Type 2 Diabetes Screening and Diagnosis

Assessment for Type 2 Diabetes in Asymptomatic Patients

  • Screening for type 2 diabetes targets asymptomatic patients who are identified as being at high risk for the condition.
  • Risk assessment is determined using the Australian Type 2 Diabetes Risk Assessment Tool (AUSDRISK) with a score of ≥12\ge 12 or by identifying patients within specific high-risk categories.

Diagnostic Pathway via Blood Glucose Testing

  • The initial assessment involves testing blood glucose through Fasting Blood Glucose (FBG) or Random Blood Glucose (RBG).

  • Diabetes Unlikely

    • Criteria: FBG <5.5 mmol/L< 5.5\,mmol/L.
    • Action: Retest the patient in three years if clinically indicated.

  • Diabetes Possible

    • Criteria: FBG between 5.5 mmol/L5.5\,mmol/L and 6.9 mmol/L6.9\,mmol/L.
    • Action: Perform an Oral Glucose Tolerance Test (OGTT).

  • Diabetes Likely

    • Criteria: FBG ≥7.0 mmol/L\ge 7.0\,mmol/L or RBG ≥11.1 mmol/L\ge 11.1\,mmol/L.
    • Action: Confirm the diagnosis with a repeat FBG test on a separate day.

Diagnostic Pathway via Glycated Haemoglobin (HbA1c)

  • Initial testing can also be performed using HbA1c levels (Test HbA1c+Test\,HbA1c+).

  • Diabetes Unlikely

    • Criteria: HbA1c <6.0%< 6.0\% (42 mmol/mol42\,mmol/mol).
    • Action: Retest the patient in three years if clinically indicated.

  • High Risk / Diabetes Possible

    • Criteria: HbA1c between 6.0%6.0\% and 6.4%6.4\% (42−46 mmol/mol42-46\,mmol/mol).
    • Action: Refer to the section titled 'Preventing progression to type 2 diabetes' and retest the patient in one year.

  • Diabetes Likely

    • Criteria: HbA1c ≥6.5%\ge 6.5\% (48 mmol/mol48\,mmol/mol).
    • Action: Confirm the diagnosis with a repeat HbA1c test (∗∗**).

Oral Glucose Tolerance Test (OGTT) Interpretation

  • The OGTT provides specific categorical diagnoses based on fasting and two-hour glucose levels.

  • Normal Glucose Tolerance (Diabetes Unlikely)

    • Fasting Glucose: <6.1 mmol/L< 6.1\,mmol/L
    • Two-hour Glucose: <7.8 mmol/L< 7.8\,mmol/L
    • Management: Retest in three years.

  • Impaired Fasting Glucose (IFG)

    • Fasting Glucose: 6.1−6.9 mmol/L6.1-6.9\,mmol/L
    • Two-hour Glucose: <7.8 mmol/L< 7.8\,mmol/L
    • Management: Retest in one year.

  • Impaired Glucose Tolerance (IGT)

    • Fasting Glucose: <7.0 mmol/L< 7.0\,mmol/L
    • Two-hour Glucose: ≥7.8 mmol/L\ge 7.8\,mmol/L and <11.1 mmol/L< 11.1\,mmol/L
    • Management: Retest in one year.

  • Diabetes Confirmed

    • Fasting Glucose: ≥7.0 mmol/L\ge 7.0\,mmol/L
    • Two-hour Glucose: ≥11.1 mmol/L\ge 11.1\,mmol/L

Clinical Definitions and Technical Requirements

  • Confirmation of Diagnosis

    • For clinical purposes, a diagnosis of diabetes should always be confirmed by repeating the abnormal test on another day.
    • Exception: Confirmation is not required if there is unequivocal hyperglycaemia presenting with acute metabolic decompensation or obvious symptoms.
    • If a confirmatory test returns a negative result, the assessment should be repeated in one year or earlier if symptoms develop.

  • HbA1c Diagnostic Limitations

    • Impaired Glucose Tolerance (IGT) and Impaired Fasting Glucose (IFG) cannot be diagnosed using HbA1c.
    • An HbA1c result of <6.5%< 6.5\% does not exclude a diagnosis of diabetes if the diagnosis is reached via glucose-based tests.

  • Medicare Benefits Schedule (MBS) Information

    • MBS Item Number 66841: Allows for diagnostic use of HbA1c only once every 12 months. The request slip should be annotated as 'HbA1c' or for Service Incentive Payment (SIP) and Practice Incentives Program (PIP) purposes.
    • MBS Item Number 66551: Used for a confirmatory HbA1c test, which should be ordered before the initiation of treatment.