Identifying monogenic diabetes in multi-racial communities such as Australia remains problematic, as prediction tools useful in people of European descent have limited value in Asian or Indigenous people.
New research from the Fremantle Diabetes Study Phase II (FDS2) found 0.24% of participants in the sub-study had maturity onset diabetes of the young (MODY) that was confirmed by genotyping.
Using a MODY probability calculator, the study identified 8% of people diagnosed with diabetes under 35 years of age and from a European background were likely to have a monogenic form of diabetes. A third of those were confirmed to have a glucokinase (GCK) gene mutation.
The same screening tool found a higher rate of probable MODY (28%) in young people from non-European backgrounds yet genotyping showed none had a known MODY mutation.
Lead author Professor Timothy Davis, from the University of Western Australia, said a MODY calculator was a useful way of pre-screening young people before requesting expensive genetic tests that were not covered by the MBS.
“You’re looking at $700 to $800 to find out if you have one of these mutations so a little bit of pre-screening with a MODY calculator makes it much more cost effective,” he said.
“However you can’t say that in the non-European populations. We didn’t find any MODY even though quite a few of them lit up on the basis of the calculator. It is a limitation of the calculator that it can only be applied to European populations.”
An accompanying editorial in the MJA said MODY genes in Asians and Indigenous Australians may differ from those in Europeans.
They also suggested BMI thresholds may need to be adjusted in MODY risk calculators to better discriminate between MODY and type 2 diabetes in certain sub-groups.
“It’s possible that they have different forms of MODY due to different mutations but there’s not a lot of research outside European populations,” Professor Davis said.
“It would probably require quite a detailed genetic study including the main type 2 diabetes-associated mutations as well, just to make sure any new genes found weren’t just genes predisposing to type 2 diabetes.”
“Non-European people have relatively high rates of type 2 diabetes at young ages and that effectively dilutes the number of cases of MODY so they are more difficult to detect I suspect. It may be they have low rates of MODY; we just don’t know.”