(February 28, 2008 - Insidermedicine) The current key criterion for the diagnosis of diabetes mellitus, a fasting blood glucose level of 7.0 mmol/L or more, may require revision as new evidence suggests that the basis for choosing this criterion may be flawed, according to research published in The Lancet.

Here are some facts about diabetes mellitus and its diagnostic criteria:

•    Both the World Health Organization and the American Diabetes Association base the diagnosis of diabetes on a fasting blood glucose level of 7.0 mmol/L or more.

•    This 7.0 mmol/L cutoff was determined based on studies demonstrating that this is the point at which the risk for retinopathy increases substantially.

•    None of these studies, however, used multiple field retinal photographs, which is currently the gold standard technique for diagnosing retinopathy.

In research out of the Centre for Eye Research Australia at the University of Melbourne, investigators analyzed three studies that used multiple field retinal photographs to determine how retinopathy rates relate to fasting blood glucose levels. Together, the studies included nearly 11,500 participants.

The overall prevalence of retinopathy in the general population was found to be between 10 and 16%. Among the three study populations, the investigators were unable to identify a specific fasting blood glucose level that could be used to reliably differentiate those with and without retinopathy. In fact, using a fasting blood glucose cutoff of 7.0 mmol/L would result in missing over 60% of cases of retinopathy.

Today's research demonstrates that the conventional criterion for diagnosing diabetes mellitus may not be as reliable as once believed. There may be a need to revise current diagnostic criteria for this condition.

For Insidermedicine in Depth, I'm Dr. Susan Sharma.