A proper diagnosis of diabetes can involve a variety of lab tests, including any of three glucose tests:

• Random glucose
• Fasting glucose
• Oral glucose tolerance test (OGTT)

Because a single positive test is not enough to confirm a diagnosis of diabetes, a series of tests may be conducted over time. In addition to these basic diabetes tests, a diagnosis of maturity-onset diabetes of the young (MODY) involves:

• A thorough review of the patient’s clinical treatment to date and its effectiveness.
  
  
• Evaluation of the severity of hyperglycemia. Young patients who develop MODY3 often exhibit markedly high glucose (blood sugar) and may be mistaken for having type 1 diabetes.
  
  
• The patient’s family history. MODY is often diagnosed in a family where one member has been diagnosed before the age of 25. The pattern of inheritance of diabetes can therefore be identified within the family.
  
  
• A comparison with the four main characteristics of MODY.
  
  
• Genetic testing to determine the gene defect causing the disease. This blood test involves examining a sample to determine if the patient’s DNA contains a genetic mutation consistent with MODY, especially if it is the same genetic mutation as that of a diagnosed relative. It is possible to be genetically tested if parents or other family members have not undergone testing. Test results are normally available within four to eight weeks, depending on the genetics laboratory.

MODY can be mistakenly diagnosed as type 1, type 2 diabetes or another form of diabetes, such as latent autoimmune diabetes of adulthood (LADA). Misdiagnosis is more likely when the patient does not have the body type or age expected for the diagnosis. For instance, a person under age 25 with a slender build does not fit the typical profile of type 2 diabetes.

Children of parents with MODY are most often diagnosed through genetic testing even before symptoms occur. Early intervention, in turn, allows physicians to offer guidance to prevent or delay the onset of the disease.

A positive genetic blood test result indicates the genetic mutation has been inherited from a family member with diabetes. With a positive result, yearly blood glucose evaluations are highly recommended.

So far at least eight types of MODY have been identified. The type of MODY for each patient should be determined, if possible, because treatment options vary depending on the type.