Steve V. Edelman, MD
Robert R. Henry, MD
Measuring Other Glycated Proteins
the shorter half-life of serum proteins (17 to 20 days) compared with hemoglobin (56 days), measurement of serum fructosamine reflects a shorter period of average glucose control (2 to 3 weeks) (Figure 13.1). Traditionally, fructosamine measurements are particularly useful for following patients with GDM.
New devices that are available or soon to be released will have the capabilities of measuring serum ketones, lipoproteins, microalbumin, and other important clinical measurements that traditionally could only be obtained by venipuncture or urine collection and measured in a laboratory.
This method of self-evaluation using capillary blood samples has become one of the more important tools for monitoring and improving glycemic control and making adjustments in the diabetes therapeutic regimen. SMBG is a relatively painless procedure that involves pricking the fingertip with a lancet to obtain a drop of blood that is placed on a test strip. Reagents on the test strip contain an enzyme that causes glucose to react with a dye to produce a color change. The color intensity is proportional to the amount of glucose present. The test strip is placed in a small, hand-held meter that quantifies the glucose concentration using reflectance spectrometry. Some test strips can be read visually; other systems measure the electrical current produced by the glucose oxidation reaction to quantify the glucose concentration. Results obtained by SMBG tend to have good agreement with plasma glucose concentrations obtained by clinical laboratory procedures if done properly. Patient technique tends to be the source of most discrepancies. Typically, plasma venous glucose measurements are within 15% of the results of whole blood capillary glucose determinations.
SMBG is not a goal in itself but rather a means of achieving the goal of normal or near-normal glycemic control. It should be considered an important part of a comprehensive treatment regimen that includes:
Goals of treatment and thus the reason for performing SMBG must be clearly defined for the patient. Patients must be motivated and capable of learning the proper technique of SMBG and committed to applying the results to modify their treatment. Health care providers must be able to discuss SMBG results in a non derogatory, helpful way that provides encouragement through open, honest communication and an atmosphere of support.
The following reasons for performing SMBG have been outlined in a consensus statement by the ADA:
1. To achieve or maintain a specific level of glycemic control — As evidenced by results of the DCCT and UKPDS, intensive therapy that is closely monitored using SMBG can help patients achieve near-normoglycemia and delay the onset and slow the progression of diabetic complications in type 1 diabetes and type 2 diabetes. Therefore, SMBG at least four times daily is essential for evaluating and adjusting insulin doses in patients on intensive insulin regimens and, with lesser frequency, for patients on less-complex insulin or combination regimens or those using oral agents and diet, directed toward achieving near normoglycemia.
2. To prevent and detect hypoglycemia — Hypoglycemia is a major complication of treatment regimens, particularly those involving intensive application of pharmacologic therapy to achieve near-normoglycemia. The elderly are particularly susceptible to hypoglycemia, and certain oral antidiabetic agents, such as the SFUs, can produce hypoglycemia. Therefore, appropriately timed SMBG is the only way to detect asymptomatic hypoglycemia so that appropriate action (adjusting insulin/oral agents, modifying diet/exercise) can be taken to prevent it from becoming severe.
3. To avoid severe hyperglycemia — Illness and certain drugs that alter insulin secretion (e.g., phenytoin, thiazide diuretics) or insulin action (e.g., prednisone) can increase the risk of severe hyperglycemia and/or ketoacidosis. SMBG should be initiated or used more frequently in all of these situations to detect hyperglycemia before it becomes severe. In addition, patients on insulin therapy can use SMBG data to adjust their insulin doses to avoid severe hyperglycemia.
4. To adjust care in response to lifestyle changes inpatients on pharmacologic therapy — Glucose levels change in response to variations in diet, exercise, and stressful situations. SMBG can help identify patterns of response to planned exercise and daily activity and help modify pharmacologic therapy during times of increased or decreased caloric consumption.
SMBG enables the patient to be involved in self-management and provides immediate feedback regarding the impact of diet, exercise, and pharmacologic therapy on blood glucose levels. Patients who are educated about SMBG, how to use the results, and how to make self-adjustments of insulin doses using algorithms (for insulin-requiring type 2 patients and type 1 patients) can achieve better daily glycemic control and have a better sense of self-control and participation in their own care. SMBG also provides worthwhile feedback that the physician and other members of the diabetes health care team can incorporate into ongoing evaluation of the treatment regimen. However, health care professionals need to make a point of requesting and reviewing a patient’s SMBG data to provide helpful guidance and encouragement.
Advantages of SMBG include:
• Accurate, immediate results for detecting hypoglycemia and hyperglycemia
• Day-to-day assessment of glycemic control
• Follow-up information after changes in treatment to enhance accurate adjustments in pharmacologic therapy
• Enhanced patient independence, self-confidence, and participation in their treatment
• Storage of test results.
Disadvantages of SMBG include:
• Discomfort of lancing the finger to obtain blood (many meters today allow alternate-site testing)
• Complexity of some testing procedures, requiring mental acuity and dexterity
• Potential malfunction of equipment that could lead to inaccurate results that may affect treatment decisions
• False results because of inaccurate technique that may affect treatment decisions.
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Buckingham B, Caswell K, Wilson DM. Real-time continuous glucose monitoring. Curr Opin Endocrinol Diabetes Obes. 2007;14:288-295.
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© Copyright 2010. Steven V. Edelman, MD, Robert R. Henry, MD, Professional Communications, Inc. All rights reserved.