1.              What are the traditional HbA_1c units and why change?

Traditionally HbA_1c was reported as a percentage of total haemoglobin.  The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) has established a new reference measurement system for the worldwide standardisation of HbA_1c.  The IFCC recommends that HbA_1c concentration be reported in mmol of HbA_1c per mol of haemoglobin (mmol/mol).  This will make comparing HbA_1c results from different laboratories and clinical research trials throughout the world much easier.  These developments are supported by the international diabetes organisations and came about because the HbA_1c assay systems used in both the DCCT and UKPDS trials were not specific for HbA_1c and were not calibrated in the manner that is now required.

The correlation between HbA_1c levels and outcomes highlighted the need to measure HbA_1c accurately and precisely so that results for a person with diabetes can be directly related to studies such as the DCCT and consequently to outcome risks.

In 1998, the EU Commission provided funding to assist the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) in completing its programme to develop a reference method and pure standards for the HbA_1c assay.  The IFCC reference method was published in 2002 and is now the means for the uniform standardisation of HbA_1c assays worldwide.  Measurements are traceable to an SI unit, the mole (mol), and are expressed in mmol/mol rather than as % which is not an SI unit.

The principal officers of the American Diabetes Association (ADA), European Association for the Study of Diabetes (EASD), International Diabetes Federation (IDF) and the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) met at a summit conference in Milan on 4^th May 2007.  It was agreed that the HbA_1c assay results be reported worldwide as IFCC (mmol/mol) and derived DCCT (%) units, using the IFCC-DCCT/NGSP master equation.  This arrangement is called dual reporting and is planned to be introduced worldwide beginning in 2010, after the agreed deadline of 31^st December 2009 for manufacturers to have traceability to the IFCC Reference System in place.

2.               When will this change happen?

In Ireland, from 1^st July 2010, all HbA_1c results will be reported both as HbA_1c (IFCC) in mmol/mol and as the familiar HbA_1c (DCCT) in percentage (%).  This dual reporting will continue until the end of 2011.

3.              What is metrology and why is it so important?

The science of measurement is called metrology and it sets out the requirements for measurement systems including those in laboratory medicine.  Amongst these is the requirement for metrological traceability.  Put simply, this is the linking of a measurement result from a patient sample through an unbroken chain of calibrations to a commonly accepted international reference.

This is a prerequisite to being able to link measurement results to a common reference when using different types of measurement equipment in different locations over time.  The implications of all this are far-reaching.  Measurement systems with full metrological traceability will enable the use of international reference ranges and the harmonisation of decision values.  This will have very important benefits for patient care, the management of long-term conditions, the detection and control of disease, ongoing medical research and the control of healthcare costs.

An important driver for metrological traceability emerged in December 1998 with the publication of the European Directive 98/79/EC on In-vitro Diagnostic Devices, which incorporated the requirement for metrological traceability into regulation.

4.               What are the HSE requirements for suppliers of HbA_1c analysers?

All HbA_1c analysis in Ireland shall be fully metrologically traceable to the IFCC standard.  Patient reports shall show the primary result as IFCC (mmol/mol).  There will be a transitional phase of “dual reporting”, where the report shall also display a secondary DCCT result (%), derived from the primary results using the IFCC-DCCT/NGSP master equation.

To support this, the HSE require from each supplier a certificate of traceability to the IFCC Reference System, issued by one of the IFCC Reference Laboratories.

5.               If I wish to supply a new analyser or reagents for HbA_1c analysis into Ireland, should I advise the HSE?

Yes, it is vital that the HSE is aware of all laboratory analysers and POCT meters providing HbA_1c results in the country, to ensure that all meet the requirements of the Consensus Agreement.

6.              What is the Master Equation?

The term Master Equation is used to describe the mathematical relationship between IFCC results and the various traditional units, and vice-versa.  The most commonly used in Ireland is the IFCC-DCCT/NGSP Master Equation, used to derive the secondary DCCT value from the primary IFCC result:

HbA_1c DCCT (%) = (0.09148 x HbA_1c IFCC (mmol/mol)) + 2.152

7.              What are the important scientific papers on this subject?

A listing of the important scientific papers on this subject will be available on this website in early March.