EASD/ADA Symposium
Monitoring of glycaemia in people with diabetes: will mean blood glucose substitute HbA1c?

Which factors affect the relationship between HbA1c and mean blood glucose?

This lecture will include a short introduction of HbA1c, a historic look back to the late 1960s, where this unusual component of human hemoglobin was noted to be increased in patients with Diabetes Mellitus (DM), and how it later was recognised as a potential clinical and research tool. The role of HbA1c in the management of DM was established in the 1990’s, in the DCCT trial and the UKPDS trial, and has since become the standard tool used by physicians to monitor long term glycaemic control of the diabetes patient.

The ongoing A1c Derived Average Glucose Study (the ADAG Study) is a multi-center, multiethnic study aiming to establish the relationship between Average Blood Glucose concentrations and HbA1c values according to the DCCT and the IFCC method in a wide range of patients with Type 1 and Type 2 diabetes in order to standardize HbA1c assays globally (by use of the IFCC- HbA1c as reference method).
Thus, the study aims to establish the best relationship between HbA1c and mean (average) blood glucose and to use this relationship to predict Average Blood Glucose from a measurement of HbA1c.

Many factors influence this relationship between HbA1c and the mean blood glucose.
It is known that any condition which alters red cell production or turnover, affects the HbA1c result; anemia, structural abnormalities in hemoglobin and liver or renal disease. Other medical conditions and some medications and vitamins are known to interfere with glycation or HbA1c measurements.

From the ADAG Study, with 700 participants intensively measuring blood glucose over a 16 week period, we will present data on the relationship between HbA1c, the mean blood glucose and a number of factors such as age, gender, type of DM and smoking. We will also present data on which way fasting glucose contribute to HbA1c as opposed to the postprandial glucose values, and on whether the variation in blood glucose during the day or from day to day alters HbA1c.
Analyses will be done for groups of fast and slow glycators (participants who ‘fall outside’ of what would have been expected from their glucose measurements) – as it has been discussed in other studies, such as the DCCT population.

Finally it will be discussed which of these factors are of clinical relevance, and how they should be addressed in practice.