What is Diabetes Mellitus? (Including Epidemiology of Diabetes) Flashcards
Define diabetes mellitus.
A group of metabolic diseases of multiple aetiologies characterised by hyperglycaemia together with disturbances of carbohydrate, fat and protein metabolism resulting from defects in insulin secretion, insulin action, or both.
Explain the classification of diabetes mellitus.
Normal;
- Fasting plasma glucose ≤ 6.0
- Random plasma glucose < 11.1 (non-diagnostic if below)
- 2 hour OGTT value ≤ 7.7
Diabetes
- Fasting plasma glucose (equal to or more than) 7.0
- Random plasma glucose (equal to or more than) 11.1
- 2 hour OGTT value (equal to or more than) 11.1
- HbA1c (equal to or more than) 48mmol/mol
All values in between are intermediate.
All units are moll/L.
Typical symptoms + 1 diagnostic blood test
OR
2 diagnostic blood tests or HbA1c level without symptoms
State the common presenting symptoms of diabetes mellitus.
- Polydipsia
- Polyuria
- Blurred vision
- Weight loss
- Infections
Name the long term complications of diabetes mellitus.
Microvascular;
- Retinopathy
- Neuropathy
- Nephropathy
Macrovascular;
- Stroke
- MI
- PVD
Diagnosing diabetes: why are these certain criteria used?
Diabetes diagnostic criteria identify a group with significantly increased premature mortality and increased risk of microvascular and cardiovascular complications.
What does intermediate hyperglycaemia (IGT and IFG) identify?
A group at higher risk of future diabetes and adverse outcomes such as CVS disease.
Explain what HbA1c is.
Glucose in the blood binds irreversibly to a specific part of haemoglobin in red blood cells, forming HbA1c.
The higher the glucose, the higher the HbA1c.
HbA1c circulates for the lifespan of the RBC, so reflects the prevailing blood glucose levels over the preceding 2-3 months.
What are the advantages of using glucose as a diagnostic tool for diabetes.
- Established method
- Smaller variation between laboratories
- More feasible in developing countries
- Directly measure molecules thought to cause diabetic complications
What are the disadvantages of using glucose as a diagnostic tool for diabetes.
- Requires a fasting state
- May require OGTT
- Higher variability within individuals
What are the advantages of using HbA1c as a diagnostic tool for diabetes.
- No need for a fasting sample
- More stable after collection
- Marker of glycemic control
- Lower variability within individuals
What are the disadvantages of using HbA1c as a diagnostic tool for diabetes.
- Measurement can be misleading with haemoglobinopathies, anaemia or renal failure
- May differ with age and ethnicity
- More costly
- Surrogate marker of hyperglycaemia
When can HbA1c not be used for diagnosis?
- All children and young people
- Pregnancy: current or recent (< 2 months)
- Short duration of diabetes
symptoms - Patients at high risk of diabetes who are acutely ill
- Patients taking medication that may cause rapid glucose rise e.g. corticosteroids, antipsychotic drugs
- Acute pancreatic damage or pancreatic surgery
- Renal failure
- HIV
What would be observed upon examination of an undiagnosed type 1 diabetic?
- Ketones on breath
- Dehydration
- May have increased RR, tachycardia, low BP
- Low grade infections e.g. thrush/balanitis
What are the symptoms of type 2 diabetes?
Often patients have no symptoms.
If they do, they are similar to type 1 + symptoms of complications.
What would be observed upon examination of an undiagnosed type 2 diabetic?
- Not ketotic
- Usually overweight but not always
- Low grade infections e.g. thrush/balanitis
