Informed Choice

Informed Choice in Screening and Health Economics

An informed choice is one in which a person understands the relevant facts about a test or treatment and then acts in line with their own values, whether that means accepting or declining. The idea matters most in population screening, where a test offered to people without symptoms helps some and harms others, and the UK National Screening Committee treats a personal informed choice as the guiding aim of every programme it approves. For health economists the idea moves the measure of success away from uptake, a parameter that drives screening models, towards the quality of each decision. Trials show that better information sometimes lowers uptake and sometimes leaves it unchanged, so the economic effects have to be modelled rather than assumed.

Knowledge, values and behaviour in the Marteau definition

Marteau, Dormandy and Michie, writing in 2001, noted an emerging consensus that an informed choice rests on relevant, good quality information and reflects the decision maker's values. Adapting an earlier definition of an effective decision, they defined an informed choice as one based on relevant knowledge, consistent with the decision maker's values and behaviourally implemented.

Their measure rated knowledge as good or poor and the attitude towards undergoing the test as positive or negative, and recorded uptake, giving eight cells. Only two cells count as informed, good knowledge with a positive attitude and the test taken, or good knowledge with a negative attitude and the test declined. The authors singled out the cell in which poorly informed people with negative attitudes undergo the test as particularly problematic, because those people would decline if better informed.

The measure combined an eight-item knowledge scale with a four-item attitude scale, and in its development study among women offered prenatal screening 18 of 42 choices were classified as informed. The authors noted that a binary split discards variation and that knowledge was more normally distributed than attitudes, which raised questions about median splits.

How the UK National Screening Committee applies informed choice

The UK NSC informed choice principles were first published in August 2018 and updated on 10 December 2024. Principle 1 says that every UK NSC approved programme should aim to facilitate a personal informed choice, which the committee calls the overarching and guiding principle. It defines a personal informed choice as a decision to accept or decline a screening test based on access to accessible, accurate, evidence-based information covering the condition, the testing process, the potential benefits, harms, limitations and uncertainties, and the potential outcomes and ensuing decisions.

The word personal signals that the decision should fit the individual's values and circumstances, and Principle 5 states that a choice to accept or decline will be equally respected. Public information should be based on the best available evidence on the test's sensitivity, specificity, predictive values and false results, and should make clear that accepting or declining is a personal choice.

The two definitions differ in a way that matters for measurement. The UK NSC defines the choice by the information a person can access, while the Marteau measure checks what the person knows and whether behaviour matches attitude.

Why uptake targets and informed choice pull in different directions

Raffle described in 2001 how public information about screening had long been aimed at achieving high uptake, with benefits stated in population terms and harms rarely mentioned. In the cervical programme, coverage targets for health authorities and payments to general practitioners that depended on 80% uptake acted, in her account, as a deterrent to giving more balanced information. She accepted that fuller information could reduce uptake and population benefit and would take more staff time.

Torgerson and Donaldson had already argued in 1994 that raising compliance often raises costs, that those costs are an opportunity cost, in screening forgone for other target populations, and that a programme can be efficient with very low compliance. A randomised trial of invitation methods in Aberdeen found that fixed appointments achieved high compliance only by reducing opportunities for screening, so that for every 100 women screened, 110 more were denied a test within a fixed budget.

Howard and colleagues showed in a model of faecal occult blood testing that the effect of participation depends on how non-participants behave in later rounds. Full participation gave USD 9,705 per life year saved. With 20% participation in later rounds the figure was USD 29,500 if anyone who missed a round never returned, but USD 11,270 if participation was random. They concluded that high participation is not necessary for a cost-effective programme.

What randomised trials show about informed choice and uptake

Two of the three trials in the table used a Marteau-style measure of informed choice as the primary outcome, and the third measured attendance. Their effects on uptake differ by programme.

In the bowel screening trial the decision aid raised knowledge and increased the share with no decisional conflict from 38% to 51%, yet uptake fell by 16 points, which the authors linked to better knowledge of the low personal benefit of screening. In the breast screening trial fewer women intended to be screened after learning about overdetection, but two-year follow-up found similar actual participation in both arms.

The 2024 Cochrane review of patient decision aids, covering 209 trials, found that they probably increase the congruence between informed values and care choices, with a risk ratio of 1.75 from 21 studies.

Informed choice inside a screening evaluation

A screening cost-effectiveness analysis often reports results per person invited, so uptake scales both costs and health gains. Supporting informed choice adds the cost of information, and it may change who attends as well as how many.

$$\Delta C = N \left[ c_a + (u_1 - u_0) c_s \right]$$

where $\Delta C$ is the incremental cost of the informed choice invitation, $N$ is the number invited, $c_a$ is the information cost per person invited, $u_0$ and $u_1$ are uptake with the standard and informed choice invitations, and $c_s$ is the cost per person screened including follow-up.

$$\Delta Q = -(u_0 - u_1) N \bar{g}_d$$

where $\Delta Q$ is the change in QALYs, $u_0$, $u_1$ and $N$ are as above, and $\bar{g}_d$ is the mean net QALY gain from screening among the people who would attend under the standard invitation but decline once informed.

A fall in uptake is therefore not automatically a loss. If those who decline once informed are people for whom harms such as overdiagnosis or invasive follow-up outweigh the benefit, $\bar{g}_d$ is low or negative and the QALY loss is small or becomes a gain. The equation assumes that information only moves people from attending to declining, and an analysis expecting new attenders would need a second term.

Worked example with a bowel screening invitation

All numbers here are illustrative. The uptake and informed choice proportions borrow the Smith trial results, while costs and QALYs are invented. A programme invites 10,000 people. With the standard invitation 75% attend and 12% make an informed choice, while with a decision aid costing GBP 8 per person invited 59% attend and 34% make an informed choice. Each person screened costs GBP 40 including follow-up, and the mean QALY gain per person screened under the standard invitation is 0.004.

$$\Delta C = 10000 \times \left[ 8 + (0.59 - 0.75) \times 40 \right] = 10000 \times (8 - 6.4) = 16000$$

where 8 is the decision aid cost per person invited, 0.59 and 0.75 are uptake with and without the aid, and 40 is the cost per person screened. The aid costs GBP 80,000 but saves GBP 64,000 in screening, a net GBP 16,000. It yields 2,200 extra informed choices (3,400 against 1,200), about GBP 7.27 per additional informed choice.

The health result depends on the 1,600 people who stop attending, against 30 QALYs (7,500 times 0.004) under the standard invitation.

The last row is GBP 16,000 divided by 1.6 QALYs. The same aid looks dominated or good value depending on the expected benefit among those who change their decision, a parameter trials rarely measure, and no row values the 2,200 extra informed choices. A cost-utility analysis alone would miss the programme's stated aim, so informed choice needs reporting as a separate outcome, as in a cost-consequence analysis.

Informed choice beside informed consent and shared decision making

Informed consent is agreement to a specific intervention after disclosure of its risks and benefits, as in informed consent for research. The DICISION authors described informed choice as differing from informed consent by its emphasis on choices that are congruent with individuals' values. A person can consent to a screening test without the choice being informed in the Marteau sense, for example when knowledge is poor or the decision runs against a stated attitude.

Shared decision making is a process, while informed choice describes the quality of a result. The NICE guideline on shared decision making (NG197), published in 2021, defines it as a collaborative process in which a person and their healthcare professional reach a joint decision about care, based on evidence and the person's preferences, beliefs and values, and notes that maternity services may call this informed decision making. The guideline describes decision aids as supporting informed, values-based decisions without advising one option over another.

Limitations and common misunderstandings about informed choice

One common error is to read informed choice as a strategy to reduce screening. The UK NSC treats accepting and declining as equally valid, and the Marteau typology counts a well-informed decision to attend as informed. The opposite error is to treat it as cost free, since better information takes staff time and can lower uptake.

Measurement has known weaknesses. Thresholds for adequate knowledge are set by the researchers, the original authors questioned median splits, and trials such as the breast screening study found that stated intentions moved more than actual participation. Marteau and colleagues also noted that how much benefit informed choice confers in screening remained to be determined.

Equity cuts both ways. Raffle warned that fuller information might deter disadvantaged groups, though she noted there was no evidence for this, and the DICISION trial found attendance of 47.5% in the most deprived third against 64.3% in the least deprived, whatever invitation people received. An evaluation should therefore report effects by deprivation group, because a programme can raise the quality of decisions while leaving the health inequality in uptake untouched.

Sources

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