Volume 4, Issue 1, April 2009
TAI, Morris
Associate Consultant, Department of Pathology and Clinical Biochemistry, Queen Mary Hospital
Introduction
The prevalence of diabetes mellitus (DM) has been increasing in recent years and DM is now a global epidemic. Haemoglobin A1c (HbA1c) plays an important role in the management of DM as the vast majority of outcome studies on diabetic complications are based on it. The most famous of such studies, which demonstrated the relationship of HbA1c to diabetic complications, are the Diabetes Control and Complications Trial (DCCT) & the United Kingdom Prospective Diabetes Study (UKPDS). HbA1c is formed via a posttranslational nonenzymatic attachment of glucose to haemoglobin in an irreversible fashion. In strict chemical terms, the molecular structure of HbA1c is β-N-(1-deoxy)-fructosyl-haemoglobin and it serves as an indicator of glycaemic control over the preceding 2- to 3- month period.
There are a great number of analytical methods used in the measurement of HbA1c. More than 20 methods were in clinical use as reported in the year 2004. The heterogeneity of methodology eventually generated concerns about comparability and usability of HbA1c, especially when patients’ data were to be compared with study results. The call for test standardization was therefore critical. Various standardization programmes have been carried out since the 1990s. The National Glycohaemoglobin Standardization Program (NGSP) and the International Federation of Clinical Chemistry (IFCC) are the two mostimportant international standardization programmes while local ones such as Japan Diabetes Society/Japanese Society for Clinical Chemistry (JDS/JSCC) and Mono-S have been adopted in Japan and Sweden respectively.