Based on the Diabetes Canada Clinical Practice Guidelines Competency Focus: 5.E (Screening), 1.G (Risk Factors) Exam Weight: Moderate
1. Screening for Type 1 Diabetes
The Rule: Routine screening for Type 1 diabetes is not recommended.
Reasoning: There is currently no evidence for effective interventions to prevent or delay Type 1 diabetes in the general population.
Limitations: Antibody screening (GAD, IA-2) is not universally available and has variable sensitivity (identifying only ~60% of future cases in some studies).
2. Screening for Type 2 Diabetes: The “Who” and “When”
Competency: Identifies the recommendations for screening.
Unlike the US guidelines (which target age 40-70 with obesity), Diabetes Canada recommends broader screening to catch the 20-40% of cases that are undiagnosed.
General Recommendation
Who: Everyone ≥ 40 years of age.
Frequency: Every 3 years.
Tool: Fasting Plasma Glucose (FPG) and/or A1C.
Earlier/More Frequent Screening
Screening should be done earlier (before age 40) and/or more frequently (every 6 to 12 months) in people with risk factors.
Use a risk calculator (like CANRISK) to assess risk.
High risk is defined as a 33% chance of developing diabetes over 10 years.
3. Risk Factors (Memorization List)
Competency: Identifies risk factors contributing to complications and diabetes development.
You must recognize these factors in case scenarios. If a patient has these, they need screening regardless of age.
Demographics & History
Age ≥ 40 years.
First-degree relative with Type 2 diabetes.
Member of a high-risk population (African, Arab, Asian, Hispanic, Indigenous, or South Asian descent; low socioeconomic status).
History of prediabetes (IFG, IGT, or A1C 6.0-6.4%).
History of Gestational Diabetes (GDM).
History of delivery of a macrosomic infant.
Vascular Risk Factors
HDL-C: <1.0 mmol/L (males) or <1.3 mmol/L (females).
Triglycerides: ≥1.7 mmol/L.
Hypertension.
Overweight or Abdominal Obesity.
Smoking.
Associated Diseases & Conditions
Polycystic Ovary Syndrome (PCOS).
Acanthosis Nigricans (sign of insulin resistance).
History of Pancreatitis.
Hyperuricemia / Gout.
Non-alcoholic steatohepatitis (NASH).
Cystic Fibrosis.
Obstructive Sleep Apnea (OSA).
Psychiatric disorders (Bipolar, Depression, Schizophrenia).
HIV infection.
Medications Associated with Diabetes
Glucocorticoids.
Atypical Antipsychotics.
Statins.
HAART (Highly Active Antiretroviral Therapy).
Anti-rejection drugs.
4. The Screening Algorithm: What do the numbers mean?
Competency: Interpreting screening results.
When you screen with FPG or A1C, the result determines the follow-up interval.
Result: Normal
Values: FPG <5.6 mmol/L AND A1C <5.5%.
Action: Rescreen as recommended (usually every 3 years).
Result: At Risk
Values: FPG 5.6 – 6.0 mmol/L OR A1C 5.5% – 5.9%.
Action: Rescreen more often.
Consider: A 75g OGTT if suspicious of T2D or high risk factors.
Result: Prediabetes
Values: FPG 6.1 – 6.9 mmol/L OR A1C 6.0% – 6.4%.
Action: Rescreen more often.
Consider: A 75g OGTT should be considered to check for Impaired Glucose Tolerance.
Result: Diabetes
Values: FPG ≥ 7.0 mmol/L OR A1C ≥ 6.5%.
Action: Confirm diagnosis (repeat test).
5. Special Clinical Notes
Schizophrenia
The incidence of T2D is 3 times higher in people with schizophrenia.
Antipsychotic medications further increase this risk.
Discordant Results
If you perform both FPG and A1C and they disagree (e.g., FPG is Normal but A1C is Prediabetes), treat the patient according to the test that is furthest to the right (the more severe result) on the algorithm.
The Role of OGTT (Oral Glucose Tolerance Test)
While FPG and A1C are the primary screening tools, the OGTT is not obsolete.
When to use: It is considered when FPG is 6.1–6.9 mmol/L or A1C is 6.0–6.4% to clarify the diagnosis.
Why: A1C misses approximately 50% of people who have prediabetes defined by an OGTT.