Glucose (SMBG) Systems

A combination of factors affect the overall performance of SMBG systems...

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• The analytic performance of the meter

• The ability of the user

• The quality of the test strips

• The downloading capacity of home and office computers.

Analytic error can range from 4% to 33%; a goal of future SMBG systems is an

analytic error of ± 5%. User performance is most affected by the quality and

extent of training, which currently is hindered by reimbursement policies

for diabetes education. Initial and regular assessments of a patient's SMBG

technique are necessary to assure accurate results. Patients need to be

advised that test strips can be adversely affected by environmental factors.

In addition, cautious use of generic test strips is warranted because of the

complex process of calibrating test strips to specific meters.

Examples and features of available blood glucose meters are shown in Table

13.2. The ADA Consensus Panel advises periodic comparisons between a

patient's SMBG system and a sample obtained simultaneously and measured by a

referenced laboratory. Remember that whole blood glucose values are

generally 15% lower than plasma values.

Who Should Perform SMBG?

Virtually all patients with diabetes should perform SMBG because of the

value of this evaluation tool in promoting improved glycemic control and

reinforcing adherence to therapy. The frequency of SMBG is dictated by the

complexity of the therapeutic regimen. For example, insulin-using type 2

diabetics (particularly those on an intensive regimen) would need to perform

more daily SMBG evaluations than patients who are achieving acceptable

glycemic control with diet, exercise, and oral agents.

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Recommended Frequency of SMBG

The frequency of SMBG varies considerably based on the complexity of the

therapeutic regimen and the clinical situation of the individual. In

addition to guiding therapy, SMBG also has educational and motivational

advantages. For example, intermittent measurements 1 to 2 hours after meals

can provide an assessment of glycemic response to various types of foods,

thus helping patients learn which foods have the greatest and least impact

on blood glucose, as well as how the size of a meal affects glucose levels.

SMBG also can help motivate patients (especially obese patients trying to

lose weight), because they can observe immediate decreases in their blood

glucose levels in response to dietary modifications, exercise, and oral

therapy.

Patients who demonstrate consistent, acceptable glucose results may require

fewer tests (i.e., one to three tests per week). However, testing

requirements may increase when metabolic control worsens.

SMBG for Patients Who Do Not Take Insulin

Traditionally, SMBG was viewed as not necessary for type 2 patients on diet

therapy or oral agents because glucose levels remained relatively stable on

these treatment regimens. For these patients, SMBG was recommended only for

monitoring short-term adjustments in therapy or for patients at risk for

hypoglycemia. Because better glycemic control has been shown to be

associated with a greater frequency of SMBG, this evaluation measure now is

recommended for all patients, including those not taking insulin. The

frequency of testing depends on how stable the patient is. Patients with

less than optimal control should monitor their levels more frequently.

SMBG recommendations for patients on diet therapy:

• Prebreakfast -- two to three tests per week

• 1 to 2 hours postdinner -- two to three tests per week.

Monitoring glucose values from these two important time points, in addition

to an A1C or fructosamine value every 3 to 6 months, is an efficient way to

follow patients on diet and oral agents.

SMBG recommendations for patients using oral agents alone or combination

therapy (daytime oral agents, evening insulin):

• Prebreakfast -- four to seven tests per week

• Prelunch -- two to three tests per week

• 2 hours postdinner -- two to three tests per week.

Patients in this category generally require one to three tests per day when

SMBG values are consistent. Patients can make nonpharmacologic changes in

their diabetic regimen depending on the results (Table 13.3).

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TABLE 13.3 — Techniques Used to Adjust for Premeal Hyperglycemia

Nonpharmacologic

• Increase the time interval between insulin injection and consumption of

the meal.

• Consume less than the usual amount of calories.

• Eliminate or replace foods containing refined carbohydrates or that have a

high glycemic index, such as fruit exchanges.

• Spread the calories over an extended period of time.

• Exercise lightly after a meal.

Pharmacologic

• Increase the amount of fast-acting insulin via an algorithm.

• Make the appropriate long-term adjustment in preceding insulin dose to

prevent hyperglycemia at a particular time if a consistent trend is

identified.

Edelman SV, Henry RR. Diabetes Reviews. 1994;3:310.

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SMBG for Patients Who Take Insulin

SMBG is critical for all patients who take exogenous insulin, particularly

those on intensive insulin regimens or on combination therapy. The type of

insulin regimen used should dictate the frequency of SMBG, with attention to

insulin pharmacokinetics and the timing of insulin injections. The best time

to evaluate the effectiveness of a dose is at the peak time of action of a

particular type of insulin.

Frequent SMBG is necessary to fine-tune an insulin regimen to the needs and

responses of a given patient. Ideally, SMBG should be performed four to six

times per day (before each meal, at bedtime, and occasionally after meals

and at 3 AM, which is the approximate time of early morning glucose nadir).

A more intensive SMBG schedule would be a preprandial and 2-hour

postprandial measurement and at bedtime, depending on the frequency of

insulin doses.

SMBG recommendations for patients on insulin therapy include:

• One injection per day -- two tests per day; no less than one to three

depending on metabolic control.

• Two injections per day -- four tests per day (before each meal and at

bedtime)

• Intensive regimen (multiple injections, external pump) -- four to seven

tests per day.

Results should be recorded in a logbook that is brought to each office visit

so the physician can evaluate the effectiveness of the insulin regimen and

determine the most appropriate insulin dosage adjustments. Selected patients

should be instructed to apply their SMBG results as the data become

available. Making immediate dosage adjustments based on SMBG feedback is

evidence of the true benefit of this self-assessment tool.

Additionally, most meter logs can be downloaded directly to a personal

computer.

When SMBG reveals premeal hyperglycemia, a number of different methods can

be used in addition to adjusting the dose of insulin to reduce daily

glycemic excursions (Table 13.3).