White Coat Underground

ResearchBlogging.orgOne of the concepts we often discuss around here is “what is disease?” As we’ve seen in the discussion of Lyme disease and so-called Morgellons syndrome, this is not always an easy question to answer. Knowing what states are disease states does not always yield a black-or-white answer. The first step is usually to define what a disease is. The next problem is to decide who in fact has that disease. The first question is hard enough, especially in disease states that we don’t understand too well. The second question can be equally tricky. To explore the scientific and philosophical issues of diagnosing an illness we will use as a model diabetes mellitus (DM). This won’t be quite as boring as you think, so don’t click away yet. (Most of the information here refers more specifically to type II diabetes, but most of it is valid for type I as well.)


Diabetes

Diabetes is a metabolic disorder characterized by elevated blood sugar levels. Sometimes very high sugar levels can lead to illness and death, such as in diabetic ketoacidosis. These days, however, people rarely die from having a high blood sugar. The elevated blood sugars of diabetes cause a host of changes in the body over time, leading to two main types of problems: microvascular complications such as blindness and kidney failure, and macrovascular complications such as heart attack and stroke. The macrovascular problems are not unique to diabetics, but the microvascular complications, such as diabetic retinopathy (DR) are unique, and a good ophthalmologist can identify a likely diabetic without even checking a blood sugar level. But blood sugar levels are how we designate someone as being diabetic.

Who is diabetic?

Having diabetes puts you at high risk for the medical complications listed above. Intervening medically can reduce these risks, so knowing who is and is not diabetic is rather important. But knowing who is diabetic is not immediately obvious. Currently, the most accepted way of diagnosing someone as being diabetic is by checking a fasting blood sugar level. But blood sugar levels a very labile. It’s not clear how well blood sugar levels correlate to the risks of diabetes. This week, the journal Diabetes Care released new guidelines from the International Expert Committee which has been tasked with examining how we decide who is, in fact, diabetic.

The damage done by high blood sugars happens over time, but a blood sugar level is a brief snapshot. What clever researchers have done in the past is evaluate patients for a common complication, diabetic retinopathy, and correlate this with blood sugar values. These studies have helped us to decide who is diabetic, as they have shown us that above a certain level, a doctor can see the retinal changes of diabetes. But using a single blood sugar measurement can miss many people who are at risk for diabetes complications.

A test we’ve used for years to monitor the long-term control of blood sugar is the glycosylated hemoglobin level (HbA1C). Hemoglobin, the molecule in red blood cells that carries oxygen, will change when exposed to high blood sugar levels. Normally, about 5% of your hemoglobin is glycosylated, that is, attached to sugar molecules. These A1C molecules reside in red blood cells whose average life span is 120 days, so A1C levels generally reflect about three months of blood sugar levels.

Studies have shown that A1C levels over 6.5-7.0% are associated with increasing complications from diabetes. The International Committee reviewed the data on blood sugar as it relates to A1C, and both A1C and blood sugar as they relate to DR. They found that an A1C of 6.5% and above is closely associated with DR. Therefore, they recommend defining diabetes as having an A1C of 6.5% or above.

Implications

Changing the way we diagnose diabetes does a few things. First, it recognizes that clinicians have been using A1C levels to “diagnose” diabetes for years. It then examines this practice and finds that what we’ve been doing likely prevents diabetic complications. The other effect it will have is to “increase” the number of diabetics as we capture more diabetics with improved testing.

This is a wonderful example of how science-based medicine works. First, a plausible hypothesis is formed (A1C levels should correlate with physical changes in diabetics), looks at the evidence (A1C levels correlate well with diabetic retinopathy), and then practice recommendations are made.

Most important, however, is the realization that practice must change if the evidence warrants. This ability to change is the fundamental difference between medicine based on science, and everything else.

References

The International Expert Committee (2009). International Expert Committee Report on the Role of the A1C Assay in the Diagnosis of Diabetes Diabetes Care DOI: 10.2337/dc09-9033

Comments

  1. #1 CyberLizard
    June 9, 2009

    So if you have an A1C of 7% but no signs of DR, are you diabetic?

  2. #2 PalMD
    June 9, 2009

    abso-friggin-lutely

  3. #3 BAllanJ
    June 9, 2009

    I have an inquisitive GP, who for some reason suspected me of at least borderline diabetes… couldn’t make the diagnosis on fasting blood sugar alone, or A1C, but sent me for a glucose challenge, which I guess let me barely slip into a category where I could be sent for diabetic diet education (2 days down at the hospital classroom). With diet and monitoring i was able to keep out of the actual diagnosis of diabetic for 5 or 6 more years… I think my A1C was still under 5%, but blood sugar spiked higher under challenge than it should have. Anyway, now I am diagnosed diabetic and take some metformin, but still well controlled, and the eye doc can’t find any effects even 10 years later.

    BTW, this is my experience in the Canadian Universal Health care system. I pay for the metformin (cheap) and the glucometer strips (not cheap, but not bad) but my work health plan reimburses me 80% of both of those charges. My GP sees me every 3 months since I’m diabetic instead of the annual I would otherwise see him. (All the GP visits, tests, education classes and access to the dietitian and nurses down at the Diabetes Education Centre at the hospital are free to me)

  4. #4 phisrow
    June 9, 2009

    Is the relationship between elevated blood sugar and elevated risk more or less linear, does it spike at some concentration, steadily increase in both magnitude and slope, or something else?

  5. #5 Ryan
    June 9, 2009

    My A1C once reached 6.5 I accept I am diabetic. However, without medication and through low-carb diet my A1CF is now consistently about 5.5 So…am I diabetic? That is, do I share all the future risk factors associated with diabetes? Given that 3-5 million people may be in my same circumstance, this seems to be a question someone should answer. Once you’ve had cancer…you always have cancer? Once diabetic you are always diabetic?

  6. #6 Arkady
    June 9, 2009

    I think you’ll find that diabetes is actually caused by an octopus demon: http://www.demonbuster.com/diabetic.html

    Be warned, you might want to turn your speakers off or at least down before visiting that site. Apparently disliking the tinny MIDI hymn is a sign of being infested with demons… As far as i can tell the site isn’t a spoof!

  7. #7 Anon
    June 9, 2009

    As the father of a diabetic son, I find this very cool.

    As a psych prof, I would love to see the “what is a disease?” bit done for, say, depression. Seems to me that diagnosing diabetes, fuzzy as it may be, is utter black and white when compared to the can of worms that is psychiatric diagnosis.

  8. #8 Kathy
    June 9, 2009

    I’m sure Dr. Pal wanted to note that this is for type 2 diabetes…type 1 (formerly juvenile) diabetes is pretty dramatic in onset and, I would imagine, fairly easy to spot in people under age 20. Sudden weight loss, lethargy, fruity-smelling breath and sky-high blood glucose levels usually nail it.

    Also, in type 1 diabetes you’re never nondiabetic or ‘borderline’, even if you can get your A1C under 6.5, because you absolutely, positively, cannot make insulin anymore, do not pass ‘Go’ or collect $200.00. Correct, Doc? :-)

    But this is splitting hairs, it’s still a real test in a real doctor’s office that determines your dx…not magic wands. Funny how woo-meisters imagine all sorts of diseases to have but I hardly hear of any who claim to be diabetic…guess that’s not as popular, eh?

  9. #9 PalMD
    June 9, 2009

    Thanks, Kathy, absocorrect. I mentioned it parenthetically in the first paragraph, but it could have been more clear.

  10. #10 Kathy
    June 9, 2009

    …oops, and then I read the last sentence of paragraph 1. I’ll go for a round of chelation therapy with Jenny McCarthy to atone ;-)

  11. #11 weemaels
    June 10, 2009

    Ola doctor,
    What know morgellon ? According to me you do not know anything of it or really not large thing. Inform and please to keep a scientific spirit. I.e.an open spirit.

  12. #12 LanceR, JSG
    June 10, 2009

    Ola doctor,
    What know phlogiston? According to me you do not know anything of this other non-existent thing or really not large thing. Inform and please to keep a scientific spirit. I.e. an open spirit. And please ignore that there is nothing real about this comment, this “disease”, or even my sense. My mind is so open that my brain fell out.

  13. #13 michael Simpson
    June 10, 2009

    @Ryan. Type 1 Diabetes mellitus is probably not reversible, short of some sort of future pancreatic replacement.

    Type 2 diabetes can be controlled to the point where medications can be eliminated. One of the methods, low carbohydrate diets, seems to have some scientific basis according to this paper. The paper even concludes that type 2 diabetes can be reversed, but I’m not sure they’re implying that one is “cured.” I’m assuming if you revert to your high carb diet, the disease will return.

    I wonder if there’s going to be some follow-up research from Duke and other centers regarding this regimen. Of course, the Atkins people are going to be all over it.

  14. #14 Joyce
    June 18, 2009

    There is a reason you call this blog The White Coat Underground. Thats exactly where it belongs. Your pompous, arrogant, sneering attitude is disgraceful, “Doctor.”
    And on and on you go, from one disease you know nothing about to another…Chronic Lyme being one of your favorites. I also have Bartonella, which you probably never even heard of, but that wouldn’t stop you for a second from shredding that to pieces as well. God help you when an infected tick finds its way to someone you love or care about, if you’re capable of it.
    You are closeminded, ignorant and cruel, and clearly get off on it. You, need to see a Dr. to reduce the size of your head and open your heart.

  15. #15 PalMD
    June 18, 2009

    What I really love about the woo is all the compassion. It warms my heart.

  16. #16 confused guy
    January 13, 2010

    im curious now, im a person with a BMI of around 28, so this puts me at increased risk of diabetes (and i work on the PC most day & this increases the risk as far as i know)

    i remember i did fasting blood sugar twice and the results were in the 91-99 range both times

    should I bother to test for A1C next time instead of fasting sugar levels? if yes, what should be the optimal level that would show I don’t have diabetes for sure?

  17. #17 confused guy
    January 13, 2010

    damn, I didn’t notice it’s a 7 months old post !!!

  18. #18 PalMD
    January 13, 2010

    I’m a big fan of checking A1C for folks with slightly high fasting BGs, but it doesn’t always get paid for.