Pre - diabetes

There are an estimated 5 million people at risk of type 2 diabetes in England (1).

Prediabetes (or Borderline diabetes) is a term that is used to signify that an individual is at risk of developing type 2 diabetes (2).

Diabetes UK state the HbA1c classify an indivual as having prediabetes is (2):

• HbA1c: 42 to 47 mmol/mol (6.0 to 6.4%)

Epidemiology:

• in a study where individuals were classified as having prediabetes if glycated haemoglobin was between 5.7% and 6.4% and were not previously diagnosed with diabetes (3):
  • prevalence rate of prediabetes increased from 11.6% to 35.3% from 2003 to 2011
    • by 2011, 50.6% of the population who were overweight (body mass index (BMI)>25) and =40 years of age had prediabetes

NICE however classifies those at "High Risk" of Type 2 Diabetes as:

• a high risk score and fasting plasma glucose of 5.5-6.9 mmol/l or HbA1c of 42-47 mmol/mol [6.0-6.4%] (1) - note the fasting plasma glucose lower limit of 5.5 mmol/l
  

NICE have outlined the process of assessing risk of a person developing Type 2 Diabetes. The following should have a risk assessment:

• all eligible adults aged 40 and above, except pregnant women
  
  
• people aged 25-39 of South Asian, Chinese, African-Caribbean, black African and other high-risk black and minority ethnic groups, except pregnant women
  
  
• adults with conditions that increase the risk of type 2 diabetes
  • particular conditions can increase the risk of type 2 diabetes. These include:
    • cardiovascular disease, hypertension, obesity, stroke, polycystic ovary syndrome, a history of gestational diabetes and mental health problems. In addition, people with learning disabilities and those attending accident and emergency, emergency medical admissions units, vascular and renal surgery units and ophthalmology departments may be at high risk

Note that GPs and other primary healthcare professionals should not exclude people from assessment, investigation or intervention on the basis of age, as everyone can reduce their risk, including people aged 75 years and over (1).

Assessing Risk of Type 2 Diabetes

• Risk identification (stage 1)
  • use a validated computer-based risk-assessment tool to identify people on their practice register who may be at high risk of type 2 diabetes
  • tool should use routinely available data from patients' electronic health records
  • if a computerbased risk-assessment tool is not available, they should provide a validated selfassessment questionnaire, for example, the Diabetes Risk Score assessment tool (available to health professionals on request from Diabetes UK)
    
    
• Risk identification (stage 2)
  • offer venous blood tests (fasting plasma glucose [FPG] or HbA1c) to adults with high risk scores
  • should also consider a blood test for those aged 25 and over of South Asian or Chinese descent whose body mass index (BMI) is greater than 23 kg/m2
    
    
  • aim is to:
    • determine the risk of progression to type 2 diabetes (a fasting plasma glucose of 5.5-6.9 mmol/l or an HbA1c level of 42-47 mmol/mol [6.0-6.4%] indicates high risk) or
    • identify possible type 2 diabetes by using fasting plasma glucose, HbA1c or an oral glucose tolerance test (OGTT), according toWorld Health Organization (WHO) criteria
      
      
• Interprtation of results
  • if moderate risk (a high risk score, but with a fasting plasma glucose less than 5.5 mmol/l or HbA1c of less than 42 mmol/mol [6.0%]):
    
    
    • tell the person that they are currently at moderate risk, and their risks could increase in the future. Explain that it is possible to reduce the risk. Briefly discuss their particular risk factors, identify which ones can be modified and discuss how they can achieve this by changing their lifestyle
      
      
  • if high risk (a high risk score and fasting plasma glucose of 5.5-6.9 mmol/l or HbA1c of 42-47 mmol/mol [6.0-6.4%]):
    
    
    • tell the person they are currently at high risk but that this does not necessarily mean they will progress to type 2 diabetes. Explain that the risk can be reduced. Briefly discuss their particular risk factors, identify which ones can be modified and discuss how they can achieve this by changing their lifestyle
    • offer them a referral to a local, evidence-based, quality-assured intensive lifestylechange programme. In addition, give them details of where to obtain independent advice from health professionals
      
      
  • if possible type 2 diabetes (fasting plasma glucose of, 7.0 mmol/l or above, or HbA1c of 48 mmol/mol [6.5%] or above, but no symptoms of type 2 diabetes):
    
    
    • carry out a second blood test. If type 2 diabetes is confirmed, treat this in accordance with NICE guidance on type 2 diabetes. Ensure blood testing conforms to national quality specifications. If type 2 diabetes is not confirmed, offer them a referral to a local, quality-assured, intensive lifestyle-change programme
      
      
• Reassessment of risk of type 2 Diabetes based on initial risk assessment results
  
  
  • if low risk (with a low or intermediate risk score)
    • offer to reassess them at least every 5 years to match the timescales used by the NHS Health Check programme. Use a validated risk-assessment tool
      
      
  • if moderate risk (a high risk score, but with a fasting plasma glucose less than 5.5 mmol/l, or HbA1c less than 42 mmol/mol [6.0%]),
    • offer to reassess them at least every 3 years
      
      
  • if at high risk (a high risk score and fasting plasma glucose of 5.5-6.9 mmol/l, or HbA1c of 42-47 mmol/mol [6.0-6.4%])
    • (this group includes people without symptoms of type 2 diabetes whose:
      • first blood test measured fasting plasma glucose at 7.0 mmol/l or above, or an HbA1c of 48 mmol/mol (6.5%) or greater, but whose second blood test did not confirm a diagnosis of type 2 diabetes
    • offer a blood test at least once a year (preferably using the same type of test)
    • offer to assess their weight or BMI

Prediabetes and cardiovascular (CV) risk (4):

• in analysis (n=84,678), absolute risk of major adverse CV events in people with HbA1c 6.4-6.5% was 0.79% higher vs HbA1c 5.8-5.9% and also numerically (not significantly) higher vs HbA1c 6.5-6.5%; findings highlight need to focus on treatment of CV risk factors in prediabetes

Notes:

• the ADA (American Diabetes Association ) have defined the HbA1c level as 5.7% to 6.4% to identify people with a high risk of developing T2DM(5)

Reference:

• NICE (July 2012). Type 2 diabetes: prevention in people at high risk (Updated September 2017)
• Prediabetes. Diabetes UK (Accessed 17/5/22)
• Mainous AG 3rd et al. Prevalence of prediabetes in England from 2003 to 2011: population-based, cross-sectional study.BMJ Open. 2014 Jun 9;4(6)
• Yahyavi SK et al. Prediabetes Defined by First Measured HbA1c Predicts Higher Cardiovascular Risk Compared With HbA1c in the Diabetes Range: A Cohort Study of Nationwide Registries. Diabetes Care Oct 2021, dc211062; DOI: 10.2337/dc21-1062.
• American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes Care 2010;33 Suppl 1:S62-9. [PMID: 20042775]