(mis)understanding medical information: healthcare professionals and laymen alike

(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

Talya Miron-Shatz, PhD.9/16/2009

http://www.princeton.edu/main/

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?



Let’s talk about shopping

Talya Miron-Shatz, PhD.What do people make of genetic testing


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.



Who should understand medical information? Or - what is shared decision making ?


paternalism shared decision making informed

choice

A conceptual framework

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

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Doctor

Doctor and patienttogetherPatient

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.



Bayesian Inference


http://upload.wikimedia.org/wikipedia/en/3/3a/Thomasbayes.jpg


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)



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?



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

Talya Miron-Shatz, PhD.What do people make of genetic counseling


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



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



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.


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.

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●○●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●


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.


Presentation format affects giving the correct answer

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probability visual frequency

Presentation form

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Presentation format affects how the risk is perceived

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probability frequency visual

Presentation form

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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.


Genetic counselors are also affected by representation(Miron-Shatz, Hanoch, and Saphire-Bernstein, submitted)

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Probability - 0-20% Risk - Low or Medium Probability - Correct Risk - Low or Medium

Horse Disease Ear Problem

Probabilistic

Frequentist


And they need to actively make sense of numbers


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.”


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.


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.


Does numeracy help?

Numeracy = the ability to deal with numbers and comprehend them.


Comprehension of risk


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).

Talya Miron-Shatz, PhD.What do people make of genetic testing?

Would verbal expressions of probability help? II

Not really… Expressions are non-complementary (Kerlitz & Budescu, 1993)

Likely = 63%, and unlikely = 14%. Intermediate expressions fluctuate more than

extreme ones. E.g., ‘probable’ vs. ‘always’

Talya Miron-Shatz, PhD.What do people make of genetic testing?

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.

Talya Miron-Shatz, PhD.What do people expect of genetic testing

False beliefs and expectations from screening:

Talya Miron-Shatz, PhD.What do people expect of testing

Worries about the screening

Talya Miron-Shatz, PhD.When does this go wrong

Willingness to pay for screening

Talya Miron-Shatz, PhD.When does this go wrong

Low numeracy individuals are

Slightly older Less educated: 48% college, 27% grad school As wealthy as high numeracy participants

However…

Talya Miron-Shatz, PhD.Who gets hurt the most

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…

Talya Miron-Shatz, PhD.Should we care

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… [email protected]

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.


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.


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?


(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


(mis)understanding medical information: healthcare professionals and laymen alike

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