Well there’s nothing like a bit of gentle peer pressure to generate some new FOAM content! Victorian GP, Dr David Corbet, recently tweeted about the new changes to HbA1c testing in the MBS criteria. A brief Twitter conversation followed and as a result, David has not only produced a handy summary about the use of HbA1c, but has also created a new Tumblr which promises to be a great new source of GP gems.
And here it is reproduced with permission:
From November 1 2014 there have been a number of changes to rebates for pathology tests that will have a significant impact on General Practitioners. The main one being the use of the HbA1c for diagnosis of Diabetes Mellitus.
For those of you short on time, here’s the low down:
you can now order a single HbA1c test every 12 months for asymptomatic high risk patients to diagnose diabetes. A result equal to or above 48 mmol/mol (or 6.5% in the old usage) is diagnostic, although lower readings don’t necessarily exclude diabetes.
Hooray! You can download the official documentation from Medicare here.
For those of you with nothing better to do, read on for a little more info and feel free to add comments, ask questions or get involved.
Many countries already use HbA1c, a measure of long term blood glucose control, for diagnosis of diabetes with threshold criteria adequately described in the literature. In Australia we use a fasting glucose of ≥ 7mmol/L (measured on two separate occasions) for diagnosis, or more commonly, having found a raised but non-diagnostic fasting glucose, a postprandial glucose ≥ 11.0 mmol/L from a Glucose Tolerance Test (GTT) (also meant to be on two separate occasions). The GTT is a time and resource consuming test, where a glucose load is given to a fasting patient and their blood glucose levels measured 3 times over a two hour period. Lots of patients have complained to me about the glucose load, primarily due to the intense sweetness and the occasional nauseous vomit.
Up until November 1 this year you could order an HbA1c to monitor control of blood glucose in a patient with known diabetes and receive the medicare rebate 4 times a year. This hasn’t changed, but now there is a rebate available to diagnose “high risk” asymptomatic patients:
Quantitation of HbA1c (glycated haemoglobin) performed for the diagnosis of diabetes in asymptomatic patients at high risk. (Item is subject to rule 25)
Rule 25 appears to relate to the frequency of testing – in this case only once every 12 months to get a rebate. A quick search on the medicare website failed to provide a list of the rules, but I’m curious to read them if anyone has access.
So, what criteria determines if a patient is high risk?
I think it’s safe to say that we can rely on the AUSDRISK guidelines / evaluation to determine high risk patients, defined as a score of 12 or more. Then again, given the machinations of medicare, it’s probably best not to assume anything!
The RACGP 2014-2015 guidelines do support the use of HbA1c ≥ 48 mmol/mol for diagnosis but state readings needed on two separate occasions. It will be interesting to see how they adjust their flow chart for diagnosis to accommodate that only one HbA1c test would get the rebate under the current system!
Limitations of the HbA1C:
Given the assay evaluates glycated haemoglobin from red blood cells, anything that reduces the survival time of red cells will change the result. This becomes important when considering co-morbidities, such as chronic renal failure, post-splenectomy, anaemia and haemoglobinopathies – although the effect of haemoglobinopathies also depends on the type and it’s recommended you talk to your local friendly path lab first if ordering the test. In patients who have had a blood transfusion or therapeutic venesection it is necessary to wait for 3 months to do the test.
The GTT costing from the MBS website shows
Fee: $18.95 Benefit: 75% = $14.25 85% = $16.15
and for the HbA1c
Fee: $16.80 Benefit: 75% = $12.60 85% = $14.30
What’s not to like! Lower cost, equivalent diagnostic test, less resource dependent, more tolerable test, meets international standards. Well done medicare.
The next post will cover some of the other changes. Including strict criteria for Vitamin D testing.