Welcome to SS Diabetes Care Sites

In 1997 and 2003, The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus recognized an intermediate group of individuals whose glucose levels, although not meeting criteria for diabetes, are nevertheless too high to be considered normal. This group was defined as having impaired fasting glucose (IFG) (FPG levels of 100 mg/dl [5.6 mmol/l] to 125 mg/dl [6.9 mmol/l]) or impaired glucose tolerance (IGT) (2-h OGTT values of 140 mg/dl [7.8 mmol/l] to 199 mg/dl [11.0 mmol/l]). Individuals with IFG and/or IGT have been referred to as having pre-diabetes, indicating the relatively high risk for the future development of diabetes. IFG and IGT should not be viewed as clinical entities in their own right but rather risk factors for diabetes as well as cardiovascular disease (CVD). IFG and IGT are associated with obesity (especially abdominal or visceral obesity), dyslipidemia with high triglycerides and/or low HDL cholesterol, and hypertension.

Structured lifestyle intervention, aimed at increasing physical activity and producing 5–10% loss of body weight, and certain pharmacological agents have been demonstrated to prevent or delay the development of diabetes in people with IGT. It should be noted that the 2003 ADA Expert Committee report reduced the lower FPG cut point to define IFG from 110 mg/dl (6.1 mmol/l) to 100 mg/dl (5.6 mmol/l), in part to make the prevalence of IFG more similar to that of IGT. However, the World Health Organization (WHO) and many other diabetes organizations did not adopt this change.

As the A1C becomes increasingly used to diagnose diabetes in individuals with risk factors, it will also identify those at high risk for developing diabetes in the future. As was the case with the glucose measures, defining a lower limit of an intermediate category of A1C is somewhat arbitrary, since risk of diabetes with any measure or surrogate of glycemia is a continuum extending well into the normal ranges. To maximize equity and efficiency of preventive interventions, such an A1C cut point, should balance the costs of false negatives (failing to identify those who are going to develop diabetes) against the costs of false positives (falsely identifying and then spending intervention resources on those who were not going to develop diabetes anyway).

Linear regression analyses of nationally representative U.S. data (NHANES 2005–2006) indicate that among the nondiabetic adult population, an FPG of 110 mg/dl corresponds to an A1C of 5.6%, while an FPG of 100 mg/dl corresponds to an A1C of 5.4%. Receiver operating curve analyses of these data indicate that an A1C value of 5.7%, compared with other cut points, has the best combination of sensitivity (39%) and specificity (91%) to identify cases of IFG (FPG 100 mg/dl [5.6 mmol/l]) (R.T. Ackerman, Personal Communication).

Other analyses suggest that an A1C of 5.7% is associated with diabetes risk similar to that of the high-risk participants in the Diabetes Prevention Program (DPP) (R.T. Ackerman, personal communication).

Hence, it is reasonable to consider an A1C range of 5.7–6.4% as identifying individuals with high risk for future diabetes and to whom the term pre-diabetes may be applied.

As is the case for individuals found to have IFG and IGT, individuals with an A1C of 5.7–6.4% should be informed of their increased risk for diabetes as well as CVD and counseled about effective strategies to lower their risks.

As with glucose measurements, the continuum of risk is curvilinear, so that as A1C rises, the risk of diabetes rises disproportionately. Accordingly, interventions should be most intensive and follow-up should be particularly vigilant for those with an A1C 6.0%, who should be considered to be at very high risk. However, just as an individual with a fasting glucose of 98 mg/dl (5.4 mmol/l) may not be at negligible risk for diabetes, individuals with an A1C5.7% may still be at risk, depending on the level of A1C and presence of other risk factors, such as obesity and family history.

Table —Criteria for the diagnosis of diabetes

1. A1C 6.5%. The test should be performed in a laboratory using a method that is NGSP certified and standardized to the DCCT assay.*

2. FPG 126 mg/dl (7.0 mmol/l). Fasting is defined as no caloric intake for at least 8 h.*

3. Two-hour plasma glucose 200 mg/dl (11.1 mmol/l) during an OGTT. The test should be performed as described by the World Health Organization, using a glucose load containing the equivalent of 75 g anhydrous glucose dissolved in water.*

4. In a patient with classic symptoms of hyperglycemia or hyperglycemic crisis, a random plasma glucose 200 mg/dl (11.1 mmol/l). *In the absence of unequivocal hyperglycemia, criteria 1–3 should be confirmed by repeat testing.

Table —Categories of increased risk for diabetes*

FPG 100–125 mg/dl (5.6–6.9 mmol/l)

IFG 2-h PG on the 75-g OGTT 140–199 mg/dl (7.8–11.0 mmol/l) IGT

A1C 5.7–6.4% *For all three tests, risk is continuous, extending below the lower limit of the range and becoming disproportionately greater at higher ends of the range.

SS Diabetes Care - News