How to smell BS
Students in the 5 PM BIO230 section had a special treat this week, which was watching me having a rage stroke before their eyes. I think my performance was pretty well received, but it is now a few days later, and my blood pressure still hasn’t gotten back to normal. The other lecture sections and my Facebook friends are probably curious as to what it was that set me off, so I thought that I might take the opportunity to try and present a reasoned, logical argument that hopefully might be instructive. Fair warning though, that the language after the break might be kind of salty in places, so if you are easily offended, you might not want to click “Read the rest of this entry!”
With that irresistible carrot out there, here is what happened: in the course of our conversation about the single most important advance in medicine, the control of deadly infectious disease through the process of vaccination, some students mentioned that they had heard that the seasonal influenza vaccine causes a serious condition called Guillain Barre Syndrome. In Guillain Barre Syndrome, the normally immunologically privileged Central Nervous System becomes targeted by a humoral immune response, in the form of antibodies directed against myelin basic protein, or MBP. MBP is a major component of the sheathes around myelinated axons of the central nervous system, and when these sheathes are attacked in an inappropriate immune response, the ability of those nerves to carry impulses becomes impaired. The only treatments for the condition serve to reduce the severity of the signs of disease; no cure currently exists. Guillain Barre Syndrome is extremely rare, with an incidence of less than 1 in 100,000 people per year, and to date it is unclear what the trigger is to lead to the condition.
So naturally, there are plenty of theories as to what “causes” Guillain Barre Syndrome, and these include a number of potential bacterial and viral infections that might serve as a trigger for immune recognition of MBP. The very best circumstantial evidence is the finding that Guillain Barre Syndrome patients frequently have antibodies against a common gastrointestinal pathogen called Campylobacter jejuni, and that antibodies directed against C. jejuni can cross react with axonal autoantigens. The unfortunate situation is that none of these triggers have been demonstrated as a cause of the condition using Koch’s Postulates, which represents our best method for determining the etiology of a disease. Incidentally, the CDC estimates that there are approximately 2.4 million cases of disease due to Campylobacter every year.
So what about the seasonal influenza vaccine? According to the CDC website, there are 80 to 160 cases of GBS across the country each week, and this rate represents the “background” rate. This rate doesn’t fluctuate outside of that range throughout the year, however seasonal influenza vaccines ARE given at certain times of the year: from mid-October through late-January. If there was a link between the two events, we should see a seasonal shift in GBS incidence that mirrors the vaccination peak, however we do not observe this.
Which brings me around, finally, to my main point. It is my fervent hope that everyone in BIO230 takes away one thing from the course: Don’t believe every damn thing you hear! To the students I include myself in this warning and admonition. We should listen to things we hear, and hopefully will have acquired through study the ability to smell bullshit when we hear it. I’ve found a couple of things over the past week or two that immediately set off my BS detector. Last week, I alerted us to the use of social media site in an effort to prolong epidemics. I also called out Dr. House for spreading bullshit on network television. The thing is that with the resources available to us today, we don’t have to take these things at face value; we can assess the validity of them with just a little bit of work. With Guillain Barre Syndrome, the anecdotal incidence presented in class didn’t jibe with the reported national incidence. A couple of clicks visiting reputable websites (the Centers for Disease Control, Pubmed, I even will accept Wikipedia in a pinch) can quickly allow us to make an informed opinion. And that’s not just our responsibility as BIO230 students, it is our responsibility as informed citizens.
BONUS: In the comment thread, describe something that you have heard (let’s keep it medically relevant!) that just doesn’t feel like it adds up. We will try to find out whether it smells like BS or not! Offer good through the first day of class after Thanksgiving.
UPDATE: Comments must be more substantial than “I heard X causes Y”; this is BONUS, and I don’t want to do all the work. Remember, this was a RANT, and I am still ANGRY!