Thursday, June 18, 2015

ADA, Me and My MODY (Maybe) - Part 2

This post is a continuation of my first post on the subject "ADA, Me and My MODY (Maybe) - Part 1" where it discussed a "Meet the Expert" session on Monogenic Diabetes with Dr. Rochelle Naylor.  Today I'll discuss what I learned on Saturday of the ADA Scientific Sessions when I was fortunate to catch Prof Andrew Hattersley in a symposia on monogenic diabetes entitled "Monogenic Diabetes Matters - Getting the Diagnosis and Treatment Right."  Prof Hattersley had a very good description of GCK that it essentially shifted the entire glucose response curve to the right.   This made the fasting blood sugar higher and it meant that the glucose mediated insulin secretion happened at a higher level than in non-diabetics.  This actually made sense to me as I have observed in my own response.  My fasting blood sugar is about 40-80 mg/dl higher than normal and that although a carby meal will shoot me up over 200 mg/dl I hardly essentially never observed readings at 300 mg/dl and above.  Prof Hattersley also noted that GCK patients will feel hypo at a normal glucose.  This is also something I observe.  And it isn't about becoming "adjusted" to the blood sugar level.  My blood sugars are very consistent, but when I get my blood sugars below 100 mg/dl I start to get that hypo feeling.

Prof Hattersley provided some interesting statistics.  He noted that 22% of MODY cases are GCK.  The NIDDK claims that 1-5% of all diabetes cases in young people are MODY.  A systematic screening done at Exeter of 2288 diabetic patients representing 6% of the diabetic population seen by Exeter found that 3% of the diabetic population had MODY.  A similar screening of 1016 pediatric diabetic patients found that 2.4% had MODY.  So Prof Hattersley suggests that MODY has a prevalence of 1-3% in both children and adults diagnosed before the age of 30 years.  In my view it is very hard extrapolating these results to the older adult population but it would seem that the same rates probably apply.

The most alarming thing that Prof. Hattersley noted was that in the UK, 80-90% of MODY patients are not diagnosed.  And the ones that are properly diagnosed take an average of 12 years from their initial diabetes diagnosis until they actually get a proper MODY diagnosis.  In the US the situation is even worse, 94% of MODY patients are not diagnosed and the ones that are diagnose, 73% are not treated correctly.  So Prof. Hattersley speculated on why it is so difficult. Part of the problem is that there is no single criteria, each MODY form presents differently.  And while there is a definitive test, genetic, that is far to expensive to apply to the population as a whole.  And the real issue is that the key indicators that let you differentiate MODY from T1 and T2 overlap, so that it is very difficult achieving good specificity and sensitivity.  He discussed the Exeter MODY Probability Calculator which I mentioned above and he said that an iPhone app based on the calculator was expected to be available in July 2015.  He noted that of course you can measure c-peptide and antibodies but he felt that cutoff points with antibodies still left some ambiguities.  He also noted that in all the world, Sweden does the best job of diagnosing MODY.  They do universal screening (presumably for pediatric patients).  All diabetic children who are antibody negative are genetically tested for MODY.  They missed very few MODY patients in this way.

Overall Prof Hattersley left me with a picture that we still don't really know that much about MODY, that patients are almost universally never properly diagnosed and are mistreated.  He raised some promise that there would be better ways of screening for MODY but I didn't come away with a lot of confidence that physicians would be able to tell the difference between T1, T2 and MODY even if they had a nifty iPhone app.

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