Thu 20 Sep 2012
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Last month three new sets of guidelines were published in the Medical Journal of Australia. These guidelines are aimed at improving the diagnosis of diabetes and chronic kidney disease. The guideline in the area of diabetes relates to the use of the HbA1c test to diagnose diabetes. The Australian Diabetes Society, the Royal College of Pathologists of Australasia, and the Australasian Association of Clinical Biochemists have all agreed that as well as the current methods of diagnosing diabetes using fasting blood glucose or the oral glucose tolerance test, the HbA1c test can now be used. A glycated haemoglobin (HbA1c) level ≥6.5% (48mmol/mol) is now also acceptable for diagnosing diabetes.
The main reason for this change is that HbA1c as a diagnostic test is widely accepted around the world as it is simpler and easier to perform because the person does not need to fast or undergo a complex oral glucose tolerance test. There are a couple of important caveats about the new guideline. The first is that there are some circumstances where the HbA1c test is unreliable, especially when red blood cells are turning over faster than usual in conditions such as haemolytic anaemia or chronic kidney or liver disease. Doctors and laboratories need to be aware of the limitations and use blood glucose testing in these situations. The second caveat is that at present there is no Medicare rebate for HbA1c as a diagnostic test. It only attracts a Medicare rebate in patients who already have a diagnosis of diabetes. Thus this new use of the test will not become widespread until the Medicare schedule is changed and this may take some time.
The two other sets of guidelines relate to chronic kidney disease. The first from the Australasian Creatinine Consensus Working Group proposes a new formula for calculating estimated glomerular filtration rate (eGFR) based on serum creatinine. New research has provided a more accurate formula that should be used by pathology laboratories. The guidelines also recommend that the same formula be used in elderly patients but should not be used in children and adolescents where just the serum creatinine should be reported.
The second kidney-related set of guidelines from the Australasian Proteinuria Consensus Working Group are about diagnosing albuminuria or proteinuria as markers of early kidney disease. Studies in Australia have shown several types of test were being used in this area and that reference ranges were not always standardised between laboratories. The new recommendation is that only the albumin-to-creatinine ratio be used and preferably on a first-morning specimen of urine. No timed urine collections are required. The guidelines also give standardised cutpoints for each sex and algorithms to follow when abnormalities are found.