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Screening for and Diagnosing Diabetes

Healthcare Provider Tool

Reset

▼ Screening and Diagnosis Calculator ► Screening and Diagnosis Calculator

Measure Fasting Plasma Glucose (FPG) and/or A1C and enter test results:

FPG:

mmol/L

A1C:

Measure 75g Oral Glucose Tolerance Test (OGTT) and enter test results:

Fasting value:

mmol/L

2hr value:

mmol/L

Calculate Screening / Diagnosis Result

Calculate

► Screening Results ▼ Screening Results

Not enough information is provided

Rescreen as recommended, every 3 years.

ERROR

Enter value for FPG and/or A1C; or OGTT only.

Normal

(Re)screen as recommended

At risk for prediabetes and type 2 diabetes

Rescreen more often

Prediabetes

Rescreen more often

Diabetes

Tests are discordant

The patient may have diabetes, suggest repeat A1C. If patient has symptoms of hyperglycemia, confirmatory / repeat test is not required, consider patient to have diabetes.

Tests are discordant

The patient may have diabetes, suggest repeat FPG. If patient has symptoms of hyperglycemia, confirmatory / repeat test is not required, consider patient to have diabetes.

Normal

IGT (prediabetes)

Possible diabetes

Confirmatory test required. If patient has symptoms of hyperglycemia, confirmatory / repeat test is not required, consider patient to have diabetes.

Diabetes

IFG (prediabetes)

IFG and IGT (prediabetes)

This test is normal

(Re)screen as recommended

This represents someone at risk

Consider A1C test, rescreen more often

This represents prediabetes

Consider A1C test, rescreen more often

This might represent diabetes

Requires second test for confirmation, consider repeat FPG and / or A1C test. If patient has symptoms of hyperglycemia, confirmatory / repeat test is not required, consider patient to have diabetes.

This represents someone at risk

Consider FPG test, rescreen more often

This represents prediabetes

Consider FPG test, rescreen more often

This might represent diabetes

Requires second test for confirmation, consider repeat A1C and / or FPG. If patient has symptoms of hyperglycemia, confirmatory / repeat test is not required, consider patient to have diabetes.

Review Clinical Practice Guidelines' Chapter 4: Screening for Type 1 and Type 2 Diabetes for more detailed information.

► Risk Factors for Type 2 Diabetes ▼ 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*
- Hypertension*
- Overweight*
- Abdominal obesity*
- Smoking
Presence of associated diseases:
- History of pancreatitis
- Polycystic ovary syndrome*
- Acanthosis nigricans*
- Hyperuricemia/gout
- Non-alcoholic steatohepatitis
- Psychiatric disorders (bipolar disorder, depression, schizophrenia†)
- HlV infection‡
- Obstructive sleep apnea§
- Cystic fibrosis
Use of drugs associated with diabetes:
- Glucocorticoids
- Atypical antipsychotics
- Statins
- 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 ▼ 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.

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

► Screening Algorithm ▼ Screening Algorithm

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.
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

► Advantages and Disadvantages of Diagnostic Tests for Diabetes ▼ Advantages and Disadvantages of Diagnostic Tests for Diabetes

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

This is only to be used as a decision support tool and is subject to these terms.
For more information, please see terms of use.

*The Canadian Diabetes Association is the registered owner of the name Diabetes Canada. All content on guidelines.diabetes.ca, CPG Apps and in our online store remains exactly the same. For questions, contact communications@diabetes.ca.