Monitoring Test
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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
Blood
Glucose Testing by Healtcare Providers
Hemoglobin
A1C Testing
Fructosamine
Microalbumin
BLOOD
GLUCOSE TESTING BY PATIENTS (back
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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.
Given the results of the Diabetes Control and Complications Trial (DCCT)
and other studies, there is broad consensus on the health benefits of
normal or near-normal blood glucose levels and on the importance, especially
in insulin-treated patients, of SMBG in treatment efforts designed to
achieve such glycemic goals.
BLOOD
GLUCOSE TESTING BY HEALTH CARE PROVIDERS FOR ROUTINE OUTPATIENT MANAGEMENT
OF DIABETES (back
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| 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. |
Comparisons
between results from patient self-testing of blood glucose in the
clinic and simultaneous laboratory testing are useful to assess
the accuracy of patient results. If such testing is performed by
health care providers using portable capillary blood testing devices
rather than standard hospital or clinic laboratory methods, rigorous
quality control procedures should be used. Participation in a voluntary
proficiency testing program for home-use testing devices is recommended.
|
| 3. |
Continuous
ambulatory blood glucose monitoring may be used to determine 24-h
blood glucose patterns and to detect unrecognized hypoglycemia;
however, its role in improving diabetes outcomes remains to be established. |
| 4. |
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
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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
at least 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
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Because the turnover of human serum albumin is much shorter (half-life
of 14-20 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. Values for GSP vary with changes in the synthesis or clearance
of serum proteins that can occur with acute systemic illness or with
liver disease. 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.
Measurement of GSP
(including fructosamine) has been used to document relatively short-term
changes (e.g., 1-2 weeks) in glycemic status, such as in diabetic pregnancy
or after major changes in therapy. However, further studies are needed
to determine if the test provides useful clinical information in these
situations.
Simultaneous measurements
of GSP and HbA1c might complement one another
and provide more useful clinical information than measurement of HbA1c
alone.
Microalbumin
(back
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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.
Diabetic nephropathy
develops in up to 45% of Type I diabetes and up to 35% in Type II patients.
Microalbuminuria
is the increased, but low urinary albumin excretion of 30-300 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.
- Early detection
of glomerular damage is important as the damage can be delayed, or
even reversed, with a tightening of glycemic control and/or drug therapy.
- Identification
of patients at risk can promote positive outcomes.
