Informed choice: understanding knowledge in the context of screening uptake

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Abstract

This study evaluates a scale measuring knowledge about a screening test and investigates the association between knowledge, uptake and attitudes towards screening. One thousand four hundred ninety-nine pregnant women completed the knowledge scale of the multidimensional measure of informed choice (MMIC). Three hundred forty-five of these women and 152 professionals providing antenatal care also rated the importance of the knowledge items. Item characteristic curves show that, with one exception, the knowledge items reflect a spread of difficulty and are able to discriminate between people. All items were seen as essential or helpful by both women and health professionals, with two items seen as particularly important and one as unimportant. There were some differences between health professionals, women with low risk results and women with high risk results. Knowledge was not associated with uptake, attitude, or the extent to which uptake was consistent with women’s attitudes towards undergoing the test.

Introduction

Informed choice presupposes that an individual has sufficient information to optimise his or her choice. This raises the question: “what is sufficient”? Some definitions of informed choice require that individuals appraise and use all available information [1]. Individuals, however, vary in their need and interest in information when facing a decision [2]. There are several approaches to quantifying the information needed. One is to use professional guidelines, such as those produced by the General Medical Council (1999) or the Royal College of Physicians (1989) [3], [4]. These state that, in order to ensure that screening is not contrary to the individual’s interests, it is necessary to explain five points: the purpose of screening; the likelihood of positive and negative findings, alongside the possibility of false positive and false negative findings; the uncertainties and risks attached to the screening process; any significant medical, social or financial implications of screening; and follow-up plans including the availability of counseling and support services. It should be noted, however, that these guidelines are not based on direct evidence, representing instead a professional consensus based on the available, often indirect, evidence. A scale assessing knowledge of prenatal screening for Down syndrome (DS) based on these guidelines has been developed and found to have acceptable validity and reliability [5], [6].

A second approach is to seek the views of those who have been offered screening, rather than the views of the professionals concerned with offering the screening. Previous studies of information recalled after genetic counseling found that patients judged information about family implications to be important more frequently than did genetic counselors [7]. On the other hand, counselors more frequently judged information about tests, diagnosis and prognosis to be important than did patients. This pattern was associated with the information actually recalled (and, therefore, of potential use in subsequent decision making). A group of 32 counselee’s followed up 2–4 weeks after a genetic counseling consultation recalled 100% of the key information points that referred to family issues, but only 68–78% of information points that referred to genetic or medical issues [8].

Of those offered antenatal screening, there are sub-groups: those who decline screening who do and do not subsequently develop the screened condition, as well as those who undergo screening and receive one of the four possible outcomes: true negative result; true positive result; false positive result; and false negative result. It is very likely that individuals with different outcomes of screening will recommend the provision of differing amounts and types of information. This raises the question of how the needs of the majority undergoing screening (i.e. those receiving true negative test results) should be pitted against those of a minority (i.e. those with other than true negative test results). If there are widely differing perceptions of the knowledge that is necessary or desirable before undergoing screening, using one measure of knowledge poses inherent problems.

A third approach to determining the information needed for an informed choice is a consequentialist one, in which the psychological outcomes of screening are compared between those with differing types and amounts of knowledge. Relevant psychological outcomes include satisfaction with information, anxiety and decision—regret. The knowledge associated with best outcomes can then be defined as good knowledge. It seems most probable that outcomes are predicted not by an informed choice per se, but by an interaction between informed choice and health outcome. Thus, the beneficial effects of making an informed choice are likely to be more marked in those with a problematic health outcome than in those with a good health outcome.

Using all three approaches is likely to provide the most valid estimate of the information needed for an informed choice. The first step in constructing a measure of knowledge is to decide on appropriate content. This is helped by starting with a sufficient number of items to cover the area comprehensively and to ask experts and other relevant groups to rank them in importance. As well as considering the appropriate content to assess in a knowledge measure, there is a need to consider how best to combine items to construct a linear scale of knowledge [9]. Items should represent the full range of difficulty, ensuring a normal or symmetrical distribution or fitting other models derived from item response theory. If possible, items should be selected in relations to objectively defined criteria. This is difficult in areas such as decisions about health care where there are no “gold standards” for good knowledge. One such area is prenatal screening for Down syndrome, where the knowledge women want or use is likely to vary considerably according to their values. Thus, for a woman with a negative attitude towards termination of pregnancy, just knowing that the test may result in it being offered may be sufficient in knowledge to reject the test. By contrast, a woman who wants to avoid giving birth to a child with Down syndrome, information about test performance will be important.

Prenatal screening for Down syndrome is currently offered to 76% of pregnant women in the UK, with more than 90% of these being offered in some form of maternal serum screening [10]. Maternal serum screening is a blood test offered at about 15–16 weeks gestation and is based on a combination of maternal age and biochemical markers measured in maternal serum. The test identifies women as low or high risk, and the latter group are offered a diagnostic test.

Knowledge has been found to be a weak determinant of screening uptake. In a systematic review, Jepson et al. (2000) found that knowledge about risk predicted uptake in only two of 11 studies and knowledge about the screening test predicted uptake in one out of six studies [11]. Further, interventions using educational materials (printed or audio-visual) or educational sessions (individual or group) had limited effectiveness. Although having good knowledge is a prerequisite for making an informed choice, it is not sufficient [5]. Informed choice also requires that people make choices that reflect their values and attitudes towards undergoing the test or procedure in question. Thus, a second key component of informed choice is for individuals to behave in line with their attitudes. This raises the question of the relationship between these two components, knowledge and attitude–behavior consistency. Little is known about the association between attitudes, knowledge and uptake in making informed choices about testing.

The first study reported in this paper investigates the psychometric properties of the knowledge scale described previously. It also compares the perceived importance of the scale items across three groups: health professionals; women with low risk results; and women with high risk results. The second study addresses the relationships between knowledge and uptake, knowledge and attitudes, and knowledge and uptake and attitude consistency.

In summary, the aims of this paper are:

  • 1.

    To evaluate a scale measuring knowledge about a screening test (Study 1).

  • 2.

    To investigate the association between knowledge, uptake and attitudes (Study 2).

Section snippets

Evaluation of the knowledge scale of the MMIC (Study 1)

This study aims to evaluate a measure of knowledge about prenatal screening for Down syndrome [5]. The scale was evaluated in two ways:

  • (a)

    By ascertaining the extent to which the items reflect the full range of difficulty level and power to discriminate between people (Sample 1).

  • (b)

    By describing the perceived importance of items amongst health professionals offering the screening test and women who have undergone the screening test and received either high or low risk results (Sample 2).

An investigation of the association between knowledge, attitudes and screening uptake (Study 2)

Study 1 demonstrated that the items that these knowledge items are good at discriminating between individuals and provides an indication of the value attached to different items. The aim of Study 2 is to examine the association between knowledge, attitudes, behavior and the consistency between attitudes and behavior.

General conclusion

The studies reported in this paper suggest that the knowledge items included in the MMIC constitute a scale, with all items contributing to the measurement of knowledge about DS screening. The knowledge items deemed to be important in professional guidelines are also seen as important by both professionals providing health care and by women undergoing screening, those receiving low risk as well as those receiving high risk results. However, the results of Study 1 suggest that the scale may be

Acknowledgements

This research was funded by a programme grant from The Wellcome Trust. SM, ED and TMM are supported by The Wellcome Trust.

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