The impact of illustrations on public understanding of the aim of cancer screening
Introduction
Informed decision-making about cancer screening requires people to understand its potential costs and benefits. Recent evidence indicates that the public overestimate the benefits of screening and are largely unaware of its short-comings or potential for adverse effects [1], [2]. As a result, efforts to promote informed decision-making have concentrated on providing information to clarify the limitations of screening [3], [4]. However, there are positive aspects of screening that need to be conveyed; one of which is that some types of cancer screening (e.g. cervical screening) do more than identify cancer early; they can actually prevent it by detecting and removing pre-cancerous lesions.
The limited evidence available indicates that the concept of a pre-cancerous lesion is poorly understood. Knowledge of pre-cancerous states for oral and cervical cancers is poor [5], [6], [7], and the terms ‘pre-cancer’ and ‘cancer’ are often assumed to be synonymous. Although cervical screening is well-established in Britain, a survey of first time attenders at a colposcopy clinic for the treatment of cervical abnormalities found that 10% of women thought an abnormal smear meant early-stage cancer [7].
Like cervical screening, flexible sigmoidoscopy (FS) screening has the potential to prevent cancer by detecting and removing the pre-cancerous lesions (adenomatous polyps), and thereby interrupting the ademoma–carcinoma sequence [8]. Few people are likely to be aware that colorectal cancer can be prevented through screening because knowledge of this type of cancer is poor [9], [10]. This is important in the UK, because colorectal cancer screening will be offered as part of the nationwide screening program from 2006, and effective ways of informing all sectors of the community about screening need to be developed.
Written leaflets are often used to convey the benefits and harms of screening, but they have limitations. People may not be attracted to written materials, some will find the content difficult to understand either because of the use of technical language in the document or their own literacy level, and the material may be hard to remember. Surprisingly, simplifying written information has been found to be more beneficial to good readers than poor readers [11]. One possible alternative approach is to use illustrations to supplement the text. Research into the value of illustrations in enhancing health communications has been scant, but a recent review [12] concluded that visual displays of information alongside text can make a useful contribution. Illustrations make written information more attractive [13], [14], and increase the likelihood that the text will be read [15], understood [14] and remembered [15], [16]. Illustrations may be particularly beneficial for people with low levels of literacy who are both least knowledgeable about cancer [17] and least likely to benefit from written information. There is also evidence that illustrations improve comprehension more among people with lower literacy or fewer years of education [14], [18].
We hypothesized that visual illustrations of the development of adenomas and their removal during FS screening would clarify written information and help people understand that FS is intended to prevent colorectal cancer. The present study compared people's understanding of the preventive aim of FS screening following written material alone or written material accompanied with illustrations.
Section snippets
Participants and procedures
Three-hundred and eighteen people, aged 60–64, registered at GP practices in Harrow (London, UK), and eligible for screening (e.g. had not had an endoscopic bowel investigation in the last 2 years) were invited to participate in an ongoing feasibility study into population-based FS screening, and were sent a timed, dated screening appointment. They were randomized either to be sent a written leaflet alone (n = 151) or a written leaflet along with a set of illustrations showing the development of
Results
Of the 123 people who had been randomly selected for interview, 25 could not be contacted after several attempts, 16 telephone numbers were incorrect and we were unable to obtain a correct number, two respondents had communication difficulties (one because of poor English and one because of Parkinson's disease), four were on holiday during the interview period, and three of the interviews were terminated prematurely because of external interruptions. Only eight people declined to be
Discussion
Our results show that simple visual information is effective in increasing people's understanding of the preventive aim of colorectal cancer screening using flexible sigmoidoscopy (FS). People who were sent the illustrations were significantly more likely to understand that the aim of FS screening was to detect polyps and prevent cancer rather than just to detect cancer. There was no evidence of enhanced recall of information provided in the text that accompanied the illustrations such as the
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