Diagnosing And Managing Diabetes- Screening for Diabetes

Recommendations

* Screening to detect pre-diabetes (IFG or IGT) and diabetes should be considered in individuals 45 years of age, particularly in those with a BMI 25 kg/m2. Screening should also be considered for people who are <45 years of age and are overweight if they have another risk factor for diabetes (Table 3). Repeat testing should be carried out at 3-year intervals. (E)
* Screen for pre-diabetes and diabetes in high-risk, asymptomatic, undiagnosed adults and children within the health care setting. (E)
* To screen for diabetes/pre-diabetes, either an FPG test or 2-h OGTT (75-g glucose load) or both are appropriate. (B)
* An OGTT may be considered in patients with IFG to better define the risk of diabetes. (E)

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Table 3?? Criteria for testing for diabetes in asymptomatic adult individuals
1. Testing for diabetes should be considered in all individuals at age 45 years and above, particularly in those with a BMI 25 kg/m2*, and, if normal, should be repeated at 3-year intervals.

2. Testing should be considered at a younger age or be carried out more frequently in individuals who are overweight (BMI 25 kg/m2*) and have additional risk factors:
??? are habitually physically inactive
??? have a first-degree relative with diabetes
??? are members of a high-risk ethnic population (e.g., African American, Latino, Native American, Asian American, Pacific Islander)
??? have delivered a baby weighing >9 lb or have been diagnosed with GDM
??? are hypertensive ( 140/90 mmHg)
??? have an HDL cholesterol level <35 mg/dl (0.90 mmol/l) and/or a triglyceride level >250 mg/dl (2.82 mmol/l)
??? have PCOS
??? on previous testing, had IGT or IFG
??? have other clinical conditions associated with insulin resistance (e.g. PCOS or acanthosis nigricans)
??? have a history of vascular disease

* May not be correct for all ethnic groups. PCOS, polycystic ovary syndrome.

There is a major distinction between diagnostic testing and screening. Both utilize the same clinical tests, which should be done within the context of the health care setting. 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 or pre-diabetes. Separate diagnostic tests using standard criteria are required after positive screening tests to establish a definitive diagnosis as described above.

Type 1 diabetes

Generally, people with type 1 diabetes present with acute symptoms of diabetes and markedly elevated blood glucose levels. 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 individuals 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 "pre-diabetic." 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.

Type 2 diabetes

Type 2 diabetes is frequently not diagnosed until complications appear, and approximately one-third of all people with diabetes may be undiagnosed. Individuals at high risk should be screened for diabetes and pre-diabetes. Criteria for testing for diabetes in asymptomatic, undiagnosed adults are listed in Table 3. The effectiveness of early diagnosis through screening of asymptomatic individuals has not been determined.

Screening should be carried out within the health care setting. Either an FPG test or 2-h OGTT (75-g glucose load) is appropriate. The 2-h OGTT identifies people with IGT, and thus, more people who are at increased risk for the development of diabetes and CVD. It should be noted that the two tests do not necessarily detect the same individuals. It is important to recognize that although the efficacy of interventions for primary prevention of type 2 diabetes have been demonstrated among individuals with IGT, such data among individuals with IFG (who do not also have IGT) are not available. The FPG test is more convenient to patients, more reproducible, less costly, and easier to administer than the 2-h OGTT. Therefore, the recommended initial screening test for nonpregnant adults is the FPG. An OGTT may be considered in patients with IFG to better define the risk of diabetes. The incidence of type 2 diabetes in children and adolescents has increased dramatically in the last decade. Consistent with screening recommendations for adults, only children and youth at increased risk for the presence or the development of type 2 diabetes should be tested (Table 4).

Table 4?? Testing for type 2 diabetes in children

Criteria:

* Overweight (BMI >85th percentile for age and sex, weight for height >85th percentile, or weight >120% of ideal for height)

Plus any two of the following risk factors:

* Family history of type 2 diabetes in first- or second-degree relative
* Race/ethnicity (Native American, African American, Latino, Asian American, Pacific Islander)
* Signs of insulin resistance or conditions associated with insulin resistance (acanthosis nigricans, hypertension, dyslipidemia, or PCOS)
* Maternal history of diabetes or GDM

Age of initiation: age 10 years or at onset of puberty, if puberty occurs at a younger age
Frequency: every 2 years
Test: FPG preferred

Clinical judgment should be used to test for diabetes in high-risk patients who do not meet these criteria. PCOS, polycystic ovary syndrome.

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.

On the basis of expert opinion, screening should be considered by health care providers at 3-year intervals beginning at age 45, particularly in those with BMI 25 kg/m2. 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 who are overweight and have one or more of the other risk factors for type 2 diabetes.

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AMERICAN DIABETES ASSOCIATION
DIABETES CARE, VOLUME 27, SUPPLEMENT 1, JANUARY 2004

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May 27, 10 • Diabetes mellitus