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Clinical guidelines

National guide to a preventive health assessment for Aboriginal and Torres Strait Islander people Second edition

Type 2 diabetes prevention and early detection

Author Dr Justin Coleman
Expert reviewers Professor David Atkinson, Professor Stephen Colagiuri


Type 2 diabetes is most commonly found in obese adults who develop increasing insulin resistance over months or years. For these patients there is a substantial ‘prediabetic’ window period of opportunity to offer preventive interventions. Screening for diabetes is safe, accurate and cost effective, and detects a substantial proportion of people who may not otherwise have received early intervention.1 This chapter discusses type 2 diabetes in adults who are not pregnant.

The prevalence of type 2 diabetes in Aboriginal and Torres Strait Islander populations is 3–4 times higher at any age than the general population, with an earlier age of onset.2 The precise prevalence is hard to pinpoint; a 2011 systematic review of 24 studies showed prevalence estimates ranged from 3.5–31%, with most lying between 10% and 20%. Diabetes prevalence in remote populations is approximately twice that of urban populations and is higher among Aboriginal and Torres Strait Islander people.3 

Aboriginal and Torres Strait Islander men and women die from diabetes at 23 and 37 times the rate of non-Indigenous Australian men and women respectively, in the 35–54 years age group.4 Large scale clinical trials have demonstrated that appropriate management of diabetes can prevent the development or delay the progression of complications such as myocardial infarction, eye disease and renal failure.5 

Obesity is a very strong predictor for diabetes; a body mass index (BMI) ≥30 kg/m2 increases the absolute risk of type 2 diabetes by 1.8–19-fold, depending on the population studied. A cohort study of non-diabetic Aboriginal adults aged 15–77 years in central Australia found that those with a BMI of ≥25 kg/m2 had 3.3 times the risk of developing diabetes over 8 years of follow up compared to those with a BMI <25 kg/m2.1 The AusDiab study found that three measures of obesity: BMI, waist circumference and waist-to-hip ratio, all had similar correlations with diabetes and CVD risk.6 Waist circumference performed slightly better than BMI at predicting diabetes in a remote Aboriginal community.7



Type 2 diabetes is generally underdiagnosed. Australia’s largest diabetes population study, which screened over 11 000 randomly selected people using an oral glucose tolerance test, found that, of the 7.4% who had diabetes, half (3.7%) had not been diagnosed previously, in an even spread across all age groups.8 A smaller study of Aboriginal and Torres Strait Islander people in Darwin found an overall diabetes prevalence of 17%, of which a third were previously undiagnosed. When those undiagnosed were assessed for diabetes complications, 19% had albuminuria, 14% had peripheral vascular disease, 6% had neuropathy and none had retinopathy.9 

Screening for undetected diabetes is an efficient method of preventing complications from this disease.1 Screening for diabetes will also detect pre-diabetes – impaired glucose tolerance (IGT) and/or impaired fasting glucose (IFG) – which cannot be detected clinically, but which is associated with an increased risk of developing diabetes and cardiovascular and other macrovascular disease.10

Screening for diabetes in adults who are not pregnant should be done on an opportunistic basis, in the primary care setting, rather than in mass screening programs.1 Aboriginal and Torres Strait Islander people should be screened for diabetes from age 18 years, rather than from 40 years in the general Australian population.1 Although historically a fasting glucose was recommended as the sole initial test,11 the 2009 National Health and Medical Research Council (NHMRC) guideline recommends a three-step process:1 First, perform a formal assessment of risk factors, this then determines who requires a fasting glucose sample, and finally, those with equivocal glucose results require an oral glucose tolerance test (OGTT).

The recommended risk assessment tool is AUSDRISK, which contains information on age, gender, ethnicity, family history, hypertension, smoking, diet, physical activity and obesity. AUSDRISK has been validated12 in the general Australian population and is available as an interactive online page or a paper printout. Those whose AUSDRISK score is ≥12 proceed to a fasting plasma glucose test (FPG), or a random blood glucose test (RBG) if this is more practical.

The use of the AUSDRISK tool in assessing whether Aboriginal and Torres Strait Islander people should have blood glucose testing is controversial. The tool incorporates lower cutoff points for waist circumference measurements that are considered specific for Aboriginal and Torres Strait Islander people; this does not necessarily take into consideration the considerable heterogeneity of this population in Australia. Some clinics may decide the time spent on the tool adds an obstacle that results in fewer patients having any diabetes assessment at all. Other clinics may find the AUSDRISK screening questions a useful prompt for discussing diabetic risk factors.

In diagnosing diabetes, if FPG or RBG indicates diabetes, unless the patient has diabetic symptoms this should be confirmed by retesting on a separate day, because intra-individual variation occurs.

A laboratory venous glucose test is more reliable than a capillary point-of-care test (finger prick), but the latter may sometimes be more practical and has the important advantage of being able to take further action on the same visit. An opportunistic random blood glucose sample is a reasonable alternative to a fasting sample in situations where the patient is unlikely to return for a fasting test, but the ‘equivocal’ range is altered to 5.5–11 mmol/L.1

Glycated haemoglobin (HbA1c), long used as a measure for assessing glycaemic control in people with diabetes, is not currently recommended for diagnosing diabetes in Australia, according to the NHMRC guidelines,1 although the 2010 USA guidelines for the first time included this indication, at a threshold of ≥6.5%.13 The recommendations may well soon change in Australia. The National Vascular Disease Prevention Alliance 2011 Australian guidelines state: ‘When a fasting sample is not possible, non-fasting glucose can be measured with further testing required if the result is ≥5.5 mmol/L. HbA1c can be used to diagnose diabetes with a level ≥6.5% being diagnostic’.14 

This recommendation has also been adopted by the World Health Organization as a diagnostic option.15 Currently, there is no Medicare rebate payable for measuring HbA1c in order to diagnose diabetes.

HbA1c results are affected by inter-laboratory variability (steadily improving), haemoglobin variants and alterations in red blood cell turnover (including pregnancy).16 Point-of-care capillary HbA1c testing has been shown to be an accurate alternative to laboratory testing in a remote Aboriginal community.17 

Behavioural interventions

People with established type 2 diabetes can have their mortality halved by intensive treatment of multiple cardiovascular risk factors.18 For those with IGT, the Finnish Diabetes Prevention Study showed that interventions aimed at modifying weight, diet and exercise not only halved the incidence of diabetes at 4 years compared to a control group (NNT=8), but maintained most of this benefit for at least 3 years after the initial intervention was ceased.19 There is strong evidence that lifestyle modifications that focus on weight loss, dietary change and increased physical activity should be offered to all individuals at high risk of developing type 2 diabetes.1 However, the recent large ADDITION randomised trial showed that early, intensive risk factor management in newly diagnosed type 2 diabetics resulted in only a small reduction in the incidence of cardiovascular events and death.18 This outcome in European patients aged 40–69 years has uncertain applicability in the Aboriginal and Torres Strait Islander context.

Dietary intervention can effectively delay or prevent diabetes. Two high quality studies have randomised people without diabetes into individual dietary counselling versus routine treatment.20 The Da Qing IGT and Diabetes Study found that, after 6 years, the group given specific dietary advice had a 33% reduction in the incidence of diabetes compared to the control group. The Oslo Diet and Exercise Study found significant reductions in fasting blood glucose, insulin resistance and body mass index compared to the control group at 1 year.20 However, an 8-year follow up study in a remote Aboriginal community found that interventions targeting the community store and community nutritional education did not alter trends towards increasing prevalence of obesity and diabetes, possibly due to the limited healthy food choices available.21

Dietary recommendations are found in the Australian dietary guidelines (see Chapter 1: Lifestyle, section on overweight/obesity).

Physical activity improves insulin sensitivity and promotes peripheral glucose uptake. The diabetic related benefits of regular exercise are not limited to subjects who are successful in losing weight. In the Finnish Diabetes Prevention Study, subjects who exercised for at least 4 hours per week but did not lose weight still had a markedly decreased incidence of diabetes compared to those who were sedentary.19 A systematic review found good evidence of reduced diabetes for walking briskly for ≥2.5 hours per week.22 Ideally, a diabetes prevention strategy involves the combined interventions of diet modification and increased exercise. A systematic review of eight trials that combined these two interventions found the relative risk of diabetes was 0.63 compared to the control groups.23 A 7-year follow up study in a remote Aboriginal community involving diet and physical activity interventions found that, despite an increase in average BMI, the prevalence of IGT decreased and diabetes prevalence did not increase, possibly due to improved physical activity.24 Watching television is associated with diabetes; in Australia, those who watch TV for more than 14 hours per week are 2.3 times as likely to develop new diabetes as those who watch less than 14 hours.8 

The national physical activity guidelines recommend a gradual increase in activity intensity to a goal of at least 30 minutes of moderate physical activity on most, preferably all, days (see Chapter 1: Lifestyle, section on physical activity).

Chemoprophylaxis and surgery

Current NHMRC guidelines state that, as many of the medications used in diabetes prevention studies have established side effects, potential benefits and harms should be taken into account before considering pharmacotherapy.1

Oral hypoglycaemic medication at the prediabetic stage can delay or prevent progression to diabetes, but is less effective than lifestyle changes. A large USA trial randomised subjects with prediabetes into an intensive lifestyle modification program, metformin or placebo.25 At 3 years, the metformin group had a 31% less progression to diabetes compared to placebo (NNT=13.9). However, the lifestyle changes group showed a significantly larger relative risk reduction of 58% (NNT=6.9) across all ages and ethnic groups, so the trial was prematurely discontinued. A meta-analysis of 31 randomised trials in people at risk of diabetes showed metformin improves weight, lipid profiles and insulin resistance, and reduces new onset diabetes by 40%.26 

Rosiglitazone and pioglitazone have consistently shown a potent beneficial effect in diabetes prevention but are associated with significant adverse effects, particularly new onset of congestive heart failure.27 

A Cochrane review showed that acarbose reduces the incidence of type 2 diabetes by 25% (NNT=10) in patients with IGT.28 A study randomising obese subjects into receiving lifestyle advice plus either orlistat (a weight loss agent) or placebo found that, in the subgroup who had IGT at baseline, orlistat gave a 45% risk reduction of progression to diabetes at 4 years.29 A high number discontinued therapy: 48% of the orlistat group and 66% of the control group.

Surgical weight loss interventions for severe obesity can result in a dramatic reduction in diabetes. The Swedish Obese Subjects Study compared subjects who had bariatric surgery with matched controls. At 2 years, the 1845 surgery cases had a 32-fold reduction in incidence of newly diagnosed diabetes.27 At 8 years, the prevalence of diabetes in the surgery group remained unchanged from baseline, but had tripled (from 7.8% to 24.9%) in the matched controls.30 

All people at risk for diabetes should be offered lifestyle advice encouraging increased physical activity and improved dietary intake, and advised as to the benefits of weight loss. People who are morbidly obese and potentially suitable for bariatric surgery should be encouraged to consider surgical referral, if available.


In remote and rural areas, poor food supply undermines efforts to address the poor nutritional status of Aboriginal and Torres Strait Islander people. Community stores are frequently the only food source outside traditional bush food.31 Various programs to influence the quality and cost of high nutritional foods in community stores have had some success; a retail co-operative in Arnhem land provided 100% freight-subsidised fruit and vegetables and doubled the intake of these foods per person at 3 years.32 However, the only study of a remote Aboriginal community store intervention that directly reported on diabetes prevalence did not show any improvement.21 More studies are needed.

Surveys in many remote and rural Aboriginal communities have shown facilities for sporting and recreational activities are lacking, yet these are a high priority for community members.33 Further studies are required to assess the association between sport uptake and diabetes in Aboriginal and Torres Strait Islander communities.

Recommendations: Type 2 diabetes prevention and early detection
Preventive intervention typeWho is at risk?What should be done?How often?Level/strength of evidence


Adults ≥18 years from regions with a high prevalence of diabetes (≥5%)
Adults with any of the following high risk conditions:

  • previous IGT or IFG
  • history of gestational diabetes mellitus
  • history of polycystic ovary syndrome
  • history of cardiovascular disease
  • current antipsychotic medication use

Measure fasting plasma glucose or random venous blood glucose
A laboratory test is preferable, but finger prick testing is an alternative. HbA1c may also be used as a screening test for the diagnosis of diabetes*
Perform oral glucose tolerance test in those with equivocal results as above
The 2006 WHO/International Diabetes Federation criteria should be used to diagnose type 2 diabetes, IGT and IFG (see Table 14.1)

Annually as part of an adult health assessment


All adults ≥18 years from regions with a low population prevalence for diabetes (<5%)

Consider screening using AUSDRISK tool to determine if blood testing is required (see Resource)
If AUSDRISK score is ≥12 then proceed as above for high risk populations

Annually as part of an adult health assessment


People <18 years with overweight/obesity

Consider the potential for early onset type 2 diabetes and consider testing according to clinical context (see Chapter 1: Lifestyle, section on overweight/obesity)




All people

Measure BMI and waist circumference
Advise minimum of 30 minutes moderate activity on most days
Encourage diet rich in vegetables, fruits, legumes, high fibre cereals, fish, and lean meats. Limit fats, salt, sugar, alcohol

Opportunistic and as part of an annual health assessment


For people overweight or obese (see recommendations in Chapter 1: Lifestyle, section on overweight/obesity)

Mothers of young babies

Encourage infant breastfeeding (see Chapter 2: Child health)


People with BMI ≥35 kg/m2

Advise intensive lifestyle modification as above
Discuss risks and benefits of bariatric surgery and consider referral if services are available (see Chapter 1: Lifestyle, section on overweight/obesity)




People with a high risk condition (see above) or at high risk of diabetes based on an AUSDRISK score ≥15

Advise intensive lifestyle modification as above
If lifestyle modification is unable to be achieved, the use of metformin, acarbose, rosiglitazone or orlistat has been shown to delay or prevent the onset of diabetes
These medications all have potential risks (in particular rosiglitazone). None is PBS funded for people without diagnosed diabetes, so their use is not recommended at present





Advocate for multifactorial and coordinated community based interventions to increase access to healthy and nutritious food and promotion of increased physical activity (see Chapter 1: Lifestyle, section on physical activity)



* HbA1c testing for the purpose of diagnosing diabetes cannot currently be claimed from Medicare

Table 14.1. Diagnostic criteria for type 2 diabetes and intermediate hyperglycaemia
Type 2 diabetes
Fasting plasma glucose* ≥7.0 mmol/L or
Random venous glucose (point of care)* ≥11.1 mmol/L or
2-hr plasma glucose† ≥11.1 mmol/L or
Glycated haemoglobin (HbA1c)‡ ≥6.5%
Impaired glucose tolerance (IGT)
Fasting plasma glucose <7.0 mmol/L and
2-hr plasma glucose† ≥7.8 and <11.1 mmol/L
Impaired fasting glucose (IFG)
Fasting plasma glucose 6.1–6.9 mmol/L and if measured
2-hr plasma glucose† <7.8 mmol/L
Fasting plasma glucose ≤6.0 mmol/L or
Random venous glucose (point-of-care) ≤6.0 mmol/L
* The diagnosis of type 2 diabetes requires two positive blood tests on separate days unless the plasma glucose is unequivocally elevated in the presence of acute metabolic decompensation or obvious symptoms such as excessive thirst and polyuria
† Venous plasma glucose 2-hr after ingestion of 75 g oral glucose load. If 2-hr plasma glucose is not measured, status is uncertain as type 2 diabetes or IGT cannot be excluded
‡ Currently recommended in some, but not all guidelines. HbA1c is not funded by Medicare for the initial diagnosis of diabetes
Source: Colagiuri S, Davies D, Girgis S, Colagiuri R 20091


AUSDRISK tool: Portals/O/Risk-test.pdf.


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