PhilStat/Med

S. Senn: “Placebos: it’s not only the patients that are fooled” (Guest Post)

Stephen Senn

Stephen Senn

Placebos: it’s not only the patients that are fooled

Stephen Senn
Head of  Competence Center for Methodology and Statistics (CCMS)
Luxembourg Institute of Health

In my opinion a great deal of ink is wasted to little purpose in discussing placebos in clinical trials. Many commentators simply do not understand the nature and purpose of placebos. To start with the latter, their only purpose is to permit blinding of treatments and, to continue to the former, this implies that their nature is that they are specific to the treatment studied.

Consider an example. Suppose that Pannostrum Pharmaceuticals wishes to prove that its new treatment for migraine, Paineaze® (which is in the form of a small red circular pill) is superior to the market-leader offered by Allexir Laboratories, Kalmer® (which is a large purple lozenge). Pannostrum decides to do a head-to head comparison and of course, therefore will require placebos. Every patient will have to take a red pill and a purple lozenge. In the Paineaze arm what is red will be Paineaze and what is purple ‘placebo to Kalmer’. In the Kalmer arm what is red will be ‘placebo to Paineaze’ and what is purple will be Kalmer.

senn-placebo

Continue reading

Categories: PhilPharma, PhilStat/Med, Statistics, Stephen Senn | 6 Comments

S. Senn: “Painful dichotomies” (Guest Post)

.

Stephen Senn
Head of  Competence Center for Methodology and Statistics (CCMS)
Luxembourg Institute of Health
Twitter @stephensenn

Painful dichotomies

The tweet read “Featured review: Only 10% people with tension-type headaches get a benefit from paracetamol” and immediately I thought, ‘how would they know?’ and almost as quickly decided, ‘of course they don’t know, they just think they know’. Sure enough, on following up the link to the Cochrane Review in the tweet it turned out that, yet again, the deadly mix of dichotomies and numbers needed to treat had infected the brains of researchers to the extent that they imagined that they had identified personal response. (See Responder Despondency for a previous post on this subject.)

The bare facts they established are the following:

The International Headache Society recommends the outcome of being pain free two hours after taking a medicine. The outcome of being pain free or having only mild pain at two hours was reported by 59 in 100 people taking paracetamol 1000 mg, and in 49 out of 100 people taking placebo.

and the false conclusion they immediately asserted is the following

This means that only 10 in 100 or 10% of people benefited because of paracetamol 1000 mg.

To understand the fallacy, look at the accompanying graph. Continue reading

Categories: junk science, PhilStat/Med, Statistics, Stephen Senn | 27 Comments

“Only those samples which fit the model best in cross validation were included” (whistleblower) “I suspect that we likely disagree with what constitutes validation” (Potti and Nevins)

toilet-fireworks-by-stephenthruvegas-on-flickr

more Potti training/validation fireworks

So it turns out there was an internal whistleblower in the Potti scandal at Duke after all (despite denials by the Duke researchers involved ). It was a medical student Brad Perez. It’s in the Jan. 9, 2015 Cancer Letter*. Ever since my first post on Potti last May (part 1), I’ve received various e-mails and phone calls from people wishing to confide their inside scoops and first-hand experiences working with Potti (in a statistical capacity) but I was waiting for some published item. I believe there’s a court case still pending (anyone know?)

Now here we have a great example of something I am increasingly seeing: Challenges to the scientific credentials of data analysis are dismissed as mere differences in statistical philosophies or as understandable disagreements about stringency of data validation.[i] This is further enabled by conceptual fuzziness as to what counts as meaningful replication, validation, legitimate cross-validation.

If so, then statistical philosophy is of crucial practical importance.[ii]

Here’s the bulk of Perez’s memo (my emphasis in bold), followed by an even more remarkable reply from Potti and Nevins. Continue reading

Categories: evidence-based policy, junk science, PhilStat/Med, Statistics | Tags: | 28 Comments

Msc Kvetch: “You are a Medical Statistic”, or “How Medical Care Is Being Corrupted”

1119OPEDmerto-master495A NYT op-ed the other day,”How Medical Care Is Being Corrupted” (by Pamela Hartzband and Jerome Groopman, physicians on the faculty of Harvard Medical School), gives a good sum-up of what I fear is becoming the new normal, even under so-called “personalized medicine”. 

WHEN we are patients, we want our doctors to make recommendations that are in our best interests as individuals. As physicians, we strive to do the same for our patients.

But financial forces largely hidden from the public are beginning to corrupt care and undermine the bond of trust between doctors and patients. Insurers, hospital networks and regulatory groups have put in place both rewards and punishments that can powerfully influence your doctor’s decisions.

Continue reading

Categories: PhilStat/Med, Statistics | Tags: | 8 Comments

Blog at WordPress.com.