You said it...

Dear Omnus Endocrinology Update, It is correctly stated in the article that both fasting glucose and 2 hour glucose results are highly variable. This acknowledgement has highlighted the flaw in using oral glucose tolerance test (OGTT) as a diagnostic gold standard. For example 30% of patients diagnosed as 'diabetic' on OGTT, may not be 'diabetic' if the test is repeated (too bad about that life insurance policy). The issues regarding haemoglobinopathies and HbA1c continues to be exaggerated. Quality laboratories use methods that either (a) can detect most abnormal haemoglobin variants before putting out a misleading HbA1c level or (b) use HbA1c methods that are unaffected by most of these common abnormalities. Similarly, patients with renal failure or anaemia are usually known as having these conditions and the caution using HbA1c for diagnosis in the future also applies to caution using HbA1c for monitoring in these patients today. What is sad is that this current issue adds to the growing list of 'trans-Atlantic' diabetes debates including (i) the definition of impaired fasting glycaemia (6.0-6.9 mmol/L (as in Australia) or 5.6-6.9 mmol/L) (ii) the place of OGTT in diagnosis of diabetes (iii) the units used for HbA1c reporting (% as IFCC or DCCT or mmol/mol) (iv) the reporting of estimated average glucose (eAG) and now (v) the use of HbA1c as a diagnostic test for diabetes. Like good colonials, New Zealand, Canada and Australia are usually comfortable disagreeing with those brash Americans. Is it possible that diabetologists and laboratorians aren't putting patients interests ahead of philosophical debates? In Australia over a quarter of a million have OGTT's each year involving an overnight fast and waiting over 2 hours for three blood tests. (Perhaps 5 million hours of fasting might actually help the nation lose some weight!?) A single non-fasting HbA1c level is certainly much more convenient (and even less expensive). Furthermore, no clinician has any doubt that a single HbA1c is a better marker of diabetic control than any number of glucose results. So why are two highly variable glucose results so much better than HbA1c for diagnosis? Ken Sikaris I am in favour of using the HbA1c as a diagnostic tool especially in the hospital and rural and remote setting. These are the areas that would benefit the most as doctors in the private hospital where I work have begun to use the HbA1c as an indicator for diabetes and although they organise a follow up GTT it rarely gets completed....