By Lilian Anekwe
A switch to using glycated haemoglobin to diagnose diabetes has been brought a step closer, after an influential report from the World Health Organisation found there was enough evidence to recommend a cut-off of 6.5%.
The recommendation to replace glucose tolerance testing with HbA1c will have major implications for GP diagnostic practice, NICE guidance and the vascular screening programme, and could significantly ramp up both practice workload and NHS costs.
The WHO report, published after an assessment of the evidence, concluded: ‘HbA1c can be used as a diagnostic test for diabetes, provided there are no conditions precluding its accurate measurement. An HbA1c of 6.5% is recommended as the cut point for diagnosis. A value less than 6.5% does not exclude diabetes diagnosed using glucose tests.’
Pulse revealed in February last year that European authorities were formally considering changing the diagnostic criteria for diabetes given the likely move from the WHO, while the American Diabetes Association switched in January 2010.
UK research has suggested the method disproportionately diagnoses South Asian patients, while other studies have suggested a cut-off of 6.5% results in false positives and negatives of 8.8% and 23.3% respectively in patients over 72.
But the WHO ruled: ‘Policymakers are advised to ensure accurate blood glucose measurement be generally available at the primary health care level, before introducing HbA1c measurement as a diagnostic test.’
Professor Kamlesh Khunti, a GP in Leicester and advisor to the Department of Health’s flagship NHS Health Check programme, said it could have to be revised to reflect the changes: ‘The DH will be making recommendations. Everyone has been waiting for the WHO to make a recommendation and it would be silly not to take it up.’
The switch may also have financial implications, as HbA1c testing is more expensive than conventional oral glucose tolerance testing.
The WHO expert group concluded there was insufficient evidence to make any formal recommendation on the interpretation of HbA1c levels below 6.5%.
Professor Khunti said that was ‘disappointing’, but overall he strongly backed the switch: ‘Our work has shown patients and healthcare professionals don’t like the oral glucose tolerance test and it’s a big barrier to screening. HbA1c has a big advantage because you can do it non-fasting. There are issues in pregnant women and with anaemia, but we can be aware of this.’
NICE guidance on type 2 diabetes, published in May 2008, is scheduled to be reviewed from May this year.
Professor Khunti: HbA1c testing has ‘big advantages’