Medical Practice Guidelines - Monitoring Test Options

Monitoring of glycemic status, as performed by patients and health care providers, is considered a cornerstone of diabetes care. Results of monitoring are used to assess the efficacy of therapy and to guide adjustments in medical nutrition therapy (MNT), exercise, and medications to achieve the best possible blood glucose control.

BLOOD GLUCOSE TESTING BY PATIENTS (back to top)
Within only a few years, self-monitoring of blood glucose (SMBG) by patients has revolutionized management of diabetes. Using SMBG, patients with diabetes can work to achieve and maintain specific glycemic goals.

BLOOD GLUCOSE TESTING BY HEALTH CARE PROVIDERS FOR ROUTINE OUTPATIENT MANAGEMENT OF DIABETES (back to top)

Recommendations
1.	Blood glucose testing (e.g., laboratory glucose or finger-stick glucose) should be available to providers for use as needed. With the availability of SMBG and glycated protein testing, routine laboratory blood glucose testing by health care providers should no longer be used to assess glycemic control except to supplement information obtained from other testing methods and to test the accuracy of SMBG. When adjusting oral glucose-lowering medication(s) in a patient not taking insulin, laboratory testing also may be appropriate.
2.	GLYCATED PROTEIN TESTING - Blood and urine glucose testing and urine ketone testing provide useful information for day-to-day management of diabetes. However, these tests cannot provide the patient and health care team with a quantitative and reliable measure of glycemia over an extended period of time. Measurements of glycated proteins, primarily hemoglobin and serum proteins, have added a new dimension to assessment of glycemia. With a single measurement, each of these tests can quantify average glycemia over weeks and months, thereby complementing day-to-day testing.

Hemoglobin A1C Testing (back to top)
GHb, commonly referred to as glycated hemoglobin, glycohemoglobin, glycosylated hemoglobin, HbA1c, or HbA1, is a term used to describe a series of stable minor hemoglobin components formed slowly and nonenzymatically from hemoglobin and glucose. The rate of formation of GHb is directly proportional to the ambient glucose concentration. Since erythrocytes are freely permeable to glucose, the level of GHb in a blood sample provides a glycemic history of the previous 120 days, the average erythrocyte life span. GHb most accurately reflects the previous 2-3 months of glycemic control.

The HbA1c value has been shown to predict the risk for the development of many of the chronic complications in diabetes, analogous to using cholesterol determinations to predict the risk for development of cardiovascular disease.

HbA1c testing should be performed routinely in all patients with diabetes, first to document the degree of glycemic control at initial assessment, then as part of continuing care. Since HbA1c reflects a mean glycemia over the preceding 2-3 months, measurement approximately every 3 months is required to determine whether a patient's metabolic control has reached and been maintained within the target range. Thus, regular measures of HbA1c permit detection of departures from the target range in a timely fashion. For any individual patient, the frequency of HbA1c testing should be dependent on the treatment regimen used and on the judgment of the clinician. In the absence of well-controlled studies that suggest a definite testing protocol, expert opinion recommends HbA1c testing two times a year in patients who are meeting treatment goals (and who have stable glycemic control) and more frequently (quarterly assessment) in patients whose therapy has changed or who are not meeting glycemic goals. Persons with diabetes also suffer from microvascular complications associated with the disease, and retinopathy is one of these complications. High HbA1c levels are linked to the development of retinopathy. Control of HbA1c levels and eye examinations which detect and allow appropriate treatment of retinopathy can, in many cases, prevent or greatly reduce visual impairment.

Fructosamine (back to top)
Because the turnover of human serum albumin is much shorter (half-life of 14 days) than that of hemoglobin (erythrocyte life span of 120 days), the degree of glycation of serum proteins (mostly albumin) provides an index of glycemia over a shorter period of time than does glycation of hemoglobin. Measurements of total glycated serum proteins (GSP) and glycated serum albumin (GSA) correlate well with one another and with measurements of HbA1c. In situations where HbA1c cannot be measured or may not be useful (e.g., hemolytic anemias, gestational diabetes), the GSP assay may be of value in the assessment of the treatment regimen. Several methods have been described that quantify either total GSP or total GSA. One of the most widely used is called the fructosamine assay. In addition, there is continuing debate as to whether fructosamine assays should be corrected for serum protein or serum albumin concentrations. A single measurement of GSP provides an index of glycemic status over the preceding 1-2 weeks, while a single measurement of HbA1c provides an index of glycemic status over a considerably longer period of time, 2-3 months.

Clinical Utility
	When Changes are being made in a diabetes treatment plan
	Fructosamine can indicate the effectiveness of treatment more timely than an HbA1c
	Can assess whether other changes should be considered
	Useful in Gestational Diabetes
	Results respond faster to improved or deteriorated glucose control
	Not subject to wide fluctuations observed in blood glucose testing
	Not subject to erroneous results when anemia or hemoglobinopathies are present (as in HbA1c)

Microalbumin (back to top)
Although albumin is present in high concentrations in serum, the renal glomeruli act as an effective barrier to prevent protein loss into the urine. Small amounts of albumin (<20 mg/L) are present in the urine of normal healthy individuals.

In 2005, diabetes was the leading cause of kidney failure, accounting for 44% of new cases that year.

Microalbuminuria is the increased, but low urinary albumin excretion of 30-299 mg/L - indicating early changes in glomerular permeability. Current dipstick technology is usually sensitive to albumin levels of 200-300 mg/L.

Increasing levels of albumin in urine indicates a progressive decline of glomerular function - leading to end-stage renal failure. Therefore, early detection by monitoring microalbumin in both Type I and II diabetic patients is advocated.

CLINICAL SIGNIFICANCE
"Detecting Hidden Renal Disease". The earliest clinical evidence of renal dysfunction in diabetic patients is the appearance of microscopic amounts of albumin in the urine (microalbuminuria). In the past, this condition often went untreated or undetected. Today, however, it is widely accepted that microalbuminuria often advances to overt albuminuria (>300 mg/day). This then leads to progressive decline in renal function and finally to end-stage renal disease.