At a Glance

Patients do not, typically, show signs or symptoms indicating increased risk for developing diabetes. However, some patients will have impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) that fails to meet the criteria for the diagnosis of diabetes but are still too high to be considered normal. Such patients have been previously referred to as prediabetic and have a significantly greater chance of developing diabetes in the future. The American Diabetes Association (ADA) recommends testing for diabetes in asymptomatic adult patients who are overweight (BMI
≥25 kg/m2) and have additional risk factors:

  • physical inactivity

  • parent or sibling with diabetes

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  • hypertension (>140/90 mmHg) or on therapy for hypertension

  • HDL cholesterol level less than 35 mg/dL (0.90 mmol/L) and/or a triglyceride level greater than 250 mg/dL (2.82 mmol/L)

  • A1C greater than or equal to 5.7%

  • impaired glucose tolerance or impaired fasting glucose on previous testing

  • history of cardiovascular disease

  • severe obesity

  • acanthosis nigricans

  • women diagnosed with gestational diabetes mellitus or who delivered a baby weighing more than 9 pounds

  • women with polycystic ovarian syndrome (PCOS)

  • other clinical conditions associated with insulin resistance

The ADA recommends testing for diabetes in all asymptomatic adult patients beginning at 45 years of age. The ADA also recommends testing for type II diabetes in asymptomatic children who are overweight by the following criteria: BMI great than the 85th percentile for age and sex, weight for height greater than the 85th percentile, or weight greater than 120% of ideal for height. In addition, at least two of the following risk factors should also be present:

  • have a first or second degree relative with type II diabetes

  • are Native American, African American, Latino, Asian American, or Pacific Islander

  • show signs of insulin resistance or conditions associated with insulin resistance (i.e., small-for-gestational-age birth weight, PCOS, hypertension, dyslipidemia, or ascanthosis nigricans)

  • have a maternal history of GDM during the child’s gestation

Testing should only be performed once the child has reached 10 years of age or at puberty if puberty occurs at a younger age.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Patients are classified by the ADA as having impaired fasting glucose when they have a fasting plasma glucose (FPG) level of 100-125 mg/dL (5.6-6.9 mmol/L) or are classified as having IGT when their 2-hour plasma glucose value in the oral glucose tolerance test (OGTT) is 140-199 mg/dL (7.8-11.0 mmol/L). The World Health Organization (WHO), however, has set the cutoff for IFG at 110 mg/dL (6.1 mmol/L). A1C testing can also be used to predict progression to diabetes, using a range of 5.7-6.4% to identify individuals with a high risk for future diabetes.

If laboratory results are normal, it is recommended that testing be repeated every 3 years.

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?

A drop in glucose levels may occur because of the continued metabolism of glucose if the specimen is not taken to the lab and tested immediately, which can lead to inaccurate reporting of blood glucose levels. Mean FPGs tend to be higher in the morning; thus, it is recommended that blood for this test be drawn during this time. In addition, plasma glucose levels, typically, vary day-to-day and can be affected by other factors, such as acute stress.

Additional Issues of Clinical Importance

Interventions, such as lifestyle modification programs and the use of pharmacologic agents, have been successfully used to decrease the rate of onset of diabetes in patients at increased risk for the disease. Patients at increased risk should be encouraged to join support programs targeting weight loss of 7% of body weight. Physical activity should also be increased to a minimum of 150 minutes/week of moderate exercise, such as walking. Although daily regiments of either Metformim, Acarbose, Orlistat, Rosiglitazone, and Vogliobose have been effective in preventing progression to diabetes, the ADA currently only recommends the use of Metformin.

It should be noted that Metformin is significantly less effective than the lifestyle changes noted, except in extremely high risk patients having risk factors for diabetes and/or more severe or progressive hyperglycemia and in patients with a BMI of at least 35 kg/m2.