Diabetes: definition, differential diagnosis and classification

Extract

• Criteria for diabetes
  • diabetic-level fasting glucose concentration (fasting plasma glucose ≥ 7.0 mmol/l) OR
  • HbA_1c ≥ 48 mmol/mol (6.5%) (check local requirements whether one or two abnormal results are required) OR
  • plasma glucose ≥ 11.1 mmol/l in a patient with symptoms, one measurement is sufficient (at any time of the day) OR
  • plasma glucose at 2 hours in oral glucose tolerance test ≥ 11.1 mmol/l.
• If there are no evident symptoms (continuous thirst, polyuria, weight loss), the diagnosis requires
  • 2 separate results exceeding the threshold value in different parameters or an abnormal result in one parameter on two different days.
  • HbA_1c ≥ 48 mmol/mol (6.5%); one measurement may be sufficient in some countries, while the WHO and some other recommendations require 2 abnormal results.
• A 2-hour glucose tolerance test is not required if the diagnostic criteria are otherwise fulfilled.
• It is worthwhile to perform a 2-hour glucose tolerance test if fasting glucose level is slightly elevated (6.1–7.0 mmol/l), HbA_1c concentration is 42–47 mmol/mol (6–6.5%) or risk test score is above threshold (see e.g. https://www.mdcalc.com/findrisc-finnish-diabetes-risk-score1).
• The risk of diabetes is increased in persons with elevated fasting glucose level or impaired glucose tolerance; see table Diagnostic threshold values of plasma glucose concentration (mmol/l) after fasting and at 2 hours in oral glucose tolerance test with 75 g of glucose (WHO )1 for threshold values.

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