Identifying people at high risk of type 2 diabetes

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Some people have an increased risk of developing type 2 diabetes. These include people with CVD, hypertension, obesity, stroke, non-alcoholic fatty liver disease, polycystic ovary syndrome (PCOS), a history of gestational diabetes, mental health conditions and people with learning disabilities. Those attending emergency departments, emergency medical admissions units, vascular and renal surgery units and ophthalmology departments may also be at high risk.35


Prediabetes is defined clinically as an HbA1c level of 42–47 mmol/mol (6.0–6.4%) or a fasting plasma glucose (FPG) level of 6.1–6.9 mmol/L.36 Prediabetes is more than just dysglycaemia; it is associated with an increased risk of all-cause death and CVD in both the general population and in those with established atherosclerotic CVD.37 Risk of death in those with prediabetes, even when glucose levels are normalised, remains higher for those with obesity and lower for those who are physically active.38


The recommendations in this section are adapted from sections 1.1–1.3 of the National Institute for Health and Care Excellence (NICE) public health guideline (PH) 38: Type 2 diabetes: prevention in people at high risk.35 These recommendations follow a two-stage strategy to identify people at high risk of type 2 diabetes (or those with undiagnosed type 2 diabetes): risk assessment and subsequent blood testing for those with a high risk score. Whole population-level screening for type 2 diabetes is not recommended. In 2019 the UK National Screening Committee concluded that there is no evidence that population-level screening is more beneficial than not screening. For this reason, we recommend that approaches to risk assessment are targeted.


Encouraging more people to take a risk assessment and testing may add pressure on services, so support from a variety of access points in primary care and the potential for new approaches, such as home testing kits is needed (see section 7.1.4)


Advice for testing for diabetes in women with PCOS is available from NICE.39


Further information on risk assessment and follow up for cardiometabolic disease in people with psychosis or schizophrenia is available in the Positive Cardiometabolic Health Resource.40


 


Figure 2: Risk identification and HbA1c testing


A flowchart of a patient's risk assessment AI-generated content may be incorrect.


Risk assessment, alongside clinical judgement, can identify people who are at high risk of developing type 2 diabetes. The assessment may consider risk factors such as age, BMI, waist circumference, ethnicity, previous gestational diabetes and steroid or antipsychotic drug treatment. Validated computer-based self-assessment tools, like QDIABETES-18 or Diabetes UK’s Know Your Risk, allow people to estimate risk without a blood test. These specific risk-assessment tools can be highlighted primarily by general practitioners (GP) and primary care nurses but also by a range of healthcare professionals in a variety of settings, including pharmacists, optometrists, occupational health nurses, and staff involved in the care of vulnerable groups.


People should not be excluded from any risk assessment on the basis of age alone.


The principle of informed consent requires healthcare professionals to fully inform patients of the consequences of any assessment or test.


Information on the implications of being at high risk and the consequences of developing the condition can be found on the Diabetes UK website. People at any level of risk can be signposted towards reliable trusted sources of support (see section 6.2).


Recommendation

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Primary care healthcare professionals should implement a two-stage strategy to identify people at high risk of type 2 diabetes (and those with undiagnosed type 2 diabetes).


·     Firstly, a risk assessment should be offered.


·     Secondly, for those with high risk scores, a blood test should be offered to investigate if they have type 2 diabetes or prediabetes.


Recommendation

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Encourage people in the following groups to have a risk assessment:


·     all adults aged 40 and above


·     people aged 25 and above of South Asian, Chinese, African-Caribbean, Black, African and other high-risk Black and minority ethnic groups,


·     adults with conditions associated with an increase the risk of type 2 diabetes.


Good practice

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When raising the issue of risk with individuals, adopt a person-centred conversation approach underpinned by professional education and support.

Recommendation

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Where risk assessment is conducted by health professionals in NHS settings outside general practice (for example, in community pharmacies) and the person is scored as high risk, the professionals involved should work to ensure the results are shared with the person and their GP practice (with permission).


Recommendation

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Primary care providers should record risk assessments that score as high risk to ensure appropriate follow up and continuity of care, with consent from the individual.


Good practice

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Robust approaches to follow up and recording (with permission) should be applied in point-of-care pharmacy testing and home blood testing.

People identified with known risk factors associated with the development of type 2 diabetes should be followed up with further diagnostic tests. The aim of the blood test is to check if the person has type 2 diabetes or to confirm their level of risk of progression to type 2 diabetes and discuss how to reduce it.


An HbA1c test measures the amount of glycated haemoglobin in venous blood. As individuals do not need to fast, and the test gives an average blood glucose over the previous 2–3 months, it is the preferred test. An HbA1c level of 42–47 mmol/mol (6.0–6.4%) indicates prediabetes.36


Plasma or capillary blood taken after a fast of 8–10 hours is tested in an FPG test. An FPG of 6.1–6.9 mmol/L is diagnostic of prediabetes.36


The 2-hour oral glucose tolerance test (OGTT) assesses the body’s ability to process a large amount of glucose. Following a fast of 8–10 hours a baseline FPG test is carried out. Then the patient is given 75 g of glucose in a solution. A second blood sample is taken 2 hours later and glucose is measured again to assess how well the patient handled the glucose load.


Blood tests should be carried out by accredited methods either within laboratories or by point-of-care testing methodologies. All methods should be monitored appropriately, and clinical governance procedures should be in place to assure the validity of the results produced. These processes must include adequate training of operators and the performance of regular quality control processes.


When interpreting results, it is important to consider other clinical conditions and medicines that may cause transient hyperglycaemia, such as long-term high-dose steroid therapy.


Consideration should also be given to people with haemoglobinopathies and anaemia, in whom the measurement of HbA1c may not be accurate or may need adjusted.


The following recommendations are from sections 1.4, 1.5 and 1.6 of NICE PH38: Type 2 diabetes: prevention in people at high risk.35


Recommendation

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Trained healthcare professionals should offer and follow up with venous blood tests (HbA1c or fasting plasma glucose) to adults with high risk scores.


Good practice

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In pregnant women an oral glucose tolerance test is acceptable as initial identification.

Good practice

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Primary care consultations are important opportunities to identify individuals at elevated risk and an opportunity to make a shared decision on whether or not a diagnostic test is indicated.

Good practice

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People should be fully informed about the blood test and possible implications before consenting. It is vital that robust decision and intervention pathways are available and explained to patients when test results are discussed.

Recommendation

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For people with possible type 2 diabetes (HbA1c of 48 mmol/mol (6.5%) or above, or fasting plasma glucose of 7.0 mmol/L or above, but no symptoms of type 2 diabetes) carry out a second blood test within 3 to 6 months of the original test. If type 2 diabetes is not confirmed, offer them a referral to a local, quality- assured, intensive treatment programme for prediabetes.


Recommendation

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Offer people with a high risk score and HbA1c of 42 –47 mmol/mol (6.0–6.4%) or fasting plasma glucose of 6.1–6.9 mmol/L a blood test at least once a year (preferably using the same type of test). This includes people without symptoms of type 2 diabetes whose:


·     first blood test measured an HbA1c of 48 mmol/mol (6.5%) or greater, or fasting plasma glucose at 7.0 mmol/L or above, but


·     second blood test did not confirm a diagnosis of type 2 diabetes.



Clinical coding

Record keeping supports following up and reassessing risk. As part of the system of record keeping and recall, the clinical coding is essential. Following a more uniform approach nationally to primary care coding of those known to be at high risk of developing type 2 diabetes is suggested.


Good practice

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Primary care providers should consider maintaining a register of patients with prediabetes and annually review and record their weight and risk factors. If the patient has comorbid cardiometabolic conditions these checks could be captured in the same annual review.

Good practice

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On diagnosis, use a single Read code for prediabetes (C11y5 – pre-diabetes), which is inclusive of prediabetes, impaired glucose tolerance, impaired fasting glycaemia and non-diabetic hyperglycaemia. In Vision use #C11y5 to locate the correct code.

The additional recall code should be used to ensure patients with prediabetes are followed up appropriately (66Az. - high risk of diabetes annual review).



Testing after gestational diabetes

Clinical cut-offs for defining individuals at high risk of developing type 2 diabetes differ slightly for those who have had gestational diabetes mellitus (GDM). The following recommendations are from SIGN 171: Management of diabetes in pregnancy and are based on evidence in the post-GDM population. They should not be applied to the general population.


Recommendation

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Advise women who were diagnosed with gestational diabetes and who have tested postnatally with an HbA1c level below 39 mmol/mol (5.7%) or a fasting plasma glucose below 6.0 mmol/L that they have a low probability of having diabetes at present, and they:


·     should continue to follow the lifestyle advice (including weight management, diet and exercise) given after the birth


·     will need an annual test to check that their blood glucose levels are normal.


Recommendation

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Advise women who were diagnosed with gestational diabetes and who have tested postnatally with an HbA1c level between 39 and 47 mmol/mol (5.7% and 6.4%) or a fasting plasma glucose between 6.0 and 6.9 mmol/L that they are at high risk of developing type 2 diabetes, and offer them advice, guidance and interventions.


Recommendation

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Advise women who were diagnosed with gestational diabetes and who have tested postnatally with an HbA1c level of 48 mmol/mol (6.5%) or a fasting plasma glucose of 7.0 mmol/L or above that they have type 2 diabetes and refer them for further care.


The following recommendations are from sections 1.6 of NICE PH38: Type 2 diabetes: prevention in people at high risk.35


Recommendation

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Offer a reassessment based on the level of risk. Use clinical judgement to determine when someone might need to be reassessed more frequently, based on their combination of risk factors.


Recommendation

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Offer to reassess people with a high risk score, but with an HbA1c less than 42 mmol/mol (6.0%) or a fasting plasma glucose less than 6.1 mmol/L or, every 3 years.


Recommendation

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Offer to reassess people with a low or intermediate risk score every 5 years using a validated risk-assessment tool.