School of PsychologyFACULTY 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 GardnerSenior Lecturer and Head of School
School of Psychology
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
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.
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
Cancer Research UK studiesBackground
• 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.
Cancer Research UK studiesFindings
• 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
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
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’
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
Testing EMA recommendations
• 339 participants• Numerical + may = 91
• Combined + may = 85
• Numerical + will = 77
• Combined + will = 86
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
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
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
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
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.