Diabetes cut-off too high for retinopathy

Lowering the threshold for fasting plasma glucose levels in diabetes diagnosis could improve retinopathy detection, Australian research suggests.

It showed that 60 per cent of retinopathy cases occur in patients with fasting blood glucose levels below 7.0mmol/l, the cut-off point recommended by the International Diabetes Federation (IDF).

The findings come from a study of 12,664 people, aged 25-97, tested for fasting plasma glucose, BP and retinopathy using multiple-field retinal photographs. Overall, 1,533 participants had retinopathy.

However, 60 per cent of these patients had fasting blood glucose below 7.0mmol/l, with some having level as low as 5.3mmol/l.

Lead researcher Dr Tien Wong, from the department of ophthalmology at the University of Melbourne, said: 'Based on these findings, the diagnostic cut-off for diabetes, which is traditionally based on when retinopathy signs occur, might have to be examined.'

Dr Brian Karet, diabetes lead for Bradford PCT, said the study highlighted the need to check for retinopathy as well as measuring fasting plasma glucose levels.

'We do not have the capacity to do this directly but could use proxy measures like microalbuminuria which has a retinopathy link,' he said.

But Dr Colin Kenny, former chairman of the Primary Care Diabetes Society and a GP in County Down, questioned whether the diagnostic criteria would be changed.

'The diagnostic criteria for fasting plasma glucose has only recently been re-examined by the IDF,' he said.

'There was criticism when the cut-off was reduced from 7.6 to 7.0mmol/l.

'I cannot see the IDF changing things quickly, but their committee might agree to re-examine the diagnostic criteria in light of this study.'

sanjay.tanday@haymarket.com

Lancet 2008; 371: 736-41

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