Situations In Which Blood Glucose Assays Are Performed
In the hospital laboratory, it is usual to performglucose assays on plasma or serum, as routine venepuncture and theavailability of centrifuges usually mean that sufficient plasma canbe harvested for assay on the main laboratory analyzer.
In othersituations, such as intensive care units or special care babyunits, it is less convenient to use plasma, either because of lackof centrifuge facilities or owing to small sample volume.
Undersuch circumstances, it is preferable to be able to present wholeblood to the analytical system, as it is in a third type ofscenario, where the patient performs the assay himself.
Miscellaneous Potentially Important Analytes Ii Insulin Antibodies
RECOMMENDATION: THERE IS NO PUBLISHED EVIDENCE TO SUPPORT THE USE OF INSULIN ANTIBODY TESTING FOR ROUTINE CARE OF PATIENTS WITH DIABETES C .
Given sufficiently sensitive techniques, insulin antibodies can be detected in any patient being treated with exogenous insulin . In the vast majority of patients, the titer of insulin antibodies is low, and their presence is of no clinical significance. Very low values are seen in patients treated exclusively with human recombinant insulin . On occasion, however, the titer of insulin antibodies in the circulation can be quite high and associated with a dramatic resistance to the ability of exogenous insulin to lower plasma glucose concentrations. This clinical situation is quite rare, it usually occurs in insulin-treated patients with type 2 diabetes, and the cause-and-effect relationships between the magnitude of the increase in insulin antibodies and the degree of insulin resistance are unclear. There are several therapeutic approaches for treating these patients, and a quantitative estimate of the concentration of circulating insulin antibodies does not appear to be of significant benefit.
See accompanying article, p. 1419.
What Are The Diabetes Testing Methods
The gold standard diagnostic method for diabetes has previously been the measurement of either fasting blood glucose or two-hour plasma glucose via an oral glucose tolerance test .2
The diagnostic criteria for a patient to be considered diabetic using FBG or OGTT is:
- FBG 7.0 mmol/l, or
- Two-hour plasma blood glucose concentration must be 11.1 mmol/l two hours following administration of a 75g anhydrous glucose via an OGTT
Although both testing methods provide a good level of accuracy, they present their own limitations. Both tests rely on a suitable application of the test within specific time periods and compliance from the patient.
Pre-test preparation for testing two-hour plasma blood glucose concentration, for example, includes providing patients with a strict diet for three days prior to testing and overnight fasting.
While the FBG test requires a minimum of 8 hours of fasting before the test can be completed. Overall, traditional diagnostic methods can seem daunting and time consuming, which makes patient compliance difficult to achieve.
The requirement to fast with traditional glucose testing methods can bea potentially difficult compliance standard to meet for some, especially those already struggling with glycemic control. Some patients may consume food or beverages within the fasting period, believing this small action would not affect the testing results but in reality this would usually mean the test would have to be repeated.
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Can Urine Samples Be Tested For Glucose
Urine samples are routinely tested for glucose as part of a urinalysis. Additional testing is usually done to identify the cause of an abnormal urine glucose result.
Glucose usually only shows up in the urine if glucose is at sufficiently high levels in the blood that some of the excess is lost in the urine, or if there is some degree of kidney damage and the glucose is leaking out into the urine.
Why You Should Check Your Blood Sugar
Testing blood glucose can help you manage diabetes by showing you:
- How well your diabetes treatment plan is working
- How exercise and food affect your blood sugar levels
- How things like stress and illness affect your levels
- How well your diabetes medication is working
- When your blood sugar levels are too high or too low
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Ive Recently Been Diagnosed With Type 2 Diabetes Will I Need To Monitor My Glucose Levels Every Day
Your healthcare practitioner will discuss with you whether you need to monitor your glucose levels. Not everyone with type 2 diabetes needs to monitor their glucose levels every day, especially if they are able to manage their diabetes and glucose levels with diet and exercise.
However, some people with type 2 diabetes must check their blood glucose levels, sometimes several times a day. This may be done using a glucose meter. You would place a drop of blood from a skin prick onto a glucose strip and then insert the strip into the glucose meter, a small machine that provides a digital readout of the blood glucose level. Alternatively, some people may use a continuous glucose monitoring device.
Your healthcare practitioner will give you guidelines for how high or low your blood sugar should be at different times of the day. By checking your glucose regularly, you can see if the diet and medication schedule you are following is working properly for you.
Who Should Be Tested For Diabetes
Anyone who has symptoms of diabetes should be tested for the disease. Some people will not have any symptoms but may have risk factors for type 2 diabetes and need to be tested. Most pregnant women should also be tested for gestational diabetes. Testing helps doctors find diabetes sooner, so they can work with their patients to manage the disease and prevent health problems.
If you have Medicare, it may cover the cost of tests if you have certain risk factors for diabetes. If you have different insurance, ask your insurance company if it covers diabetes tests.
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Miscellaneous Potentially Important Analytes I Insulin And Precursors
RECOMMENDATION: THERE IS NO ROLE FOR ROUTINE TESTING FOR INSULIN, C-PEPTIDE, OR PROINSULIN IN MOST PATIENTS WITH DIABETES. DIFFERENTIATION BETWEEN TYPE 1 AND TYPE 2 DIABETES MAY BE MADE IN MOST CASES ON THE BASIS OF THE CLINICAL PRESENTATION AND THE SUBSEQUENT COURSE. THESE ASSAYS ARE USEFUL PRIMARILY FOR RESEARCH PURPOSES. OCCASIONALLY, C-PEPTIDE MEASUREMENTS MAY HELP DISTINGUISH TYPE 1 FROM TYPE 2 DIABETES IN AMBIGUOUS CASES, SUCH AS PATIENTS WHO HAVE A TYPE 2 PHENOTYPE BUT PRESENT IN KETOACIDOSIS B .
RECOMMENDATION: THERE IS NO ROLE FOR MEASUREMENT OF INSULIN CONCENTRATION IN THE ASSESSMENT OF CARDIOMETABOLIC RISK, BECAUSE KNOWLEDGE OF THIS VALUE DOES NOT ALTER THE MANAGEMENT OF THESE PATIENTS B .
The clinical utility of measuring insulin, C-peptide, or proinsulin concentrations to help select the best antihyperglycemic agent for initial therapy in patients with type 2 diabetes is a question that arises from consideration of the pathophysiology of type 2 diabetes. In theory, the lower the pretreatment insulin concentration, the more appropriate might be insulin, or an insulin secretagogue, as the drug of choice to initiate treatment. Although this line of reasoning may have some intellectual appeal, there is no evidence that measurement of plasma insulin or proinsulin concentrations will lead to more efficacious treatment of patients with type 2 diabetes.
2. Analytical considerations
What Does A Blood Sugar Test Do
Your doctor may order a blood sugar test to see if you have diabetes or prediabetes. The test will measure the amount of glucose in your blood.
Your body takes carbohydrates found in foods like grains and fruits and converts them into glucose. Glucose, a sugar, is one of the bodys main sources of energy.
For people with diabetes, a home test helps monitor blood sugar levels. Taking a blood sugar test can help determine your blood sugar level to see if you need to adjust your diet, exercise, or diabetes medications.
Ketoacidosis occurs when your body starts using only fat for fuel. Hyperglycemia over a long period can increase your risk for neuropathy , along with heart, kidney, and eye diseases.
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The Role Of Glucose Testing
There are several different reasons a doctor may recommend glucose testing for you. These include screening, diagnosis, and monitoring.
Screening means using tests to find health problems before those problems cause any symptoms or signs that you or your doctor might notice.
If you are over 40, overweight or obese, or have a heightened risk of developing diabetes, your doctor may order one or more screening glucose tests to find prediabetes or diabetes. People with prediabetes have glucose levels that are higher than normal but not high enough to be diagnosed with diabetes.
Diagnosis is the use of tests and procedures to determine what underlying health condition might be causing noticeable signs and symptoms.
If you have symptoms of diabetes, high blood sugar, or low blood sugar, your doctor may order glucose testing for you. Glucose testing may be accompanied by other blood or urine tests to make an accurate diagnosis.
If you have been diagnosed with diabetes or prediabetes, your doctor may want you to track your blood glucose levels with an at-home glucose testing or monitoring device. Your doctor may also recommend periodic laboratory testing during check-ups to learn how your condition is being managed.
Random Blood Sugar Test
This measures your blood sugar at the time youre tested. You can take this test at any time and dont need to fast first. A blood sugar level of 200 mg/dL or higher indicates you have diabetes.
|140 mg/dL or below
*Results for gestational diabetes can differ. Ask your health care provider what your results mean if youre being tested for gestational diabetes.Source: American Diabetes Association
If your doctor thinks you have type 1 diabetes, your blood may also tested for autoantibodies that are often present in type 1 diabetes but not in type 2 diabetes. You may have your urine tested for ketones , which also indicate type 1 diabetes instead of type 2 diabetes.
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Besides Glucose What Other Tests Might Be Done
Hemoglobin A1c is an indicator of long-term glucose control that is commonly ordered in patients with prediabetes and diabetes and can also be used as a screening test. Other less common tests, such as islet autoantibodies, insulin, and C-peptide, may sometimes be performed along with these tests to help determine the cause of abnormal glucose levels, to distinguish between type 1 and type 2 diabetes, and to evaluate insulin production.
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When Is It Ordered
Screening and Diagnosis
The American Diabetes Association recommends diabetes screening when you are age 45 or older. Several health organizations, including the ADA, recommend screening when you have risk factors, regardless of age. You may be at risk if you:
- Are overweight, obese, or physically inactive
- Have a close relative with diabetes, such as parent, siblings, aunt or uncle
- Are a woman who delivered a baby weighing more than 9 pounds or who has a history of gestational diabetes
- A woman with polycystic ovary syndrome
- Are of a high-risk race or ethnicity, such as African American, Latino, Native American, Asian American, Pacific Islander
- Have high blood pressure or are taking medication for high blood pressure
- Have a low HDL cholesterol level and/or a high triglyceride level
- Have prediabetes identified by previous testing
- Have a history of cardiovascular disease
The U.S. Preventive Services Task Force recommends screening for abnormal blood glucose as part of a risk assessment for cardiovascular disease in adults ages 40 to 70 who are overweight or obese.
If the screening test result is within normal limits, the ADA and USPSTF recommend rescreening every 3 years. People with prediabetes may be monitored with annual testing.
A blood glucose test may also be ordered when you have signs and symptoms of abnormal blood glucose levels.
High blood glucose :
A1c Blood Sugar Tests
The A1C test measures the percentage of glucose bound hemoglobin in a persons blood.
According to The National Institutes of Health , this gives a general picture of a persons blood glucose levels over the past 23 months .
Abnormal A1C test results do not necessarily mean a person has diabetes. A doctor will confirm these findings with another blood glucose test.
The doctor may recommend running more tests, such as blood work, to rule out other conditions that can affect blood sugar levels.
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What Happens During The Test
Most people can take an A1C test at any time without preparing beforehand. However, a doctor may sometimes request that a person avoids eating or drinking for 8 hours before the test.
Women who are pregnant may need to drink a sugary beverage 1 hour before the test.
A doctor or nurse will collect a blood sample, usually from a vein in the arm or hand. They will send the sample to a laboratory for analysis.
Prevent Type 2 Diabetes
If your test results show you have prediabetes, ask your doctor or nurse if there is a lifestyle change program offered through the CDC-led National Diabetes Prevention Program in your community. You can also search for an online or in-person program. Having prediabetes puts you at greater risk for developing type 2 diabetes, but participating in the program can lower your risk by as much as 58% .
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When Should You Test Your Blood Sugar
It depends on which type of diabetes you have:
- Type 1 diabetes. Itâs up to your doctor. They could suggest you test anywhere between four and 10 times a day. For example, you could test before meals and snacks, before and after exercise, before bed, and even during the night. You may also need to check more often if youâre sick, making changes to your daily routine, or starting a new medication.
- Type 2 diabetes. It depends on what you take to treat your diabetes:
- Insulin. The doctor may tell you to test a few times a day, depending on the type and amount of insulin you use. Youâll probably test before meals and at bedtime if you’re taking multiple daily injections. You may need to test only twice daily, before breakfast and dinner, if you only use a long-acting insulin.
- Medications. If you use drugs to manage diabetes, your doctor will tell you how often to check your blood sugar.
- Lifestyle changes. If youâre relying on diet and exercise, you may not need to test your blood sugar daily.
American Diabetes Association: “Choosing a Blood Glucose Meter,” tion: “Standards of Medial Care in Diabetes — 2014,” “A1C and eAG,” âChecking Your Blood Glucose.â
Mayo Clinic: âBlood sugar testing: Why, when and how,â âType 2 diabetes.â
The National Diabetes Information Clearinghouse.
National Diabetes Foundation Program.
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Types Of Blood Sugar Tests
You can take a blood sugar test two ways. People who are monitoring or managing their diabetes prick their finger using a glucometer for daily testing. The other method is drawing blood.
Blood samples are generally used to screen for diabetes. Your doctor will order a fasting blood sugar test. This test measures your blood sugar levels, or a glycosylated hemoglobin, also called a hemoglobin A1C test. The results of this test reflect your blood sugar levels over the previous 90 days. The results will show if you have prediabetes or diabetes and can monitor how your diabetes is controlled.
When and how often you should test your blood sugar depends on the type of diabetes you have and your treatment.
Do All Blood Glucose Assays Measure The Same Thing
The simple answer is, “No”.
Having said that,laboratory methods using plasma, essentially a homogeneous matrix,do generally agree quite well because the assay responds to theglucose dissolved in the entire volume of the sample and resultsare usually expressed in terms of concentration of glucose per unitvolume of plasma, e.g. in mmol/L.
For methods using whole blood,the situation is very different and partly depends on whether theblood sample is first hemolyzed or diluted in some way before themeasurement is performed.
Understanding this depends on theknowledge that red cells and plasma contain different amounts ofdissolved solids such as proteins and, hence, have differentproportions of water per unit volume, the water content of a volumeof red cells being lower than that of an equal volume of plasma.
Glucose is dissolved in the water of thespecimen and equilibrates freelybetween the red cells and plasma of a whole-blood specimen, so theconcentrations in plasma water and red-cell water are the same, butthe concentration in total red-cell contents is lower than inplasma and the concentration in a volume of whole blood liessomewhere in between, varying with the hematocrit of the specimen.
Consequently, the glucose concentration influencing theassay system will be determined by whether the assay responds tothe concentration in the water, in the plasma, in the red cells, ina mixture of plasma and red cells, or in a dilution of the bloodspecimen.
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