CDECB Competency Focus: 1.B, 1.D, 4.4.F, 5.D Exam Weight: High (Foundational Knowledge)
1. Diagnostic Criteria for Diabetes
Competency 1.D: Identifies the diagnostic criteria for all types of diabetes.
For the CDE exam, you must memorize these specific thresholds. Remember that in Canada, all glucose values are measured in mmol/L.
The 4 Diagnostic Tests
Diabetes is diagnosed if any of the following criteria are met:
Test
Threshold
Notes
FPG (Fasting Plasma Glucose)
≥ 7.0 mmol/L
Fasting = No caloric intake for at least 8 hours.
A1C (Glycated Hemoglobin)
≥ 6.5%
Must use a standardized, validated assay.
2hPG (75 g OGTT)
≥ 11.1 mmol/L
The standard oral glucose tolerance test.
Random PG
≥ 11.1 mmol/L
Measured at any time of day, regardless of last meal.
2. Confirmatory Testing Rules
Competency 1.D / Critical Thinking: Applying rules to discordant or uncertain results.
The guidelines have specific algorithms for when to confirm a diagnosis. You cannot diagnose everyone on a single test result.
Symptomatic vs. Asymptomatic
Symptomatic Hyperglycemia: If the patient has classic symptoms (polyuria, polydipsia, weight loss), a single test in the diabetes range is sufficient. Do not delay treatment.
Asymptomatic: If a single test is in the diabetes range, a repeat confirmatory test must be done on another day.
Which Test to Repeat?
Ideally: Repeat the same test to confirm.
Exception: If the initial positive test was a Random PG, confirm with an alternate test (FPG, A1C, or OGTT).
Two Different Tests: If two different tests (e.g., FPG and A1C) are both available and both are above the threshold, the diagnosis is confirmed.
Dealing with Discordance (Conflicting Results)
If one test is positive for diabetes and one is negative:
Repeat the test that was above the diagnostic cut-point.
Make the diagnosis based on the result of the repeat test.
EXAM ALERT: If a young or lean individual presents with symptomatic hyperglycemia and ketonuria (suspected Type 1), do not delay treatment to perform confirmatory testing. Rapid metabolic deterioration can occur.
3. Diagnosis of Prediabetes
Competency 1.D: Identifies the diagnostic criteria for prediabetes.
Prediabetes places individuals at high risk for developing diabetes and cardiovascular complications.
- Impaired Fasting Glucose (IFG): FPG 6.1 – 6.9 mmol/L.
- Impaired Glucose Tolerance (IGT): 2hPG in a 75 g OGTT 7.8 – 11.0 mmol/L.
- Prediabetes (A1C): A1C 6.0% – 6.4%.
4. Differentiating Types of Diabetes
Competency 1.B: Distinguishes between major types of diabetes.
Use this table to answer case-based questions distinguishing Type 1, Type 2, and Monogenic diabetes.
Feature
Type 1 Diabetes
Type 2 Diabetes
Monogenic Diabetes
Age of Onset
Usually <25 years (but can be any age).
Usually >25 years (but increasing in adolescents).
Usually <25 years.
Weight
Usually thin/normal.
>90% are overweight/obese.
Similar to general population (often non-obese).
Auto-antibodies
Present (GAD, ICA).
Absent.
Absent.
Inheritance
Infrequent (5-10%).
Frequent (75-90%).
Autosomal Dominant (Multigenerational).
Insulin Status
Absent (low C-peptide).
Present (normal/high C-peptide).
Usually present.
5. Limitations of the A1C Test
Competency 4.4.F: States the definition, limitations, and interpretation of A1C.
A1C reflects average glucose over 2–3 months. It is convenient but not perfect.
Who Should NOT be Diagnosed with A1C?
Do not use A1C for diagnosis in:
Children and adolescents (as the sole diagnostic test).
Pregnant women (routine screening).
Suspected Type 1 diabetes.
Those with cystic fibrosis.
Those with factors affecting A1C accuracy (see below).
Factors Affecting Accuracy
False Highs: Iron deficiency, B12 deficiency, decreased erythropoiesis (e.g., renal failure), splenectomy.
False Lows: Use of Iron/B12/EPO, chronic liver disease, antiretrovirals, splenomegaly.
Ethnicity: African Americans, Hispanics, and Asians may have A1C values up to 0.4% higher than Caucasians at similar glucose levels.
Age: A1C rises by up to 0.1% per decade of life.
6. Metabolic Syndrome
Competency 5.D: Identifies risk factors for macrovascular complications.
Diagnosis requires ≥ 3 of the following 5 criteria:
Elevated Waist Circumference:
Canada/USA/Europid: Men ≥102 cm, Women ≥88 cm.
Asian/South & Central American: Men ≥90 cm, Women ≥80 cm.
Elevated Triglycerides: ≥ 1.7 mmol/L (or on drug treatment).
Reduced HDL-C: Men <1.0 mmol/L, Women <1.3 mmol/L (or on drug treatment).
Elevated Blood Pressure: Systolic ≥130 mmHg or Diastolic ≥85 mmHg (or on antihypertensive treatment).
Elevated Fasting Glucose: FPG ≥ 5.6 mmol/L (or on drug treatment for elevated glucose).
Exam Trap: Notice that the FPG threshold for Metabolic Syndrome is ≥5.6 mmol/L, whereas the threshold for diagnosing Prediabetes (IFG) starts at 6.1 mmol/L. Read the question carefully to see which definition they are asking for!