(Mis)understanding medical
information: healthcare
professionals and laymen alike
Talya Miron-Shatz, Ph.D.
Center for Health and Wellbeing
Princeton University
Talk at the School of Public
Affairs, Baruch College
9/16/2009
Talya Miron-Shatz, PhD.
Agenda






Who should understand medical information?
What do people make of genetic testing?
What do they expect of testing?
When does this go wrong?
Who gets hurt the most?
Should we care?
6/11/2009
Talya Miron-Shatz, PhD.
Let’s talk about shopping
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
Meaning and value are
actively inferred



We – you, me, everybody – base our
judgment and evaluation of alternatives on
the way in which they are represented to us.
This is because humans are wired to save
cognitive effort.
By acknowledging this, one can influence
(bias) behavior.
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
Who should understand
medical information? Or what is shared decision
making ?
A conceptual framework
paternalism
shared decision making
informed
choice
Depends on the patient-clinician
interaction, plus other elements
Charles C, Gafni A, and Whelan T, Shared decision-making in the medical encounter: what does it
mean? (Or it takes at least two to tango). Soc Sci Med, 1997. 44: p. 681-92.
Shared Decision Making





Shared decision making involves at least two
(often many more) participants—the health
professional and the patient
Both parties take steps to participate in the
process
Information sharing is a prerequisite
Information is needed about both ‘risks’ and
‘values’
A decision is made or deferred
Shared decision making:
skills









Problem definition
Portray equipoise
Portray options
Check understanding
Explore ideas, concerns, expectations
Role preference
Decision making
Deferment if necessary
Review arrangements
Elwyn, 2001
Shared decision
making
‘Involving the patient in the
decision making, to the extent
that they desire’
Key skills or ‘competences’
Do patients
want to be
involved in
decisions ?
Who should make treatment
decisions?
Picker Europe Survey 8000 patients, 8 countries, Jul 2002
60
50
40
30
20
Doctor
Doctor and patient
together
Patient
10
0
Coulter A and Magee H, eds. The European patient of the future. 2003, Open University Press: Maidenhead.
“There is a 30% chance of rain
tomorrow.” (Gigerenzer et al.)
1. It will rain in 30% of the area.
2. It will rain for 30% of the time.
3. On 30% of days like this it rains.
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
Bayesian Inference
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
P(A|B) is NOT p (B|A)


A = The effect (genotype), what we see
B = What we are seeking (disease, phenotype)
P(B│A) = P(B) X P(A│B)
P(A)
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
A relatively simple
scenario…




The probability of colon cancer is 0.3%
If a person has colon cancer, the probability
of a positive test result is 50%
If a person does not have colon cancer, the
probability of a positive test result is 3%
What is the probability that a person has
colon cancer, if he tests positive?
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
If you test positive for colon
cancer, do you have it?





P(A) = p(A|B) + p (A|B’)
P(A|B) = .5
p (A|B’) = 0.03 X 0.997 = 0.02991
P(B│A) =
P(B) X P(A│B) = 0.003 X 0.5
P(A)
0.02991
What do people make of genetic
counseling
Talya Miron-Shatz, PhD.
=?
Rephrasing as Natural
Frequency




Out of every 10,000 people, 30 will have
colon cancer.
Out of these people, 15 will test positive.
Out of the remaining 9,970 people, 300 will
test positive.
How many of the people who test positive
have colon cancer?
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
Results from a current study
(Miron-Shatz, Hanoch, Graef & Sagi, forthcoming, J. of Health Communication)


264 Princeton students participated in an online
survey about genetic screening
Students read a hypothetical letter to an expectant
mother who had an elevated risk of having a baby
with Down syndrome



Probabilistic
Frequentist
Visual
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
Probabilistic presentation


The probability of giving birth to a baby with
Down syndrome for a woman with normal
results is 1:724
The probability of giving birth to a baby with
Down syndrome for a woman with your
abnormal result is 1:181
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
Frequentist presentation


One out of every 724 fetuses of women your
age will be diagnosed with Down syndrome.
One out of every 181 fetuses of women your
age with screening results that are identical
to yours will be diagnosed with Down
syndrome.
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
Visual presentation

The white circle in the picture represents the only fetus with Down
syndrome out of all the fetuses of women your age who have not yet
been screened. There are 724 circles in the picture.
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●○●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
●●●●●●●●●●●●●●●●●●●
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
Visual presentation

The white circle in the
picture represents the
only fetus with Down
syndrome out of all the
fetuses of women
whose screening
results were identical to
yours. There are 181
circles.
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
Percent correct answer
Presentation format affects
giving the correct answer
70
60
50
40
30
20
10
0
probability
visual
Presentation form
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
frequency
PErcentages risk evaluations
Presentation format affects
how the risk is perceived
70
60
50
don't know
40
low
30
medium
20
high
10
0
probability
frequency
Presentation form
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
visual
In your opinion, how clear will it
be for a woman who received the
letter whether a 1:181 chance of
having a fetus with Down
Syndrome is good or bad?
The probabilistic and frequentist
presentations are perceived as equally clear.
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
Genetic counselors are also
affected by representation
(Miron-Shatz, Hanoch, and Saphire-Bernstein, submitted)
100.0%
90.0%
80.0%
70.0%
60.0%
Probabilistic
50.0%
Frequentist
40.0%
30.0%
20.0%
10.0%
0.0%
Probability - 0-20%
Risk - Low or Medium
Probability - Correct
Horse Disease
What do people make of genetic
testing
Risk - Low or Medium
Ear Problem
Talya Miron-Shatz, PhD.
And they need to actively
make sense of numbers
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
From the official National Cancer
Institute (NCI) website
“According to estimates of lifetime risk, about
13.2% (132 out of 1,000 individuals) of
women in the general population will develop
breast cancer, compared with estimates of 36
to 85% (360-850 out of 1000) of women with
an altered BRCA1 or BRCA2 gene. In other
words, women with an altered BRCA1 or
BRCA2 gene are 3 to 7 times more likely to
develop breast cancer than women without
alterations in those genes.”
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
I
Breast cancer will develop in all women age 36 to
85.
II Breast cancer will develop in 36 to 85 percent of
women who are found to have BRCA1 and
BRCA2 alterations.
III Women who have BRCA1 and BRCA2 alterations will
exhibit 36 to 85 percent of the symptoms associated
with breast cancer.
IV Women who are found to have alterations in the
genes called BRCA1 and BRCA2 have 36% to
85% higher chance of developing breast cancer.
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
Lifetime risk of breast cancer
(Hanoch & Miron-Shatz, submitted)



An online survey, 284 women
47.5% chose the correct interpretation.
46.1% chose option iv, associating alterations
in the BRCA1/2 genes with a 36% to 85%
higher chance of developing breast cancer.
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
Does numeracy help?

Numeracy = the ability to deal with numbers
and comprehend them.
What do people make of genetic
testing
Talya Miron-Shatz, PhD.
Comprehension of risk
70
60
Percentage
50
40
Low Numeracy (scored 0-8)
High Numeracy (scored 9-11)
30
20
10
0
Most appropriate correct
What do people make of genetic
testing
Numeric risk correct
Talya Miron-Shatz, PhD.
Would verbal expressions of
probability help? I

Not really… The ranking for various
expressions is more or less constant, but the
meaning differs according to context.

‘Rare side effects’ mean 1/1000 for using
beta blockers, and 1/5 for antihistamines.
(Kong et al, 1986, NEJM).
What do people make of genetic testing?
Talya Miron-Shatz, PhD.
Would verbal expressions of
probability help? II


Not really… Expressions are noncomplementary (Kerlitz & Budescu, 1993)
Likely = 63%, and unlikely = 14%.
Intermediate expressions fluctuate more than
extreme ones.

E.g., ‘probable’ vs. ‘always’
What do people make of genetic testing?
Talya Miron-Shatz, PhD.
Importance of aspects of BRCA
screening test (Miron-Shatz & Diefenbach)



Give me information about my BRCA1 and
BRCA2 status: 76% very important.
Tell me with certainty whether I will develop
breast cancer: 32% very important. *
Tell me what to do in case I have breast
cancer 34% very important. *
* 50% the test cannot do that.
What do people expect of
genetic testing
Talya Miron-Shatz, PhD.
False beliefs and expectations
from screening:
70
60
Percentage
50
40
Low Numeracy (scored 0-8)
High Numeracy (scored 9-11)
30
20
10
0
Absolute risk
What to do
Participants who correctly responded: The test cannot do that
What do people expect of
testing
Talya Miron-Shatz, PhD.
Worries about the
screening
3
Mean worry
2.5
2
1.5
1
0.5
0
Low Numeracy (scored 0-8)
When does this go wrong
Talya Miron-Shatz, PhD.
High Numeracy (scored 9-11)
Willingness to pay for
screening
300
Willingess to pay in USD
250
200
150
100
50
0
Low Numeracy (scored 0-8)
When does this go wrong
Talya Miron-Shatz, PhD.
High Numeracy (scored 9-11)
Low numeracy individuals are

Slightly older
Less educated: 48% college, 27% grad school
As wealthy as high numeracy participants

However…


Who gets hurt the most
Talya Miron-Shatz, PhD.
Do patients understand what
we are talking about?

A recent review (Elwyn et al.) found that
counselors seldom ask about comprehension.

Some patients think genes are – in your
brain… in your knees…
Should we care
Talya Miron-Shatz, PhD.
Conclusions

Due to the nature of human cognition,
presentation of information matters:



Framing affects desirability of alternatives.
The frequentist form is associated with better
understanding than the probabilistic form.
To facilitate understanding, whoever
communicates information should
acknowledge this.
To conclude…
tmiron@princeton.edu
Clinical implications



Even seemingly ‘neutral’ or ‘objective’
presentations of information carry emotional
and cognitive implications.
Frequentist representation facilitates the
understanding of probabilistic information.
We cannot assume comprehension.
To conclude…
tmiron@princeton.edu
Implications for training


Presenting information is a learned skill.
The psychological aspects of decision
making should be incorporated into medical
and genetic counseling training programs.
To conclude…
tmiron@princeton.edu
What we learned thus far





What do people make of genetic testing?
What do they expect of testing?
When does this go wrong?
Who gets hurt the most?
Should we care?
3/22/2016
Talya Miron-Shatz, PhD.
(Mis)understanding medical
information: healthcare
professionals and laymen alike
Talya Miron-Shatz, Ph.D.
Center for Health and Wellbeing
Princeton University
Talk at the School of Public
Affairs, Baruch College
9/16/2009
Talya Miron-Shatz, PhD.