This article assesses the value of whole-body screening (WBS) by reviewing current data and “deconstructing” the examination. Through an analysis of the most common important diseases likely to be detected by WBS, the author investigates whether the sum of such detection events offer enough benefit to warrant the cost.
is a Professor and the Vice-Chairman for Development in the
Department of Radiology, University of Alabama at Birmingham,
Birmingham, AL and is Vice-President of the Society of Computed
Body Tomography and Magnetic Resonance (SCBT/MR).
Controversies about medical screening tests often center on
ethics and economics.
Knowledgeable opinions regarding these issues abound but beg to be
put into perspective with the simple question of whether the
screening test works. Unfortunately, scientific proof always comes
at a high price and with long delay, if ever. Furthermore,
whole-body screening (WBS) with computed tomography (CT) did not
originate within the scientific community, which has received it
coolly and has studied it little.
The purpose of this article is to assess the value of WBS by
reviewing what little we know about it and to evaluate it by
deconstructing the examination. That is, by analyzing the most
common important diseases that are likely to be detected by WBS, we
may learn whether the sum of such detection events are likely to
lead to enough benefit to warrant the cost.
Whole-body screening is unusual among screening tests because it
is intended to detect multiple conditions. The press and radiology
literature usually refer to WBS as a practice of performing CT
examinations of the chest, abdomen, and pelvis. The scan protocol
is usually at a low radiation dose and with no contrast
administration, intended to provide CT scanning at relatively lower
risk and cost compared with conventional CT. The subjects of these
scans are usually self-referred, asymptomatic individuals.
Some centers perform scans with intravenous contrast material to
increase the detection rate and improve the characterization of
abnormalities. However, this adds time, cost, and risk. A recent
article cited the example of a successful malpractice suit against
a radiologist who performed a contrast-enhanced WBS on an
asymptomatic person who then died from an anaphylactic reaction.
The purpose of the chest CT component of the scan is primarily
for early detection of lung cancer, which represents a distinct
controversy, and will not be discussed further.
Therefore, this article will address WBS as a noncontrast
examination of the abdomen and pelvis.
CT colonography (CTC) is not usually considered part of WBS
because it requires bowel preparation, multidetector helical
scanning, and expert radiologists and technologists with focused
training and experience. CT colonography has received considerable
attention, is under intense study, and already represents a
promising screening technique for colon cancer and colon polyps.
Ironically, while CTC is not included as a part of WBS, CTC
actually represents a form of WBS because the entire abdomen and
pelvis are scanned without contrast. Therefore, regardless of
whether WBS becomes an accepted method for screening patients, it
will be important to learn how to manage patients undergoing WBS
because so many will have CTC.
Conclusions regarding the value of WBS often hinge on
differences about how to measure the value of a screening
examination. Proposed measures of success may include: 1) the
detection rate of cancers; 2) the detection rate of other medical
conditions; 3) the value conferred by self-referring consumers, who
may believe that they are exerting increased control over their
health; and 4) the value the consumer experiences by increased
contact with a physician, usually in reassuring them of their
health. There is no disagreement that WBS detects diseases and thus
can lead to improving the health of some subjects. What is in doubt
is whether the value of the lives extended by detecting diseases
with WBS is greater than the cost measured in both health outcomes
Limitations of screening: False-positives, overdiagnosis,
and incidental findings
Why isn't medical screening as beneficial as it intuitively
seems? It would be, except for the disadvantages of false-
positives, overdiagnosis, and incidental findings, which will be
defined and discussed more fully. This trio of obstacles to
accuracy leads us to finding many more lesions than actually could
harm the subject. Identifying such false lesions may actually lead
to costs and harm, because of additional testing and procedures.
These adverse effects can be measured in pain, anxiety, morbidity,
loss of productivity, and even death.
False-positives represent the most well-recognized source of
error on screening tests. However, the magnitude of the problem is
often underappreciated. For example, if one considers testing a
population of 100,000 people with a prevalence of disease of 1%,
using a test with a high sensitivity and specificity of 95%, this
would lead to 950 true-positive tests, but also 4950 false-positive
tests, for a positive predictive value of only 16% (Personal
communication, G. Scott Gazelle, MD, PhD, MPH, March 2003). This
would lead to a large number of other tests to verify or exclude
Overdiagnosis is a more insidious form of false-positive because
it signifies a true detection of the target disease, but in a form
that would not lead to mortality or morbidity. An example would be
a small renal cell carcinoma (RCC) that grows so slowly that it
would not reach a significant size or metastasize before the
patient dies of other causes. Overdiagnosis is surprisingly common
and varies with the condition considered.
It is well known by radiologists (and less known by other
clinical physicians and even less so by healthcare consumers) that
incidental lesions of no clinical consequence are extraordinarily
common. These incidental findings can be described as benign
lesions that do not lead to symptoms, morbidity, or mortality.
These include such conditions as adrenal nodules and liver lesions
that are too small to characterize. Unfortunately, radiologists
have not come to a consensus on the rational management of such
findings, and inconsistently recommend further studies.
How, then, can we decide whether to do a specific type of
medical screening? The commonly accepted requirements for an
effective screening test are: 1) the disease should be common and
associated with clinically important mortality or morbidity; 2) the
screening test should be available, acceptable, feasible, and
sufficiently accurate to detect early disease;
3) earlier diagnosis and treatment should be associated with
improved prognosis; and 4) the sum of benefits should outweigh the
sum of potential harms and costs.
Lesions found with WBS
The conditions that CT can find in the abdomen and pelvis that
might fit these criteria--especially ones that are accepted as
being associated with clinically important mortality or
morbidity--include: 1) liver lesions, 2) adrenal nodules, 3)
abdominal aortic aneurysms, 4) renal cell carcinoma, and 5) ovarian
carcinoma, each of which will be considered individually.
Additional abdominal conditions may be detectable on abdominal
scans, such as colon cancer, or lung cancer in the upper abdominal
images. However, specialized CT screening tests have been developed
for these conditions and are under extensive study, as noted above.
Miscellaneous conditions may also occur, as outlined in a Web site
of a screening organization:
[Our] Full Body Scan is the world's most complete health
evaluation. The Full Body Scan can safely and accurately detect
over 100 life-threatening diseases in the arteries, heart, lungs,
liver and other major vital organs before its too late.
This Web site, and sites of other screening companies, list
detectable conditions including lymphoma, pancreatic cancer,
gallstones, kidney stones, osteoporosis and many others. However,
while all of these conditions are reported on abdominal and pelvic
CT, the probability of benefit of detecting asymptomatic
gallstones, kidney stones, or even lymphoma by CT is doubtful. Such
conditions as osteoporosis and carotid stenosis have their own more
sensitive, more specific, and less expensive tests.
Two studies have evaluated the importance of small liver lesions
(<1.0 to 1.5 cm).
These studies have primarily evaluated cancer patients, finding a
frequency of 13% and 17% of such lesions, with a malignancy rate of
12% and about 22%. However, of 262 patients without a primary
malignancy among the 1454 studied, not one small liver nodule was
I performed an informal review of 100 consecutive outpatient
abdominal CT examinations, excluding patients with cirrhosis,
obvious liver metastases, or polycystic kidney and liver disease.
Small liver lesions were present in 22% of these patients, many
with multiple lesions. It is likely that the increased resolution
with modern helical and multidetector CT has increased the
visibility of small lesions. Therefore, the probability that a
small lesion is clinically important in someone without a known
malignancy (the vast majority of screening candidates) is much less
than 1%, while the chance of finding at least one small lesion is
What about detecting liver lesions >1.5 cm? An example of the
difficulty in managing such findings is highlighted in the case of
an 18-year-old woman with renal calculi who had an incidentally
discovered liver lesion approximately 2 cm in diameter (Figure 1).
At a follow-up scan 6 months later, the lesion had appeared to
grow. The patient and her parents expressed great concern and
encouraged the physician to pursue the finding. A contrast-enhanced
scan demonstrated that the lesion was the same size as on the
original scan and was a benign hemangioma.
Most lesions >1.5 cm are benign hemangiomas, focal nodular
hyperplasia, noncalcified granulomas, or hamartomas. This
illustrated example highlights the futility of attempting to
minimize the pursuit of some lesions, because most physicians would
probably consider the apparent growth as an appropriate indication
for further study. Structured criteria for decisions to pursue such
lesions based on cystic appearance, number of lesions, age, and
history of malignancy may help minimize unnecessary studies.
Adrenal nodules have been the subject of several recent studies
and even of an NIH Adrenal Incidentaloma Consensus Conference in
However, an asymptomatic adrenal nodule in a person without a
primary cancer diagnosis is rarely clinically important. The
prevalence of adrenal nodules in otherwise healthy people is
reported as 0.4%, and approximately 4% in patients with a prior
history of cancer. However, in our informal review discussed above,
we discovered small nodules in >10% of patients. One presumed
objective of finding adrenal nodules is to prevent death from
adrenal cortical carcinoma, which is usually fatal. However, this
disease is rare, affecting only 4 to 12 people in 1,000,000 and
only 1 in 4000 adrenal nodules. Also, evidence suggests that early
detection is unlikely to lengthen life.
Detecting adrenal metastases from other cancers is unlikely to
substantially affect outcome. There is little evidence that
asymptomatic, benign, hormonally active adrenal nodules represent a
significant public health problem or that detecting them would be a
cost-effective justification for screening. The consensus
conference re-port recommended that incidentally discovered adrenal
nodules be worked up with a history, physical examination,
biochemical evaluation, and possibly more imaging.
However, in its conclusions, the conference report stated that
they: ...call into question the advisability of the current
practice of intense clinical follow-up of this common condition.
Therefore, the types of lesions likely to be detected, the
frequency with which nodules are detected (requiring further
imaging or biopsy), and the low probability of affecting outcomes
makes adrenal nodule detection a poor justification for CT
Abdominal aortic aneurysms
Abdominal aortic aneurysms (AAA) account for approximately
10,000 deaths per year in the United States. This accounts for 1.2%
of the mortality in men over the age of 65 years and is a small
fraction of the total deaths from other cardiovascular diseases.
However, studies have suggested there is value to ultrasound
screening for AAA, with studies showing a mortality reduction from
ruptured AAA of 21% to 55%.
Therefore, while ultrasound screening may reduce deaths, the
cost-effectiveness of screening with CT remains in doubt because of
the relatively low prevalence in the population. Furthermore, if
one chose to screen for AAA, ultrasound would be a better choice,
because it is cheaper, yet still has a high sensitivity and
specificity. Therefore, even if it is concluded that screening for
AAA should be done, it still cannot be used to justify WBS.
Renal cell carcinoma
The rate of deaths per year in the United States from RCC is
approximately 12,000--similar to that for AAA--although 31,000 new
cases per year are detected. This represents approximately 2% of
deaths from all forms of cancer. While radiologists are quite
familiar with the common discovery of incidental RCC during CT
scanning for other reasons, the question must be asked as to what
benefit derives from such discoveries. Analysis of incidence and
death statistics reveals that the rate of detection of RCC has
increased three-fold more than the increase in mortality from RCC
; this increase is almost certainly related to the marked increase
in the use of CT and other imaging studies. Sixty-one percent of
all cases of RCC are now discovered incidentally, and most are
cured. There is a marked discrepancy between death statistics of
3.5 per 100,000 population and detection rate of lesions in the few
ultrasound screening studies that have been done of 1 to 3 in 1000.
Also, RCC is found in 22% of autopsies.
All of these facts infer that a high percentage of cases of RCC
represent disease that the patient would die with rather than from,
which is termed pseudodisease and represents overdiagnosis.
Therefore, the increased detection rate caused by screening is
likely to lead to a substantial number of unnecessary radical or
partial nephrectomies, with their consequent morbidity and small
mortality. Therefore, the cost-effectiveness of screening for RCC
does not seem highly plausible, based on the relatively low
incidence of disease and the high rate of pseudodisease. Thus, it
is difficult to use the detection of early RCC to justify WBS.
There has been substantial interest in ultrasound screening for
ovarian carcinoma because it is usually discovered in a late stage
and has a poor cure rate. There are approximately 24,000 new cases
of ovarian cancer yearly in the United States with approximately
14,000 deaths. Studies of screening have been disappointing, with
one report showing the detection of 17 cancers among more than
and another finding 17 stage I cancers in more than 183,000
Unfortunately, with today's technology, one must conclude that
screening is not cost-effective for ovarian carcinoma. Again, as
with AAA, even if one were to believe that screening was a
reasonable strategy, most would agree that ultrasound is less
expensive and would have a much higher sensitivity and specificity
than CT for early-stage cancer. Therefore, detecting ovarian cancer
also cannot be used to justify WBS.
The practice of whole-body CT screening has led to a raucous
debate over the wisdom and ethics of performing such screening for
self-paying, asymptomatic volunteers. Subjects for such studies are
often implicitly promised peace of mind or extended life from early
detection of otherwise fatal diseases.
In this article, I have reviewed the five most common
potentially fatal diseases that proponents of WBS might cite as
justifying this test. In each case, the probability of benefit is
doubtful or an alternative screening test is more reasonable.
Therefore, it is also likely that the sum of additional instances
of false-positive findings, pseudodisease, and incidental findings
from WBS would likely lead to considerable additional cost,
morbidity, and even mortality from subsequent tests and procedures.
Even accurate early detection of disease may not translate to
lengthening life. Does the benefit to helping one sick person
balance the harm caused to one or several healthy ones? I believe
that this analysis suggests that WBS is currently not a reasonable