Is HbA1c or glucose the better test for diagnosing diabetes?

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Latest news on HbA1c

The 46th Annual Meeting of the European Association for the Study of Diabetes took place 20th - 24th September in Stockholm, Sweden. Presentations at the meeting included 'WHO new diagnostic criteria 2010' and several short presentations on 'HbA1c for diabetes mellitus diagnosis: need for reassessment'.

On behalf of the WHO Working Group on the Definition, Diagnosis and Classification of Diabetes Mellitus, KGMM Alberti presented the 'provisional' new criteria for the diagnosis of diabetes. Alberti summarised the changes in diagnostic criteria that have taken place since the late 1970s up to the recent recommendations for adding an HbA1c cutpoint as a diagnostic tool.

Of main importance for the  Working Group was that WHO has to be cognisant of the needs and capabilities of all health systems world-wide. The committee has thus agreed upon the following recommendations to WHO:

• For practical reasons glucose tests continue to be preferred to diagnose diabetes in many situations. No change from previously agreed cut points. Note! Improvements in quality assurance and performance of assays are needed and better awareness of pre-analytical errors
•  HbA1c can be used as a diagnostic test for diabetes providing that stringent quality assurance test are in place and assays are standardised to criteria aligned to the international reference values

Find out more about how to test for HbA1c.

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Diagnosis with HbA1c - is it better than glucose (2)?

As a measure of glycaemia, HbA1c is less variable within and between individuals than measures of acute glucose control  - Rohlfing et al.Clin Chem 2002;48:1116

The Expert Committee on Diagnosis of Diabetes was convinced that the HbA1c assay has several technical, including pre-analytic and analytic, advantages which, when combined with ease of performance and its much improved standardisation, made it an excellent candidate as a diagnostic tool.

Specifically, HbA1c has the following advantages compared with the currently used laboratory measurements for glucose:

• Better index of overall glycaemic exposure
• At least as good at predicting risk for long-term complications (retinopathy)
• Similar standardisation
• Substantially less pre-analytic instability
• Substantially less biologic variability
• No need for fasting or timed samples
• Relatively unaffected by acute (e.g. stress or illness-related) perturbations in glucose levels
• Used to guide management and adjust therapy

Read the full report.

Find out more about how to test for HbA1c.

What do you think? To join the debate about HbA1c versus glucose, please post your comments on our blog.

Diagnosis with HbA1c - is it better than glucose (1)?

The WHO Guidelines on What Diagnostic Tests Should be Used to Define Glycaemic Status are now about ten years old. Since their publication, the HbA1c test has been standardised - >99% of assays in US and Europe are standardised by the NGSP program to the DCCT standard.

The HbA1c assay is now also widely available and interfering factors have been recognised and minimised.

Find out more about how to test for HbA1c.

What do you think? To join the debate about HbA1c versus glucose, please post your comments on our blog.

Are glucose tests a waste of time (2)?

Type 2 diabetes onset can be subtle, without symptoms and without a clear separation of glucose values from the non-diabetic distribution. Glucose levels fluctuate extensively within the day and between days, and also in response to stress.

The correlation of individual glucose levels with chronic glycaemia is relatively weak and more complete, frequent measurements of daily glucose levels over time are necessary to capture average glycaemia adequately. - David M. Nathan, M.D., AACC, March 31, 2010

Find out more about how to test for HbA1c.

What do you think? To join the debate about HbA1c versus glucose, please post your comments on our blog.

Are glucose tests a waste of time (1)?

"There is no clear division between diabetics and non-diabetics in their FPG (fasting plama glucose) concentration or their response to an oral glucose load." - National Diabetes Data Group, Diabetes 1979;28: 1039-57

Find out more about how to test for HbA1c.

What do you think? To join the debate about HbA1c versus glucose, please post your comments on our blog.

How accurate is fasting plasma glucose for diagnosing diabetes?

The WHO Guidelines on What Diagnostic Tests Should be Used to Define Glycaemic Status show that fasting plasma glucose will fail to diagnose approximately 30% of people with diabetes.

In an older population, it has been reported that 70% of women and 48% of men aged 50-89 years had new diabetes diagnosed solely by an elevated two hour plasma glucose.

Read the WHO Guidelines.

Find out more about how to test for HbA1c.

What do you think? To join the debate about HbA1c versus glucose, please post your comments on our blog.

Do you really know what the WHO guidelines on blood glucose measurement recommend?

The WHO Guidelines on What Diagnostic Tests Should be Used to Define Glycaemic Status state:

Glucose should be measured immediately after collection by near patient testing, or if a blood sample is collected, plasma should be separated immediately, or the sample should be collected into a container with glycolytic inhibitors (e.g. NaF) and placed on ice-water until separated prior to analysis.

If your samples are going off to the lab, how accurate are the results?

Read the WHO Guidlines.

Find out more about how to test for HbA1c.

What do you think? To join the debate about HbA1c versus glucose, please post your comments on our blog.

NHS health checks best practice

The NHS document Putting Prevention First states, in the section on diabetes risk assessment, that either a fasting plasma glucose (FPG) or an HbA1c test can be used to identify those at high risk of developing or having diabetes.

Using an HbA1c test means the patient doesn’t need to fast, which we all know can be difficult for some people.

Read the full document.

Find out more about how to test for HbA1c.

What do you think?  To join the debate about HbA1c versus glucose, please post your comments on our blog.

Glycated haemoglobin superior to fasting glucose for assessing cardiovascular risk

A unique longitudinal study was published in the New England Journal of Medicine earlier this year about the advantages of HbA1c over fasting glucose.

The 15 year study based on 11,092 black and white, non diabetic adults concluded: “glycated haemoglobin (HbA1c) was similarly associated with risk of diabetes and more strongly associated with risks of cardiovascular disease and death from any cause as compared with fasting glucose”

New England Journal of Medicine 2010; 362:800-11. Published March 4, 2010. Read the full paper.

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