Risk factors for type 2 diabetes
- Age ≥40 years
- First-degree relative with type 2 diabetes
- Member of high-risk population (e.g., African, Arab, Asian, Hispanic, Indigenous or South Asian descent, low socioeconomic status)
- History of prediabetes (lGT, lFG or A1C 6.0–6.4%)*
- History of GDM
- History of delivery of a macrosomic infant
- Presence of end organ damage associated with diabetes:
- Microvascular (retinopathy, neuropathy, nephropathy)
- CV (coronary, cerebrovascular, peripheral)
- Presence of vascular risk factors:
- HDL-C <1.0 mmol/L in males, <1.3 mmol/L in females*
- TG ≥1.7 mmol/L*
- Abdominal obesity*
- Presence of associated diseases:
- History of pancreatitis
- Polycystic ovary syndrome*
- Acanthosis nigricans*
- Non-alcoholic steatohepatitis
- Psychiatric disorders (bipolar disorder, depression, schizophrenia†)
- HlV infection‡
- Obstructive sleep apnea§
- Cystic fibrosis
- Use of drugs associated with diabetes:
- Atypical antipsychotics
- Highly active antiretroviral therapy‡
- Anti-rejection drugs
- Other (see Appendix 1)
- Other secondary causes (see Appendix 1)
AIC, glycated hemoglobin; CV, cardiovascular; GDM, gestational diabetes; HDL-C, high density lipoprotein cholesterol; HIV, human immunodeficiency virus-1; IFG, impaired fasting glucose; IGT, impaired glucose tolerance.
When to screen for type 2 diabetes
- Screen every 3 years in individuals ≥40 years of age
- Screen every 3 years in individuals at high risk according to a risk calculator
- Screen earlier and/or more frequently (every 6 to 12 months) in people with additional risk factors for diabetes (see below)
- Screen earlier and/or more frequently in people at very high risk according to a risk calculator
Conditions that lead to misleading A1C include: hemoglobinopathies, hemolytic anemia, iron deficiency, severe renal or liver disease. Link to Table 1, Monitoring for Glycemic Control.
- Validated Assay: A1C must be measured using a validated assay standardized to the National Glycohemoglobin Standardization Program-Diabetes Control and Complications Trial reference.
- Ethnicity: Studies indicate that African Americans, American Indians, Hispanics and Asians have A1C values that are up to 0.4% higher than those of Caucasian patients at similar levels of glycemia (17,18). Research is required to determine if A1C levels differ in African Canadians or Canadian First Nations.
- Age: A1C values are affected by age, rising by up to 0.1% per decade of life (20,21). More studies may help to determine if age- or ethnic-specific adjusted A1C thresholds are required for diabetes diagnosis.
- Special Populations: A1C is not recommended for diagnostic purposes in children, adolescents, pregnant women or those with suspected type 1 diabetes.
Chapter 4: Figure 1. Screening and diagnosis algorithm for type 2 diabetes.
|Chapter 3: Table 5
Diagnosis of prediabetes
|2hPG, 2-hour plasma glucose; AlC, glycated hemoglobin; FPG, fasting plasma glucose; IFG, impaired fasting glucose; IGT, impaired glucose tolerance; OGTT, oral glucose tolerance test.|
|2hPG in a 75 g OGTT (mmol/L)||7.8–11.0||IGT|
Advantages and disadvantages of diagnostic tests for diabetes
|2hPG, 2-hour plasma glucose; A1C, glycated hemoglobin; CVD, cardiovascular disease; FPG, fasting plasma glucose; OGTT, ral glucose tolerance test.|
|2hPG in a
75 g OGTT