You can have what we call a ‘diagnostic genetic test’ which will look for a change in one of the genes known to cause MODY. In 80% (or 4 out of 5) of MODY families a change in one of these genes will be found. This will confirm that you have MODY and the particular type of MODY will also be identified.
What difference will having a diagnostic genetic test make to me?
If MODY is confirmed by a diagnostic genetic test any uncertainty about your type of diabetes will be removed. Knowing which type of MODY you have means that you can be given specific advice about the best treatment for your diabetes. We recommend having a diagnostic genetic test particularly when it may lead to changes in the treatment you are taking for your diabetes.
What does the diagnostic genetic test involve?
The test involves having a blood sample taken from your arm. This can be taken locally and sent to us in the post. The sample will be sent with a diagnostic genetic testing form that is completed by your referring doctor. This may be the doctor involved in your diabetes care, your GP or the doctor from your clinical genetics service.
The blood sample is sent to the molecular genetics laboratory at the Royal Devon and Exeter Hospital where the DNA (or genetic information) is removed from some of the blood cells. The DNA will be examined to see whether or not you have a change in one of the genes known to cause MODY. The remaining DNA is then stored in a freezer. The decision of which MODY gene to check first will be based on details of your own and your family’s diabetes.
In 20% (or 1 out of 5) of MODY families a change in one of the known MODY genes may not be found. We know there are other genes likely to cause MODY that have not yet been identified and your stored sample may be retested as new MODY genes are discovered.
Will other tests be done on my blood sample?
The blood sample you provide will only be tested for changes in genes known or likely to cause MODY. Your blood sample will not be tested for conditions other than diabetes.
How will I find out the result of my diagnostic genetic test?
Diagnostic genetic testing can take some time, particularly if we need to look at more than one of the MODY genes. The results will be sent directly to the doctor who sent your sample and completed the testing form.
Will my genetic test result affect my treatment?
We may recommend changes in your diabetes treatment following your test result, depending on the type of MODY that is confirmed and the diabetes treatment you are taking, for example people with HNF-1a MODY may be changed to tablets called sulphonylureas, if they have not tried these before, as these work particularly well for those with this type of MODY and people with glucokinase MODY are unlikely to need treatment except sometimes during pregnancy.
Will my genetic test result affect other members of my family?
If a change in one of the known MODY genes is identified in you this means that other members of your family who also have diabetes could also have a diagnostic genetic test. This could confirm whether or not their diabetes is caused by the same change in the gene. Family members not known to have diabetes could decide whether or not they would like a predictive genetic test.
How can I find out more information?
You can contact your local Genetic Diabetes nurse or contact Dr. Maggie Shepherd at the Royal Devon and Exeter hospital: