Explaining risks: turning numerical data into meaningful picturesBMJ 2002; 324 doi: https://doi.org/10.1136/bmj.324.7341.827 (Published 06 April 2002) Cite this as: BMJ 2002;324:827
All rapid responses
Edwards, Elwyn and Mulley have neatly summarised the state of our
knowledge on risk communication [BMJ 6 April 2002]. However,I have three
further points to add.
First, readers may be interested in the risk ladder we developed to
display the risks associated with anaesthesia and some everyday risks for
comparison [1, 2].
Second, I think the authors have either chosen not to address, or
been unaware of the fact, that communication about risk and safety takes
place throughout a consultation and not simply when the conversation turns
specifically to that issue. Likewise, in written materials, it is located
not only in the section headed ‘what are the risks?’ but rather pervades
the whole document. My experience with the Royal College of Anaesthetists’
Patient Information Project has brought home to me that patient
information is not simply about putting facts down on paper. Rather, it
throws the entire implied relationship between clinician and patient into
focus and nowhere is this better demonstrated than in the related issues
of safety and risk. The choice of words and the professional self-image we
project may be more powerful influences on patients’ decisions than
precise numerical estimates of risk, or their visual analogues. Take for
instance the following text, typical of a preoperative leaflet about
Q What happens once I am asleep?
A You are never left alone during an operation. Your anaesthetist stays
with you and keeps you safe, pain free and unaware of what is going on.
Drugs are constantly being given to you throughout the operation to make
sure you are kept safe…
Here, a question, which could be simply one of curiosity is used as an
opportunity both for reassurance and also possibly for education about the
role of anaesthetists in general. The answer mentions safety, but not the
question. Is the writer of the booklet justified in assuming that patients
regard anaesthesia as being so risky that an answer to a simple question
about procedure can be expected to allude to safety as a matter of course?
For the patient who had not considered that anaesthesia might be risky
would this be a disconcerting change of tone? Further, if it is necessary
to be kept safe, this begs the question of what patients need to be kept
safe from. The excesses of the surgeon? The undesired effects of the
anaesthetic? Electrical, infectious or other hazards? Without
qualification, ‘safe’ is not only meaningless but may actually provoke
anxiety. The analysis can continue but I have made my point.
Last, it is right to consider risks and it is certainly a cause for
concern that we lack reliable data for many risks. More sobering still is
the thought that for many healthcare interventions we are still waiting
for reliable evidence of benefit .
 Adams AM, Smith AF Risk perception and communication: recent
developments and implications for anaesthesia. Anaesthesia 2001; 56: 745-
 Adams AM, Smith AF Probability of winning the National Lottery –
a reply (letter) Anaesthesia 2002; 57: 186-7 (revised version of ladder)
 Smith R Where is the wisdom? The poverty of medical evidence. BMJ
1991; 303: 798-9
Competing interests: No competing interests
Editor - The recent review of risk communication in the health care
setting by Edwards et al raises some important points . The paper
highlights the essential role of individuality in patients' understanding
of risk and consequent decision-making, illustrating the heterogeneity of
risk perception. Yet the suggestion that clinicians should compare
medical risks with 'everyday' risks sits uncomfortably with individuality
and varied understanding of risk information by patients. Patients'
perceptions of these 'well known risks (for example car crashes)' are
likely to be equally varied. In a study examining the understanding of
'simple' probabilities (such as rolling dice), a wide range of over- and
underestimations of probability was seen . The consequences for
misunderstanding these analogies could be grave, with patients
accepting/declining treatments through misconceptions of probability with
potentially fatal results.
The use of pictorial formats to assist the risk communication process
is a significant advance, but caution should be advised in those patients
with hemianopia and neglect - especially in the authors' quoted example of
atrial fibrillation and stroke . Although the authors report that bar
chart formats have been shown by studies to be preferable, one should not
forget the practical advantages of crowd figure formats. Our work with
crowd figures has shown good understanding by both younger (unpublished
data) and older patients . We would encourage the adoption of a 'wipe-
clean' crowd figure format, allowing easy and rapid illustration of any
probability information - considerably more practical and dynamic than pre
-printed bar charts for specific conditions.
Competing Interests: None
Elderly Services, St James's Hospital, Leeds, LS7 9TF
School of Computing & Mathematics, University of Huddersfield
1.Edwards A, Elwyn G & Mulley A
Explaining risks: turning numerical data into meaningful
2.Fuller R, Dudley NJ, Blacktop J
Can we explain risk to older people by using probabilities associated with
tossing coins, rolling dice and drawing cards?
Abstract of communications to the British Geriatric Society 2002 - In
3. Price CJ, Curless RH, Rodgers H
Can stroke patients use visual analogue scales?
4. Fuller R, Dudley NJ, Blacktop J
Risk communication and older people - understanding of probability and
risk information by medical inpatients aged 75 years and older
Age & Ageing 2001;30:473-476
Competing interests: No competing interests
The risk communication literature has been useful in providing
recommendations for how information about risk might be presented to
patients.(1-3) It has also emphasised that risk communication is a two-way
process, that people’s responses to risk rest on qualitative and
quantitative aspects of a potential risk outcome, and that the way
information is framed affects decisions. The fields of risk communication
and informed decision making uphold the individual’s right to autonomous
choice. They also recommend that people receive all relevant information
to make informed decisions about their health. These guidelines are
usually based on decisions about treatments where individual preferences
are primary and decisions against the grain of current evidence are
unlikely to affect the health of others (such as with cancer treatment or
screening). Many treatment decisions carry no right or wrong answer
because there is uncertainty regarding outcomes. The principle of autonomy
underpins these guidelines.
However, there are situations where patient choices, which may be
rational under the guidelines of autonomous decision making, can have
significant repercussions for the wider community. Childhood immunisation
against eradicable diseases provides an example. As diseases approach
eradication or are well controlled, the risk posed by a vaccine could
eventually be higher than for the disease it prevents.(4) Given both
absolute and relative risk estimates, fully informed and rational
individuals might rightly reject vaccination. If all individuals reacted
in this way and ceased vaccinating, the population would be vulnerable to
re-importation of a disease and outbreaks would ensue. In this context,
the decision not to vaccinate a child may bear little consequence for them
but when enough individuals choose this action, population or “herd”
immunity is threatened and outbreaks occur. Hardin referred to this
situation as the tragedy of the commons.(5) Over-fishing, industrial
pollution of rivers, use of fossil fuels and unsustainable population
growth also create a scenario where the aggregate costs of individual
actions threaten populations and future generations.
Proponents of autonomous informed decision making shun persuasion.
They rightly point out the problems when people are not fully informed
about risks or feel pressured to make a decision. Although the concept of
shared decision making acknowledges the role of the clinician, few
writings in the patient decision literature confront situations where
fully informed individuals make informed decisions that have deleterious
effects on the wider community.(6-8)
In situations where informed autonomous individual choices put the
community or future generations at risk, guidelines are needed for ways of
upholding the ethical and legal imperative of valid consent while
acknowledging the wider population effects of an individual’s decision.
Further discussion on this difficult balance appears indicated.
1. Edwards A, Elwyn G, Mulley A. Explaining risks: turning numerical
data into meaningful pictures. BMJ 2001;324:827-30.
2. National Research Council. Improving risk communication. Washington:
National Academy of Sciences, 1989.
3. Bogardus ST, Holmboe E, Jekel JF. Perils, pitfalls and possibilities in
talking about medical risk. JAMA 1999;281(11):1037.
4. Chen RT, Hibbs B. Vaccine safety: current and future challenges.
Pediatric Annals 1998;27:445-55.
5. Hardin G. The tragedy of the commons. Science 1968;162:1243-8.
6. Gwyn R, Elwyn G. When is a shared decision not (quite) a shared
decision? Negotiating preferences in a general practice encounter. Social
Science and Medicine 1999;49:437-47.
7. Raffle AE. Information about screening - is it to achieve high uptake
or to ensure informed choice? Health Expectations 2001;4:92-98.
8. Parker M. The ethics of evidence-based patient choice. Health
Competing interests: No competing interests
Editor – Edwards1 et al provided us with an excellent reminder of how
central risk perception and communication are to us in our work. Two
issues of paramount importance in the context of risk communication are
the role of trust and the ever-present spectre of uncertainty.
The amount of trust the public has in government, business and also
the medical profession has come under scrutiny over recent years2. Trust
is fragile, difficult to nurture and easily destroyed yet it lies at the
heart of any attempt at risk communication. If we do not trust the source
of information we are unlikely to heed their warnings and take appropriate
It is important to recognise the difference between risk and
uncertainty. Risk is when we know what the probabilities of events
occurring are; uncertainty is when the probabilities are unknown. In
uncertain situations we cannot rely on quoting relative or absolute risks
or using pictorial aids. As outlined by Edwards it is important to
recognise that uncertainty exists in many circumstances. We all like hard
facts and prefer certainty but in reality this is possible on few
occasions. The perception among some people is that science and medicine
produce hard facts with cast iron guarantees. This perception has partly
been generated by the medical profession itself in its paternalistic
attitude and its unwillingness to admit uncertainty in case it is seen as
a weakness. The medical profession is changing and so are public
perceptions but this view still persists among many people. Part of the
risk communication process should therefore be aimed at over coming this
The BSE enquiry3 highlights the close relationship between trust and
uncertainty. The following key messages from the Phillips report are
pertinent to us all in whatever speciality we work and apply at both
individual and organisational levels.
1. To establish credibility it is necessary to generate trust
2. Trust can only be generated by openness
3. Recognise uncertainty where it exists
4. Precautionary measures are important even when risk has been unproved
5. Trust people to respond rationally to openness.
If uncertainty is recognised and openly discussed it helps generate trust,
which in turn leads to better risk communication and management and may
build more trust.
1Edwards A, Elwyn G, Mully A. (2002) Explaining risks: turning
numerical data into meaningful pictures. BMJ 324:827-330 (6th April)
2Ferriman A. (2001) Poll shows public still has trust in doctors. BMJ
3Phillips N.A. (2000) Report, evidence and supporting papers of the
inquiry into the emergence and identification of bovine spongiform
encephalopathy (BSE) and variant Creutzfeldt-Jakob disease (vCJD) and the
action taken in response to it up to 20 March 1996 the BSE inquiry.
Department of Health. London The Stationary Office 2000
Competing interests: No competing interests
Edwards et al in their paper on risk presentation highlight the
complexity of communicating risk to patients(1). Whilst we agree with the
reported conclusions, at least equal emphasis should be given to improving
GPs’ own understanding and confidence in utilising risk information.
We have recently developed and evaluated a computerised decision
support system to assist GPs in the management of stroke patients. Based
upon a series of decision analytical models, the system offers risk data
in several formats for 960 patient profiles commonly encountered in
primary care: Numerical (absolute risks, relative risks, NNTs), graphical
and pictorial options are available to the user.
Evaluation of the system included an in-depth qualitative exploration
of risk understanding and risk presentation preferences. Among the key
themes to emerge were that risk measures elicit very varied responses from
GPs and are not understood or integrated into consultations by all.
Several practitioners expressed uncertainty and acknowledged limitations
in their own understanding when discussing the value to their practice of
the various formats.
“Absolute risk reduction and relative risk reduction - I find
difficult to understand the difference and I think it would be very
difficult to explain to patients.” GP12
“ … this risk business, I find it quite difficult. … a bit mind-
To a degree, our findings echo the view of Ham and Alberti reported
in the same issue, that there is a “lack of understanding of or proper
explanation of risk by the profession”(2). The implications are that if
GPs have a poor understanding of what risk information means, they will be
reluctant to draw upon support tools to assist their own decision making.
Furthermore, if GPs are not comfortable with risk concepts, then they will
be less willing to discuss risks with patients.
“… [GPs] have considerable difficulty getting their head around [risk
data]. … I don’t think I have that confidence in both telling [patients]
what their individual risk is and telling them what it means.” GP03
In the drive to implement evidence-based practice, GPs are
increasingly required to assess and evaluate risk. Unless practitioners
understand the concept of risk and are comfortable in applying and
discussing these risks with patients, then the future rollout of support
systems and decision aids will continue to meet with resistance.
1. Edwards A, Elwyn G, Mulley A. Explaining risks: turning numerical data
into meaningful pictures. BMJ 2002; 324: 827-830.
2. Ham C, Alberti KGMM. The medical profession, the public, and the
government. BMJ 2002;324:838-842
Competing interests: No competing interests
The Edwards' et al., proposed assessment standard deserves a standing
"Comparison with everyday risks is valuable, such as where the risk (for
example, stroke in atrial fibrillation) is compared with other well known
risks (for example, road crashes). These comparisons should be integrated
into patient information materials. Absolute risks (with appropriate
scales) should be given greater prominence than relative risks in both
information for patients and journals for professionals. Lifetime risks
should be given, with relevant information about risks in relevant time
spans as additional information. The influence of framing should be
countered by using dual representations (loss and gain, mortality and
survival data). Be clear about whether the task is to read an exact value,
compare two risks, assess trends, or judge proportions; a display should
provide the relevant but minimum information needed for these tasks."
Would such an assessment apply in discussing risks to menopausal patients
prior to being treated with hormone replacement therapy?
An increase in mammographic density was much more common among women
taking continuous combined HRT (40%) than for those using oral low-dose
estrogen (6%) and transdermal (2%) treatment. The increase in density was
already apparent at the first visit after starting HRT. During long-term
follow-up, there was very little change in mammographic status. HRT
regimens were shown to have different effects on the normal breast. There
is an urgent need to clarify the biological nature and significance of a
change in mammographic density during treatment and, in particular, its
relation to symptoms and breast cancer risk. 
Estrogen conjugates are generally considered as inactivated forms
devoid of any estrogenic activity. In some therapies, such as that used
during menopause, high dose of estrogen sulfate are currently used as non
estrogenic agent. However, precaution should be taken since a considerable
amount of this conjugate can be converted into estradiol-17 beta (E2), the
most biologically active hormone. In vitro, estrone sulfate (E1S), is
converted into estrone (E1) and E2 by the action of estrogen sulfatase and
17 beta-oxydoreductase enzymes. Since the half life E1S in plasma is much
higher than that of other estrogens, this conjugate could provide a
continuous supply of E2 to estrogen target cells, which may be
biologically important. Arredondo suggests an important role of estrogen
sulfates in breast carcinoma. 
One report shows that 4-hydroxyequilenin is capable of causing dna
damage in vivo. The data showed that 4-hydroxyequilenin induced four
different types of DNA damage that must be repaired by different
mechanisms. This is in contrast to the endogenous estrogen 4-
hydroxyestrone where only depurinating guanine adducts have been detected
in vivo. These results suggest that 4-hydroxyequilenin has the potential
to be a potent carcinogen through the formation of variety of DNA lesions
in vivo. 
In another study, the metabolism of equilenin in two lines of human
breast-cancer cells, MCF-7 and MDA-MB-231. MCF-7 cells respond to
treatment with Ah-receptor agonists with induction of cytochromes P450 1A1
and 1B1, whereas in MDA-MB-231 cells P450 1B1 is predominantly induced. In
microsomal reactions with cDNA-expressed human enzymes, both P450s 1A1 and
1B1 catalyzed the 4-hydroxylation of 17beta-dihydroequilenin, whereas with
17beta-estradiol as substrate P450 1A1 catalyzes predominantly 2-
hydroxylation and P450 1B1 predominantly 4-hydroxylation. Since P450 1B1
is constitutively expressed and both P450s 1A1 and 1B1 are inducible in
many extrahepatic tissues including the mammary epithelium, these results
indicate the potential for 4-hydroxylation of equilenin and 17beta-
dihydroequilenin in extrahepatic, estrogen-responsive tissues. 
Estrogen exposure is a major risk factor for breast cancer. Increased
estrogen responsiveness of breast epithelium may enhance this effect. The
level of estrogen receptor expression was reported higher in patients with
breast cancer than in control subjects and it was related to breast cancer
risk in postmenopausal women (P trend <_.005. expression="expression" declined="declined" as="as" expected="expected" in="in" premenopausal="premenopausal" control="control" subjects="subjects" the="the" menstrual="menstrual" cycle="cycle" progressed="progressed" but="but" rose="rose" breast="breast" cancer="cancer" patients="patients" p="p" trend="trend" _.015.="_.015." overexpression="overexpression" of="of" estrogen="estrogen" receptors="receptors" normal="normal" epithelium="epithelium" may="may" augment="augment" sensitivity="sensitivity" and="and" hence="hence" risk="risk" cancer.="cancer." _5="_5"/> "Communicating about risks should be a two way process in which
professionals and patients exchange information and opinions about those
risks. Professionals need to support patients in making choices by turning
raw data into information that is more helpful to the discussions than the
Prior to Hormone Replacement Therapy [HRT] the question is: Should a
patient's circulating estrogen levels be evaluated in order to determine
an effectual safe dose? Do excessive exogenous estrogen-receptive
substances present a risk for estrogen-receptor positive breast cancer
outcome? It appears that the risk assessment presentation should embrace
the potential for circulating estrogen levels or estrogen receptor breast
epithelial expression evaluation prior to HRT prescription in patients
with familial history of breast cancer. This action might be employed in
the ideal patient advisory relationship.
 Lundstrom E, Wilczek B, von Palffy Z, Soderqvist G, von Schoultz
B. Mammographic breast density during hormone replacement therapy: effects
of continuous combination, unopposed transdermal and low-potency estrogen
regimens. Climacteric. 2001 Mar;4(1):42-8.
 Loza Arredondo MC. [Estrogenic sulfuration and desulfuration
processes and their significance in breast carcinoma] Ginecol Obstet Mex.
1994 Sep;62:296-9. NOTE: Sulfate conjugates of the B-ring unsaturated
estrogens, equilin, equilenin, and 8-dehydroestrone, and their 17alpha-
and 17beta-dihydro analogues, constitute about 54% of PREMARIN, the most
commonly prescribed estrogen formulation in estrogen replacement therapy.
 Zhang F, Swanson SM, van Breemen RB, Liu X, Yang Y, Gu C, Bolton
JL. Equine estrogen metabolite 4-hydroxyequilenin induces DNA damage in
the rat mammary tissues: formation of single-strand breaks, apurinic
sites, stable adducts, and oxidized bases. Chem Res Toxicol. 2001
 Spink DC, Zhang F, Hussain MM, Katz BH, Liu X, Hilker DR, Bolton
JL. Metabolism of equilenin in MCF-7 and MDA-MB-231 human breast cancer
cells. Chem Res Toxicol. 2001 May;14(5):572-81.
 Khan SA, Rogers MA, Khurana KK, Meguid MM, Numann PJ. Estrogen
receptor expression in benign breast epithelium and breast cancer risk. J
Natl Cancer Inst. 1998 Jan 7;90(1):37-42.
 Explaining risks: turning numerical data into meaningful pictures
Adrian Edwards, Glyn Elwyn, and Al Mulley BMJ 2002; 324: 827-830.
I have no competing interests in this subject area.
Bill Misner Ph.D.
Competing interests: No competing interests