Which relatives to test?

Once a monogenic cause of diabetes has been identified in one individual then other family members with diabetes should also be offered genetic testing to see if they also have the same genetic change.

These other family members may have previously been told they have ‘Type 1’, ‘Type 2’ or ‘gestational diabetes’.

It is important not to assume all family members have the same cause of diabetes as it is possible to have different causes of diabetes within the same family. In addition we have a very small number of individuals with a dual diagnosis, for example co-existing Type 1 diabetes and HNF1A MODY, so confirming the correct cause of diabetes by molecular genetic testing is extremely important. The cost of testing other family members is significantly cheaper (up to 10 times cheaper) compared to the cost of finding the specific genetic change in the proband.