Diabetes Diagnosis, Classification and Aetiology

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Diabetes Diagnosis, Classification and Aetiology

• Theresa Smyth
• Nurse Consultant in Diabetes

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Definition of Diabetes Mellitus

• WHO (1999)
• a metabolic disorder of multiple aetiology
  characterised by chronic hyperglycaemia with
  disturbances of carbohydrate, fat and protein
  metabolism resulting from defects in insulin
  secretion, insulin action or both
• World Health Organisation (1999) Definition,
  Diagnosis and Classification of Diabetes Mellitus
  and its Complications, World Health Organisation,
  Geneva.

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Common symptoms of Diabetes Mellitus

• Polyuria / Nocturia
• Excessive thirst and appetite
• Weight Loss
• Lethargy
• Blurred Vision
• Skin infections
• Vaginal infections

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Diagnosis of Diabetes Mellitus

• Blood glucose levels - venous samples
• 1 sample is diagnostic if symptoms are present 2
  samples if asymtomatic
• Fasting plasma glucose of gt 7.0mmols
• Random plasma glucose of gt 11.1mmols
• Plasma glucose of gt 11.1mmols 2 hours after an
  oral glucose tolerance test (OGTT).

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WHO (1999) Definition biochemical - GTT

• Venous Plasma
• Fasting gt7.0mmol/l DIABETES
• Fasting 6.1-7.0 mmol/l Impaired Fasting Glycaemia
• 2 hour level gt11.0 mmol/l DIABETES
• 2 hour 7.8 11.0 mmol/l Impaired Glucose
  Tolerance

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Impaired Fasting Glucose (IFG)

• Fasting plasma glucose gt 6.0mmol/l and 6.9 mmol/l
• Intermediate state between normal glucose
  tolerance and diabetes
• Present in 5 of the population and increasing
  with age
• Has greater risk CVD

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Impaired Glucose Tolerance (IGT)

• Fasting plasma glucose lt7.0 mmol/l and OGTT 2
  hour value gt7.8 mmol/l but lt11.1 mmol/l
• Intermediate state between normal glucose
  tolerance and diabetes
• Individuals often manifest hyperglycaemia only
  when challenged with oral glucose in an OGTT
• 2-5 of people with IGT progress to diabetes per
  year
• IGT associated with increase risk of developing
  cardiovascular disease

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Diagnosis

• ADA
• Fasting Plasma Glucose only
• Simpler
• Reproducible
• Screening plus diagnosis
• WHO
• OGTT
• Fasting Plasma Glucose misses out 1/3rd !!
• IGT

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Diagnosis Random Plasma Glucose

• Easier to do
• Insufficient data to determine lower limit for
  initial screening test
• To increase sensitivity and specificity lower
  cutoff
• Australia
• RPG gt 5.5 OGTT
• European guidelines
• FPG 5-6 rpt FPG 1year
• FPG 6.1-6.9 - OGTT

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Steps in Diagnosis without GTT

• Step 1
• Symptomatic or Glycosuria of Incidental
  hyperglycaemia
• Check random venous plasma
• IF
• gt11.0mmol/l DIABETES
• gt5.5 mmol/l but less than 11mmol/l then Step 2

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Steps in Diagnosis without GTT (cont)

• Step 2
• Check fasting venous plasma
• If gt 7.0mmol/l then REPEAT and if confirmed
  DIABETES
• If gt6.0 mmol/l then need GTT
• If gt5.0 then consider annual check assess CVS
  risk factors.

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Classification

• Type 1 Diabetes
• Type 2 Diabetes
• Other Specific Types
• e.g. Chronic or recurrent pancreatitis, MODY,
  drug induced
• Gestational

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Type 1 Diabetes

• Formally know as IDDM
• Beta cell destruction autoimmune
• Tend to be under 40 years
• Tend to present with ketones and weight loss
• Usually Lean
• Markers of autoimmunity islet cell antibodies
• Family history positive in 10 of cases
• 30-50 concordance in identical twins

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Type 2 Diabetes

• Formally known NIDDM
• Disorder of insulin action and insulin secretion
• Usually obese
• Usually over 50 years but coming down!
• No markers of autoimmunity
• Family history positive in 30 of cases
• Nearly 100 concordance in identical twins

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Type 2 Diabetes

• Approx 90 of all diabetes cases world wide
• Maybe no symptoms - often not diagnosed
  missing million Diabetes UK
• Patients may have lost up to 50 of beta cell
  function at diagnosis
• A further 25 will be lost within 6 yrs of
  diagnosis (UKPDS, 1998)

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Maturity Onset Diabetes in the Young (MODY)

• Uncommon approx 2 of all diabetes
• Relative insulinopenia
• Before 25 years
• Mutation in gene encoding for beta cell
• Different types 6 different genes identified
• 1- may not need any drug treatment
• 2 - may need insulin
• 3 - is often sulphonylurea sensitive

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Type 2 or MODY
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Who gets diabetes?

• Estimated that 2 million people in the UK have
  diabetes mellitus
• ?750,000 to one million undiagnosed cases
• A new patient is diagnosed with type 2 diabetes
  every 5 minutes
• The number of cases are due to increase to 3
  million by 2010
• Diabetes UK Fact Sheet (2000) and Audit
  Commission Testing Times (2000)

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Who Gets Diabetes?

• Diabetes is becoming more common
• Type 1 diabetes is increasing in children,
  particularly in under 5s
• Type 2 diabetes is increasing across all groups,
  including young people, and particularly among
  black and minority groups
• Elderly
• 1 in 20 over 65s
• 1 in 5 over 85s
• 7 25 of people in care homes
• ¼ of Asians over the age of 60
• Diabetes National Service Framework Standards
  Department of Health 2001 Audit Commission
  Testing Times (2000)

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Three million by 2010
3000
2500
2000
Diabetes prevalence (thousands)
1500
1000
500
0
1995
2000
2010
Amos AF et al. Diabet Med 199714(Suppl 5)S1S85
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Obesity and Diabetes

• As a country becomes wealthier so does the
  incidence of obesity and diabetes
• Coca Colonisation
• McDonaldisation
• 22 of women and 20 of men in the UK are obese
• Type 2 diabetes now seen in Caucasian children
  due to obesity

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The Size of the Problem

• Microvascular complications - affecting the
  smaller blood vessels
• Eye (diabetic retinopathy), kidneys,
  (nephropathy) and nerves (neuropathy)
• Macrovascular complications affecting the
  larger arteries
• Resulting in coronary heart disease (CHD),
  stroke, and peripheral vascular disease
• 50 of patients already have one or more vascular
  complication at diagnosis to Type 2 diabetes
  (UKPDS, 1990)

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The Size of the Problem

• 80 of people with DM will die prematurely from
  long term complications
• Patients with DM can expect to live 5-10 years
  less than someone without diabetes
• 70-75 of Type 2 DM will die of CVD
• (BDA - Counting the Cost - 1996)
• Cardiovascular mortality
• 2-3 Xs higher in men with DM
• 3-5 Xs higher in women with DM
• (UKPDS, 1998)

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HbA1c

• Glycosylated haemoglobin
• Average blood glucose over last 8-12 weeks
• Is not diagnostic