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Screening Tests – Cumulative Incidence of False Positives

It’s easy to think of medical tests as black and white. If the test is positive, you have the disease; if it’s negative, you don’t. Even good clinicians sometimes fall into that trap. Based on the pre-test probability of the disease, a positive test result only increases the probability by a variable amount. An example: if the probability that a patient has a pulmonary embolus (based on symptoms and physical findings) is 10% and you do a D-dimer test, a positive result raises the probability of PE to 17% and a negative result lowers it to 0.2%.

Even something as simple as a throat culture for strep throat can be misleading. It’s possible to have a positive culture because you happen to be an asymptomatic strep carrier, while your current symptoms of fever and sore throat are actually due to a virus. Not to mention all the things that might have gone wrong in the lab: a mix-up of specimens, contamination, inaccurate recording…

Mammography is widely used to screen for breast cancer. Most patients and even some doctors think that if you have a positive mammogram you almost certainly have breast cancer. Not true. A positive result actually means the patient has about a 10% chance of cancer. 9 out of 10 positives are false positives.

But women don’t just get one mammogram. They get them every year or two. After 3 mammograms, 18% of women will have had a false positive. After ten exams, the rate rises to 49.1%. In a study of 2400 women who had an average of 4 mammograms over a 10 year period, the false positive tests led to 870 outpatient appointments, 539 diagnostic mammograms, 186 ultrasound examinations, 188 biopsies, and 1 hospitalization. There are also concerns about changes in behavior and psychological wellbeing following false positives.

Until recently, no one had looked at the cumulative incidence of false positives from other cancer screening tests. A new study in the Annals of Family Medicine has done just that. (more…)

Posted in: Clinical Trials, Diagnostic tests & procedures

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The China Study

One of our readers asked that we evaluate a book I had not previously heard of: The China Study: Startling Implications for Diet, Weight Loss and Long-Term Health, by nutrition researcher T. Colin Campbell, PhD, with his non-scientist son Thomas M. Campbell II. The China Study was an epidemiologic survey of diet and health conducted in villages throughout China and is touted as “the most comprehensive study of nutrition ever conducted.” The book’s major thesis is that we could prevent or cure most disease (heart disease, cancer, diabetes, autoimmune diseases, bone, kidney, eye and other diseases) by eating a whole foods plant-based diet, drastically reducing our protein intake, and avoiding meat and dairy products entirely.

Opinions of the book

There’s a lot of praise for this book on the Internet. It was named VegNews Book of the Year. PETA loves it (not surprisingly). Heather Mills McCartney calls it inspirational. It was featured on Oprah.com and endorsed by two of her favorite doctors: Mehmet Oz and Dean Ornish. Its author was even interviewed on Coast to Coast AM.

But I also found this critical review which makes some excellent points and accuses the authors of misrepresenting the findings of the study. And this commenter on an Amazon.com forum also charges Campbell with misrepresenting the data from the study and points out numerous flaws in his reasoning.

Problematic references

I didn’t look at the praise or criticism of others until after I read the book, and the following represents my independent impressions. I approached the book as I do any book with scientific references: I read until I come across a statement of fact that strikes me as questionable and then I check the references given for the statement. This immediately got me off on the wrong foot with this book. In the first chapter I found the statement:

Heart disease can be prevented and even reversed by a healthy diet. (more…)

Posted in: Book & movie reviews, Cancer, Nutrition

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Bad Books

In the interests of fairness and intellectual honesty, I’ve forced myself to read a lot of really bad books. The True Believer tells me his guru’s book is the Real Stuff. He tells me I have a closed mind and won’t look at anything outside establishment dogma, and if I only read the book and understood Dr. Quack’s evidence and arguments, I would be a True Believer too. I have tried, really I have. I’ve given the Dr. Quacks every chance to convert me, and I’ve hoped to learn something new, but I’m always disappointed. I’ve come to the point that I feel like I’m reading the same book over and over: it is always a mixture of real science, pseudoscience, and speculation, based on cherry-picked evidence and argued with the same logical fallacies.

I recently got hooked into reading another one by a correspondent who had called me an “ignorant relic” for writing a “grossly ignorant article” about alternative medicine. I suggested he read R. Barker Bausell’s book Snake Oil Science and a couple of others, which he promised to do. Then he said, “If I am willing to buy three books that you have suggested and read them and you are not willing to read what I have suggested, then that pretty much says all that needs to be said.”

I was willing, even though the very title of the book suggested that its message was incompatible with the scientific evidence as I know it: How to Prevent and Treat Cancer with Natural Medicine. The authors are big names in naturopathic and herbal medicine: Michael Murray, Tim Birdsall, Joseph Pizzorno, and Paul Riley. It’s nowhere near as bad as some of the bad books I’ve read, but it is a good example of the genre and I’ll use it to illustrate why I call them bad.

It offers “an arsenal of disease-fighting tools for prevention, treatment, and coping with side effects” (Yes, it offers tools; but do those tools work?) And it promises to “change your internal environment so cancer can’t survive.” (Wow! If it could really do that, every oncologist in the world would enthusiastically adopt these methods and the authors would be eligible for a Nobel prize.)
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Posted in: Book & movie reviews, Herbs & Supplements, Science and Medicine

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The (Not-So-)Beautiful (Un)Truth about the Gerson protocol and cancer quackery

Note added by editor: The complete movie is now available on YouTube:

The Beautiful Truth

Although this blog is about medicine, specifically the scientific basis of medicine and threats to the scientific basis of medicine regardless of the source, several of us also have an interest in other forms of pseudoscience and threats to other branches of science. One branch of science that is, not surprisingly, critical to medicine is the science of biology, and the organizing theory of biology is the theory of evolution, which was first reported by Charles Darwin and subsequently synthesized with the developing science of genetics in the early 20th century and then with our increasing knowledge of molecular biology, genomics, and proteonomics whose rise ushered us into the 21st century. However, the implications of evolution, namely that humans and apes both evolved from a common ancestor and that humans, for all their belief of being different and superior to animals, are in fact related to animals in the great chain of life going all the way back to single-celled organisms, does not go down well with certain religious fundamentalists, particularly Christian fundamentalists. Whereas I (and I daresay several of my cobloggers) find the interconnectedness of life, including humans, implied by Darwin’s theory to be beautiful and uplifting, many fundamentalists see it as a profound threat to their world view. Consequently, they have attacked the theory of evolution at every turn and tried to insert creationism, particularly the latest incarnation of creationism known as “intelligent design,” into science classes as an “alternative” to “Darwinism.” The manner in which they torture science, logic, and reason to try to cast doubt on a theory that is every bit as rock solid in terms of massive quantities of experimental and observational evidence to support it as any other theory in science, if not more so, is legendary and well documented at blogs such as The Panda’s Thumb and websites such as Talk Origins.

Although one day I plan on writing about how insights from evolutionary theory have led to deeper understandings of human disease and strategies to improve human health in the future, this time I want to concentrate on the similarities in techniques of spreading disinformation between creationists and purveyors of unscientific medical “treatments.” For background, first, you need to be aware of a movie that was released in April. The movie, Expelled!: No Intelligence Allowed was released. Starring Ben Stein at his most unctuous sporting a bullhorn and styling himself as a conservative, buttoned-down version of Angus Young through his choice of apparel in its promotional material, the movie’s main theme is that any academic who “questioned Darwinism” is “expelled” from academia. The basic idea is that “intelligent design” creationism is being “suppressed” by biologists who just can’t accept the thought of the existence of a “designer” (i.e., God). Indeed, the movie goes so far as to equate biologists and scientists who accept the theory of evolution as the best current explanation for the diversity of life to Hitler and the Nazis and their “suppression” of “alternatives” (word choice intentional) to “Darwinism” to Nazi and Stalinist persecution of dissidents and perceived threats to the regime. The movie even features a sequence where Ben Stein visits Dachau and Auschwitz, as though to imply that biologists are busy firing up the ovens for the Brave Maverick Scientists who “dissent from Darwin.”

These Brave Maverick Scientists are a lot like the Brave Maverick Doctors who champion unscientific medicine. After all, Kevin Trudeau has made a cottage industry and sold millions of books based on the claim that there are “natural cures” that “they” (as in doctors, pharmaceutical companies, and the government) don’t want you to know about and that as a consequence the full forces of these groups are being marshalled to “suppress” them and “persecute” the Brave Maverick Doctors who dare to question the “orthodoxy” of “allopathic medicine,” up to and including claims of “Nazi”-like suppression. (Just read those repositories of quackery NaturalNews.com and Whale.to if you don’t believe me.) For the “alternative medicine” movement, it’s all there, in websites, blogs, and books. But one thing that the movement pushing unscientific treatments has lacked, and that’s a movie to call its own, a movie to spread the same message.

That is, until now.

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Posted in: Cancer, Dentistry, Health Fraud, Science and the Media

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“Urban Zen” and homeopathy at Beth Israel Medical Center, or: Dr. Gorski destroys his chances of ever being invited to join the faculty at BIMC or the Albert Einstein College of Medicine

I guess I never really wanted to work in Manhattan anyway. At least, that’s what I keep telling myself.

I mean, why on earth would I want to? What’s the attraction? Living in the heart of it all, all those shows and all those amazing cultural activities, all those world-class restaurants? Being close to Boston, Philadelphia, and other cool East Coast cities, which are all just a quick Acela train ride away? Who cares about those things, anyway?

Apparently I don’t, because I’m about to destroy my chances of working at what has been considered one of the premiere academic hospitals in New York City, specifically Beth Israel Medical Center, an academic affiliate of the Albert Einstein College of Medicine. It’s possible for me to have been ignored when I first included the Albert Einstein College of Medicine and its affliated Continuum Center for Health & Healing in my roll call of shame as a medical center that has not just added woo to its offerings, but actively embraced it. At the time I originally discovered it, though, its offerings seemed limited to fairly mild woo, the usual stuff like acupuncture, what I like to call “gateway modalities” that centers embrace first because they’re relatively tame and commonplace. All too commonly, though, dabbling in gateway modalities leads to the “hard stuff,” outright quackery with zero scientific basis like homeopathy, reflexology, and craniosacral therapy. Such is the pathway an academic medical center follows when it degenerates from science-based medicine to what Dr. R. W. famously dubbed “quackademic medicine,” usually driven by a few famous true believers, which, alas, is exactly what happened at fearless leader Steve Novella’s institution of Yale, thanks to Dr. David Katz and his “more fluid concept of evidence.”

In any case, last week, I realized that I’ve been completely neglecting the aforementioned roll call of shame. Perusing it, I now realize that it’s been over five months since I did a significant update to it. You just know that, given the rate of infiltration of unscientific medical practices into medical academia as seemingly respectable treatment modalities that there must be at least several new additions to this roll of shame. Alas, even today, having been shamed myself by the realization of my failure to keep the list updated, I’m not going to do the full update and revamping that the Roll Call of Quackademic Medicine cries out for. However, that doesn’t mean I can’t do a piecemeal addition here and there. That doesn’t mean I can’t point out new additions as they pop up, even if it takes me a while to find the time to give the list the facelift it cries out for. It doesn’t mean I can’t call out hospitals like Beth Israel when they fall into woo, especially when they dive into quackademic medicine in a big way for cancer patients.
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Posted in: Cancer, Homeopathy, Medical Academia, Science and the Media

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On the nature of “alternative” medicine cancer cure testimonials

No doubt you’ve come across them before, either on the Internet, printed advertisements, or radio and TV ads: Alternative medicine cancer “testimonials.” They are the primary means by which “alternative” therapies for cancer (or just about any other disease) are promoted and the primary “evidence” that is used to “prove” the efficacy of non-evidence-based therapies. There’s no doubt that they sure can sound convincing. Typically, what you will see or hear is a chipper-looking and -sounding person who claims that this treatment “cured” his or her cancer. These testimonials almost always include many or all of these elements: First, the cancer patient receives the diagnosis, after which she is lost and suffering at the hands of “conventional” doctors, who either cannot or do not wish to understand and who cannot do anything for her. Often, this will take the form of the classic alt-med cliche that the patient was “sent home to die.” Then, when all hope seems lost, the patient discovers an alternative medicine “healer” or treatment. It is not infrequently described in quasireligious terms, like a revelation or something that brings the patient out of the darkness and into the light. Naturally, there is resistance from the patient’s doctors, family, and/or friends, who warn against it, with doctors warning of dire consequences if the patient abandons conventional medicine. But the patient, convinced by dubious practitioners, friends, and, of course, previous testimonials, “sees” that the treatment “works” in a way that medical science cannot and survives. Infused with fervor, the patient now wants to spread the word. Often, the patient is now selling the remedy. Perhaps you’ve seen such testimonials or heard them on the radio and thought: “Gee, this sounds great. I wonder if it works.”

The answer is: Almost certainly not.
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Posted in: Cancer, Health Fraud, Science and the Media, Surgical Procedures

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