Reset
Measure Fasting Plasma Glucose (FPG) and/or A1C and enter test results:
Or
Measure 75g Oral Glucose Tolerance Test (OGTT) and enter test results:
- 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.
See Individualizing Your Patient’s A1C target, Chapter 9: Monitoring Glycemic Control, Table 1
Click here to view the Canadian Diabetes Risk Questionnaire (CANRISK) (printable and downloadable version)
Click here to view the Canadian Diabetes Risk Questionnaire (CANRISK) interactive online questionnaire
Chapter 4: Figure 1. Screening and diagnosis algorithm for type 2 diabetes.
Chapter 3: Table 5
Diagnosis of prediabetes |
|---|
| Test | Result | Prediabetes category |
| FPG (mmol/L) | 6.1–6.9 | IFG |
| 2hPG in a 75 g OGTT (mmol/L) | 7.8–11.0 | IGT |
| A1C (%) | 6.0–6.4 | Prediabetes |
| Parameter | Advantages | Disadvantages |
|---|
| 2hPG, 2-hour plasma glucose; A1C, glycated hemoglobin; CVD, cardiovascular disease; FPG, fasting plasma glucose; OGTT, ral glucose tolerance test. |
| FPG | - Established standard
- Fast and easy
- Single sample
- Predicts microvascular complications
| - Sample not stable
- High day-to-day variability
- Inconvenient (fasting)
- Reflects glucose homeostasis at a single point in time
|
2hPG in a
75 g OGTT | - Established standard
- Predicts microvascular complications
| - Sample not stable
- High day-to-day variability
- Inconvenient
- Unpalatable
- Cost
|
| A1C | - Convenient (measure any time of day)
- Single sample
- Predicts microvascular complications
- Better predictor of CVD than FPG or 2hPG in a 75 g OGTT
- Low day-to-day variability
- Reflects long-term glucose concentration
| - Cost
- Misleading in various medical conditions (e.g., hemoglobinopathies, iron deficiency, hemolytic anaemia, severe heaptic or renal disease)
- Altered by ethnicity and aging
- Standardized, validated assay required
- Not for diagnostic use in children and adolescents** (as the sole diagnostic test), pregnant women as part of routine screening for gestational diabetes***, those with cystic fibrosis or those with susected type 1 diabetes
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