Screening, diagnosis and classification of diabetes

A. Prof Jonathan Shaw

Associate Director Baker IDI

Melbourne

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Identifying people at risk of developing type 2 diabetes• Test everyone – mass screening

• Test people who have risk factors for diabetes

• Undertake large-scale, non-invasive, self completed screening, with a validated tool, followed by blood tests for those at high-risk– FINDRISK– AUSDRISK

AUSDRISK•Self-completed risk score

•Developed and validated on Australian data

•Calculates 5-yr risk of developing diabetes

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1. Your age group?Under 35 years 0 pts35 – 44 years 2 pts45 – 54 years 4 pts55 – 64 years 6 pts65 years or over 8 pts

2. Your gender?Female 0 ptsMale 3 pts

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3. Ethnicity/Country of birth:3a. Are you of Aboriginal, Torres Strait Islander, Pacific Islander or Maori descent?

No 0 ptsYes 2 pts

3b. Where were you born?Australia 0 ptsAsia 2 ptsMid-East, N Africa 2 ptsS Europe 2 ptsOther 0 pts

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4. Have either of your parents, or any of your brothers or sisters been diagnosed with diabetes (type 1 or type 2)?

No 0 ptsYes 3 pts

5. Have you ever been found to have high blood glucose (sugar) (e.g. in a health examination, during an illness, during pregnancy)?

No 0 ptsYes 6 pts

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6. Are you currently taking medication for high blood pressure?

No 0 ptsYes 2 pts

7. Do you currently smoke cigarettes or any other tobacco products on a daily basis?

No 0 ptsYes 2 pts

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8. How often do you eat vegetables or fruit?

Everyday 0 ptsNot everyday 1 point

9. On average, would you say you do at least 2.5 hours of physical activity per week (eg 30 minutes a day on 5 or more days a week)?

Yes 0 ptsNo 2 pts

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10. Your waist measurement taken below the ribs (usually at the level of the navel)?

For those of Asian or Aboriginal or Torres Strait Islander descent:Men Women< 90 cm < 80 cm 0 pts90 – 100 cm 80 – 90 cm 4 pts>100 cm > 90 cm 7 pts

For all others:Men Women< 102 cm < 88 cm 0 pts102 – 110 cm 88 – 100 cm 4 pts> 110 cm > 100 cm 7 pts

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Your risk of developing type 2 diabeteswithin 5 years:

≤ 5: Low riskApproximately one person in every 100 will develop diabetes.

6-14: Intermediate riskFor scores of 6-8, approximately one person in every 50 will develop diabetes.For scores of 9-14, approximately one person in every 20 will develop diabetes.

15 or more: High riskFor scores of 15-19, approximately one person in every seven will develop diabetes.For scores of 20 and above, approximately one person in every three will develop diabetes.

Diagnostic criteria for diabetes

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Diagnostic thresholds should be defined by• Their association with clinically meaningful

abnormalities

• Level above which intervention is effective

• Associations with intermediate (metabolic) disturbances

• Normal limits of a healthy population– mean + 2SD– 9?th percentile

• Bimodal distribution

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Cut-points for diabetes based on

• Identifying a glucose threshold for the presence of complications

• Bi-modal distribution of blood glucose

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Cut-points for diabetes based on• Identifying a glucose threshold for the

presence of complications

• Bi-modal distribution of blood glucose

Relative risk of CVD mortality by 2-hr glucose - DECODE

6

5

4

3

2

1

0

Rel

ativ

e ri

sk

0 2 4 6 8 10 12 14 16 2-hour plasma glucose (mmol/l)

<3.0>14.5

Normal IGT Diabetes

Pima

Egypt

US - NHANES

7.6-12.5

7.2-9.9

6.7+

Range of FPG thresholds

ADA. D Care 1997;20:1183-97

Limitations of associations with complications

• Thresholds have been based on micro- not macrovascular disease

• Estimates of threshold values are imprecise (variation between populations, wide limits of deciles)

• All data are cross-sectional – longitudinal analyses would be likely to give lower cut-points

• ‘Diabetic retinopathy’ occurs at non-diabetic glucose levels

• Studies need to have more cases of retinopathy, and be able to use more severe levels of retinopathy

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HbA1C for DIAGNOSIS

PRO StableTime averagedReproducibleFasting not required

CON Standardisation essentialExpensiveNot freely availableProblems with anaemia, haemoglobinopathiesPoor QA schemes in many countriesFew data availableCutpoint uncertain

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Prevalence of Sickle cell disorders

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PLASMA GLUCOSE for DIAGNOSIS

PRO DM is disorder of raised glucoseTime honouredMuch dataAllows international comparisonsAccurate assay (?)

CON Based on cross-sectional data in relatively small numbers of studiesMajor pre-analytical problemsOGTT required – FPG inadequateOften poor QA

Page 21: Baker IDI Diabetes Care July 2009

Recommends using HbA1c as the preferred diagnostic test for diabetes

at a cut-point of 6.5%

Classification of diabetes

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WHO reports on classification 1965, 1980, 1985, 1998, 2006

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POSSIBLE 2009 WHO CLASSIFICATION OF DIABETES MELLITUS

1. Type 1 diabetes (-cell destruction)

2. Type 2 diabetes

3. Other specific types

4. Gestational diabetes mellitus

5. Undefined

ADA, WHO, 1997

Classic Onset Type 1 

Age of onset

Usually under 30 Usually 30 - 60 Usually over 30 years (except for MODY)

Present-ation

Rapid onset of thirst, polyuria, weight loss

Gradual onset of milder symptoms

Often asymptomatic; may present with complications or gradual onset of symptoms. 85% obese. Part of Metabolic Syndrome.

Ketonuria Usually present May be absent Absent (except with severe stress eg infection, infarction)

Anti-GAD antibodies

Present in approx 80% at diagnosis

C-peptide level

Low or absent, but may be low-normal initially (remission phase)

Normal-high (ie hyperinsulinemia)

Treatment Insulin required urgently to prevent ketoacidosis

Insulin required, but not urgently

Healthy eating and exercise, may require oral agents, and/or insulin later

Classic Onset Type 1 Slow Onset Type 1(LADA)

Type 2

Absent

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Summary• Screening

– Begin with non-invasive score

– Blood testing in those with a high score

• Diagnosis– HbA1c may become an accepted test

– Clinical diagnosis requires confirmation with a 2nd test

• Classification– Differentiation between type 1 and 2 increasingly difficult

– For most patients, classification, and need for insulin can be determined on simple, clinical criteria

Page 27: Baker IDI

Summary• Screening

– Begin with non-invasive score

– Blood testing in those with a high score

• Diagnosis– HbA1c may become an accepted test

– Clinical diagnosis requires confirmation with a 2nd test

• Classification– Differentiation between type 1 and 2 increasingly difficult

– For most patients, classification, and need for insulin can be determined on simple, clinical criteria

Page 28: Baker IDI

Summary• Screening

– Begin with non-invasive score

– Blood testing in those with a high score

• Diagnosis– HbA1c may become an accepted test

– Clinical diagnosis requires confirmation with a 2nd test

• Classification– Differentiation between type 1 and 2 increasingly difficult

– For most patients, classification, and need for insulin can be determined on simple, clinical criteria

Page 29: Baker IDI

Summary• Screening

– Begin with non-invasive score

– Blood testing in those with a high score

• Diagnosis– HbA1c may become an accepted test

– Clinical diagnosis requires confirmation with a 2nd test

• Classification– Differentiation between type 1 and 2 increasingly difficult

– For most patients, classification, and need for insulin can be determined on simple, clinical criteria

Some things are more complicated than screening and diagnosing diabetes!

Some things are more complicated than screening and diagnosing diabetes!