Furthering the discussion

My original intent was to go through Dr. Novella's and Orac's criticisms individually and take it from there. On second thought I decided not to take that approach. Instead, here is my response.

Firstly, I am grateful that there has been so much discussion about our views. Amid many valid points in their posts made with a skillful turn of the phrase, I saw quite a lot of sarcasm as well. I am sure that the tone of my original post is what incited it, and for that I am sorry: I really do want to have a civil discussion about these ideas, as I realize that we are all learning all the time, and the only way to gain a better understanding of a topic is through discourse. So, again, I apologize for setting the confrontational tone, and will try to avoid it in the future.

I do believe our views are more same than different. We both (SBM group and I) understand that science evolves, that evidence is not stagnant and the sense of certainty frequently conveyed to the lay public by the media is oftentimes misplaced. We simply disagree on the extent to which there is uncertainty in evidence. While it is true that the oft-cited 5-20% number representing the proportion of medical treatments having solid evidence behind them is very likely outdated, the kind of evidence we are talking about is a different matter.

In the hierarchy of evidence, depending on where you look, it is either meta-analyses or the randomized controlled trial that is the gold standard. The latter is a great proof of concept tool, but it is necessarily limited in its external validity, or generalizability. The reason for this is that these trials, frequently done for regulatory purposes, very limited types of patients, exert extremely stringent controls on the total care of the patient (or else are criticized for not doing so if they fail to do so), focus on short-term and surrogate outcomes (hence, the use of cholesterol lowering as a marker for cardiac mortality, for example), and do a fairly abysmal job as a rule considering the sources of heterogeneity of response. The interventions come to market and are typically used in a much broader population based on the evidence of the RCT. This paper, one of many in the same vein, is a nice illustration of a perennial problem with trial evidence, where real-world use of a therapy goes far beyond the available evidence. And although this paper addresses issues with evidence used for reimbursement, these are the same studies that feed guideline recommendations. Certainly meta-analyses, which are a way to combine the data from multiple RCTs in a systematic way, when done well can give us greater confidence of the direction and the magnitude of the treatment effect, but they in no way overcome the generalizability issues of their component RCTs.

The next rung of the evidence ladder is observational data, specifically cohort studies first prospective, then retrospective. I am actually a great fan of observational data, as I have mentioned in the past. Cohort studies give us the opportunity to examine what happens in the real world without imposing artificial conditions necessary in a clinical trial. Observational data can be great when describing epidemiology of a particular disease, the frequency of a given exposure, how different characteristics can modify the relationship between the exposure and the outcome. One of the most attractive features of cohort studies is that the population can be observed over long period of time -- just look at the Nurses' Study, the Framingham Cohort, and others. But these types of studies also have important limitations, and these are readily acknowledged as a heightened susceptibility to bias (especially in the retrospective studies), the possibility of misclassifying important events, and, despite our best efforts to adjust for it, residual confounding. I will come clean and admit my affection for observational data, even despite the fact that it is lower on the totem pole of evidence than an RCT. I really love this paper by Rothman and Greenland that takes a bird's eye view of our research debates. The whole paper really tickles the brain, but I will quote from a section of it briefly here:

Impossibility of Proof

Vigorous debate is a characteristic of modern scientific philosophy, no less in epidemiology than in other areas. Perhaps the most important common thread that emerges from the debated philosophies stems from 18th-century empiricist David Hume’s observation that proof is impossible in empirical science. This simple fact is especially important to epidemiologists, who often face the criticism that proof is impossible in epidemiology, with the implication that it is possible in other scientific disciplines. Such criticism may stem from a view that experiments are the definitive source of scientific knowledge. Such a view is mistaken on at least two counts. First, the nonexperimental nature of a science does not preclude impressive scientific discoveries; the myriad examples include plate tectonics, the evolution of species, planets orbiting other stars, and the effects of cigarette smoking on human health. Even when they are possible, experiments (including randomized trials) do not provide anything approaching proof, and in fact may be controversial, contradictory, or irreproducible. The cold-fusion debacle demonstrates well that neither physical nor experimental science is immune to such problems.

Some experimental scientists hold that epidemiologic relations are only suggestive, and believe that detailed laboratory study of mechanisms within single individuals can reveal cause–effect relations with certainty. This view overlooks the fact that all relations are suggestive in exactly the manner discussed by Hume: even the most careful and detailed mechanistic dissection of individual events cannot provide more than associations, albeit at a finer level. Laboratory studies often involve a degree of observer control that cannot be approached in epidemiology; it is only this control, not the level of observation, that can strengthen the inferences from laboratory studies. Furthermore, such control is no guarantee against error. All of the fruits of scientific work, in epidemiology or other disciplines, are at best only tentative formulations of a description of nature, even when the work itself is carried out without mistakes.

What follows in the hierarchy of evidence are case-control studies, done for some very specific reasons, then case reports and finally expert opinion. When evidence-based guidelines are developed, a comprehensive systematic literature review is undertaken, and all the evidence is examined and ranked. Based on these papers, a recommendation is made and a strength of this recommendation is reported based on the quality of the underlying evidence. This is an arduous and costly process, and it is commendable that it is undertaken. At the same time, given the limitations of the components of the guideline, the final product can be quite inconclusive or even misleading (I hate to bring it up, but look at the screening mammography debate, as well as the recent HRT recommendation reversal). I think it is obvious that I believe in the scientific method, I am simply not convinced that we have done such a great job generating trustworthy evidence in many instances. At the same time, I am not totally nihilistic about what we know, but am somewhere between thinking we have good evidence for a lot of stuff vs. not having any for anything at all.

Allow me one more piece of evidence, if you will, though this is merely anecdotal coming from my dual experience as an author and peer reviewer. I am occasionally floored by the quality of peer review. I have had reviews say on the one hand that of course the paper should be accepted, since it comes from such a reputable group, and on the other reject out of hand papers based on the reviewers' profound lack of understanding of the methods employed. And lest I sound like a crybaby, let me say that I welcome a well-reasoned rejection. What I am talking about is not that. And this is not a surprise, since pretty much anyone can sign up to be a peer reviewer, since, to the best of my knowledge, there is no set of qualifications that journals ask for in their reviewers. And this, so far as I know, applies even to such high caliber publications as JAMA.

So, these are my thoughts on evidence-based medicine. I welcome responses to this, as my understanding of this science is constantly evolving, and differing well-reasoned opinions really help me get a better handle on this stuff.

I will try to tackle my CAM argument next. If I in any way implied in my remarks that I encourage allopathic physicians (by the way, I am not using it in a derogatory way, but merely as it is defined here; in fact, until today I was blissfully unaware of its negative connotation) to be purveyors of CAM, I sincerely apologize. I am pretty sure, however, that I have never made such a statement, as this is not what I believe. My belief is that all modalities that may impact what happens to public's health need to be evaluated for safety, not question. I think we both agree, since there is really no reason to think that something like homeopathy has anything that can help, by the same token we do not believe that it have anything that can hurt. Same with healing crystals, reiki and prayer. So, if a person wants to engage in these activities, and they are perfectly safe physically, be my guest. Other modalities, such as chiropractic, acupuncture, herbalism and the like, definitely need to be evaluated more stringently, as there is reason to think that they may cause harm. And the decisions about their use must be made based on the probability of harm vs. the perceived probability of benefit. Why do I think that these should not be regulated the same way as allopathic treatments? Well, herbs grow naturally and I dare say we have little to say about what our patients grow in their back yards, unless of course the thought is to regulate them the way we do marijuana. As for chiropractic, it is already regulated, though to what extent I am not sure, and would love to hear from someone who knows. Since its techniques most resemble surgical interventions, the level of evidence for them should perhaps be the same as that which we demand in the surgical literature. This is just a thought, and I am not sure that I am correct in this, so other views are, as always, welcomed. What is coming through for me is that perhaps my call to equipoise was a little over the top, as I do not seem to be approaching the above CAM issues in a frequentist, but more in a Bayesian way (though I remain committed to equanimity). Yet, there is something to be said about the frequentist approach, even though it is not my way generally. The frequentist approach, which is what underlies the bulk of our traditional clinical research, does not rely on differential prior probabilities for different possible associations, but treats them all equally. Despite many disadvantages, one obvious advantage is that we do not discount potential associations that do not have biologic plausibility, given our current understanding of biology, and sometimes help us stumble on brand new hypotheses. So, clearly, there is a tension here, and I am still working on what is the better way, if any.

My final words will be about vaccination. It is disheartening to be lumped with "anti-vaxers", as has been done in the comments to Dr. Novella's and Orac's posts. While my bruised ego will survive this insult, I would like to question this assertion. Nowhere have I said that vaccinations are a bad idea or present a real danger to our children. The hype surrounding the vaccination-autism "debate" is abhorrent to me. What I have stated, however, is that I am of the opinion that we have gone a bit overboard with some of them, one being the chicken pox vaccine. Now, this does not make me an "anti-vaxer"; this just makes me a bit skeptical. The way I view the data is that the advantages for this vaccine are mostly economic, in that they prevent parents from missing days at work. Now, I am certainly not opposed to making such a vaccine available to parents who desire it, but I am not convinced that it should be a prerequisite for my kid to go to school. Given that there is always a possibility of an adverse reaction, no matter how small that possibility is, if the risk of it may outweigh the benefit (and here I do not mean the benefit of having mom show up at work), it has to be weighed very carefully. And even though the question asked by one of the comments raises the issue of an immunocompromised child worrying about potentially being exposed to chicken pox, given the known issues with breakthrough disease, I am not sure that immunizing all of his/her contacts would produce anything other than a false sense of security. My sentiment about the HPV vaccine is similar, to respond to another comment. For reasons laid out here and elsewhere on my blog, I am pretty convinced that it would be a compete subversion of the intent of vaccinations to make it into another mandated shot. To date HPV is merely a recommendation, whose validity I am free to question, though last I heard there was movement afoot to make it mandatory. If in your informed opinion your daughter should get vaccinated against HPV, well then I have very little to say about it. But if I were to counsel an individual patient in the context of my understanding of the data, I would be very upfront with my view.

To me the fact that there are such heated debates about this stuff is a testament exactly to how NOT straightforward our science is. I do understand that as a researcher I can afford a certain amount of analysis paralysis that is unacceptable at the bedside. However, I think we (and the press) do a disservice to the patients, to ourselves and the science if we are not upfront about just how uncertain much of what we think we know is. I could not have said it better than this story about Dr. Devereaux's presentation at the recent ASA meeting did here:

It would be nice if we could all agree that science is not static, but rather progresses and regresses. We learn, and then find out that some of what we thought we had learned was wrong, and set about using that information to seek the next level of truth. Repeat, ad infinitum. Personally, I’d love it if my doctors couched every bit of advice with, “Here’s what we think we know today.”

But I suspect that wouldn’t sit well with many patients, who want certainty (as if there is such a thing). And it especially seems like a difficult proposition in our contentious society, where anti-science nay-sayers like to jump on contradictory findings to challenge the basic value of science overall.

That is exactly NOT what I am trying to do. I am merely reflecting on many of the issues that threaten the validity of what we think we know. I am confident that disclosure and transparency not only lead to better science, but they also lead to science that can withstand the test of nay-sayers.

I have come to the end. I am not sure that I have addressed each and every one of the criticisms, though I hope that I have addressed the majority; I am sure you will point out what I missed. A couple of things about comments: Tomorrow I will be in the air most of the day and may not have the opportunity to sign on to approve comments. So, please, if your comment does not go up until Wednesday, do not think that it has been rejected. Also, I really would like to keep it civil and, though I did not apply this rule today, I will not accept any overt insults or name calling from either side of the debate.

I am sincerely looking forward to continuing this discussion!