The document summarizes research into how best to communicate risk information about medication side effects to patients. It discusses several studies that tested different formats for presenting side effect risk, including percentages, verbal descriptors like "common" and "rare", and absolute frequencies. The studies found that verbal descriptors alone led to less accurate understanding, while percentages and absolute frequencies generally performed better. However, people may still overestimate low risks regardless of format. The latest study tested recommendations by the EMA to use a combination of words and frequencies bands, finding some evidence it increased perceived risk of side effects compared to numerical information alone. Overall, the research suggests heterogeneity in how people understand risk information and no single format achieves shared understanding.

1. School of Psychology
FACULTY OF MEDICINE AND HEALTH
Improving health information to promote health literacy
Factors influencing the perception of side
effect risk information – reflections and
prospects for research
Peter Gardner
Senior Lecturer and Head of School
School of Psychology
p.h.gardner@leeds.ac.uk

2. Patient Information Leaflets
(PILs)

3. Getting better…?

4. Which parts of the leaflet do
people read?
Side effects 96%
How and when to take it 91%
What is your medicine for? 85%
Things to do before you take 66%
What is in your medicine? 53%
MORI Survey for Medicines Partnership, 2003, 2004
Ask about Medicines Week

5. Testing the EU terms
EU People
Very common > 10% 54%
Common 1 - 10% 34%
Uncommon 0.1 - 1% 11%
Rare 0.01 - 0.1% 8%
Very rare < 0.01% 4%
Knapp, Raynor, Berry (2004) Quality & Safety in Health Care.
Berry, Knapp, Raynor (2002) Lancet.

6. What about online Information?
Using a pop-up on a medicine page of Cancerhelp.org.uk
(now ‘About Cancer’ pages)
• 8 on-line studies since 2004
• Publications in British Journal of Health Psychology, Drug Safety, Patient Education
and Counseling, Health Expectations.
• Tested alternative formats for presenting side effect risk on perceptions
of risk
• Controlled design with random allocation
• Taxol, Ibuprofen, Tamoxifen
• Approximately 15 participants per month
• Participants more likely to have a personal interest

7. Cancer Research UK studies
Background
• Broadly, the suite of studies have tested the effect of
stating the risk of side effects as verbal descriptors,
percentages and frequency statements and combinations
of these formats.
• Started off with the premise that ‘Natural Frequencies’ are
more concrete and would probably work better
• e.g. If 100 people took this medicine, 3 would get
constipation.

8. Cancer Research UK studies
Findings
• The evidence suggests that verbal descriptors (“common”/
“rare”) on their own produce markedly less accurate
estimations of risk
• Percentages generally perform well, but some evidence
that these are not so good for low risks
• More specific statements about frequency show some
superiority over frequency bands (“affects more than 1 in
10 patients”) but may not be so feasible
• People prefer combined statements (“affects 1 in 500
people (0.2%)”) but are no more accurate in their
estimation of risk

9. Cancer Research UK studies
Impact

10. Cancer Research UK studies
Latest study

11. Testing EMA recommendations
• EMA requires a combination of words and frequency
bands
Common: may affect up to 1 in 10 people
• NICE suggest that verbal descriptors should not be used
without numerical information
• It could be argued that these recommendations are on the
basis of consensus, not evidence

12. Testing EMA recommendations
• Two questions:
• Does the use of the verbal descriptor ‘frame’ patients’
understanding leading to overestimation of risk?
• Does the use of two indicators of uncertainty lead to
confusion?
‘may affect’ and ‘up to 1 in 10’
• Compare with
‘will affect’ and ‘up to 1 in 10’

13. Testing EMA recommendations
• 2 x 2 factorial design
• Numerical format vs. Combined verbal and numerical
• ‘will affect’ vs. ‘may affect’
• Presented with information on 10 potential side effects; 2
each from the 5 EC frequency bands
• Asked to provide risk estimates for 5 of the side effects; 1
from each of the bandings

14. Scenario

15. Testing EMA recommendations
• 339 participants
• Numerical + may = 91
• Combined + may = 85
• Numerical + will = 77
• Combined + will = 86

16. Participants

17. Testing EMA recommendations
• Asked to provide risk estimates for 5 of the side effects; 1
from each of the bandings and a rating of the perceived
risk of experiencing ANY of the side effects
• Also completed 5 Likert scales regarding:
• Satisfaction with the information
• Severity of the side effects
• Likelihood of experiencing a side effect
• General risk to health
• Effect on decision to continue treatment

18. Results
Numerical vs. Combined

19. Results
• No differences between ‘may’ and ‘will’ conditions on
perceptions of side effect risk
• Little difference in Likert ratings between the conditions
• Higher perceived likelihood of experiencing side effects in the combined
condition
• No evidence of interactions between the variables

20. Results
‘May’ vs. ‘Will’

21. Conclusions
• Possible framing effect of verbal descriptors
• Variability of response suggests lack of shared
understanding of risk descriptions
• Problem of overestimation still prevalent in ‘numerical
only’ condition, but…
• Low incidence rates mean that people are more likely to overestimate than
underestimate
• Heterogeneity of risk perception responses may mean it is impossible to
get shared understanding
• Precise risk information is difficult to obtain anyway

22. Future research
• Need for replication of findings with different medicines
• Are there other factors involved?
• Numeracy (see Gardner et al, 2011)
• Other individual differences
• Emotional reaction to different types of treatment
• Need to investigate the effect on actual behaviour

23. References
Berry, D.C., Knapp, P. and Raynor, D.K. (2002). Provision of information about drug side effects to
patients. Lancet, 359, 853-4.
Gardner, P.H., McMillan, B.R.W., Raynor, D.K., Woolf, E., Knapp, P. (2011). The effect of numeracy on the
comprehension of information about medicines in users of a patient information website. Patient
Education and Counseling, 83, 398-403.
Knapp, P., Gardner P.H., Carrigan N., Raynor, D.K. and Woolf, E. (2009). Perceived risk of medicine side
effects in users of a patient information website: a study of the use of verbal descriptors, percentages
and natural frequencies. British Journal of Health Psychology,14, 579-94.
Knapp, P., Gardner, P.H., Raynor, D.K., Woolf, E. and McMillan, B.R.W. (2010). Perceived risk of
Tamoxifen side effects: a study of the use of absolute frequencies or frequency bands, with or without
verbal descriptors. Patient Education and Counseling, 79(2), 267-271.
Knapp, P.R., Gardner, P.H. and Woolf, E. (2015). Combined verbal and numerical expressions increase
perceived risk of medicine side-effects: a randomized controlled trial of EMA recommendations. Health
Expectations, published online 26 Jan 2015, doi: 10.1111/hex.12344.
Knapp, P., Raynor, D.K. and Berry, D.C. (2004). Comparison of two methods of presenting risk information
to patients about the side effects of medicines. Quality and Safety in Health Care,13, 176-80.
Knapp, P., Raynor, D.K., Woolf, E., Gardner, P.H., Carrigan, N. and McMillan, B.R.W. (2009).
Communicating the risk of side effects to patients: an evaluation of UK regulatory recommendations.
Drug Safety, 32(10), 837-849.