High A1C sufficient for diabetes diagnosis

An HbA1c of 6.5% or higher is sufficient to make a diagnosis of diabetes without the need to check fasting glucose levels or perform an oral glucose tolerance test, according to new guidelines from the American Diabetes Association. HbA1c correlated well with the microvascular and, to a lesser extent, macrovascular complications of diabetes. However it had not previously been recommended for diagnosis because of concerns – since resolved – about standardisation of the assay. “There is an inherent logic to using a more chronic versus an acute marker of dysglycaemia, particularly since the HbA1C is already familiar to clinicians as a marker of glycaemic control,” the ADA statement noted. Advantages of using HbA1C included greater convenience, with no need for fasting, and fewer fluctuations during times of stress or illness. However, it was more costly and in some circumstances, such as in patients with certain forms of anaemia and haemoglobinopathies, may not correlate as well with average glucose levels. The recommendation is consistent with the findings of a recently-reported Australian study among about 2,500 Melbourne patients referred for a glucose tolerance test and 6,000 AusDiab participants. An HbA1C of 5.5% or less reliably ruled out diabetes and a level of 7.0% or more was strongly correlated with a diagnosis by conventional glucose estimations. Levels of 6.5-6.9% indicated diabetes was highly probable. Diabetes Care 2010; 33; S62-S69....