  |
|
| |||||||||||||
|
|
About Us
Managing Diabetes |
 |
|
|
| ||
|
|
Lab Tests To Monitor Glucose Control And Insulin Production Glucose The glucose test is a snapshot, a still photograph of a moving picture. It tells what the blood glucose level was at the moment it was collected. The fasting blood glucose level (collected after an 8 to 10 hr fast) is used to screen for and diagnose diabetes and pre-diabetes . An oral glucose tolerance test (OGTT / GTT) may also be used to diagnose diabetes and pre-diabetes but, according to the American Diabetes Association, two tests (either the fasting glucose or the OGTT) should be done at different times in order to confirm the diagnosis. The OGTT involves a fasting glucose, followed by the patient drinking a standard amount of a glucose solution to "challenge" their system, followed by another glucose test two hours later. Gestational diabetes is a temporary type of hyperglycemia seen in some pregnant women, usually late in their pregnancy. Almost all pregnant women are screened for gestational diabetes between their 24th and 28th week of pregnancy using a 1 hour glucose challenge. If the blood glucose is high, they are considered at risk of developing gestational diabetes and they will undergo further testing. Diabetics must monitor their own blood glucose levels, often several times a day, to determine how far above or below normal their glucose is and to determine what oral medications or insulins they may need. This is usually done by placing a drop of blood from a finger prick onto a plastic indicator strip and then inserting the strip into a glucometer, a small machine that provides a digital readout of the blood glucose. In those with suspected hypoglycemia , glucose levels are used as part of the "Whipple triad" to confirm a diagnosis. This test can be used to screen healthy individuals for diabetes and pre-diabetes , because diabetes is a common disease that begins with few symptoms. Screening for glucose may occur at public health fairs or as part of workplace health programs. It may also be ordered as part of a routine physical exam. Screening is especially important for people at high risk of developing diabetes -- those with a family history of diabetes, those who are overweight, and those who are more than 40 to 45 years old. The glucose test may also be ordered to help diagnose diabetes and hypoglycemia when someone has symptoms of hyperglycemia such as:
or of hypoglycemia, such as:
Glucose testing is also done in emergency settings to determine if low or high glucose is contributing to symptoms such as fainting and unconsciousness. If a patient has pre-diabetes (characterized by fasting or OGTT levels that are higher than normal but lower than those defined as diabetic) their doctor will order a glucose at regular intervals to monitor their progress. With known diabetics, doctors will order glucose levels in conjunction with other tests such as: insulin and C-Peptide to monitor insulin production, and hemoglobin A1c to monitor glucose control over a period of time. Diabetics will self check their glucose, once or several times a day, to monitor glucose levels and to determine treatment options. Pregnant women are usually screened for gestational diabetes late in their pregnancies, unless they have symptoms earlier or have had gestational diabetes with a previous child. When a woman has gestational diabetes, her doctor will usually order glucose levels throughout the rest of her pregnancy and after delivery to monitor her condition. High levels of glucose most frequently indicate diabetes but many other diseases and conditions can also cause elevated glucose. The following information summarizes the meaning of the test results. These are based on the clinical practice recommendations of the American Diabetes Association.
Also known as: HbA1c, Glycohemoglobin, Glycated hemoglobin, Glycosylated hemoglobin The test for A1C indicates how well you have controlled your diabetes over the last few months. Even though you may have some very high or very low blood glucose values, A1C will give you a picture of the average amount of glucose in your blood over that time period. The result can help you and your doctor know if the measures you are taking to control your diabetes are successful. Depending on the type of diabetes that you have, how well your diabetes is controlled, and your doctor, your A1C may be measured 2 to 4 times each year. The American Diabetes Association recommends testing your A1C:
When someone is first diagnosed with diabetes or if control is not good, A1C may be ordered more frequently. A healthy person without diabetes will have an A1C between 4% (0.04) and 6% (0.06). If you are diabetic, the closer your A1C is to 6% (0.06), the better your diabetes is in control. For every 1% (0.01) increase in A1C, blood glucose increases approximately 30 mg/dL (1.67 mmol/L) and the risk of complications increases.
Fructosamine Fructosamine testing has been available since the 1980s. Both fructosamine and A1C tests are used primarily as monitoring tools to help diabetics control their blood sugar, but the A1C test is much more popular and more widely accepted. However, the American Diabetes Association (ADA) recognizes both tests and says that fructosamine may be useful in situations where the A1C cannot be reliably measured. Instances where fructosamine may be a better monitoring choice than A1C include:
Since the fructosamine concentrations of well-controlled diabetics may overlap with those of non-diabetics, the fructosamine test is not useful as a screen for diabetes . Although not widely used, the fructosamine test may be ordered whenever the doctor wants to monitor a patient's average glucose over the past 2 to 3 weeks. It is primarily ordered when a diabetic treatment plan is being instituted or altered in order to monitor the effect of the change in diet or medication. Fructosamine levels also may be ordered when a diabetic patient is pregnant, or when they have an acute or systemic illness that may change their glucose and insulin requirements for a period of time. The fructosamine test may be used when monitoring is required and an A1C test cannot be reliably used. If a patient's fructosamine is increased, then the patient's average glucose over the last 2 to 3 weeks has been elevated. In general, the higher the fructosamine concentration the higher the average blood glucose level. Trends may be more important that absolute values. If there is a trend from a normal to high fructosamine, it may indicate that a patient's glucose control is not adequate – that they are getting too much sugar, too little insulin, or that their insulin treatment has become less effective. Normal fructosamine levels may indicate that a patient is either not diabetic (and therefore should not be monitored) or that he has good diabetic control. A trend from high to normal fructosamine levels may indicate that changes to a patient's treatment regimen are effective. Fructosamine results must be evaluated in the context of the patient's total clinical findings. Falsely low fructosamine results may be seen with decreased protein levels, increased protein loss, or a change in the type of protein produced by the body. In this case, a discrepancy between the results obtained from daily glucose monitoring and fructosamine testing may be noticed. Also, someone whose glucose concentrations swing erratically from high to low may have normal or near normal fructosamine and A1C levels but still have a condition that requires frequent monitoring. High levels of vitamin C (ascorbic acid), lipemia (high amount of fat in the blood), hemolysis (breakdown of RBCs), and hyperthyroidism can interfere with test results.
Insulin Insulin tests are performed to help evaluate insulin production, diagnose an insulinoma (insulin-producing pancreatic islet cell tumor), and to help determine the cause of hypoglycemia. Insulin levels are sometimes used in conjunction with the glucose tolerance test (GTT) . Blood glucose and, sometimes, insulin levels are measured to evaluate insulin resistance, particularly in obese individuals. Insulin levels are most frequently ordered following an abnormal glucose test and/or when a patient has acute or chronic symptoms of hypoglycemia , such as sweating, palpitations, hunger, confusion, visual problems, and seizures (although these can be caused by other conditions). Insulin and C-peptide are produced by the body at the same rate as part of the activation and division of proinsulin in the pancreas. Both may be ordered to evaluate how much insulin in the blood is due to endogenous production (what your body is making) and how much is from exogenous (produced outside the body) sources. Insulin tests will reflect the total, while C-peptide will reflect only the endogenous insulin. Your doctor also may order both tests to verify that an insulinoma has been successfully removed. If you are one of the few people who have received an islet cell transplant to restore your insulin-producing capability, your insulin level may be monitored to determine whether or not this procedure is successful over time. Insulin levels must be evaluated in context. If fasting insulin and glucose levels are normal, most likely the body's glucose regulation system is functioning normally. If insulin is elevated and glucose is normal and/or moderately elevated, then there may be some insulin resistance at the cellular level. If the insulin is low and the glucose is high, then most likely there is insufficient insulin being produced. If insulin levels are normal or elevated and glucose levels are low, then the patient is hypoglycemic due to excess insulin. Elevated insulin levels are seen with: 1. Acromegaly Decreased insulin levels are seen with: 1. Diabetes
C-Peptide A C-Peptide test can be used when a patient has newly diagnosed type 1 or type 2 diabetes , to help determine how much insulin the patient's pancreas is still producing and whether or not that insulin is being used effectively. Type 1 diabetes is an autoimmune process that often starts in early childhood and involves the almost complete destruction of the beta cells over time. Eventually, little or no insulin (or C-peptide) is produced, leading to a complete dependence on exogenous insulin. In type 2 diabetes, often called “adult-onset diabetes,” a combination of factors leads to decreased insulin production and increased insulin resistance, along with some beta cell damage. Type 2 diabetics usually are treated with oral drugs to stimulate their body to make more insulin and/or to cause their cells to be more sensitive to the insulin that is already being made. Eventually, type 2 diabetics may make very little insulin and require injections. Any insulin that the body does make will be reflected in their C-peptide level; therefore, the C-peptide test can be used to monitor beta cell activity and capability over time and to help your doctor determine when to begin s upplementing your insulin. C-peptide measurements also can be used in conjunction with insulin and glucose levels to help diagnose the cause of documented hypoglycemia and to monitor its treatment. Symptoms of hypoglycemia may be caused by excessive supplementation of insulin, alcohol consumption, inherited liver enzyme deficiencies, liver or kidney disease , or insulinomas (tumors of the islet cells in the pancreas that can produce uncontrolled amounts of insulin and C-peptide). C-peptide levels may be ordered if you have newly diagnosed diabetes , as part of an evaluation of your “residual beta cell function” (how much insulin your beta cells are making). With type 2 diabetes, the test may be ordered if your doctor wants to monitor the status of your beta cells and insulin production over time and to determine if/when insulin injections may be required. C-peptide blood and urine levels also may be monitored to check your renal function and C-peptide clearance rate. C-peptide levels may be done when there is documented acute or recurring hypoglycemia . Symptoms include sweating, palpitations, hunger, confusion, visual problems, and seizures, although these symptoms also can occur with other conditions. The C-peptide test may be used to help separate excessive insulin production from excessive administration and to help diagnose insulinomas. If you have had your pancreas removed or are one of the few patients to have had pancreas islet cell transplants (in order to restore your ability to make insulin), your C-peptide levels may be monitored to verify the effectiveness of treatment and continued success of the procedure. High levels of C-peptide generally indicate high levels of insulin. This may be due to excessive insulin production, a response to high levels of blood glucose caused by glucose intake and/or insulin resistance. (With insulin resistance, the body's cells do not use insulin normally to transport glucose inside the cell. The cells become “starved for glucose,” interpret that as a lack of insulin, and signal the body to make more.) High levels of C-peptide also are seen with insulinomas and may be seen with hypokalemia , pregnancy , Cushing's syndrome, and renal failure. During a glucose tolerance test (GTT) , there will often be a temporary 5 to 6 fold increase in C-peptide levels. Even though they are produced at the same rate, C-peptide and insulin leave the body by different routes. Insulin is processed and eliminated by the liver, while C-peptide degrades and is removed by the kidneys. Since the half-life of C-peptide is about 30 minutes to insulin's 5 minutes, normally there will be about 5 times as much C-peptide in the bloodstream as insulin. Add to this the fact that a person's kidneys and/or liver may not be clearing insulin and C-peptide out efficiently and you end up with an inherent imprecision in the C-peptide test. It can give your doctor important information about your beta cells and insulin production, but it is not perfect. You will need to fast for a C-peptide blood test if the results will be used to evaluate hypoglycemia. |
||||||||||||||||||||||||
|
|||||||||||||||||||||||||