The screening industry
BMJ 2003; 326 doi: https://doi.org/10.1136/bmj.326.7395.0/f (Published 26 April 2003) Cite this as: BMJ 2003;326:f
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I Have just had a call from my partner to whom is at work and was
listening to the news which stated that 80% of people having full body
scans was possible cancer recipients, as we both have had total body scans
two weeks ago,I am 55 and my partner 40,who was having continual head
aches and was advised to have a CT along with blood tests etc,we went with
the total on our own innitiative,I would like to get the opinion of your
colleagues. regards, c.j.c
Competing interests:
None declared
Competing interests: No competing interests
I applaud Dr's Ed Cooper ( 28 April 2003) and G.H Hll (29 April 2003
) for taking Christopher Buttery ( 26 April 2003) to task in the matter
of HIV screening. Professor Buttery states ' For example screening
young adults for HIV antibodies where the prevalence is 1 per thousand is
likely to provide a false positive rate of 98% .'
Where, one might ask, did the prevalence rate of 1 per thousand come
from ?. This has been brought to attention in the past in a published
letter (BMJ 1999; 319: 1573 - 11 December ) in response to Spiegelhalter
et al's excellent BMJ article on bayesian methods in health technology
assessment (BMJ 1999; 319: 508-512 -21 August ). It represents the
incidence of HIV infection in female blood donors in the United States in
1986 !! .
The combination of this figure and an assumed fale positive rate of
0.005% for combined Westerm blot and enzyme linked immunosorbent assay
(ELISA) by Meyer and Pauker (N Engl J Med 1987; 317: 234-238) posed the
question - 'Screening for HIV: can we afford the false positive rate ?.'
The seeds of doubt regarding HIV/AIDS, resulting frm that
publication, produced a profound change in medical philosophy and a legacy
of suffering through ignorance and miscalculation, which may well be
historically remembered as a major medical 'wrong turn'.
James E Parker
Competing interests:
None declared
Competing interests: No competing interests
Has the health industry finally gone mad? And sadly have the money
spinners lost their clinical integrity by making a play on the “what if”
principle? Perhaps the value of money is tastier than the elixir of life.
This powerful suggestive notion of “what if…it were me?” may earn
screening companies millions, but at what cost and to whom? Not only have
we a “pill for (almost) every ill”, health is at risk of entering a
booming culture of screening for every eventuality. Richard Smith's
editorial on whole-body scanning in the States is a point in hand.
Mortality reduction for specific diseases demonstrated by good evidence
cannot be a mandate for nationwide just-in-case top-to-tail screening.
So who are the victims, perhaps thousands of people who are rich
enough, educated enough or concerned enough? Perhaps Tudor Hart's inverse
care law falls down at this point. Deprived people who cannot access whole
body scanning will be spared the anxiety and over investigation of
incidentalomas. Or does it fall down? It’s an inverse care law, but is
the prime objective for commercial screening to care or to make money?
The screening companies are well aware of this psychology, in fact their
business depends on it. The “what if” principle goes far beyond
screening, MMR example par excellence and some are making money from
single vaccines although one hopes altruistically.
Consequences from mass screening are far reaching. Issues regarding
the calibre of the test and over-investigations aside, the themed issue
“too much medicine” springs to mind once more. Will we run the risk of
becoming a nation of chronically ill patients? Do negative tests
reinforce our unhealthy lifestyles, will there be public pressure to make
the tests available on an already drained NHS in which case what will
happen to those who are really sick? The arguments are many.
It may be too late for the States. We must police our NHS, ourselves
as healthcare professionals and the commercial sector before the nation
becomes a victim of greed at the expense of health by play on our health
beliefs.
Competing interests:
None declared
Competing interests: No competing interests
The most successful screening technique has been the Pap smear. Its
use, even in an opportunistic way, like in the U.S. and Canada, has
resulted in an over 70% reduction in death rates due to cancer of the
cervix. The test has few false positives and an acceptable rate of false
negatives – that correct themselves when the test is repeated at
recommended intervals. The newer techniques of human papillomavirus (HPV)
detection will show a negative predictive value near 100% after age 30.
Since the oncogenic types of HPV are recognized as the cause of cervical
cancer, their absence, particularly if the HPV-DNA test is repeated at
least once, assures that the patient is not at risk for cervical cancer.
In developing countries cancer of the cervix is still the major cause of
cancer deaths in women. Screening for this disease with the techniques at
hand should not be dismissed so lightly by epidemiologists who would have
liked to see case-control series that were never done.
Competing interests:
None declared
Competing interests: No competing interests
R. Smith limits the meaning of ‘screening’ to the new –or old-
diagnostic tools which are responsible of a large number of false positive
results and cause of sufferance and futile- sometimes expensive-
interventions. The editorial arises a generic sense of worrying for
what technology and economic pressure can do: rational ignorance can be an
individual option –whereas in countries like Italy non attendance in
service screening is primarily related to fatalistic attitude towards a
threatening disease. The question for scientists is how to intervene in
the biomedical development and challenge the wild growth of biotechnology
applied to predictive medicine, including genetic susceptibility (1).
New technological devices for cancer diagnosis are promoted with the
perspective of the best sensitivity for early detection , but there are no
criteria and guidelines for the evaluation of screening outcomes (2). So
far, the initiative of randomised clinical trials for the evaluation of
efficacy is based on scientific interest and there is no limit of the use
of technology for diagnostic/predictive purposes.
We should take a decision: either technologic development is dangerous and
we should fight to stop it or we must deal with the monster. That means
to ask for regulated processes before marketing and the evaluation of the
efficacy by means of public health supported research to assess outcomes
and side effects. Screening researchers have promoted outcome evaluation
but, in the absence of public health regulation in the use of diagnostic
devices , this is not what spontaneously happens, as prostate cancer
screening history showed in exemplar way. PSA started to be used at the
end of eighties ; the peak of incidence in USA occurred in early nineties
and the randomised clinical trials for screening evaluation have been
started, with great difficulties and poor funding, in USA and Europe about
in 1994.
Lung cancer screening by CT Scan , hopefully, should not have the same
story.
Swenson recalled the recently launched NCI randomised trial might give the
correct response in regard to the efficacy of CT Scan screening for
reducing lung cancer mortality, avoiding the fork between the rejection
of the potential benefits of new technology and the wild and harmful
diffusion of technology without control. Similar initiatives are planned
in Europe within an established US/UE collaboration, but in the absence of
public health coordinated funding.
We should not forget the essential contribution of the trials in the early
seventy for the ending of ineffective Chest X Ray screening; and we should
not forget that mainly in the context of clinical trials and organised
service screening we have learnt a lot about the best approach to cancer
screening in order to minimise the harm.
Smith is personally justified in his predication , but rational
ignorance will not discourage the widespread, spontaneous use of screening
tests in the absence of public health knowledge and cost/harm-benefit
evaluation.
1)Etzioni R, Urban N, Ramsey S, McIntosh M, Schwartz S, Reid B,
Radich J, Anderson G, Hartwell L.
Early detection: The case for early detection.
Nat Rev Cancer. 2003 Apr;3(4):243-52
2 ) Paci E.
Mammography and beyond: developing technologies for the early detection of
breast cancer- Book Report.
Breast Cancer Res 2002, 4:123-125
Competing interests:
None declared
Competing interests: No competing interests
Screening is an instantaneous picture of a an ongoing disease process
It does not provide any information whether the patient gets better or
worse. All along disease progression host and disease maintain an
equilibrium, and the aim of treatment is to shift it in favor of the
patient. The nature of this balance is revealed only by examining the
patient. Many physicians tend to ignore this important dimension of
disease, and base their judgment solely on the scan which turns to be an
important source of Iatrogenesis.
Gershom Zajicek M.D.
Professor of Experimental Medicine and Cancer Research.
The Faculty of Medicine. The Hebrew University of Jerusalem.
P.O.B 12272. Jerusalem 91120. Israel.
E-mail: gzajicek@what-is-cancer.com
Competing interests:
None declared
Competing interests: No competing interests
I interpret a false diagnosis proportion of 98% on the basis of a
test to mean that the positive predictive value of the test is 2%. The
positive result is right 2% of the time and wrong 98% of the time.
Positive predictive value is dependent on the prevalence of disease in the
population. For 100% sensitivity and 95.1% specificity (two values that
are, indeed, independent of prevalence), the positive predictive value
will be 2% if the disease prevalence is 1/1000.
Competing interests:
None declared
Competing interests: No competing interests
Wrong. A false positive rate of 98% means a true negative
rate(specificity) of 2%.These figures refer to the results of the test on
those without disease. Neither specificity nor sensitivity are (usually)
affected by the prevalence of disease in the population: they are features
of the test methodology. These concepts are frequently misunderstood, even
by experts. How on earth are we going to educate the public if the pundits
can't get it right?
Competing interests:
None declared
Competing interests: No competing interests
Many readers of the BMJ are supporters of EBM and I suppose this
article will warm their belief that those of us promoting cancer screening
are good hearted but wrong headed fools. I have stage D2 prostate cancer
and it probably could have been detected with early screening---so I am
one of those people who support primary and secondary screening programs.
But:
I think the issues are relatively simple---the M.D. needs to test for
specific diseases based on a complete history and physical exam. Using
gender and age demographics depersonalizes the process and we end up with
everyone lining up for PET scans because they don't trust the Doctor's
ability, or managed care's willingness, to take care of them. Primary
screening should not be separate from the process of forming a therapeutic
relationship with a doctor. It is in the crucible of this relationship
that discussions of screening and prevention can take place.
Perhaps the debate regarding screening should include the question of
how we increase the level of trust between the patient and his Doctor?
This trust has been undermined and the result is an increase in self-
directed and, at times, the ill-advised movement of people towards self-
diagnosis and self-directed care. The dynamic of this process is
dangerous. The patient fails to consult the Doctor when he should and the
Doctor finds himself in the awkward position of opposing a screening
procedure the patient believes in.
The BMJ argument should include the question of why the promoters of
algorithms need to use statistics to shape their clinical practice? The
Doctor needs to take a stand and say to his patient that he; "cares about
him and he will do everything he needs to do to work with him to keep him
well." Maybe then the idea of lining up for a PET scan won't seem so
important. The anxiety that will be created by false positives is already
in the air. The Doctors need to dispel this anxiety with wisdom and
knowledge and patients need to listen.
This means that evidence based medicine needs to take a back seat for
awhile until the debate about screening assumes a shape we can deal with.
As of today the patients are trying to increase the "evidence" so that
their Doctors have the tools to help them. If we --the patients---could
learn that good health care sometimes relies on the mysteries and wisdom
inherent with good Doctors we would all sleep better.
Competing interests:
I am a consumer/patient and I don't work in health care or receive any money from anyone in health care or the pharmacy industry. I am a school social worker and stone sculptor.
Competing interests: No competing interests
A Fool and his money...
Even in public health systems, enterprising radiology clinics
advertise
these excessive total body scans. Their prices seem very reasonable, for
the promise they make. While banning them initially seems a sensible
approach, it is unlikely to be effective, because their promise is so
seductive that most politicians believe in them, and the radiation dose is
not so high as to be dangerous.
But their greatest danger is not extra radiation, but the on-cost of
following up the false positive findings. This adds extra workloads and
cost to the public system. One source of this is the lack of feedback to
radiologists about the outcome of their observations. It has been shown
in mammography screening programs that close connection between
radiologists and the clinical team improves radiological diagnosis and
reduces error. Perhaps calculations should be made of the cost of
follow-up examinations, and they should be charged back to the clinic
that referred the patients. Private screening clinics would then have to
charge much higher rates, and be very careful about over-calling minor
abnormalities. The higher price of the exam would deter many potential
customers, though not all, but at least these people would be paying for
the real costs to the rest of society to obtain the "insurance" (pace
Sasieni) that they desire.
Competing interests:
None declared
Competing interests: No competing interests