Introduction

1. Introduction What does the HbA1c method have to do with the price of grapes? Well, until recently, there was no standard against which different methods could be calibrated, and therefore what was reported as HbA1c in one lab could not be directly compared to others. Attempts were made to ‘align’ results produced across the UK to those mentioned in the DCCT, and this did help, but now the International Federation of Clinical Chemistry (IFCC) has produced a standard and has specified how HbA1c should be measured; from July, results will be reported in these new ‘IFCC’ units, which can be directly compared between centres. For a while, the old ‘DCCT’ aligned values will be reported alongside, until everyone can ‘get a feel’ for the new values. Leaflets have been produced nationally to help explain the change. There are three slightly different leaflets – one for people with diabetes, one for healthcare professionals, and one specifically for laboratory professionals. A separate Scottish version of each one has also been produced. Why change? Imagine buying some grapes. The price in one shop is 50p per fruit, another shop quotes 30p per fruit, and a third shop quotes 10p per fruit, so where do you buy your grapes? The 10p shop sounds like a much better deal, but in fact it had ‘calibrated’ its ‘fruit’ scales using blueberries - so a grape weighing the same as four blueberries actually costs 40p. The 50p shop, on the other hand, ‘calibrated’ its ‘fruit’ scales using grapefruit, so for only 50p you got a whole bunch of grapes! To solve the problem, each shop needs a standard grape to calibrate the scales for grapes, and the prices need to be adjusted accordingly… What are the targets? Further information What is HbA1c? Copies of the Scottish leaflets are avaiable on the website at www.diabetesinscotland.org.uk. Currently, general targets for HbA1c of around 6.5 - 7.5% are set for an individual, taking into consideration their risk of severe hypoglycaemia, cardiovascular status of these targets are 48 mmol/mol and co-morbidities. The new IFCC equivalent and 59 mmol/mol respectively, with the nondiabetic reference range of 4.0% to 6.0% becoming 20 mmol/mol to 42 mmol/mol. Glucose in the blood binds irreversibly to haemoglobin in red blood cells, forming HbA1c. The higher the glucose, the more HbA1c is formed. HbA1c circulates for the lifespan of the red blood cell, so the level in blood reflects the prevailing blood glucose levels over the preceding 2-3 months. Serial measurements of HbA1c show how an individual’s glucose control, and thus risk of complications, changes in response to alterations in management. Target HbA1c levels can be set for individual patients and therapy adjusted accordingly. HbA1c Understanding the change William G. Simpson 4th Grampian Diabetes Professional Conference Richard Donald Suite, Pittodrie, Aberdeen Wednesday, 27th May 2009 Departments of Clinical Biochemistry Conclusion From July 2009, HbA1c results from laboratories across the UK will be reported in a new way, which will improve consistency between laboratories. For a while, laboratories will report the old (DCCT-aligned) results alongside these new (IFCC) results.