Archive for the 'Cave!' Category

Cave: Ignoring the NNT

How would you like to double your chances of winning the lottery? Just buy two tickets!

Statistically, this is true, but is that a reason to spend more money on something that most likely offers no return on investment?

Yet, in medical research, study after study shows impressive improvement in relative risk for this, that and the other intervention but a small or even negligible effect on absolute risk.

For example, I just read a study in the New England Journal of Medicine comparing giving a new osteoporosis drug to women with osteoporosis and a prior history of an osteoporotic fracture for one year, followed by an older drug for one year to just giving the older drug for two years. The two drug regimen lowered an osteoporotic woman’s risk of hip fracture by 38%.

The number of hip fractures in the combination treatment group was 41 out of 2046 patients, and in the single drug group it was 66 out of 2047 patients.

In absolute numbers, treating 2046 patients reduced the hip fracture risk by 25 cases. The number of women one would need to treat to avoid one hip fracture, the “NNT”, is 2046 divided by 25, or 81.

That NNT isn’t terribly impressive, especially in light of the fact that 12 more patients in the new drug group had a cardiovascular event in the first year than in the old drug group.

The editorial accompanying this article does say “In sum, ARCH revealed that romosozumab has great potential as a short-term anabolic treatment for osteoporosis. However, until the cardiovascular and endocrine effects of this antibody are clarified, romosozumab will remain more a part of our expectations than our armamentarium.” But if the drug company starts promoting the relative risk reduction of this treatment, doctors could be misled and patients could come to harm.

Here are some more examples of he Number Needed to Treat for some common health interventions, published in a post I wrote 7 years ago:

1) Shingles vaccine doses given in order to avoid one case of shingles: 59.

2) Ear infections treated with Amoxicillin to avoid one ruptured eardrum: 20.

3) Cortisone shots to relieve one sore shoulder: 3.

4) Aspirin prescriptions to prevent one heart attack: 200.

5) Prostate cancers treated in order to prevent one death: 18-48 (most men with prostate cancer don’t die from their disease).

6) Adenomatous colon polyps removed to prevent one colon cancer: 50 (only 2% of “precancerous polyps” actually turn into cancer).

May I never forget to consider the NNT…

Cave: The Patient Who Suggests a Diagnosis Before Telling You His Symptoms

Sir William Osler wasn’t exactly wrong when he said “Listen to your patient, he is telling you the diagnosis”, but he didn’t mean it literally. His patients did not offer up esoteric and complete medical diagnoses on a silver platter. They left him clues in plain language that he listened carefully to in order to make the correct diagnosis.

His words were penned in an era when medical information was scarce among non-medical people. There was no Dr. Google, Dr. Oz or Dr. House to educate the public about diseases or medical terminology a century ago.

In a way, I think doctors today have to do more filtering of what our patients say in order to get the medical history straight.

For example, Mrs. LaVerdiere made an appointment for nausea some time ago. As soon as I walked into the exam room, she started telling me about how she must have eaten a spoiled crabmeat sandwich on her trip to a coastal fishing village the weekend before. Her conversation was full of theories as to why she was feeling unwell and her husband wasn’t. I finally got her to describe in great detail exactly what she felt, and the gnawing pain that radiated to her back did not fit with a simple case of food poisoning. Her CT scan showed the smallest pancreatic cancer ever diagnosed at Cityside Hospital and she underwent a Whipple procedure as easily as any routine minor surgery.

Mrs. Waller describes ordinary bodily sensations in the most dramatic terms and throws terminology around that rocks me out of my country doctor habitual way of plain-talking. She has, over the years, described ordinary itches as “you know how it feels when you’ve been bitten by a thousand fire ants”, headaches as “I felt like I was about to pop a Berry aneurysm”, and indigestion as “pyloric stricture”. I have the distinct impression she is always trying to make my job easier by describing things in more or less medical terms, in case I forgot to speak English.

During my tenure in medicine, the tendency for patients to offer explanations and theories instead of just describing what they feel has increased dramatically since the creation of the Internet. But I have also come to realize that there have always been people who are simply not able to recognize and describe what they are feeling, particularly emotions. They therefore tend to describe the bodily sensations that their unrecognized emotions produce, or, even harder to decipher, they are only capable of reporting other people’s observations of their own appearance or behavior.

Most of us recognize that anxiety or other strong emotions can cause heart palpitations or abdominal pain, hence our use of expressions like ”gut-wrenching”, but some of us are only aware of the bodily sensation and are clueless about their own emotions that trigger them. They are also usually skeptical about any suggestion of such a connection.

Hedda Brown is one of those people I have always struggled to diagnose, no matter what ailed her. Only a few years ago did I learn the word for her condition – alexithymia, inability to recognize emotions. She would answer questions like “tell me more about in what way you don’t feel well” with stories like this:

“I knew I wasn’t feeling right yesterday morning. I didn’t want breakfast. Harry, my husband, took one look at me and said I looked peaked and told me I looked like I was about to vomit. My daughter also noticed something about me. She said I looked like I was dehydrated. She acted real nice all of a sudden, instead of her usual way of ignoring me, she offered to make me a cup of tea or make me an omelet, but I just didn’t want any.”

No matter how much time I give Hedda to tell her story, I get very little to work on. So I usually try some direct questions, like “did you have chills” or “did your belly hurt”, but even that kind of inquiry usually results in answers about other people’s observations or theories.

I have finally come to realize that Hedda carries with her more than a lifetime’s worth of grief, which now and then erupts as a sensation she has no words for. Because she is so unaware of her emotions, the most I could ever expect from her is a general bodily sensation, like “a pain here” or “not hungry”. In the beginning, she underwent a fair number of tests, but as she has started to trust me more, we have had a few conversations along the lines of “maybe your body is trying to tell you something”. It is a slow process.

Thinking about Sir William’s famous quote, perhaps it could be adapted for the Internet age this way:

“Listen to your patient’s story; he is telling you the diagnosis.”


Osler said “Listen to your patient, he is telling you the diagnosis”. Duvefelt says “Listen to your patient, he is telling you what kind of doctor he needs you to be”.

BOOKS BY HANS DUVEFELT, MD

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