Wednesday, May 30, 2007

The Irony of Science and Celiac Disease

My blog posts don't usually get a lot of comments.  Many posts don't get any comments at all, so when I get a handful of comments on one post, I start to think that I have hit a resonant note with people.  Well, either that or that I have had the same post at the top of my blog for almost a month.  That DOES tend to allow more time for people to comment on it.  Anyway, my last post on the misunderstood nature of an undiagnosed celiac, or undiagnosed anything, has prompted more shouts of "Amen, Brother!" than anything I have written in the past year.
 
As I write this, I am taking a break from writing experimental details for my doctoral dissertation, which I defend in July.  Soon I will become Dr. ElwoodCity, and move to Home Town and join the Faculty of Science and Technology at Home Town College.  For the past several years I have been working on the development of smarter imaging agents for the diagnosis of breast cancer.  I mention this so you can see my comments in the context of someone who is clearly not "anti-science".
 
This is going to be a long post, because this is a big topic.
 
The thing is, there a limitations on diagnostic medicine, and those limitations contribute to the number of people who are undiagnosed for celiac disease.  This is not in itself a problem.  The problem is that far too many people don't understand what those limitations are, and so fail to even see them.  If you don't see any limitations for diagnostic medicine, you are also going to be blind to the limits of what Scientists and Doctors to know about your health.  Whatever they say must be both accurate and precise.
 
This was my main complaint with Kate Murphy's article.  It implied over and over that if you have a positive test, you should be on a gluten free diet, because the test determines whether you have celiac disease.  If you have a negative test, the only reason you would go gluten free is because you are buying into the newest fad diet.  I'm sorry, but that just reveals who doesn't know what about science, and it isn't good.
 
The main thing that science tries to accomplish is the removal of uncontrolled variables.  We figure out everything that may be affecting the outcome, and change them one at a time, keeping the others constant.  That way we can say how each factor influences the outcome.  In my field, that isn't more complicated than figuring out how you want to change a recipe.  Cooks optimize recipes much the same way I optimize a chemical reaction.  It is pretty simple when all the variables are things you control, like ingredients and temperatures.  In the human body, it is just a tad bit more complicated.
 
The genetic differences in human populations, as well as lifestyle choices, will occasionally make the result of any diagnostic test worthless for one individual.  This is why science preaches against relying on anecdotal evidence.  Think for example if we were trying to decide upon a new set of dietary recommendations, and someone asked you what you ate in order to feel healthy?  Would your answers be applicable at all to the people who live next door?  To the majority of the population?  No, because the people who frequent this blog have a completely different set of variables controlling how they interact with food than the majority of the population.  Diagnostic tests are designed for the majority, not the individual.
 
The solution to this is to decide upon an acceptable threshold for false positives and false negatives.  You take a population, divide them into groups of yes and no, responders and non-responders, and you give them the new test.  Then you decide how to interpret the results so that the most people with a yes result are found, without including too many people from the no group.  The result is that a certain number of people who should be yes are missed - a false negative.  Some people who should be no are included in the yes group - a false positive.  Every test has false positives and false negatives.
 
The current method of predicting response to hormone therapy for breast cancer patients has only a 5% false negative rate.  That is really good.  It has a false positive rate of 60%, though, meaning that if the test predicts that you will respond to hormone therapy, you have only a slightly better than 50/50 chance that you actually will.  This is why I have a research topic.  Shouldn't there be a way to improve that?
 
So here is the question - What is the false negative rate tests for celiac disease?  Does anyone know?  The gold standard test is endoscopy, which implies that the blood tests, while good, have either higher false negatives or higher false positives.  To figure it out, we need to take a population and divide it into people who have celiac disease and people who don't, then perform endoscopies on all of them to see how the endoscopy results correlate with who has celiac disease, and who doesn't.  Now, aside from the fact that that is a complicated study that no one cares enough to do, how are you going to do the initial division into groups?  How are you going to select celiacs from "normal" people to have something to correlate your data to?
 
The only way I can think of is to put people on a gluten free diet, and see who feels better and who doesn't.  Wait a minute... I think I've heard that somewhere before...
 
Oh yeah! It was in an article in the New York Times, by Kate Murphy.  "The final proof is reversal of symptoms on a gluten-free diet."  Thanks, Kate, for helping us know how we can know definitively whether we should be on a gluten free diet or not.  The irony of the whole situation is that the people who claim authority for the diagnostic tests because they come from "science" understand the process less well, and is less scientific, than someone who just stopped eating wheat, barley, rye and oats (sometimes) to see if they would feel better.
 
So here's to you, undiagnosed celiac scientists!
 
(And this doesn't even address the issue of medical doctors, and their ability to think outside the box.  That could be another whole post on its own, but I need to get back to work.)

6 comments:

  1. Ahh...science. Understanding the benefits and limitations of science make me the bane of some doctor's and the ideal patient to others. I made my oncologist crazy when I disagreed with her statistical reasoning on the drug she recommended for my early stage breast cancer. However, my radiation oncologist was impressed that I understood the statistical advantages of the treatments and the limitations. She was willing to have detailed discussions with me...although as a radiation oncologist she was in the business of calculating numbers.

    My diagnosis for gluten sensitivity followed an interesting diagnostic path. My hematologist/internal medicine specialist told me I had antibodies and needed to do a gluten free diet test. After I got better and asked if I should have a biopsy, she said, "Why? You got better." When I questioned her about the diagnosis, she told me that I had an autoimmune problem (hypothyroid) that meant she should think of celiac disease, plus I was lactose intolerant. Then she said that other things can cause villous atrophy, such as having a dairy problem. So, she made the diagnosis based on other factors that she had the lab draw blood to measure and the diet.

    Science...it's a beautiful thing.

    Sheltie Girl @ Gluten A Go Go

    ReplyDelete
  2. Well, I'm not a science person AT ALL (which is an understatement). LOL But I have to say, one thing I appreciate about you and all your brainy-ness is that you're good at explaining things to those of us not quite as immersed in that field. Good post!

    ReplyDelete
  3. stephanie12:54 PM

    Well said. And thank you for writing it the way you did. My 2 year old son had the positive blood tests, but his biopsy just showed inflammation and not a positive for CD and it was suggested he go gluten free. I limited his gluten and noticed a difference on the days I did and the days I forgot to. When I switched pediatricians, she was puzzled and followed up with the gastroenterologist who told her, he has celiac and needs to be gluten free. The day she called I had given him gluten at every meal so his first 'attack' came. Timing is everything. So, according to science does he really have it if his biopsy wasn't positive? Confusing as heck.

    I've been gluten free for a month along with him and my health has improved (and I lost 11 pounds). I didn't bother getting tested because I started it with him and could tell my past health history really could have been CD the whole time except 20 years ago they never tested me for it.

    ReplyDelete
  4. My understanding is that to "officially" have celiac disease, so that you get to claim GF food as a medical expense deduction on your taxes, in the U.S. you need to have a doctor's note saying that you have celiac disease. In Canada, you have to have a positive biopsy result.

    I think that reflects on the view that governments have of Science (Big S). On the other hand, if you try the diet and feel a lot better, and you have done your best to rule out other factors like sleep habits, and food poisoning or whatever, that is pretty scientific.

    Whether you decide to tell people you are an undiagnosed celiac, or that you just feel a lot better when you don't eat gluten, I'm glad you feel so much better.

    ReplyDelete
  5. Anonymous7:36 AM

    For the past 8 years I've "felt better" eating a gentler gluten diet. I began using spelt flour instead of regular wheat. I seem to be becoming more intolerent to that now, but many "gluten-free" products contain ingredients that I also react to , such as corn (swollen joints) and potato flour. I was glad to find your blog and your recommendations, especially idea that a diagnosis can let you claim GF foods as a tax deduction! My husband will be thrilled!

    ReplyDelete
  6. Aside from being so much cheaper, being aboe to control all the ingredients that go into your food is a great advantage to baking your own.

    The Maestro gets a rash whenever he eats corn, so we try to minimize his corn intake. That is not easy to do using commercial GF foods, but pretty easy when I'm baking. I just substituted tapioca starch for corn starch.

    ReplyDelete