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On the alert for type 2 diabetes:
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Earn Category I CME credit by reading this article and the associated article and successfully completing the post-test. Successful completion is defined as a cumulative score of at least 70% correct. This material has been reviewed and is approved for 1 hour of clinical Category I (Preapproved) CME credit by the AAPA. The term of approval is for 1 year from the publication date of January 2004. |
Learning objectives
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Disclosure of conflict of interestThe author has indicated no relationships to disclose relating to the content of this article. |
Diabetes mellitus is a family of metabolic disorders caused by a diminished level of insulin production, insulin resistance, or both, producing chronic hyperglycemia that can damage the eyes, kidneys, heart, nerves, and vascular system.1,2 It is the sixth leading cause of death in the United States and is a growing public health burden.
The terms insulin-dependent and non-insulin-dependent diabetes that were formerly used to describe the two primary types of disease have been replaced by a more complex and descriptive nomenclature that reflects a greater understanding of the various etiologies of diabetes. The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus identified four categories of diabetes, which were approved by the American Diabetes Association (ADA) in 1997 and modified in 1999 (see Table 1).3 Type 1 diabetes denotes disease caused by pancreatic islet ß-cell destruction that renders patients prone to ketoacidosis and includes diabetes caused by an autoimmune process and diabetes of unknown etiology. Patients with type 2 diabetes may be predominantly insulin resistant with a relative insulin deficiency or have a predominant secretory defect with insulin resistance.
TABLE 1
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Type 1 diabetes Drug or chemical induced Endocrinopathies Genetic defects in insulin action Genetic defects of ß-cell function Infection Other genetic syndromes sometimes associated with diabetes Uncommon forms of immune-mediated diabetes |
| Source: American Diabetes Association.3 |
The Expert Panel identified two additional categories of diabetes—gestational diabetes mellitus and other specific types. This article and the article that follows focus on the diagnosis and management of type 2 diabetes.
Patients with type 2 diabetes have insulin resistance and have—at least initially—a relative insulin deficiency. They do not have an autoimmune disorder that destroys ß-cells and have none of the disorders causing hyperglycemia listed in the "Other specific types" classification shown in Table 1. Patients with type 2 diabetes are typically older and overweight.2,3 More than half of patients are older than 65 years at the time of diagnosis, and the diagnosis is made 13 times more often in patients between the ages of 65 and 74 years than in patients younger than 45 years.4 Recent data reveal that diabetes is a growing problem among adolescents and children older than 10 years in the United States, especially as obesity becomes more prevalent in children.5 Excess weight likely adds to insulin resistance, and even those patients who are not overweight often carry excess weight around the abdomen. Patients who have type 2 diabetes seldom experience the spontaneous ketoacidosis seen in type 1 diabetes, but when ketoacidosis does occur it is usually caused by the stress of a comorbidity.1,3
Type 2 diabetes often goes undiagnosed for many years because of the insidious onset of the hyperglycemia. Elevated blood glucose levels quietly cause damage over the prolonged period before the diagnosis is made, placing the patient at risk of microvascular and macrovascular complications later in life.
Insulin levels in type 2 diabetes can be normal or elevated. The elevated blood glucose levels seen in these patients, however, indicate that insulin secretion is inadequate to meet rising insulin resistance. Insulin resistance can be treated, and the condition may improve with exercise, weight loss, and pharmacotherapy. However, insulin secretion seldom returns to normal functioning.
The risk factors for type 2 diabetes include a family history of the disease, age greater than 45 years, body mass index (BMI) greater than 25, previously identified impaired fasting glucose (IFG) or impaired glucose tolerance (IGT), physical inactivity, and a history of gestational diabetes mellitus. Certain ethnic groups, including African-Americans, Hispanic Americans, Native Americans, Asian Americans, or Pacific Islanders, are also at increased risk. Furthermore, hypertension and dyslipidemia are frequently seen in patients who have type 2 diabetes.
Nearly half of older adults have metabolic syndrome (also known as insulin resistance syndrome), a condition that is associated with dyslipidemia, particularly high LDL and low HDL cholesterol and increased triglyceride and apolipoprotein levels. Hypertension, insulin resistance, glucose intolerance, hyperglycemia, and visceral or truncal adiposity are also found in metabolic syndrome, which puts the patient at increased risk for cardiovascular disease and increased mortality from both cardiovascular disease and other causes. Most patients who have type 2 diabetes have metabolic syndrome.6-8 Although a genetic component seems likely, both the ADA and the Expert Committee note that the genetic involvement for this disease is complex and not clearly defined.3
An estimated 29% of diabetes cases are undiagnosed.4 The progression of this disease is insidious, so early diagnosis and treatment are important to minimize the damage that can occur before the patient notices symptoms. Microvascular changes can be detected in the retina of an affected patient up to 7 years before the disease is diagnosed.7
The ADA-recommended screening criteria for asymptomatic patients are shown in Table 2. Because of the significant increase in the incidence of type 2 diabetes in persons aged 45 years and older, testing is indicated in that group. Recent data from the CDC showed that diabetes had been diagnosed in 9.1% of persons between 45 and 59 years of age and in 19.2% of those older than 60 years.9
TABLE 2
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Consider screening for diabetes every 3 y in all patients >45
y and in younger patients who |
| Key: BMI, body mass index; IFG, impaired fasting glucose; IGT, impaired glucose tolerance. |
| Source: American Diabetes Association.3 |
Patients who have a normal test result should be retested every 3 years because any microvascular changes that may have occurred in a patient who has developed type 2 diabetes in the interim will be minimal. Younger patients at risk for developing the disease should be tested.1,3 In addition, any patient who has unexplained weight loss, polyuria, polydipsia, polyphagia, blurred vision, or any signs or symptoms of complications of hyperglycemia should be tested for diabetes.1,3
The ADA recommends the fasting plasma glucose (FPG) test as the most cost-effective screening tool for diabetes (fasting is defined as no caloric intake for at least 8 hours before the test). The 75-g oral glucose tolerance test is also an acceptable diagnostic test for diabetes, but the FPG test is easier for the patient, less expensive, and equally effective. Although capillary blood glucose testing is useful in self-monitoring of treatment regimens, variability among units and imprecision make it inappropriate as a diagnostic tool. Glycosylated hemoglobin A1C testing is useful for monitoring glycemia and treatment regimens but should not be used in screening or to make the initial diagnosis of diabetes.1,3
Normoglycemia is defined as an FPG level of less than 110 mg/dL or a 2-hour postload glucose (2-h PG) challenge (75 of anhydrous glucose) less than 140 mg/dL (see Table 3).1,3 Results higher than the normal limit should be confirmed on a subsequent day. A diagnosis of diabetes is given if, on a subsequent day, the FPG level is 126 mg/dL or higher or the 2-h PG level is 200 mg/dL or higher. (FPG between 110 and 126 mg/dL on the subsequent test results in a diagnosis of IFG.) Polyuria, polyphagia, unexplained weight loss, blurred vision, and a casual plasma glucose concentration higher than 200 mg/dL on the day of initial test are diagnostic of diabetes. If the clinical picture indicates, an asymptomatic patient whose casual plasma glucose level is greater than 200 mg/dL should return on a subsequent day for the more definitive FPG or 2-h PG testing.3
TABLE 3
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| Normoglycemia FPG <110 mg/dL OR 2-h PG <140 mg/dL Impaired fasting glucose FPG 110-125 mg/dL Impaired glucose tolerance 2-h PG 140-199 mg/dL Diabetes Symptoms of diabetes and a casual plasma glucose concentration >200 mg/dL OR FPG >126 mg/dL OR 2-h PG >200 mg/dL |
| Key: FPG, fasting plasma glucose; 2-h PG, 2-hour postload glucose. |
| Source: American Diabetes Association.3 |
FPG levels between 110 mg/dL and 126 mg/dL on a subsequent day suggest IFG, and 2-h PG levels between 140 mg/dL and 200 mg/dL suggest IGT. Both of these conditions are risk factors for diabetes, and patients who have one of these diagnoses require more frequent follow-up, preferably annually, as well as care (eg, weight and nutrition counseling, increased exercise, and treatment for hypertension and dyslipidemia if indicated) than those with normoglycemia.1,3
Estimates are that 8 million Americans have undetected type 2 diabetes, with quiet microvascular damage that can be ongoing for years before a diagnosis is made. Early diagnosis and treatment can decrease the morbidity and burden of this growing public health problem.
REFERENCES
1. American Diabetes Association. Standards of medical care for patients with diabetes mellitus. Diabetes Care. 2002;25(suppl 1):S5-S20.
2. World Health Organization. Definition, diagnosis and classification of diabetes mellitus and its complications [Report of a WHO consultation]. Geneva, Switzerland: WHO; 1999:1-37.
3. American Diabetes Association. Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care. 2002;25(suppl 1):S7.
4. Centers for Disease Control and Prevention. Prevalence of diagnosed diabetes by age, United States, 1980-2000. Available at: http://www.cdc.gov/diabetes/statistics/prev/national/fig3.htm . Accessed November 21, 2003.
5. American Diabetes Association. Consensus statement: Type 2 diabetes in children and adolescents. Diabetes Care. 2000;23:381-389.
6. Bloomgarden ZT. Obesity, hypertension, and insulin resistance. Diabetes Care. 2002;25:2088-2097.
7. Lorenzo C, Haffner SM, Okoloise M, et al. The metabolic syndrome as predictor of Type 2 diabetes. Diabetes Care. 2003;26:3153-3159.
8. Ford ES, Giles WH. A comparison of the prevalence of the metabolic syndrome using two proposed definitions. Diabetes Care. 2003;26:575-581.
9. Centers for Disease Control and Prevention. Prevalence of diabetes and impaired fasting glucose in adults—United States, 1999-2000. MMWR Morb Mortal Wkly Rep. 2003;52:833-837.
Fred Friel. On the alert for type 2 diabetes: When to screen for this quiet, deadly disease. JAAPA January 2004;17:19-24.
Copyright © 2004, Advanstar/Medical Economics Healthcare Communications at Montvale, NJ 07645-1742. All rights reserved.
