Diabetes Tests

Glycated Hemoglobin (HbA1c)

The 7% HbA1c Goal

Diabetes Screening Tests

Glycated Hemoglobin (HbA1c)

When you get a GHb test, it's like getting your blood's batting average.

sst. Hey bud. What’s your GHb? Oh yeah? Sounds good. I’m hoping to get better numbers myself in the next month or so.

Ten years ago, you probably hadn’t heard of the glycohemoglobin test. Today, it seems everybody’s talking about it. (You’ve probably heard of the most common one—the HbA1C.)

A glycohemoglobin (GHb) test tells you what your average blood glucose level was over the past 4 months, yet it requires only a single drop of blood, collected at any time of day. GHb testing is being used routinely all around the world to help people with insulin-dependent (type I) diabetes and non-insulin-dependent (type II) diabetes manage their disease. The test has also played an important role in many diabetes research projects, including the recently completed Diabetes Control and Complications Trial (DCCT).

Despite all the talk about GHb, many people don’t clearly understand what the GHb test is and what it does. Do you know the answers to the most commonly asked questions about the GHb test? Let’s find out.

What is glycohemoglobin?

Hemoglobin is a protein molecule inside red blood cells that carries oxygen from the lungs to all the cells and tissues of the body. Like all other proteins, hemoglobin can link up with sugars, such as glucose. Glucose in your bloodstream is constantly entering your red blood cells and linking up with, or glycosylating (glycating means the same thing) hemoglobin.

Once the hemoglobin gets glycosylated, it stays glycosylated. If your blood glucose was high last week, then more of your hemoglobin was glycosylated than usual. This week, your blood glucose might be back under control again, but your red blood cells will still be carrying the "memory" of last week’s high blood glucose level. That memory will not be erased completely until the last of the red blood cells now in your blood have died and been replaced by fresh cells which contain fresh hemoglobin. That takes about 4 months.

The more glucose there is in the blood, the more hemoglobin will become glycosylated. About 5 percent of the hemoglobin of a person who doesn’t have diabetes is glycosylated. In a person with diabetes, the level is typically higher because of the higher blood glucose levels.

How much higher depends on what the person’s average blood glucose level has been. For example, if average blood glucose is 120 milligrams per deciliter (mg/dl), the GHb is about 6 percent. An average blood glucose level of 330 will produce a GHb of about 13 percent. (See insert)

Is GHb the same thing as hemoglobin A1C (pronounced A-one-C)?

All hemoglobin-glucose linkages are considered to be glycohemoglobins or GHbs. Hemoglobin A1C (also written HbA1C) is a very specific GHb in which the hemoglobin-glucose linkage takes place at only one place on the hemoglobin molecule. Some GHb test methods measure only hemoglobin A1C while others measure all GHbs together. Other terms you may encounter include hemoglobin A1, total glycated hemoglobin, or total GHb. Again, these are just different forms of GHb.

It doesn’t matter which form of GHb is measured. Each can provide the same useful information about your average blood glucose levels. What complicates things is that different GHb tests give different numbers. A "7 percent" on one test is the same as a "9 percent" using another test, even though both indicate the same average blood glucose level.

This problem will be solved only when all test numbers are reported on the same scale. The American Diabetes Association and other national organizations are working hard to develop standards so that the results from one laboratory will be directly comparable to results from another. For now, it is very important that your doctor knows how to translate your GHb result into your average blood glucose level.

How long is the blood glucose memory of this test?

Some articles say 4 months, others say 2 to 3 months, and still others say weeks-to-months. Can’t the experts agree?

The GHb level is not a simple average of all the blood glucose level ups-and-downs over the past 4 months. It is a "weighted average."

An individual red blood cell lives 120 days—about 4 months. But you don’t get a complete turnover of red blood cells once every 4 months. Old ones are constantly dying, and new ones are constantly being produced. At any one time, some of your red blood cells will be old, some middle-aged, and some young.

The GHb result is affected more by recent blood glucose levels than by older ones. Blood glucose levels from 3 to 4 months ago contribute only about 10 percent to the result. That’s because most of the red blood cells that were around then have died off. Your blood glucose levels over the past month count more—they contribute about one-half to the result. That’s what is meant by a weighted average.

Because of this, GHb results can be a bit misleading at times. For example, let’s say your blood glucose levels were near-normal during January, February, and March, but were high during April. Your GHb level will indicate a higher average blood glucose level than what it really was over the entire previous 4 months, because April counted more in the GHb result than did January.

The other side of the coin is that if your blood glucose levels had been well controlled the past month but high for several months before, the GHb level would indicate a somewhat lower average blood glucose than what it actually had been.

Your best protection against being misled by a GHb result is to have your GHb level checked at regular intervals.

How often should I have my GHb level measured?

The ADA recommends that the GHb level first be measured at the time of diagnosis and initiation of treatment. Thereafter, the test should be done at least twice a year in people with non-insulin-dependent (type II) diabetes who don’t use insulin; four times a year in people with insulin-dependent (type I) diabetes or those with type II diabetes who use insulin. It should be done more frequently in people with either type I or type II diabetes whose blood glucose levels are not well controlled.

These are just guidelines. The actual frequency of testing should be decided by you and your health-care team.

I am not sure if my doctor has been ordering the GHb test on me. How do I find out?

Finally, an easy answer! Just ask your doctor. If necessary, give your doctor a copy of this article.

If my blood glucose control improves quite a bit, how long does it take to see it in my GHb test?

As we discussed above, it takes about 4 months to see all the effects of a change in blood glucose levels. But you don’t need to wait 4 months to see a meaningful change in your GHb level after your blood glucose control changes. Depending on how great the change is (up or down), your GHb test can show quite a big change after only one to two weeks. On the practical side, it’s probably not very useful to check a GHb level more than once a month.

My friend and I both have diabetes but we go to different doctors. My friend said her last GHb was 10

percent and her doctor was very pleased. My doctor gets pretty upset when my level is over 9 percent. What gives?

Remember that GHb tests done in different laboratories may give different numbers that mean the same thing when they are translated into the average blood glucose level. It’s likely that your friend’s doctor does not use the same laboratory to measure the GHb test as your doctor does. One other possibility is that your friend has had a much more difficult time controlling her blood glucose levels than you, and the test result was quite an improvement over the time before. Each person should work with his or her health-care team to set GHb goals.

If the GHb test can tell my average blood glucose level for months at a time, why do I need to do blood glucose tests every day?

A GHb level is akin to a baseball player’s season batting average. The batting average provides useful information about overall batting success. But the season batting average can’t help much with batting success in a single game.

The blood glucose tests you do yourself measure the level of glucose in your blood at the time of the test. These are very important for the day-to-day management of your diabetes. They may prompt you to eat a snack, take more insulin, or exercise more or less. The steps you take because of your daily blood glucose results will be reflected in your next GHb.

OK, if I’m doing at-home tests every day, why do I need a GHb test?

Because you can’t do enough tests every day to get the full picture. The GHb test gives you the full picture.

Let’s say you have type II diabetes and you test your blood glucose once a day, before breakfast. The level is usually around 120 mg/dl. But your last GHb test tells you that your average blood glucose is more like 250. That’s worth knowing.

You’ll rarely get the pleasant surprise of a low GHb. If you get a surprise, it will almost always be a high GHb. That will come from "hidden" high blood glucose levels—the times when your blood glucose was high, but you didn’t know because you didn’t test your blood then.

You need to figure out why there is this difference between your daily recorded value and your GHb result. Your health-care team will probably advise you to test your blood more often for a few weeks, or to test at different times.

Doing this, you may discover, for example, that your after-dinner blood glucose level is often higher than 200. There’s your answer. You can discuss these results with your health-care team and make the appropriate changes in your diabetes regimen. You might alter your meal plan or try to increase your activity level. Changes in your treatment plan—increasing your oral medication dose or even starting insulin—might also be considered.

Here’s another example. Your son is 14 years old and has had type I diabetes since he was 5. He tests his blood glucose three or four times each day and the results are excellent—almost always between 70 and 140. But his last two GHb results were very high, indicating an average blood glucose level of about 300. Why?

This situation requires major detective work. Rarely, a medication that a person is taking interferes with the GHb result, and the reading is too high. Some people have unusual types of hemoglobin that fool the test. (Also, GHb results can be too low in people with certain anemias or recent blood loss.)

What’s most likely, however, is that your son’s home blood glucose tests results are not accurate. It’s possible that he’s doing his test readings incorrectly or that his glucose meter is defective.

It’s also possible that he records "better" values than what his meter shows, so that he won’t get a lecture from his doctor. That’s understandable, but it isn’t good for his health.

Whatever the reason, it’s very important to solve the mystery so your son and his health-care team can work to get the best blood glucose levels that are possible for him.

What did they learn about GHb in the Diabetes Control and Complications Trial?

The purpose of the DCCT was to determine if people who kept their blood glucose levels in the near-normal range developed fewer complications than people whose average blood glucose levels were higher (see Forecast, Sept. 1993, pp. 39–78). The DCCT results showed that there is a direct link between the glycohemoglobin levels and the risk of developing the complications. (The test used in the DCCT was the HbA1C.)

People who had GHb levels of about 7 percent had a much lower risk of developing complications of the eyes, kidneys, and nerves compared with people who had levels of about 9 percent. (On this scale, under 6.05 percent was the non-diabetic level.)

A high GHb is definitely a risk factor for diabetic complications.

What should my GHb test result be?

There is no easy answer to this question. It’s not possible to recommend that all people with diabetes aim for any specific GHb level. For one thing, GHb tests done in different laboratories may give different numbers, even from the same blood sample.

But more important, goals for GHb must be individualized. For example, people with type I diabetes are rarely able to achieve and maintain GHb levels in the nondiabetic range without experiencing frequent episodes of hypoglycemia (low blood glucose). On the other hand, many people with type II who are not on insulin can get near-normal glucose levels safely.

But remember that the DCCT showed that any improvement in GHb levels lowers your risk for developing complications. You may be able to improve your GHb levels. Discuss with your health-care team what your goal should be and how to reach it.

Wouldn’t GHb be a good test for diabetes screening and for diagnosis?

Maybe. The gold standard for diagnosis of diabetes is the oral glucose tolerance test (OGTT), even though it’s rarely necessary to perform the test to diagnose diabetes. Recent studies suggest that GHb may be useful to confirm, and perhaps to diagnose, diabetes. We predict that GHb will replace the OGTT as a diagnostic tool, but more studies are still needed. (We do know that GHb is not sensitive enough for diagnosing gestational diabetes.)

Sure, you test your glucose level several times a day. You're aware of diet and exercise issues and do your best to stay on track. But what about your hemoglobin A1c level? What does it mean and why is it so important? When is the last time you had it checked? How often should you have it checked?

The hemoglobin A1c test is a simple lab test that shows the average amount of sugar in your blood over the last two to three months. It's the best way to find out if your blood sugar is under control. All people with type 2 diabetes should have a hemoglobin A1c test at least twice a year. If your treatment changes or if your blood sugar level stays too high, you should get a hemoglobin A1c test at least every three months until your blood sugar level improves. Regular testing will help you and your doctor to track your blood sugar levels over time and plan long-term treatment options to reach your target level of control.

Hemoglobin is an oxygen-carrying pigment-it's what makes red blood cells red. The hemoglobin A1c test, sometimes called a glycated hemoglobin test, measures the proportion of hemoglobin molecules in your red blood cells that have glucose attached to them (and thus are "glycated"). Once glycated, a hemoglobin molecule stays that way throughout the 3- to 4-month lifecycle of its red blood cell. Red blood cells are continually dying and being replaced, so at any given time they have a range of ages in your body. In a sense, your blood tells the history of your glucose level over the last few months. For example, if your levels were not in control three weeks ago, glycated hemoglobin will persist in the blood cells that were active at that time. If your blood sugar tends to go up at night, when you are less likely to self-monitor, your HbA1c test will indicate a higher average level of blood sugar than you found through self-monitoring.

The hemoglobin A1c goal for people with type 2 diabetes is less than 7%. The findings of a major diabetes study, the Diabetes Control and Complications Trial (DCCT), showed that people who keep their hemoglobin A1c levels close to 7% have a much better chance of delaying or preventing complications that affect the eyes, kidneys, and nerves than people with hemoglobin A1c of approximately 9%. The United Kingdom Prospective Diabetes Study (UKPDS), a 20-year study that involved more than 5000 people with type 2 diabetes, showed that intensive blood glucose control significantly reduces the risk of major diabetic eye disease and early kidney damage. The study concluded that complications from diabetes should not be seen as a natural and expected outcome-good management of blood glucose and blood pressure can prevent or delay complications for many people.

You can do a lot to bring down a high blood sugar level and get it under control. Start by asking your healthcare provider for a hemoglobin A1c test. If your hemoglobin A1c test result is too high, talk to your healthcare provider about how to lower it. (A change in treatment is almost always needed if your hemoglobin A1c is over 8%.) Keep the 7% goal in sight, but remember that lowering your hemoglobin A1c levels by any amount improves your chances of staying healthy. To get your blood sugar under control, follow a daily diet plan, stick to a physical activity program, take your prescribed type 2 diabetes medicines, and consult your healthcare provider often.

Screening for Diabetes

American Diabetes Association

Diabetes Care 25:S21-S24, 2002
© 2002 by the American Diabetes Association, Inc.

	INTRODUCTION

 
Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both. Type 2 diabetes, the most prevalent form of the disease, is often asymptomatic in its early stages and can remain undiagnosed for many years.

The chronic hyperglycemia of diabetes is associated with long-term dysfunction, damage, and failure of various organs, especially the eyes, kidneys, nerves, heart, and blood vessels. Individuals with undiagnosed type 2 diabetes are also at significantly higher risk for stroke, coronary heart disease, and peripheral vascular disease than the nondiabetic population. They also have a greater likelihood of having dyslipidemia, hypertension, and obesity. Because early detection and prompt treatment may reduce the burden of diabetes and its complications, screening for diabetes may be appropriate under certain circumstances. This position statement provides recommendations for diabetes screenings performed in physicians’ offices and in other health care settings.

This position statement does not address screening for type 1 diabetes or gestational diabetes mellitus (GDM). Because of the acute onset of symptoms, most cases of type 1 diabetes are detected soon after symptoms develop. Widespread clinical testing of asymptomatic individuals for the presence of autoantibodies related to type 1 diabetes cannot be recommended at this time as a means to identify persons at risk. Reasons for this include the following: 1) cutoff values for some of the immune marker assays have not been completely established in clinical settings; 2) there is no consensus as to what action should be taken when a positive autoantibody test result is obtained; and 3) because the incidence of type 1 diabetes is low, testing of healthy children will identify only a very small number (<0.5%) who at that moment may be "prediabetic." Clinical studies are being conducted to test various methods of preventing type 1 diabetes in high-risk individuals (e.g., siblings of type 1 diabetic patients). These studies may uncover an effective means of preventing type 1 diabetes, in which case targeted screening may be appropriate in the future.

For information on screening for GDM, refer to the American Diabetes Association’s position statement "Gestational Diabetes Mellitus."

	DIABETES PREVALENCE AND RISK FACTORS

 
The estimated prevalence of diabetes among adults was 7.4% in 1995; this is expected to rise to 9% in 2025. However, specific population subgroups have a much higher prevalence of the disease than the population as a whole. These subgroups have certain attributes or risk factors that either directly cause diabetes or are associated with it.

The correlation of a risk factor(s) with development of diabetes is never 100%. However, the greater the number of risk factors present in an individual, the greater the chance of that individual developing or having diabetes. Conversely, the chance of an asymptomatic individual without any risk factors having or developing diabetes is relatively low.

The risk of developing type 2 diabetes increases with age, obesity, and lack of physical activity. Type 2 diabetes is more common in individuals with a family history of the disease and in members of certain racial/ethnic groups. It occurs more frequently in women with prior GDM or polycystic ovary syndrome and in individuals with hypertension, dyslipidemia, impaired glucose tolerance (IGT), or impaired fasting glucose (IFG).

	PRINCIPLES TO ASSESS THE VALUE OF SCREENING FOR TYPE 2 DIABETES

 
There is a major distinction between diagnostic testing and screening. When an individual exhibits symptoms or signs of the disease, diagnostic tests are performed, and such tests do not represent screening. The purpose of screening is to identify asymptomatic individuals who are likely to have diabetes. Separate diagnostic tests using standard criteria are required after positive screening tests to establish a definitive diagnosis.

Generally, screening in asymptomatic populations is appropriate when seven conditions are met: 1) the disease represents an important health problem that imposes a significant burden on the population; 2) the natural history of the disease is understood; 3) there is a recognizable preclinical (asymptomatic) stage during which the disease can be diagnosed; 4) tests are available that can detect the preclinical stage of the disease, and the tests are acceptable and reliable; 5) treatment after early detection yields benefits superior to those obtained when treatment is delayed; 6) the costs of case finding and treatment are reasonable and are balanced in relation to health expenditures as a whole, and facilities and resources are available to treat newly diagnosed cases; and 7) screening will be a systematic ongoing process and not merely an isolated one-time effort.

For diabetes, conditions 1–4 are met. Conditions 5–7 have not been met entirely because there are no randomized clinical trials documenting the effectiveness of screening programs in decreasing mortality and morbidity from diabetes, and some controversy exists regarding the cost-effectiveness of screening and whether screening as currently carried out is a systematic and ongoing process.

Randomized clinical trials would be the best means to evaluate the benefits and risks of diabetes screening and early treatment. However, rigorous studies that apply currently available treatments to a screened group but not to a control group have not been done and are unlikely to be performed soon because of feasibility, ethical concerns, and costs. Thus, while it is well established that treating diabetes diagnosed through standard clinical practice is effective in reducing diabetic microvascular complications, it is unknown whether the additional years of treatment that might be received by individuals diagnosed through screening would result in clinically important improvements in diabetes-related outcomes. A large clinical trial, the Diabetes Prevention Program (DPP), is underway in the U.S. It is designed to answer the question of whether treatment with lifestyle interventions or metformin for patients with IGT or IFG detected through a screening program will reduce the incidence of type 2 diabetes. If the DPP demonstrates a reduction in the incidence of type 2 diabetes as a result of one or more of the interventions, then more widespread screening for these conditions, which would incidentally detect many cases of asymptomatic diabetes, may be justified.

The effectiveness of screening may also depend on the setting in which it is performed. In general, community screening outside a health care setting may be less effective because of the failure of people with a positive screening test to seek and obtain appropriate follow-up testing and care or, conversely, to ensure appropriate repeat testing for individuals who screen negative. That is, screening outside of clinical settings may yield abnormal tests that are never discussed with a primary care provider, low compliance with treatment recommendations, and a very uncertain impact on long-term health. Community screening may also be poorly targeted, i.e., it may fail to reach the groups most at risk and inappropriately test those at low risk (the worried well) or even those already diagnosed.

	General Recommendations for the Evaluation of High-Risk Individuals

 
Based on the lack of data from prospective studies on the benefits of screening and the relatively low cost-effectiveness of screening suggested by existing studies, the decision to test for diabetes should ultimately be based on clinical judgment and patient preference.

On the basis of expert opinion, evaluation of the general population should be considered by their health care provider at 3-year intervals beginning at age 45. The rationale for this interval is that false negatives will be repeated before substantial time elapses, and there is little likelihood of an individual developing any of the complications of diabetes to a significant degree within 3 years of a negative screening test result. Testing should be considered at a younger age or be carried out more frequently in individuals with one or more of the risk factors shown in Table 1.

Table 1— Major risk factors for type 2 diabetes

Family history of diabetes (i.e., parents or siblings with diabetes) Overweight (BMI 25 kg/m2) Habitual physical inactivity Race/ethnicity (e.g., African-Americans, Hispanic-Americans, Native Americans, Asian-Americans, and Pacific Islanders) Previously identified IFG or IGT Hypertension (140/90 mmHg in adults) HDL cholesterol 35 mg/dl (0.90 mmol/l) and/or a triglyceride level 250 mg/dl (2.82 mmol/l) History of GDM or delivery of a baby weighing >9 lbs Polycystic ovary syndrome

 
Patients presenting to health care providers with symptoms of marked hyperglycemia, including polyuria, polydipsia, weight loss (sometimes with polyphagia) and blurred vision, should receive diagnostic testing for diabetes, as should those with potential complications of diabetes or with any other clinical presentation in which diabetes is included in the differential diagnosis. Such diagnostic testing, however, does not constitute screening.

The incidence of type 2 diabetes in children and adolescents has been shown to be increasing. Consistent with screening recommendations for adults, only children and youth at substantial risk for the presence or the development of type 2 diabetes should be tested. Although there are insufficient data to make definite recommendations, the American Diabetes Association consensus statement titled "Type 2 Diabetes in Children and Adolescents" recommends that overweight (defined as BMI >85th percentile for age and sex, weight for height >85th percentile, or weight >120% of ideal [50th percentile] for height) youths with any two of the risk factors listed below be screened. Testing should be done every 2 years starting at age 10 years or at the onset of puberty if it occurs at a younger age. Testing may be considered in other high-risk patients who display any of the following characteristics:

• Have a family history of type 2 diabetes in first- and second-degree relatives;
   
• Belong to a certain race/ethnic group (Native Americans, African-Americans, Hispanic Americans, Asians/South Pacific Islanders);
   
• Have signs of insulin resistance or conditions associated with insulin resistance (acanthosis nigricans, hypertension, dyslipidemia, polycystic ovary syndrome).
   

	TESTS

 
The best screening test for diabetes, the fasting plasma glucose (FPG), is also a component of diagnostic testing. The FPG test and the 75-g oral glucose tolerance test (OGTT) are both suitable tests for diabetes; however, the FPG test is preferred in clinical settings because it is easier and faster to perform, more convenient and acceptable to patients, and less expensive. An FPG 126 mg/dl (7.0 mmol/l) is an indication for retesting, which should be repeated on a different day to confirm a diagnosis. If the FPG is <126 mg/dl (7.0 mmol/l) and there is a high suspicion for diabetes, an OGTT should be performed. A 2-h postload value in the OGTT 200 mg/dl (11.1 mmol/l) is a positive test for diabetes and should be confirmed on an alternate day. Table 2 presents the diagnostic criteria for diabetes. Fasting is defined as no consumption of food or beverage other than water for at least 8 h before testing.

Table 2— Criteria for the diagnosis of diabetes

Normoglycemia IFG or IGT Diabetes* FPG <110 mg/dl FPG 110 and <126 mg/dl (IFG) FPG 126 mg/dl 2-h PG <140 mg/dl 2-h PG 140 and <200 mg/dl (IGT) 2-h PG 200 mg/dl     Symptoms of diabetes and casual plasma glucose concentration 200 mg/dl

^* A diagnosis of diabetes must be confirmed, on a subsequent day, by measurement of FPG, 2-h PG, or random plasma glucose (if symptoms are present). The FPG test is greatly preferred because of ease of administration, convenience, acceptability to patients, and lower cost. Fasting is defined as no caloric intake for at least 8 h.

This test requires the use of a glucose load containing the equivalent of 75 g anhydrous glucose dissolved in water. 2-h PG, 2-h postload glucose.

 
Nondiabetic individuals with an FPG 110 mg/dl (6.1 mmol/l) but <126 mg/dl (7.0 mmol/l) are considered to have IFG, and those with 2-h values in the OGTT 140 mg/dl (7.8 mmol/l) but <200 mg/dl (11.1 mmol/l) are defined as having IGT. Both IFG and IGT are risk factors for future diabetes. Normoglycemia is defined as plasma glucose levels <110 mg/dl (6.1 mmol/l) in the FPG test and a 2-h postload value <140 mg/dl (7.8 mmol/l) in the OGTT.

If necessary, plasma glucose testing may be performed on individuals who have taken food or drink shortly before testing. Such tests are referred to as casual plasma glucose measurements and are given without regard to time of last meal. A casual plasma glucose level 200 mg/dl (11.1 mmol/l) with symptoms of diabetes is considered diagnostic of diabetes. A confirmatory FPG test or OGTT should be completed on a different day if the clinical condition of the patient permits.

Laboratory measurement of plasma glucose concentration is performed on venous samples with enzymatic assay techniques, and the above-mentioned values are based on the use of such methods. The A1C test values remain a valuable tool for monitoring glycemia, but it is not currently recommended for the screening or diagnosis of diabetes. Pencil and paper tests, such as the American Diabetes Association’s risk test, may be useful for educational purposes but do not perform well as stand-alone tests. Capillary blood glucose testing using a reflectance blood glucose meter has also been used but because of the imprecision of this method, it is better used for self-monitoring rather than as a screening tool.

	OTHER CONSIDERATIONS

 
In screening for disease, it is crucial that an interpretation of the screening test results be provided to the patient and that follow-up evaluation and treatment are made available. Also, it is important to consider that certain drugs, including glucocorticoids and nicotinic acid, may produce hyperglycemia.

	COMMUNITY SCREENING

 
Although there is ample scientific evidence showing that certain risk factors predispose individuals to development of diabetes, there is insufficient evidence to conclude that community screening is a cost-effective approach to reduce the morbidity and mortality associated with diabetes in presumably healthy individuals. While community screening programs may provide a means to enhance public awareness of the seriousness of diabetes and its complications, other less costly approaches may be more appropriate, particularly because the potential risks are poorly defined. Thus, based on the lack of scientific evidence, community screening for diabetes, even in high-risk populations, is not recommended.

	CONCLUSION

 
Diabetes is frequently not diagnosed until complications appear, and approximately one-third of all people with diabetes may be undiagnosed. Although the burden of diabetes is well known, the natural history is well characterized, and there is good evidence for benefit from treating cases diagnosed through usual clinical care, there are no randomized trials demonstrating the benefits of early diagnosis through screening of asymptomatic individuals. Nevertheless, there is sufficient indirect evidence to justify opportunistic screening in a clinical setting of individuals at high risk. Also, clinicians should be vigilant in evaluating clinical presentations suggestive of diabetes.

A summary of screening recommendations is included in Table 3. 

Table 3— Summary of major recommendations

Recommendations Evidence grading* Evaluation for type 2 diabetes should be performed within the health care setting. Patients should be screened at 3-year intervals beginning at age 45; testing should be considered at an earlier age or be carried out more frequently if diabetes risk factors are present. E Diabetes risk factors include a family history of diabetes; overweight defined as BMI 25 kg/m2; habitual physical inactivity; belonging to a high-risk ethnic or racial group; previously identified IFG or IGT; hypertension; dyslipidemia; history of GDM or delivery of a baby weighing >9 lbs; and polycystic ovary syndrome. B The FPG is the recommended screening test. The OGTT may be necessary for the diagnosis of diabetes when the FPG is normal. The FPG is preferred for screenings because it is faster and easier to perform, more convenient, acceptable to patients, and less expensive. C Diagnostic testing should be performed in any clinical situation in which such testing is warranted; health care providers should not consider whether a person meets screening criteria in such cases. E Screening outside of health care settings, or community screening, has not been shown to be beneficial and may result in some harm; this type of screening is not recommended. E

^* Scientific evidence was ranked based on the American Diabetes Association’s grading system. The highest ranking (A) was assigned when there is supportive evidence from well-conducted generalizable randomized controlled trials that are adequately powered, including evidence from a meta-analysis that incorporated quality ratings in the analysis. An intermediate ranking (B) was given to supportive evidence from well-conducted cohort studies, registries, or case-control studies. A lower rank (C) was assigned to evidence from uncontrolled or poorly controlled studies or when there is conflicting evidence with the weight of the evidence supporting the recommendation. Expert consensus (E) is indicated, as appropriate. For a detailed description of this grading system, refer to Diabetes Care 25 (Suppl. 1):S1, 2002.

	Footnotes

 
The recommendations in this paper are based on the evidence reviewed in the following publication: Screening for type 2 diabetes (Technical Review). Diabetes Care 23:1563–1580, 2000.

The paper was peer-reviewed, modified, and approved by the Professional Practice Committee and the Executive Committee, October 2000.

Abbreviations: DPP, Diabetes Prevention Program; FPG, fasting plasma glucose; GDM, gestational diabetes mellitus; IFG, impaired fasting glucose; IGT, impaired glucose tolerance; OGTT, oral glucose tolerance test.

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