The new direction in diabetes diagnosis: the latest research offers more information on the prevention and management of diabetes mellitus. (Review of Systems, Part IV).

As primary-care doctors, we have an ever growing role in managing our patients' overall health. This is especially apparent in our patients with diabetes mellitus. This disease affects not just the eyes but almost every system in the body.

The prevalence of diabetes continues to grow--approximately 17 million people, or 6% of the U.S. population, have the disease today, the American Diabetes Association (ADA) reports. Direct and indirect costs totaled $132 billion in 2002, up 35% from five years earlier. (1)

Fortunately, our knowledge about the disease continues to grow as well. New research can help us more clearly identify which patients are at risk, which type of diabetes they have, and how we might delay the onset of the disease or perhaps even prevent it altogether.

We must work alongside other health-care professionals to educate these patients about how they can prevent the onset of diabetes, or at least minimize its sequelae. This fourth and final installment of the series "Review of Systems" looks at how we can take the latest thinking on diabetes mellitus and translate that into advice we can offer our patients.

What is Diabetes?

Diabetes mellitus (DM) is a group of metabolic diseases. It is characterized by hyperglycemia that results from defects in insulin secretion, insulin action or both. (2) The ADA defines DM as any of the following:

* A fasting plasma glucose of 126mg/dl or higher.

* A nonfasting plasma glucose 200mg/dl or higher.

* An oral glucose tolerance test of 200mg/dI or higher in the two-hour sample.

Additionally, the ADA defines a fasting blood sugar level of 1 10mg/dl as the upper limit of normal for glucose. Patients with a fasting glucose level of 110-126mg/dl or an oral glucose test of 110-200mg/dl are also classified as having impaired glucose tolerance (IGT). (3) We consider patients to have IGT when they respond abnormally to the oral glucose tolerance test but do not meet the criteria required to diagnose DM.

New Classifications

Traditionally, we classified DM as type 1 insulin-dependent (IDDM) and type 2 non-insulin dependent (NIDDM). We also referred to type 1 and type 2 diabetes as juvenile-onset and adult-onset diabetes, respectively.

Although we still use the terms type 1 and type 2 diabetes, we have eliminated the IDDM and NIDDM classifications, and added new categories. (2) Today, we have these four categories:

* Prediabetes. This newer classification includes all individuals with IGT. They are likely to develop diabetes within a decade of initial evaluation. These individuals also are at increased risk for cardiovascular disease, including myocardial infarction and stroke. (4, 5)

Obesity itself causes some degree of insulin resistance. The Centers for Disease Control and Prevention (CDC) defines obesity as an excessively high amount of body fat in relation to body mass. Individuals with a body mass index (BMI) of 30kg/[m.sup.2] or more are considered obese. The CDC classifies individuals with increased body weight in relation to height and a BMI of 25-29kg/[m.sup.2] as overweight. (For more on obesity, see "Obesity: Alarming Statistics," page 60.)

To help identify prediabetic patients sooner and initiate timely intervention, physicians should give fasting glucose or oral glucose tolerance tests to patients at high risk of developing diabetes. …