Tackling the lurking beast

Testing for HbA1c to monitor glycaemic control is only set to increase as the incidence of diabetes in the UK continues to grow. We asked Ian Parfrement, Director of Hospital IVD, Roche, why UK laboratories should consider switching from the traditional HPLC method to adopt the immunoassay method, which is widely used throughout Europe and North America

It is estimated that around 2.5 million people in the UK have been diagnosed with diabetes¹. A further half a million are undiagnosed, unaware that they have the disease, and even more are at great risk of developing the condition due to the presence of pre-diabetes or metabolic syndrome².  

The prevalence of diabetes in England alone is staggering and growing, having increased from 3.3% in 2004/2005 to 4.1% in 2008/2009³ and rates of type 2 diabetes are set to almost double by 2020⁴. About 100,000 new cases are diagnosed every year⁵.

This growing population of people with diabetes is putting more and more pressure on local services as they diagnose, monitor and treat the condition. It accounts for approximately 5% of NHS expenditure – equating to around £3.5 billion per year⁵.

In a Department of Health document published earlier this year, the national Clinical Director for Diabetes, Dr Rowan Hillson MBE, observed that the government expects improvements in quality and productivity to drive changes to services, and that this would be achieved by identifying how to improve quality and efficiency and by sharing of best practice⁶. Of course, all of this needs to be considered against the backdrop of ever tightening budgets and demands for cost savings.

Manufacturer of the cobas range of clinical analysers, Roche claims that such improvements in quality and efficiency can be made in the area of Hb1Ac testing.  

Some glucose present in the bloodstream binds to haemoglobin to form HbA1c⁷. The level of HbA1c in blood is directly proportional to the average level of glucose in the blood over the previous 2-3 months and so it is a good indicator of how well diabetes has been controlled in that time period. It is used to monitor glycaemic control and to help make treatment decisions. It is recommended that people with diabetes are tested when they are first diagnosed and at least twice a year after that, more frequently if there has been poor control or if there has been a change in treatment plan⁷.

The percentage of HbA1c in blood should be less than or equal to 48 mmol/mol (6.5%) where diabetes is well controlled (although very low levels may indicate the possible occurrence of hypoglycaemic episodes in people with diabetes)⁷. The traditional method for measuring HbA1c levels is HPLC, however the improvement of the immunoassay method for HbA1c over the years has resulted in more and more laboratories around the world adopting this method routinely, since it is easily consolidated onto existing clinical chemistry analyser platforms.

“In the United States and many parts of Europe, HbA1c testing is now undertaken routinely on clinical analysers using the immunoassay method,” commented Ian Parfrement.  “However, this method is less commonly used in the UK, where the HPLC method is still common practice.”

“The result produced by some HPLC HbA1c test methods may be affected by interference caused by haemoglobin variants and so the laboratory may advise caution by the GP in interpretation of the result because of the possible presence of variants. This can leave the GP in a quandary. He has requested an HbA1c test to monitor a patient’s diabetes and information about the possible presence of variants is of no additional benefit for this purpose. All that is wanted and needed is an accurate HbA1c result that is not compromised by such variants.”

“In addition to providing information that is not needed and can potentially hinder treatment of a diabetic patient, the HPLC method often requires dedicated staff to interpret and validate abnormal chromatograms,” he continued. “This is very time consuming; one lab told us that they spend around an hour a day on this activity alone. By contrast, the Roche Tina-quant [a] HbA1c Gen 2  assay (and soon to be released Generation 3 assay)simply requires the addition of this assay to the test menu on the appropriate cobas analyser, which allows a whole panel of tests to be performed. It provides an HbA1c measurement within seconds and, since it is not affected by interference from most Hb variants, no further interpretation is required.”

“This is established technology,” he continued. “Roche has 20 years’ experience in HbA1c assay development and today more than 50 million HbA1c tests are run every year on cobas platforms.”

In the past, there have been concerns that haemoglobinopathies, resulting in the presence of haemoglobin (Hb) variants, can interfere with HbA1c test results but some new generation HbA1c immunoassays, including the Roche Tina-quant [a] HbA1c Gen 2 assay, demonstrates no interference from common Hb variants. A list of analysers most frequently used to measure HbA1c and whether they are affected by common Hb variants is provided by the National Glycohemoglobin Standardization Program (NGSP), this is important information and is available for download at www.ngsp.org/factors.asp.

“Since many UK labs are not familiar with the immunoassay method, they might mistakenly think that it will cause them problems if Hb variants are present. This is not the case for labs with cobas platforms. The design of the antibody used in our new assays means that there is no interference from common Hb variants (such as HbAS, HbAC, HbAE and HbAD), Hb acetylayion, carbamylation or labile A1c,” explained Parfrement. “This is because it will only recognise the glycated N-terminal end of the Hb beta chain, giving greater test accuracy. This means that no interpretation of results is required, even in the presence of known haemoglobinopathies, which saves valuable time and frees up staff for other important tasks.”

“The lack of interference from Hb variants and chemically modified haemoglobins is an important consideration,” he stressed. “If these forms of Hb are not distinguished from glycated Hb, they could lead to an incorrect estimation in HbA1c with subsequent implications for treatment management decisions.”

The consensus of the American Diabetes Association (ADA), the European Association for the Study of Diabetes (EASD), the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and the International Diabetes Federation (IDF) Working Group on Harmonisation of HbA1c Testing is that HbA1c test results should be standardised worldwide and that the IFCC reference system should be used to implement standardisation of HbA1c test methods⁸.

“For laboratories to be confident in adopting a new method for HbA1c testing, it is important for them to see evidence that its performance is comparable to reference methods,” said Parfrement. “Our new assays are certified by the NGSP as traceable to the Diabetes Control and Complications Trial (DCCT) reference method in addition to being IFCC certified for traceability to the IFCC reference method for HbA1c. In addition, they show very good correlation with commercial HPLC methods and excellent precision (CV <2.0%).”

Roche insists that integrating HbA1c into your routine by adding the assay to your clinical chemistry analyser testing portfolio is in line with the government’s drive towards greater efficiency.

“Adopting the Roche Tina-quant[a] HbA1c Gen 2 assay where there is already the appropriate cobas platform installed to run it, could allow laboratories to reduce the overall cost per analysis and will provide immediate efficiency benefits,” Parfrement continued. “Since it uses common reagents to other Roche assays, workflows are streamlined and up to 200 results are produced per hour (compared with only 35 results per hour for many HPLC methods in the UK). No interpretation of results is required, there is faster test throughput and more rapid turnaround of results, with quality assured.”

“Distribution of results within and between sites is also achievable through the cobas connectivity options that allow the analysers to interface with hospital information systems.  This also means that if the HPLC system is no longer needed for HbA1c testing, only one interface is required rather than two – again this is more efficient.”