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Joslin’s Diabetes Deskbook, 2nd Updated Edition, Excerpt #7: What Is the Best Test to Screen for Pre-Diabetes?

Jun 4, 2012

By Richard S. Beaser, M.D., and Richard Jackson, MD





Can you name 7 symptoms of diabetes besides the classic symptoms of polyuria, polydipsia, and polyphagia as well as weight loss?….



A patient suspected of having diabetes can be screened using the fasting plasma glucose test or an OGTT following a 75-gram glucose load (see Table 2-2). The ADA recommends using the fasting plasma glucose test because of its simplicity. A glucose value of >126 mg/dl after an 8-hour fast is diagnostic for diabetes if it can be confirmed by a similarly elevated value on a different day. The conditions of impaired fasting glucose and impaired glucose tolerance are classified as "Pre-Diabetes" and are considered risk factors for future diabetes and for cardiovascular disease. As described above, the A1C is an ideal test for this type of screening since it doesn’t need to be done when the patient is fasting….

The benefits of community screening have also been debated for some time, with many arguing against the cost-effectiveness of this practice. In its position statement on Screening for Type 2 Diabetes, the ADA states that 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." (ADA Position Statement; Diabetes Care 27 (Suppl 1):S13, 2004)

Nevertheless, most acknowledge that macrovascular risk, while not as clearly and demonstrably related alone to hyperglycemia, clearly is associated with hyperglycemia, as well as with a number of other related and accompanying conditions such as dyslipidemia, hypertension, and hypercoagulability. Reducing the risk brought on by hyperglycemia as well as by those other metabolic conditions are all important objectives of a comprehensive treatment plan for type 2 diabetes. At the time of this writing, there is an ongoing discussion about refining the criteria for increased risk — the "cardiometabolic syndrome" — and considering other factors such as abdominal adiposity in the consideration of risk stratification. Therefore, identification of people at increased risk for macrovascular disease, who thus may have any of the recognized risk factors present, is as important as diagnosing diabetes itself — which is just one on that list of risks.

Pending any revisions of the recommendations, it is clear that those with high-risk characteristics listed in Table 2-3 should not be ignored just because their fasting glucose is below 100 mg/dl. High-risk characteristics, regardless of glucose metabolic status, should trigger screening for other risk factors such as lipid disorders or hypertension, and antiplatelet therapy should be considered. Certainly, those patients who already have impaired fasting glucose (fasting plasma glucose 100–125 mg/dl), particularly if they have other high-risk characteristics, but even if they do not, should probably be considered for oral glucose tolerance testing to gauge the postprandial glucose pattern, and thus implicitly both the macrovascular risk and the likelihood of progression on to true diabetes.

Symptoms of Diabetes

Diabetes has been referred to as "the great imitator," as it can present with varied symptoms and problems. With significant hyperglycemia, however, the classic symptoms — including the "polys": polyuria (frequent urination), polydipsia (frequent consumption of liquids), and polyphagia (increased consumption of food), as well as weight loss, blurred vision, and fatigue — usually become manifest.Onset of type 1 diabetes is usually more rapid than that of type 2 diabetes. Yet, the rate of beta-cell destruction can vary, tending to be more rapid in infants and children and slower in adults. Ketoacidosis may be present on presentation, particularly in those with rapid onset. However, in the adults, who may have residual beta-cell function for some time, this mode of presentation is much less likely. Extremely slow onset can lead to the mistaken assumption that the patient has type 2 diabetes.

Because type 2 diabetes usually develops more slowly, it may lead to insidious development of barely noticeable symptoms. The fact that one-third of all people who actually have diabetes have not yet been diagnosed is not surprising — these symptoms can often be missed. Therefore, it is important to be aware of signs and symptoms that might suggest underlying diabetes and thus lead to the proper diagnosis. Such symptoms themselves may develop gradually and often go unnoticed for considerable periods of time. Alternatively, with the rapid onset of type 1 diabetes, some signs and symptoms may appear abruptly and rapidly increase in severity. Either way, once symptoms are recognized, testing for the presence of diabetes should be performed and treatment, if the diagnosis is made, should begin.

Other signs and symptoms suggestive of diabetes include:

Skin Symptoms. Diabetes classically has been thought to produce itching of the skin, usually in the genital (especially vaginal) or anal areas. This can cause severe discomfort. Carbuncles, furuncles, and difficulty in healing wounds also may be found. People with untreated diabetes may have very high levels of lipids in the blood, which may cause small, raised bumps on the skin called xanthomas. Usually, such symptoms represent significant elevations of glucose levels that have been present for some time.

Gynecological Problems. Women with diabetes are prone to developing the fungal infections candidasis or moniliasis when their glucose levels are not well-controlled. This may result in pruritis of the vagina, sometimes accompanied by a chronic discharge. Unfortunately, it is not unheard of for a gynecologist to be the first to discover signs of diabetes.

Impotence. Diabetes can lead to erectile dysfunction. While this is a form of diabetic neuropathy that usually occurs after diabetes has been present for some time, undiagnosed, and thus untreated, diabetes can hasten the development of this complication (see Chapter 19).

Testosterone Levels. The association of low testosterone levels in men with type 2 diabetes and/or the metabolic syndrome has also been described recently, and monitoring of testosterone levels may be warranted, with consideration of replacement therapy if indicated based on symptoms and other safety considerations. Testosterone replacement improves glucose values, A1C and other components of the metabolic syndrome.

Neuropathies. The development of diabetic neuropathic symptoms usually occurs after the disease has been present for a long period. However, as seen with impotence, when the diabetes is present but asymptomatic and therefore unrecognized for some time, signs of nerve damage may be the first hint that diabetes is present. Typical presenting symptoms include numbness, burning, tingling, or intense sensitivity in areas of the skin such as the feet and legs. These symptoms are often worse at night, with characteristic nighttime leg cramps being an example. Occasionally, facial nerve palsies may lead to presentation with blurry or double vision that disappears when one eye is closed. This usually disappears by itself in about 4 to 6 weeks. However, diabetes and neuropathy are not the cause of all such symptoms, and, obviously, other causes should be sought if diabetes is not present.

Fatigue. While fatigue may be the earliest and most common symptom of diabetes, it is such a nonspecific symptom that the majority of people with this complaint have developed it due to some other cause — or if it is caused by diabetes, it is frequently misdiagnosed. If the fatigue is due to diabetes, the fatigue usually disappears after treatment, though this might take some time.

Blurred Vision. Complaints of blurred vision are a classic presenting symptom of diabetes. Glucose accumulating in the lens of the eye causes changes in its shape and results in visual disturbances. Reduction and stabilization of glucose levels usually can correct this problem.

However, this process may take 2 to 3 months, and it is recommended that ophthalmologic evaluation for corrective lenses be deferred until after the glucose control has been stabilized. If visual disturbances are really disruptive to the patient’s lifestyle, then changes in corrective lenses during the process of initiating glucose control may be needed, but with the understanding that there may be a number of changes in prescription before the vision stabilizes. If the clinician has a heightened index of suspicion when a patient presents with one of the symptoms described above, and if he or she recognizes the high-risk categories (see Table 2-3), there is an increased likelihood that the proper diagnosis will be made in a timely manner.

Standards of Care

In this era of managed care and disease management, the trend in the medical profession is to develop "standards of care" or "care guidelines." The motivation for preparing these documents varies depending on who is writing them. On one extreme, some focus on cost savings and limiting patients’ access to expensive services, and on the other, some advocate extensive use of services, assuming that this approach will best ensure good health. The best approach is probably somewhere in between. Studies to determine optimal utilization of services, balancing cost against outcome, have been initiated in recent years.

The ADA publishes its standards of care annually in Diabetes Care. Based on these standards, other published data, and our own clinical experiences, the Clinical Oversight Committee of the Joslin Diabetes Center has developed its own Clinical Guidelines for Adults with Diabetes. These Guidelines can be found on Joslin’s web site, www.joslin.org.

Keep in mind that clinical care guidelines are constantly changing based on new knowledge and clinical experience. The decision to publish such guidelines in a book of this nature is a "double-edged sword" in that parts of the recommendations are likely to have been changed long before the rest of the book is out of date. Yet the inclusion of this material provides an outline of what such standards should include. Readers who regularly care for people with diabetes are encouraged to keep abreast of the literature, so that they are aware of modifications in national standards of care that may affect these guidelines.


Copyright © 2010 by Joslin Diabetes Center. All rights reserved. Reprinted with permission. Neither this book nor any part thereof may be reproduced or distributed in any form or by any means without permission in writing from Joslin. Note: Joslin does not endorse products or services.

For Excerpt #1 from the Joslin Diabetes Deskbook, 2nd Ed, in this series, just click here.

For Excerpt #2 from the Joslin Diabetes Deskbook, 2nd Ed, in this series, just click here.

For Excerpt #3 from the Joslin Diabetes Deskbook, 2nd Ed, in this series, just click here.

For Excerpt #4 from the Joslin Diabetes Deskbook, 2nd Ed, in this series, just click here. 

For Excerpt #5 from the Joslin Diabetes Deskbook, 2nd Ed, in this series, just click here. 

For Excerpt #6 from the Joslin Diabetes Deskbook, 2nd Ed, in this series, just click here. 

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Please Note: Reasonable measures have been taken to ensure the accuracy of the information presented herein. However, drug information may change at any time and without notice and all readers are cautioned to consult the manufacturer’s packaging inserts before prescribing medication. Joslin Diabetes Center cannot ensure the safety or efficacy of any product described in this book.

Professionals must use their own professional medical judgment, training and experience and should not rely solely on the information provided in this book to make recommendations to patients with regard to nutrition or exercise or to prescribe medications.

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