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What Are the Dangers in Screening for Diseases?

The moral imperative to know the harms of procedures is great.

Theodore Dalrymple


October 1, 2013 - 3:00 pm


Like politicians, doctors are inclined to believe that doing something (especially when it is them doing it) is better than doing nothing. They mistake benevolent intentions for good results, believing that the first guarantee the second. How can philanthropy go wrong?

Besides, doing something stimulates the economy in a way that doing nothing cannot possibly match. If people did only what was necessary, or what was good for them, or what was right, the whole of our economy would soon collapse.

Be that as it may, and for whatever reason, clinical trials that have positive results are more likely to be published than those with negative results. Thanks to several well-publicized scandals, this publication bias, as it is called, is on the decline. GlaxoSmithKline, one of the largest pharmaceutical companies in the world, has promised that henceforth it will publish the results even of trials that are unfavorable to their products as well as those that are favorable.

A paper by Danish researchers just published in the British Medical Journal assesses the extent to which published reports of trials of screening procedures, such as mammography, colonoscopy, PSA-levels, etc., report their harmful effects and consequences as well as their positive ones.

This is particularly important ethically because screening reverses the usual relationship between patient and health-care system. In screening it is the health-care system that initiates the contact, not the other way round. Screening is offered to healthy people, or at least to those complaining of nothing; moreover, the chances of benefit from screening are often slight and those who do benefit from them do so in a sense at the expense of those who are harmed by them. The moral imperative to know the harms of screening is therefore great.


Can colonoscopies sometimes do more harm than good?

It will probably by now not come as a surprise to readers to learn that the Danish researchers found reports of experiments on screening procedures to be peculiarly lacking in details about the harmful effects of those procedures. They considered reports on 57 trials for screening for several different kinds of cancer (that is, all those that had been done in the world to an acceptable standard), using ten different technological techniques.

These trials involved 3,416,036 participants. They looked to see whether the reports contained quantified evidence about seven possible harms of screening: overdiagnosis, false positive findings, bodily complications from screening procedures, negative psychosocial consequences of screening, additional numbers of invasive procedures consequent upon screening, all-cause mortality (important because extra surgical procedures, for example, would have a mortality rate), and the withdrawal of participants because of complications of the screening procedures. It is necessary to know these things before a doctor can properly advise a patient to have a screening procedure, or before a patient can make an informed decision.

In only one of the 57 trials was a figure given for the number of withdrawals from completion of the trial because of complications caused by the screening procedure. In only two trials were the figures given for false positives and four trials for overdiagnosis. This contrasts with 51 trials that measured cancer-specific mortality, the reduction of which is the aim of screening procedures. All-cause mortality — more important to the patient than cancer-specific mortality — was measured half as often cancer-specific mortality.

The authors are uncompromising in their conclusion: doctors are recommending procedures on a vast scale on the basis of inadequate knowledge that also precludes informed consent on the part of patients. This is because the harms as well as the benefits of a procedure should be known before recommending or agreeing to it. All the more is this so where the initiative for the procedure comes from the doctor and not from the patient.


images courtesy shutterstock / Tyler Olson / Sebastian Kaulitzki

Theodore Dalrymple, a physician, is a contributing editor of City Journal and the Dietrich Weismann Fellow at the Manhattan Institute. His new book is Second Opinion: A Doctor's Notes from the Inner City.

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All Comments   (12)
All Comments   (12)
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Oh, leave it to the real docs, Theo.

Your decade and a half of experience as a shrink in a Limey provincial hospital don't amount to a hill of beans in this crazy world.
50 weeks ago
50 weeks ago Link To Comment
Several yrs ago my dads dr added a new med & told my dad to take it at bedtime because it could make him dizzy. My dad took it in the morning, went shopping & would up on the store floor. (Stores really don't like seniors citizens on the floor.) They called an ambulance & brought him to the ER. We had my dads dr call the ER dr & he explained about the new med. The ER dr didn't care and ordered one test after another that all showed negative. After 4 days of this nonsense my father signed himself out against medical orders. My parents got a 5 figure hospital bill not counting all the dr bills. Just because 1 jerk ER dr didn't listen to the patients dr.
51 weeks ago
51 weeks ago Link To Comment
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51 weeks ago
51 weeks ago Link To Comment
Dartmouth's medical college has done fantastic work on the topic of too many medical procedures.

"The Dartmouth Atlas data suggests that as much as 30 percent of health care is waste," says Ellen Meara, a Dartmouth health economist. And as for what’s driving the problem? Meara says: follow the money. "As a healthcare provider, you’re paid much more to deliver procedures."

Basically, the Dartmouth research shows that when doctors buy equipment to perform screenings or procedures, they suddenly find that their patients "need" those things, despite the fact that outcomes don't improve.

My dentist provides a clear example. She bought an oral cancer screening device, a new profit center for her practice. Now that she owns it, her patients are told how important this screening is, and she'll offer it at a reduced cost. What she fails to tell us is that the test has a 50% positive and negative predictive value. In other words, half the positives will be false, requiring traumatic, costly biopsies for nothing, while half the actual pre-cancerous tissue will be missed. The bottom line is that old fashioned screening techniques are more reliable, but she can't charge extra for that. Instead, she will rely on a less accurate, hi-tech gadget that she charges extra for.
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51 weeks ago
51 weeks ago Link To Comment
A friend of mine just turned 50. The turd sample found blood; they gave him a colonoscopy and later a sigmoidoscopy, which expands the intestines like a balloon for better viewing. They determined he had a hemorrhoid, but the expansion of the colon compressed a nerve and now his right leg is in pain and he can no longer drive and has ended up on disability.
51 weeks ago
51 weeks ago Link To Comment
I think a LOT of these "routine" screening procedures are done to prevent malpractice suits. Period. I am at a low risk for breast cancer. No female on either side of my family has EVER had breast cancer. I have never found a lump, nor has my doc. But every year they want me to have a mammogram, which even the government has warned against.

Same thing with colonoscopies. Nobody in my family has EVER had colon cancer. But when I turned 50 my doc said I had to have a colonoscopy. So I went and had it done. 15 minutes later the colorectal surgeon came into the recovery area and said my colon was clean as a whistle. Not even a little polyp. Then he said, "I'll see you again in 10 years." I told him I'd gotten to age 50 without anything growing in there, so I'd see him again in 50 years!" He just laughed.
51 weeks ago
51 weeks ago Link To Comment
decrease your liability with no cost to you!
that's the reason the tests are done.
extra tests, delaying urgent surgery, just so an i can be dotted and a t crossed.
everyday, every hospital
can't blame docs for protecting themselves. or you can, but you would do the same
51 weeks ago
51 weeks ago Link To Comment
Many studies only look at a small part of the picture. You need to know if a screening test will effect disease specific outcomes before you can get the much larger sums of money to study for all cause mortalitiy. Typically, you have to publish those results for peer response before you can hope to get bigger grants. The problem occurs when people take those initial results and run with them before the entire program is evaluated for the program specific harms, effects on all cause mortality etc. Medical researchers have become much better at reporting harms of screenings for accepted screening tests (prostate cancer screening, colon cancer screening etc) but not for all (breast cancer screening). Even if the data are there, for example the increased age of initial screening for breast cancer and lengthened intervals between mammograms) it can be hard to get practioners to change. Self interst plays some part, but more of it is the general inertia of medical knowledge and of patient expectations.
51 weeks ago
51 weeks ago Link To Comment
OK, we would be far better off with better tests, and better doctors to interpret them.
51 weeks ago
51 weeks ago Link To Comment
yes, a "better" test with no false positives, false negatives, complications and at a low cost. oh, yes, and not the current crop of morons who provide medical care?

or we do better at looking at risk/benefit and cost to determine what is "best"

the best currently exists, until better comes along
51 weeks ago
51 weeks ago Link To Comment
"...doctors are recommending procedures on a vast scale on the basis of inadequate knowledge that also precludes informed consent on the part of patients. This is because the harms as well as the benefits of a procedure should be known before recommending or agreeing to it."

Agree completely.

How many people know that the sodium phosphate bowel-cleansers that were formerly in common use prior to colonoscopy have been linked to kidney damage ?

Consider rampant mammography and the lack of awareness about potential long term cumulative damage from radiation exposure itself. Even though the US has one of the highest if not the highest percentage of breast cancers in the world, the number of cases per 100,000 of the population is still very low in absolute numbers.
51 weeks ago
51 weeks ago Link To Comment
Doctors have also have a strong moral hazard whenever ordering tests or treatments, because those come with payment and because doctors have so much more information than there patients.

Unfortunately, recommendations for screening come with financial strings. Recommendations for PSA screening are illustrative. The government, who will pay for much of these screenings, recommends against. The American Urological Association (i.e., the doctors performing and benefiting from this test) recommends for. And the American Cancer Society (a philanthropic organization which is mostly interested in curing and preventing cancer) only recommends an informed decision be made by the patient with the doctor.
1 year ago
1 year ago Link To Comment
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