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NIHR Signal Comparing blood tests to detect diabetes during NHS health checks

Published on 26 August 2015

doi: 10.3310/signal-000114

This NIHR-funded study estimated the long-term cost effectiveness of using two recommended blood tests – glycated haemoglobin or fasting blood glucose - to detect type 2 diabetes during NHS health checks. Several screening strategies were tested. In most cases the glycated haemoglobin test was more likely to be cost effective than a fasting blood glucose. But results were based on modelled data sourced from a Leicestershire diabetes database and populations may be different in other regions leading to different results. The researchers included scenarios with and without pre-screening to filter out people with a low risk of diabetes before either blood test.

The lifetime cost savings (£12), and health benefits per person, were small. The HbA1c cost-benefit advantage depended on the tested population having a high prevalence of diabetes and the uptake of glycated haemoglobin being greater than for fasting blood glucose test. Those participating in health checks may prefer the glycated haemoglobin test as it does not require an overnight fast. Commissioners should exercise caution in applying the findings to their local populations if they differ from those studied here in Leicestershire.

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Why was this study needed?

In the UK, an estimated 850,000 people have type 2 diabetes without knowing it, and a further 7 million people are at high risk of developing type 2 diabetes. The NHS health check, a free health MOT for all adults in England aged 40 to 74, checks the health of a person’s heart and blood vessels. Identifying people who have type 2 diabetes, or are at high risk of developing it, is part of the check.

People in these two categories are offered a blood test to confirm their diagnosis or raised risk. The blood test using glycated haemoglobin (HbA1c) is taken the same day, or after a planned fast in the case of a fasting blood glucose test. The cost of a single fasting blood glucose test is about £12 and an HbA1c test is about £14. The HbA1c test is becoming more popular as it does not require the patient to come back after an overnight fast. This study was funded by the NIHR to establish which of the two available tests was most cost-effective over the long term.

What did this study do?

This study estimated the long-term cost and health implications of using fasting blood glucose or HbA1c tests to detect adults with, or at high risk of, type 2 diabetes during the NHS Health Check.  

The main analysis used 8,147 adults from Leicester with a high prevalence of diabetes – around 5.7%. They were contrasted with a group of 3,906 adults from East Anglia with a lower diabetes prevalence of around 2.3%.  

Long-term costs and health were estimated using an adapted NICE public health guideline model called the Sheffield Type 2 Diabetes Model. This estimated probable treatment pathways, complications, and death rates for people taking the tests over an 80-year period.

The study also looked at the impact of pre-screening to select people at highest risk of diabetes before the blood tests. No pre-screening was compared with a general practice computer-based risk score or a finger-prick blood test.

What did it find?

  • In most scenarios HbA1c had a higher chance (about 95 to 98%) of being more cost effective than fasting blood glucose. This included scenarios using no pre-screening, computer-based risk scores, or the finger-prick blood tests to filter out people with a low risk of diabetes before the blood tests.
  • In most scenarios the lifetime cost savings, and health benefits per person per year, were very small.
  • The lowest cost option used a computer-based diabetes risk score pre-screening step. In this scenario, compared with fasting blood glucose, HbA1c would save about £12 over a person’s lifetime (£78 vs. £66). It also added eight days of life lived in good health per year for each person tested.
  • With no pre-screening stage, HbA1c would save £30 per person compared with fasting blood glucose for the same eight day annual health gain. But the overall costs were slightly higher (£105 vs. £75).
  • The HbA1c cost advantage depended on the population having a relatively high prevalence of diabetes, such as the Leicester group, and the uptake of HbA1c being higher than fasting blood glucose. 

What does current guidance say on this issue?

The 2012 NICE guideline on prevention of type 2 diabetes says that people attending the NHS Health Check who have not been diagnosed with diabetes, cardiovascular disease, stroke or kidney disease should be offered an initial risk assessment. If they are at increased risk of diabetes they will be offered a blood test, either HbA1c or fasting blood glucose, but the guidance does not specify a preference. People identified as being at risk will be advised and helped to lose weight (if appropriate), become more physically active and improve their diet.

What are the implications?

The findings are consistent with the 2012 NICE guideline and current (2015) NHS Health Check procedures for screening for type 2 diabetes.  This study suggested HbA1c is more likely to be cost effective over the long-term compared with fasting blood glucose. But commissioners should be aware that the HbA1c advantage depended on the population having a relatively high prevalence of diabetes and the uptake of HbA1c being greater than fasting blood glucose. These assumptions may not be true in all regions in England.

Citation

Gillett M, Brennan A, Watson P, et al. The cost-effectiveness of testing strategies for type 2 diabetes: a modelling study. Health Technol Assess 2015;19(33).

Bibliography

Department of Health Science, University of Leicester. Leicester Practice Risk Score [internet] Leicester: University of Leicester; undated.

NHS Choices. What happens at an NHS Health Check? [internet] London: NHS Choices; 2014.

NHS England. NHS Diabetes Prevention Programme [internet] Leeds: NHS England; 2015.

NICE. Preventing type 2 diabetes: risk identification and interventions for individuals at high risk. PH38. London: National Institute for Health and Care Excellence; 2012.

WHO. Use of glycated haemoglobin (HbA1c) in the diagnosis of diabetes mellitus. Abbreviated report of a WHO consultation. Geneva: World Health Organisation; 2011.

Why was this study needed?

In the UK, an estimated 850,000 people have type 2 diabetes without knowing it, and a further 7 million people are at high risk of developing type 2 diabetes. The NHS health check, a free health MOT for all adults in England aged 40 to 74, checks the health of a person’s heart and blood vessels. Identifying people who have type 2 diabetes, or are at high risk of developing it, is part of the check.

People in these two categories are offered a blood test to confirm their diagnosis or raised risk. The blood test using glycated haemoglobin (HbA1c) is taken the same day, or after a planned fast in the case of a fasting blood glucose test. The cost of a single fasting blood glucose test is about £12 and an HbA1c test is about £14. The HbA1c test is becoming more popular as it does not require the patient to come back after an overnight fast. This study was funded by the NIHR to establish which of the two available tests was most cost-effective over the long term.

What did this study do?

This study estimated the long-term cost and health implications of using fasting blood glucose or HbA1c tests to detect adults with, or at high risk of, type 2 diabetes during the NHS Health Check.  

The main analysis used 8,147 adults from Leicester with a high prevalence of diabetes – around 5.7%. They were contrasted with a group of 3,906 adults from East Anglia with a lower diabetes prevalence of around 2.3%.  

Long-term costs and health were estimated using an adapted NICE public health guideline model called the Sheffield Type 2 Diabetes Model. This estimated probable treatment pathways, complications, and death rates for people taking the tests over an 80-year period.

The study also looked at the impact of pre-screening to select people at highest risk of diabetes before the blood tests. No pre-screening was compared with a general practice computer-based risk score or a finger-prick blood test.

What did it find?

  • In most scenarios HbA1c had a higher chance (about 95 to 98%) of being more cost effective than fasting blood glucose. This included scenarios using no pre-screening, computer-based risk scores, or the finger-prick blood tests to filter out people with a low risk of diabetes before the blood tests.
  • In most scenarios the lifetime cost savings, and health benefits per person per year, were very small.
  • The lowest cost option used a computer-based diabetes risk score pre-screening step. In this scenario, compared with fasting blood glucose, HbA1c would save about £12 over a person’s lifetime (£78 vs. £66). It also added eight days of life lived in good health per year for each person tested.
  • With no pre-screening stage, HbA1c would save £30 per person compared with fasting blood glucose for the same eight day annual health gain. But the overall costs were slightly higher (£105 vs. £75).
  • The HbA1c cost advantage depended on the population having a relatively high prevalence of diabetes, such as the Leicester group, and the uptake of HbA1c being higher than fasting blood glucose. 

What does current guidance say on this issue?

The 2012 NICE guideline on prevention of type 2 diabetes says that people attending the NHS Health Check who have not been diagnosed with diabetes, cardiovascular disease, stroke or kidney disease should be offered an initial risk assessment. If they are at increased risk of diabetes they will be offered a blood test, either HbA1c or fasting blood glucose, but the guidance does not specify a preference. People identified as being at risk will be advised and helped to lose weight (if appropriate), become more physically active and improve their diet.

What are the implications?

The findings are consistent with the 2012 NICE guideline and current (2015) NHS Health Check procedures for screening for type 2 diabetes.  This study suggested HbA1c is more likely to be cost effective over the long-term compared with fasting blood glucose. But commissioners should be aware that the HbA1c advantage depended on the population having a relatively high prevalence of diabetes and the uptake of HbA1c being greater than fasting blood glucose. These assumptions may not be true in all regions in England.

Citation

Gillett M, Brennan A, Watson P, et al. The cost-effectiveness of testing strategies for type 2 diabetes: a modelling study. Health Technol Assess 2015;19(33).

Bibliography

Department of Health Science, University of Leicester. Leicester Practice Risk Score [internet] Leicester: University of Leicester; undated.

NHS Choices. What happens at an NHS Health Check? [internet] London: NHS Choices; 2014.

NHS England. NHS Diabetes Prevention Programme [internet] Leeds: NHS England; 2015.

NICE. Preventing type 2 diabetes: risk identification and interventions for individuals at high risk. PH38. London: National Institute for Health and Care Excellence; 2012.

WHO. Use of glycated haemoglobin (HbA1c) in the diagnosis of diabetes mellitus. Abbreviated report of a WHO consultation. Geneva: World Health Organisation; 2011.

The cost-effectiveness of testing strategies for type 2 diabetes: a modelling study

Published on 8 May 2015

Gillett, M.,Brennan, A.,Watson, P.,Khunti, K.,Davies, M.,Mostafa, S.,Gray, L. J.

Health Technol Assess Volume 19 , 2015

BACKGROUND: An estimated 850,000 people have diabetes without knowing it and as many as 7 million more are at high risk of developing it. Within the NHS Health Checks programme, blood glucose testing can be undertaken using a fasting plasma glucose (FPG) or a glycated haemoglobin (HbA1c) test but the relative cost-effectiveness of these is unknown. OBJECTIVES: To estimate and compare the cost-effectiveness of screening for type 2 diabetes using a HbA1c test versus a FPG test. In addition, to compare the use of a random capillary glucose (RCG) test versus a non-invasive risk score to prioritise individuals who should undertake a HbA1c or FPG test. DESIGN: Cost-effectiveness analysis using the Sheffield Type 2 Diabetes Model to model lifetime incidence of complications, costs and health benefits of screening. SETTING: England; population in the 40-74-years age range eligible for a NHS health check. DATA SOURCES: The Leicester Ethnic Atherosclerosis and Diabetes Risk (LEADER) data set was used to analyse prevalence and screening outcomes for a multiethnic population. Alternative prevalence rates were obtained from the literature or through personal communication. METHODS: (1) Modelling of screening pathways to determine the cost per case detected followed by long-term modelling of glucose progression and complications associated with hyperglycaemia; and (2) calculation of the costs and health-related quality of life arising from complications and calculation of overall cost per quality-adjusted life-year (QALY), net monetary benefit and the likelihood of cost-effectiveness. RESULTS: Based on the LEADER data set from a multiethnic population, the results indicate that screening using a HbA1c test is more cost-effective than using a FPG. For National Institute for Health and Care Excellence (NICE)-recommended screening strategies, HbA1c leads to a cost saving of pound12 and a QALY gain of 0.0220 per person when a risk score is used as a prescreen. With no prescreen, the cost saving is pound30 with a QALY gain of 0.0224. Probabilistic sensitivity analysis indicates that the likelihood of HbA1c being more cost-effective than FPG is 98% and 95% with and without a risk score, respectively. One-way sensitivity analyses indicate that the results based on prevalence in the LEADER data set are insensitive to a variety of alternative assumptions. However, where a region of the country has a very different joint HbA1c and FPG distribution from the LEADER data set such that a FPG test yields a much higher prevalence of high-risk cases relative to HbA1c, FPG may be more cost-effective. The degree to which the FPG-based prevalence would have to be higher depends very much on the uncertain relative uptake rates of the two tests. Using a risk score such as the Leicester Practice Database Score (LPDS) appears to be more cost-effective than using a RCG test to identify individuals with the highest risk of diabetes who should undergo blood testing. LIMITATIONS: We did not include rescreening because there was an absence of required relevant evidence. CONCLUSIONS: Based on the multiethnic LEADER population, among individuals currently attending NHS Health Checks, it is more cost-effective to screen for diabetes using a HbA1c test than using a FPG test. However, in some localities, the prevalence of diabetes and high risk of diabetes may be higher for FPG relative to HbA1c than in the LEADER cohort. In such cases, whether or not it still holds that HbA1c is likely to be more cost-effective than FPG depends on the relative uptake rates for HbA1c and FPG. Use of the LPDS appears to be more cost-effective than a RCG test for prescreening. FUNDING: The National Institute for Health Research Health Technology Assessment programme.

Two alternative blood tests are available to check a person’s blood sugar control and see whether they have, or could be at risk of developing type 2 diabetes. Glycated haemoglobin (HbA1c) measures the amount of glucose bound to the oxygen-carrying red blood cells. This gives an overall indication of how well the person’s blood sugar has been controlled over life of the red blood cell, which is around three/four months. Blood glucose shows how much sugar is present in the person’s blood at that moment in time when they have the blood test. A fasting sample is more reliable than non-fasting because if a person has recently eaten their blood sugar levels could be quite variable making it harder to know whether they have diabetes or not.

Expert commentary

NICE recommend a two stage approach to identifying those at risk of diabetes and those with asymptomatic undiagnosed type 2 diabetes. This process involves utilising a non-invasive risk assessment tool, followed by a blood test. Fasting blood glucose or HbA1c can be used for the second stage. Those with a high glucose result receive a repeat blood test on which type 2 diabetes would be diagnosed. This study assessed the cost effectiveness of a number of scenarios for both stages.  For the first stage they found that using a non-invasive risk assessment tool was more cost effective than using a random blood test, which corroborates the NICE recommendation. For the second stage, on the whole they found that it was more cost effective to use HbA1c than fasting blood glucose. Those screening for type 2 diabetes may wish to consider this evidence when choosing which test to use. Using HbA1c may increase uptake to screening as it does not require an overnight fast, which may be a barrier to participation.

Dr Laura Gray, Senior Lecturer of Population and Public Health Sciences, University of Leicester