Self-tests on body materials are widely available to the general public [1
]. These tests give consumers the opportunity to test themselves on medical conditions without consulting a health professional first. Self-tests are available for conditions such as diabetes, high cholesterol, kidney disorders, Chlamydia or prostate cancer [1
]. In a recent study among Dutch Internet users, 18% of the respondents had ever performed a self-test and 66% of all respondents considered to use a self-test in the future [3
]. Tests can be performed at home ('home tests'), in which the consumer is responsible for all aspects of the test: performing the self-test, interpretation of the test-result and follow-up behaviour. These tests can be bought on the Internet and are available in drugstores or pharmacies. Other ways of self-testing are 'streetcorner' tests, in which a test is performed by trained personnel in public places (for example in a supermarket), or 'direct access' and 'home collect' tests, in which a sample is taken at a laboratory or at home, is analysed in a laboratory and the results are sent to the consumer by mail or email.
Self-testing does have advantages as well as disadvantages, and the debate on whether self-testing should be encouraged or rather discouraged is still ongoing [4
]. Self-testing can be considered as an easy way for consumers to gain more insight in their health status, it might lead to early detection of disease, and fits in with our current views on patient autonomy. On the other hand, there are concerns about self-testing, for example whether consumers have sufficient knowledge to enable appropriate use of self-tests, such as insight in indications for testing, and whether they consider the possibility of obtaining false positive or false negative results. Consumers who perform a self-test often perform these tests for reassurance, because the test is offered by an organisation at no costs, or out of curiosity [8
], and respond quite straightforward to the test result: they generally have a high level of confidence in self-tests, visit a doctor in case of an abnormal test result and are reassured by a negative test result [2
]. Consumers with an intention towards self-testing also perceive these benefits of self-testing, although they experience several barriers as well, such as doubts concerning the reliability of self-tests and not knowing how to interpret the test result (Grispen et al: An intention to self-testing: a qualitative study regarding consumers' considerations and information needs about self-testing, submitted)
To support consumers in deciding whether they want to perform a self-test or not, objective information on self-tests could be provided to stimulate consumers to weigh the pros and cons of self-testing. Their decision should be based on knowledge as well as personal values, in which these personal values are related to intention, for example, a positive attitude should lead to a positive intention; a so-called informed choice. Consumers with an intention towards self-testing indicated they experienced benefits as well as barriers in self-testing. In other words, they experienced feelings of ambivalence towards self-testing [10
]. If these feelings are not resolved and people have to make a decision, they experience feelings of discomfort. Therefore, ambivalent attitude holders have the urge to integrate these feelings into one response; they want to 'choose sides' [10
]. To support patients in making a choice that is the best choice in their specific situation, for example for patients facing treatment and screening decisions, decision aids have been developed. These decision aids have shown to improve people's knowledge of options and reduce difficulty in decision making [11
We developed a web-based decision aid on self-testing http://www.zelftestwijzer.nl
, which provides information on self-tests in general, and test specific information on self-tests for diabetes and cholesterol. The web-based decision aid was based on clinical practice guidelines, previous research on self-testing [3
], the International Patient Decision Aid Standard (IPDAS) [14
], and the Health Belief Model (HBM) [16
]. The decision aid provides information on self-testing, as well as a value clarification tool to weigh the pros and cons of self-testing. The aim of this study is to investigate the effect of the web-based decision aid on knowledge of self-testing, informed choice, ambivalence and psychosocial concepts.
Health Belief Model
The Health Belief Model (HBM) [16
] was used as the theoretical framework during the development of the decision aid and will be used in its evaluation as well. According to the HBM, an individual's decision to engage in health-related behaviour is based on their evaluation of the severity of and the susceptibility to a particular condition or illness and the belief that a certain action is effective in reducing their susceptibility to or the severity of this condition. Furthermore, individuals are only inclined to engage in health-related behaviour if they perceive more benefits than barriers associated with that behaviour and if certain cues (for example in self-testing: having a neighbour with diabetes, or the offering of free tests) are present that trigger action. Finally, self-efficacy, the individual's confidence in his or her capability to successfully perform a certain action, is an important concept within the HBM.
Besides the concepts of the HBM, additional concepts of the Theory of Planned Behaviour (TPB) [17
] were used in the development and evaluation of the decision aid, namely subjective norm, anticipated regret, moral obligation and response efficacy. These concepts have been shown to contribute to the explanation of health-related behaviour [18
In previous research we found that individuals who intend to perform a cholesterol or diabetes self-test perceived strong benefits as well as strong barriers towards using a self-test (Grispen et al: An intention to self-testing: a qualitative study regarding consumers' considerations and information needs about self-testing, submitted). Individuals who hold both strong positive and negative beliefs or feelings towards a certain action or attitude object are considered to be ambivalent [10
]. An important distinction needs to be addressed concerning the ambivalence concept, namely the difference between potential ambivalence [23
] and felt ambivalence [24
]. Potential ambivalence concerns the coexistence of beliefs that are associated with incongruent evaluations related to a certain behaviour or attitude object. Individuals do not necessarily have to be aware of this incongruence and therefore potential ambivalence can be implicit. Felt ambivalence refers to simultaneously having positive and negative emotions towards a certain behaviour or attitude object. For felt ambivalence to occur, the individual needs to be aware of his conflicting feelings between the two sides of the behaviour or attitude object. These conflicting feelings lead to psychological discomfort which is experienced as being unpleasant. Ambivalent attitude holders are motivated to solve this psychological discomfort by integrating their conflicting feelings in one evaluate response. When this is achieved, ambivalence and the related psychological discomfort are solved [10
Study aim and research questions
The principal aim of the proposed study is to evaluate the effect of the decision aid on knowledge of on self-testing. The following research questions were formulated:
1. Do consumers who have been exposed to the decision aid have more knowledge of self-testing than the control group?
2. Do consumers who have been exposed to the decision aid more often make an informed choice in self-testing than consumers in the control group?
3. Do the intervention and control groups differ in level of attitudinal ambivalence?
4. What is the effect of the decision aid on the psychosocial factors that predict self-test use for diabetes and cholesterol?
5. Is there a difference between the intervention and control group in follow-up behaviour 3 months after the use of the decision aid?