Before requesting genetic testing for MODY, check islet autoantibodies (GAD and IA-2, and ZnT8 where available) and a C-peptide. Positive antibodies make MODY very unlikely. Persisting C-peptide several years after diagnosis, with low insulin needs, supports a monogenic cause. These two results sharpen the referral and spare a costly test in many patients.
- Antibody-positive diabetes points to autoimmune type 1 diabetes, not MODY.
- Detectable C-peptide beyond the first few years of insulin treatment supports a non-autoimmune cause.
- A strong family history across generations, with onset before about 35, raises the pre-test probability.
- Online MODY probability calculators help decide whether testing is worthwhile.
Why it matters
Most suspected MODY turns out not to be MODY, and simple tests can tell you which.
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