How do we know who to screen and when to screen for diabetes in Canada? Do we screen for Type 1 diabetes or only type 2 diabetes? Read on to learn more about the current Canadian diabetes screening approaches.
Screening for Type 1 Diabetes
Type 1 diabetes is primarily caused by an immune response that destroys the beta cells of the pancreas: the cells that make insulin. Evidence tells us that those who develop type 1 diabetes often pass through a series of immune changes that lead to the full destruction of the beta cells of the pancreas. Family history, gender, and other health factors also play a role. We cannot recommend community-based screening for type 1 diabetes at this time because there is a lack of evidence that it can be prevented and the autoimmune tests needed to diagnose are not widely available.
Screening for Type 2 Diabetes
Because there is a much higher risk of developing type 2 diabetes among the Canadian population, screening for type 2 diabetes has benefit. When you subgroup people by their ethnicity, diabetes diagnosis risks increase for many including those individuals from an Asian, African and Indigenous backgrounds. It is estimated that the changes leading to the onset of type 2 diabetes begin to happen 4-7 years prior to diagnosis so screening initiatives are vital to catching pre-diabetes and diabetes early and starting the interventions needed to protect health.
Screening using CANRISK
Type 2 diabetes risk can be assessed using the Canadian Diabetes Risk Assessment Questionnaire (CANRISK). CANRISK is a statistically valid tool available online or in pdf form that is suitable for community screening initiatives to identify those individuals at high risk for diabetes. It is validated for adults over age 40 and but not validated for children, teens or younger adults. The risk scores were developed using Caucasian population and may not be accurate for risk assessment in ethnic populations.
Risk Factors for Type 2 Diabetes
Since the CANRISK tool has not been validated for Canada’s varied ethnic population, it can be helpful to review additional risk factors for Type 2 diabetes that may affect the population you work with. The CANRISK tool does not cover each identified risk factor for developing type 2 diabetes but assesses for a few of the more common risk factors such as age over 40, carrying extra body weight, high blood pressure, physical activity and history of gestational diabetes.
Other risk factors for type 2 diabetes not assessed in CANRISK include:
- Presence of vascular risk factors such as abnormal blood cholesterol values (HDL-C <1.0 mmol/L in males, <1.3mmol/L in females, triglycerides higher than 1.7 mmol/L), active smoker, and overweight with particular increased risk with abdominal obesity.
- Presence of associated conditions such as history of pancreatitis, polycystic ovarian syndrome, acanthosis nigricans, schizophrenia, HIV infection, obstructive sleep apnea and gout.
- Use of drugs associated with diabetes such as use of antiretroviral or anti-psychotic medications, anti-rejection drugs or statins.
Laboratory Screening for Diabetes
The 2018 Clinical Practice Guidelines for the Management of Diabetes advise to screen individuals over the age of 40 every 3 years for diabetes, and more frequently in those at higher risk. Screening can assess fasting plasma glucose (FPG), Hemoglobin A1c (a measure of glucose control over the last 90 days) or use an oral glucose tolerance test (OGTT). The following chart shows us the values of each diagnosis.
- FPG ≥7.0 mmol/L Fasting = no caloric intake for at least 8 hours
- Or A1C ≥6.5% (in adults) Using a standardized, validated assay in the absence of factors that affect the accuracy of the A1C (no anemia) and not for suspected type 1 diabetes
- Or 2hPG in a 75 g OGTT ≥11.1 mmol/L
- Or Random PG ≥11.1 mmol/L Random = any time of the day, without regard to the interval since the last meal.
It should be noted that in the absence of systematic hyperglycemia (high blood sugars found in asymptomatic individuals who have no noted increased thirst, hunger, urination etc.), a second confirmatory lab test is required in order to diagnose diabetes. More information on screening for diabetes in Canada can be found at http://guidelines.diabetes.ca/screening
Screening for diabetes in Canada using community-based screening approaches has significant merit in the early diagnosis, treatment and management of type 2 diabetes. There is no current recommendation to screen for type 1 diabetes at this time. To screen for type 2 diabetes we have readily accessible risk assessment tools available for community-based screening to identify those individuals at high risk for type 2 diabetes, and also laboratory screening options available through physicians for assessment and diagnosis. Any health care provider looking to Make a Difference in the lives of Canadians should set screening for type 2 diabetes as a priority.
Michelle Archer, RD, CDE
Registered Dietitian and Certified Diabetes Educator
Diabetes Training 101 Inc.