Building Competency in Diabetes Education THE ESSENTIALS

3-28 | CHAPTER 3

• Better predictor of macrovascular disease than FPG or 2hPG in a 75 g OGTT

• Not for diagnostic use in children, adolescents, pregnant women or those with suspected type 1 diabetes

• Low day-to-day variability • Reflects long-term glucose concentration

2hPG = 2-hour plasma glucose; A1C = glycated hemoglobin; FPG = fasting plasma glucose; OGTT = oral glucose tolerance test Reprinted from Diabetes Canada 2018 Clinical Practice Guidelines (1)

Prediabetes The diagnosis of prediabetes includes IFG, IGT or an A1C of 6.0% to 6.4%; the

recommendations were established because the evidence suggests that, at these values, individuals are at risk for the complications of diabetes, including CVD (1). While some individuals who are diagnosed with IFG or IGT may not progress to diabetes, if they have metabolic syndrome, as well, then they will be at risk for CVD and early intervention would be beneficial. Diabetes Canada differs from the American Diabetes Association (ADA) in the values assigned to define prediabetes (see Table 7 below for the differences). The TOPICS 4 study showed that a FPG of 6.1-6.9 mmol/L and an A1C level between 6.0% and 6.4% predicted a 100% conversion to type 2 diabetes in five years (26).

Table 7. Diagnosis of prediabetes (1) Test Diabetes Canada

Prediabetes category

ADA

FPG mmol/L

6.1 - 6.9

IFG

5.6 - 6.9

2hPG in 75g OGTT (mmol/L)

7.8 -11.0

IGT

7.8 - 11.1

A1C (%) 5.7 - 6.4 2hPG = 2-hour plasma glucose; IFG = impaired fasting glucose; A1C = glycated hemoglobin; IGT = impaired glucose; FPG = fasting plasma glucose; OGTT = oral glucose tolerance test 6.0 - 6.4 Prediabetes

Both the FPG and OGTT are appropriate diagnostic tests for diabetes. An OGTT is not required to diagnose type 2 diabetes if the fasting results are elevated. An OGTT is not suitable for persons who are acutely ill or hospitalized. If used, patients should be made aware of the instructions provided below (see Figure 5).