Showing posts with label bias. Show all posts
Showing posts with label bias. Show all posts

Tuesday, February 5, 2013

The World's Worst Coin Trick?

Ben Goldacre – whose Bad Pharma went on sale today – is fond of using a coin-toss-cheating analogy to describe the problem of "hidden" trials in pharmaceutical clinical research. He uses it in this TED talk:
If it's a coin-toss conspiracy, it's the worst
one in the history of conspiracies.
If I flipped a coin a hundred times, but then withheld the results from you from half of those tosses, I could make it look as if I had a coin that always came up heads. But that wouldn't mean that I had a two-headed coin; that would mean that I was a chancer, and you were an idiot for letting me get away with it. But this is exactly what we blindly tolerate in the whole of evidence-based medicine. 
and in this recent op-ed column in the New York Times:
If I toss a coin, but hide the result every time it comes up tails, it looks as if I always throw heads. You wouldn't tolerate that if we were choosing who should go first in a game of pocket billiards, but in medicine, it’s accepted as the norm. 
I can understand why he likes using this metaphor. It's a striking and concrete illustration of his claim that pharmaceutical companies are suppressing data from clinical trials in an effort to make ineffective drugs appear effective. It also dovetails elegantly, from a rhetorical standpoint, with his frequently-repeated claim that "half of all trials go unpublished" (the reader is left to make the connection, but presumably it's all the tail-flip trials, with negative results, that aren't published).

Like many great metaphors, however, this coin-scam metaphor has the distinct weakness of being completely disconnected from reality.

If we can cheat and hide bad results, why do we have so many public failures? Pharmaceutical headlines in the past year were mostly dominated by a series of high-profile clinical trial failures. Even drugs that showed great promise in phase 2 failed in phase 3 and were discontinued. Less than 20% of drugs that start up in human testing ever make it to market ... and by some accounts it may be less than 10%. Pfizer had a great run of approvals to end 2012, with 4 new drugs approved by the FDA (including Xalkori, the exciting targeted therapy for lung cancer). And yet during that same period, the company discontinued 8 compounds.

Now, this wasn't always the case. Mandatory public registration of all pharma trials didn't begin in the US until 2005, and mandatory public results reporting came later than that. Before then, companies certainly had more leeway to keep results to themselves, with one important exception: the FDA still had the data. If you ran 4 phase 3 trials on a drug, and only 2 of them were positive, you might be able to only publish those 2, but when it came time to bring the drug to market, the regulators who reviewed your NDA report would be looking at the totality of evidence – all 4 trials. And in all likelihood you were going to be rejected.

That was definitely not an ideal situation, but even then it wasn't half as dire as Goldacre's Coin Toss would lead you to believe. The cases of ineffective drugs reaching the US market are extremely rare: if anything, FDA has historically been criticized for being too risk-averse and preventing drugs with only modest efficacy from being approved.

Things are even better now. There are no hidden trials, the degree of rigor (in terms of randomization, blinding, and analysis) has ratcheted up consistently over the last two decades, lots more safety data gets collected along the way, and phase 4 trials are actually being executed and reported in a timely manner. In fact, it is safe to say that medical research has never been as thorough and rigorous as it is today.

That doesn't mean we can’t get better. We can. But the main reason we can is that we got on the path to getting better 20 years ago, and continue to make improvements.

Buying into Goldacre's analogy requires you to completely ignore a massive flood of public evidence to the contrary. That may work for the average TED audience, but it shouldn't be acceptable at the level of rational public discussion.

Of course, Goldacre knows that negative trials are publicized all the time. His point is about publication bias. However, when he makes his point so broadly as to mislead those who are not directly involved in the R&D process, he has clearly stepped out of the realm of thoughtful and valid criticism.

I got my pre-ordered copy of Bad Pharma this morning, and look forward to reading it. I will post some additional thoughts on the book as I get through it. In the meantime,those looking for more can find a good skeptical review of some of Goldacre's data on the Dianthus Medical blog here and here.

[Image: Bad Pharma's Bad Coin courtesy of flikr user timparkinson.]

Thursday, July 19, 2012

Measuring Quality: Probably Not Easy

I am a bit delayed getting my latest post up.  I am writing up some thoughts on this recentstudy put out by ARCO, which suggests that the level of quality in clinical trials does not vary significantly across global regions.

The study has gotten some attention through ARCO’s press release (an interesting range of reactions: the PharmaTimes headline declares “Developingcountries up to scratch on trial data quality”, while Pharmalot’s headline, “WhatProblem With Emerging Markets Trial Data?”, betrays perhaps a touch more skepticism). 

And it’s a very worthwhile topic: much of the difficultly, unfortunately, revolves around agreeing on what we consider adequate metrics for data quality.  The study only really looks at one metric (query rates), but does an admirably job of trying to view that metric in a number of different ways.  (I wrote about another metric – protocol deviations – in a previous post on the relation of quality to site enrollment performance.)

I have run into some issues parsing the study results, however, and have a question in to the lead author.  I’ll withhold further comment until I head back and have had a chance to digest a bit more.

Tuesday, July 10, 2012

Why Study Anything When You Already Know Everything?

If you’re a human being, in possession of one working, standard-issue human brain (and, for the remainder of this post, I’m going to assume you are), it is inevitable that you will fall victim to a wide variety of cognitive biases and mistakes.  Many of these biases result in our feeling much more certain about our knowledge of the world than we have any rational grounds for: from the Availability Heuristic, to the Dunning-Kruger Effect, to Confirmation Bias, there is an increasingly-well-documented system of ways in which we (and yes, that even includes you) become overconfident in our own judgment.

Over the years, scientists have developed a number of tools to help us overcome these biases in order to better understand the world.  In the biological sciences, one of our best tools is the randomized controlled trial (RCT).  In fact, randomization helps minimize biases so well that randomized trials have been suggested as a means of developing better governmental policy.

However, RCTs in general require an investment of time and money, and they need to be somewhat narrowly tailored.  As a result, they frequently become the target of people impatient with the process – especially those who perhaps feel themselves exempt from some of the above biases.

A shining example of this impatience-fortified-by-hubris can be
4 out of 5 Hammer Doctors agree:
the world is 98% nail.
found in a recent “Speaking of Medicine” blog post by Dr Trish Greenhalgh, with the mildly chilling title Less Research is Needed.  In it, the author finds a long list of things she feels to be so obvious that additional studies into them would be frivolous.  Among the things the author knows, beyond a doubt, is that patient education does not work, and electronic medical records are inefficient and unhelpful. 

I admit to being slightly in awe of Dr Greenhalgh’s omniscience in these matters. 

In addition to her “we already know the answer to this” argument, she also mixes in a completely different argument, which is more along the lines of “we’ll never know the answer to this”.  Of course, the upshot of that is identical: why bother conducting studies?  For this argument, she cites the example of coronary artery disease: since a large genomic study found only a small association with CAD heritability, Dr Greenhalgh tells us that any studies of different predictive methods is bound to fail and thus not worth the effort (she specifically mentions “genetic, epigenetic, transcriptomic, proteomic, metabolic and intermediate outcome variables” as things she apparently already knows will not add anything to our understanding of CAD). 

As studies grow more global, and as we adapt to massive increases in computer storage and processing ability, I believe we will see an increase in this type of backlash.  And while physicians can generally be relied on to be at the forefront of the demand for more, not less, evidence, it is quite possible that a vocal minority of physicians will adopt this kind of strongly anti-research stance.  Dr Greenhalgh suggests that she is on the side of “thinking” when she opposes studies, but it is difficult to see this as anything more than an attempt to shut down critical inquiry in favor of deference to experts who are presumed to be fully-informed and bias-free. 

It is worthwhile for those of us engaged in trying to understand the world to be aware of these kinds of threats, and to take them seriously.  Dr Greenhalgh writes glowingly of a 10-year moratorium on research – presumably, we will all simply rely on her expertise to answer our important clinical questions.