Diagnosing Diabetes

You are asking an extremely pertinent question as the lines between type 1 and type 2 are often blurred. We differentiate between type 1 and type 2 diabetes based on physical appearence (presence of obesity, acanthosis nigricans- dark velvety pigmentation in neck, armpit areas etc), laboratory work and response to medication. The lab work is very important to determine if any insulin is being made by the individual. So, we measure c-peptide level which is an indirect observation of insulin manufactured by the patient. If it is normal or elevated, the patient may be in a "honeymoon" period and making some insulin even if type 1, or type 2. We also measure the presence of antibodies to the pancreas (GAD-65 antibodies etc.) that may show evidence of autoimmunity. If the patient "looks" like a type 2 physically and has positive antibodies against the pancreas, we, as pediatric diabetologists, call the patient a type 1.5.  Most importantly, we observe the course of the patient's response to medication. Generally if someone has type 2 diabetes, they will respond well to oral medication and perhaps a basal insulin such as Lantus or Levemir. If they require higher insulin doses, and eventually show minimal or no amount of C-peptide, we consider these people most likely type 1. 

As far as genetic types of diabetes such as MODY and Permanent Neonatal Diabetes (PND), there are genetic tests that are conducted by several laboratories (Athena Diagnostics, for example) to determine if, indeed, the patient has MODY or PND. For example, tests are run looking at the DNA for these mutations (ie: KCNJ11 mutation in PND).

I hope I have answered your questions sufficiently. Please comment if you would like any further information. I would be happy to discuss further.

Just another question, because I am curious. What would prompt you to think that the diagnosis might be specifically MODY and not just run of the mill Type 1? Or is this something you just automatically test for?

Thanks.

I think about MODY in patients that do not have the typical physical evidence of type 2 diabetes (obesity, acanthosis etc.) and behave like a type 2 patient. In my experience, MODY patients are often thin and seem to have minimal insulin requirements and can often be treated with oral medication. However, at different times, MODY patients require insulin and sometimes not. There is often a very strong family history in one of the parents, grandparents, aunts and uncles without the type 2 phenotype due to dominant inheritance patterns. I do not automatically test for MODY unless I am very suspicious as the genetic test is very expensive and I have to justify to the insurance company.

Once again, I would be happy to answer any further inquiries.