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RESEARCH
Impact of an informed choice invitation on uptake of
screening for diabetes in primary care (DICISION):
randomised trial
Theresa M Marteau, professor of health psychology,1 Eleanor Mann, research assistant in psychology,1
A Toby Prevost, reader in medical statistics,5 Joana C Vasconcelos, medical statistician,2 Ian Kellar, research
psychologist,2 Simon Sanderson, senior clinical research associate,2 Michael Parker, professor of bioethics
and director,3 Simon Griffin, assistant director,4 Stephen Sutton, professor of behavioural science,2
Ann Louise Kinmonth, foundation professor of general practice2
ABSTRACT
Objective To compare the effect of an invitation promoting
informed choice for screening with a standard invitation
on attendance and motivation to engage in preventive
action.
Design Randomised controlled trial.
Setting Four English general practices.
Participants 1272 people aged 40-69 years, at risk for
diabetes, identified from practice registers using a
validated risk score and invited to attend for screening.
Intervention Intervention was a previously validated
invitation to inform the decision to attend screening,
presenting diabetes as a serious potential problem, and
providing details of possible costs and benefits of
screening and treatment in text and pie charts. This was
compared with a brief, standard invitation simply
describing diabetes as a serious potential problem.
Main outcome measures The primary end point was
attendance for screening. The secondary outcome
measures were intention to make changes to lifestyle and
satisfaction with decisions made among attenders.
Results The primary end point was analysed for all 1272
participants. 55.8% (353/633) of those in the informed
choice group attended for screening, compared with
57.6% (368/639) in the standard invitation group (mean
difference −1.8%, 95% confidence interval −7.3% to
3.6%; P=0.51). Attendance was lower among the more
deprived group (most deprived third 47.5% v least
deprived third 64.3%; P<0.001). Interaction between
deprivation and effect of invitation type on attendance
was not significant. Among attenders, intention to change
behaviour was strong and unaffected by invitation type.
Conclusions Providing information to support choice did
not adversely affect attendance for screening for
diabetes. Those frommore socially deprived groupswere,
however, less likely to attend, regardless of the type of
invitation received. Further attention to invitation content
alone is unlikely to achieve equity in uptake of preventive
services.
Trial registration Current Controlled Trials ISRCTN
73125647.
INTRODUCTION
Population screening programmes are an increasingly
important component of health care. Their public
health benefits depend on the participation of most
people at risk, although each individual has low odds
of personal benefit.1 Response rates to invitations to
attend formedical screening varyby condition and cul-
ture and are notably lower among socially deprived
groups.2 Invitations are traditionally brief and aim to
achieve high attendance rates. They most often pro-
vide information about the prevalence and severity of
the disease to be screened for, and rarely describe the
absolute chances of individual benefit or harms.3 Pol-
icy in the United Kingdom and elsewhere now advo-
cates that participation should reflect “informed
choice,” which can be defined as individual choices
informed by the nature and frequency of individual
benefits and harms of screening and actions consistent
with participants’ values.4 This differs from informed
consent by its emphasis on choices that are congruent
with individuals’ values.5
This policy change is not yet evident in the content of
invitations people routinely receive to participate in
screening programmes. This may reflect concern that
people reading information about the limited indivi-
dual benefits and possible harms of screening will feel
less positive about screening and not attend.6 7
A particular concern is that providing information to
support individual choice might have a differential
effect on attendance across social groups, resulting in
even lower uptake amongmore socially deprived peo-
ple, an example of the “inverse care law.”8 Social depri-
vation is associated with an orientation more towards
the present than the future.9 Information that the ben-
efits of screening through early diagnosis of disease
accrue in the future while the harms and burdens of
screening and preventive treatment are more
1King’s College London, Psychology
Department (at Guy’s), Health
Psychology Section, Psychology
and Genetics Research Group,
Guy’s Campus, London SE1 9RT
2University of Cambridge
Department of Public Health and
Primary Care, Cambridge
3The Ethox Centre, Division of
Public Health and Primary Health
Care, University of Oxford
4MRC Epidemiology Unit, Institute
of Metabolic Science, Box 285,
Addenbrooke’s Hospital,
Cambridge CB2 0QQ
5King’s College London,
Department of Primary Care and
Public Health Sciences, Guy’s
Campus, London SE1 3QD
Correspondence to: T M Marteau
theresa.marteau@kcl.ac.uk
Cite this as: BMJ 2010;340:c2138
doi:10.1136/bmj.c2138
BMJ | ONLINE FIRST | bmj.com page 1 of 7
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immediate may thus reduce attendance, particularly
among more socially deprived groups.10 This would
include more of those at highest risk of disease for
whom the benefits of screening might be greatest,11
including those at risk of type 2 diabetes, a common,
serious condition that can remain undiagnosed until
complications occur.12 The adverse consequences of
screening are likely to be limited13 and intensive treat-
ment of screen detected patients is likely to be
beneficial.14
Screening for type 2 diabetes and cardiovascular risk
provides examples of situations where change in beha-
viour is an important component of preventive action
and for which population based screening pro-
grammes for people at risk are now being proposed
and implemented.15 16 The evaluation of screening
invitations therefore needs to include assessment of
effects on motivation to change behaviour if diabetes
were diagnosed.
We tested three hypotheses when comparing the
informed choice invitation with a standard invitation.
Firstly, that attendance at screening for diabetes would
be lower after receipt of an informed choice invitation.
Secondly, that an interaction exists between the type of
invitation and social deprivation, such that attendance
would be lower among those from more socially
deprived groups. Thirdly, that among those who
attend for screening, intentions to change behaviour
to reduce the risk of complications, if diabetes were
subsequently diagnosed, would be stronger after an
informed choice invitation.
METHODS
More details of the trial methods can be found in the
published protocol.17 We recruited participants from
four practices based in the English counties of Cam-
bridgeshire and Suffolk, each of which varies in degree
of deprivation.We assessed the level of social depriva-
tion by using the index of multiple deprivation 2007,
which is based on UK postcodes. One practice was
from the least deprived postcode fifth, one from the
middle fifth, and two from the most deprived fifth.
We identified potentially eligible participants from
practice registers using aMIQUEST search for routine
data, which was used to calculate diabetes risk scores
for all adults aged 40-69 without known type 2 dia-
betes. MIQUEST is the National Health Service
licensed softwareused to extract information fromgen-
eral practicemedical records. The validated score used
age, sex, body mass index, and prescribed oral anti-
hypertensive and steroid drugs.12
No standard approach is used to select groups for
screening. Systematic reviews and modelling studies
suggest that restricting screening to those at high risk,
as we have done, might be the most cost effective
approach.18 We randomly sampled household clusters
in the top 25% of the risk score distribution to generate
the 1500people approached for the study.Thepractice
in the most deprived area provided data only on body
mass index, which we used to identify 407 people at
high risk. High body mass index (top fourth) is a
good proxy measure of diabetes risk.12 We subse-
quently excluded 43 people with known diabetes
who were pregnant, breast feeding, psychotic, or had
a life threatening illness. The remainder were sent let-
ters by their general practitioner asking them to return
a reply paid opt-out form to their practice within
28 days if they did not wish to receive an invitation
for practice based screening. Overall, 183 people
optedout (183/1500; 12.2%) andwe excluded a further
twobecause consent letterswere returnedundelivered.
Those who opted out were older than those who parti-
cipated, but similar in terms of deprivation and sex.
Randomisation
We randomly assigned 1272 participants to receive
one of two invitations to screening: an extended invita-
tion designed to facilitate informed choice, or a short,
standard invitation. Members from the same house-
hold were assigned to receive the same invitation
type (mean cluster size 1.14). Randomisation was
done at once for all participants in each practice and
was undertaken by the study statistician from a central
site. For each practice separately, allocations were gen-
erated simultaneously in a batch by random numbers
using Excel spreadsheet software, stratifying by num-
ber of participants in the household.
We cluster randomised 281 people with at least one
other participant from the same household. Clinical
and trial staff taking measurements and entering data
were unaware of the study arm to which participants
hadbeen assigned. Fifty six participants did not receive
an invitation: 53 were not sent an invitation and three
Allocated to receive
standard invitation (n=639)
Allocated to receive informed
choice invitation (n=633)
Sent invitation (n=618)Sent invitation (n=601)
Received invitation (n=617)Received invitation (n=599)
Sample at high risk of type 2 diabetes (n=1500)
Randomised (n=1272)
Excluded (n=228):
Criteria not met (n=43)
Opted out (n=183)
Opt-out form undelivered (n=2)
Invitation not sent (n=32):
Died (n=1)
Record unavailable (n=3)
Left practice (n=13)
Unknown (n=15)
Attended screening appointment (n=353):
Completed questionnaire (n=332)
Did not consent (n=19)
Ineligible (n=2)
Attended screening appointment (n=368):
Completed questionnaire (n=347)
Did not consent (n=18)
Ineligible (n=2)
Questionnaire missing (n=1)
Invitation returned undelivered (n=2) Invitation returned undelivered (n=1)
Invitation not sent (n=21):
Died (n=3)
Record unavailable (n=1)
Left practice (n=9)
Late exclusion by general practitioner (n=2)
Unknown (n=6)
Flow of participants through trial
RESEARCH
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invitations were returned undelivered. Among those
attending for screening, consent to participate further
was obtained at screening appointments.
Standard invitation
The standard invitation reflected those commonly
used to invite people to screening for diabetes and cor-
onaryheart disease219 andwas based on examples used
in a trial and a national pilot of screening.20 21
The text stated that screening was offered because
the participant may have a higher chance of develop-
ing type 2 diabetes and that diabetes is a common,
often undiagnosed condition with serious long term
consequences (see web extra).
Informed choice invitation
The informed choice invitation contained the same
information as the standard invitation, along with
information about the risk of diabetes and its complica-
tions and the consequences of screening and treatment,
including a description of the possible harms asso-
ciated with attending for screening. The invitations
drew on best evidence andwere based on theUKGen-
eral Medical Council guidelines for consent.22 These
recommend that the following information is pre-
sented when obtaining consent for screening: the pur-
pose of screening; details of diagnosis and prognosis
with andwithout treatment; and the probability of ben-
efits and risks, presented with an emphasis on patient
choice (see web extra).
Drawing on these guidelines, the draft invitation text
was developed iteratively using “think-aloud” meth-
ods with volunteers.23 The method requires respon-
dents to verbalise their thoughts while reading the
invitation and has typically been used to examine deci-
sionmaking.24 25 In this case we used the verbal reports
to ascertain where information was not being under-
stood as intended and then refined the text by using
readability tools.26 By using a decisional balance
sheet we encouraged participants to make a choice
that reflected their values. Texts of both invitations
were comprehensible to those with reading ages of 11
and above.27
These invitations were developed and evaluated in a
study inwhich 417 adultswithout knowndiabeteswere
randomised to receive one of the invitations. Levels of
informed choice were significantly higher two weeks
after receipt of the informed choice invitation com-
pared with the standard invitation (42.9% v 11.2%; dif-
ference 31.7%, 95% confidence interval 22.5% to
40.5%)27—an outcome largely attributable to higher
levels of knowledge.
Procedure
Participants were invited by letter sent from their gen-
eral practice to attend pre-assigned screening appoint-
ments for diabetes with a research nurse at their
practice. Appointments took about 20 minutes and
were done according to a written clinical protocol.
The research nurse recorded attendance as partici-
pants arrived and sought their written consent to be
screened for diabetes. Consent was also sought to com-
plete research questionnaires at the consultation and
by post four weeks later. Thirty seven participants
(5%) declined consent to complete questionnaires and
four met the exclusion criteria (three had diagnosed
diabetes and one was judged unable to give consent).
The nurse carried out a finger prick random capillary
blood glucose test using a glucose analyser based on
the glucose dehydrogenase reaction (HemoCue B-glu-
cose analyser; HemoCue, Angelholm, Sweden). The
optimal screening test remains uncertain,18 but suitable
tests certainly include capillary blood samples in the
non-fasted state, as used in this trial.
The stability of the analyses was checked daily and
an external calibration with the quality assurance
scheme was undertaken monthly. Participants were
given their results immediately, along with brief stan-
dardised advice about healthy lifestyle. Those with
blood glucose levels of 5.5 mmol/l or more were
invited to return for a fasting capillary blood glucose
test and a full cardiovascular risk assessment, carried
out by the research nurse. The nursemeasured the fast-
ing blood glucose level, full lipid profile, height,
weight, blood pressure, and cardiovascular risk score.
Patients were given further standardised advice on life-
style, and those with fasting blood glucose levels of
6.1mmol/l ormorewere referred to their general prac-
titioner for further testing and confirmation of a diag-
nosis of diabetes. Four weeks after the appointment for
the random glucose blood test, attenders were posted a
follow-up questionnaire, which included a measure of
satisfaction with their decision.
Outcome measures
The primary outcome measure was attendance for
screening. This was recorded by the research nurse
and measured as the proportion of those invited who
attended for screening. The secondary outcome mea-
sures were intention to make changes to lifestyle and
satisfaction with decisions made.
We assessed the intention to make changes to life-
style if diabetes were subsequently diagnosed among
attenders using the arithmetic mean of three intention
Table 1 | Personal characteristics of participants randomised to receive an invitation for
screening
Variable Overall (n=1272)
Informed choice
invitation arm (n=633)
Standard invitation
arm (n=639)
% (No) women 45.5 (579) 47.6 (301) 43.5 (278)
Mean (SD) age (years) 55.5 (8.1) 55.4 (8.0) 55.6 (8.2)
Mean (SD) body mass index* 33.6 (6.0) 33.8 (6.0) 33.4 (6.0)
% (No) obese* 69.1 (817) 69.4 (413) 68.8 (404)
% (No) prescribed antihypertensives† 44.3 (383) 43.6 (187) 45.0 (196)
Mean (SD) index of multiple deprivation
2007 score‡
20.1 (10.3) 20.1 (10.0) 20.0 (10.5)
*Based on 595 participants in the informed choice arm and 587 in the standard invitation arm.
†Based on 429 participants in the informed choice arm and 436 in the standard arm from three practices,
unavailable from one practice.
‡Score combines several indicators, chosen to cover a range of economic, social, and housing issues at district
level, into a transformed index from 0-100. UK average is 21.67; eastern England regional average is 15.40. Top
10% deprived areas have average scores above 50.
RESEARCH
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items relating to treatment adherence, reducing fat
intake, and increasing physical activity (Cronbach’s
α=0.58). Itemswere rated on a 7 point scale—for exam-
ple, “If the tests show that you definitely do have dia-
betes, how likely is it that you will increase the amount
of physical activity that you do over the next 3months?
” (1 extremely unlikely to 7 extremely likely).
Satisfaction with the decision was assessed among
attenders at four weeks by postal questionnaire using
the mean of three items (Cronbach’s α=0.92)—for
example, “How sure are you that the decision you
madewas the right one for you?” (1 not at all to 7 extre-
mely).
Statistical analysis
We determined that a sample size of 1200 participants
would provide 90% power to detect a 10% difference
between arms in the proportion attending for screen-
ing using a χ2 test at the 5% level of significance.Assum-
ing an average attendance of 65%2 gave an expectation
of 780 attenders. Full response to the initial question-
naire allowed 80% power to detect a small effect size
(0.2 standardised difference) between arms in the
intention measure using a t test at the 5% level of sig-
nificance.
We tested the first hypothesis by comparing atten-
dance rates in the informed choice and standard invita-
tion arms using the χ2 test in an intention to treat
analysis. For the second hypothesis, we used logistic
regression to test for moderating effects of social depri-
vation on the impact of invitation type on attendance
by including an interaction between arm and social
deprivation index. We carried out per protocol ana-
lyses for both these hypotheses, which excluded parti-
cipants who did not receive an invitation (n=56) and
those randomised but subsequently found to meet
exclusion criteria (n=4). For the third hypothesis we
used a t test to assess the difference between attenders’
intentions to change behaviour in the informed choice
arm compared with standard invitation arm. Using a t
test we also compared the groups for satisfaction with
the decision. All tests were two tailed and assessed at
the 5% level of significance. Further analyses that
allowed for clustering of participants in randomised
households were defined as secondary owing to the
anticipated small mean cluster size. The results of
these did not materially affect the primary results or
conclusions.
RESULTS
Recruitment to the trial started in November 2006 and
ended in July 2008.We analysed screening attendance
for all 1272 randomised participants (figure). Baseline
characteristics of the two groups were similar (table 1).
Those invited for screeningweremiddle agedmen and
women, many of whom were obese or taking anti-
hypertensive drugs. Overall, 721 (56.7%) of the rando-
mised participants attended. Compared with
attenders, non-attenders were younger, had a higher
body mass index, lived in more deprived areas, and
were less likely to be prescribed antihypertensive
drugs (table 2).
Attendance at screening for diabetes was not signifi-
cantly lower after an informed choice invitation com-
pared with a standard invitation: 56.7% v 57.6%
(difference −1.8%, 95% confidence interval −7.3% to
3.6%, P=0.51; table 3). The interaction between type
of invitation and social deprivation was not significant.
However, attendance fell with increasing deprivation
(64.3% in the lowest third v 47.5% in the highest third,
P<0.001). Per protocol analyses did not affect these
findings.
Overall, 680/721 participants (94.3%) agreed to
answer questionnaires at first attendance and 525/721
(72.8%) returned their four week follow-up question-
naires. Intention to make changes to lifestyle at first
attendance was unaffected by screening invitation:
mean intention to change behaviour if diabetes were
to be diagnosed was 5.84 (SD 1.09) in the informed
choice arm and 5.84 (SD 1.04) in the standard invita-
tion arm. Satisfaction with the decision to attend (mea-
sured in the four week follow-up questionnaire) was
high and unaffected by screening invitation: mean
6.47 (SD 0.84) in the informed choice arm and 6.48
(SD 0.87) in the standard invitation arm (difference
−0.01, 95% confidence interval −0.17 to 0.16; P=0.90).
No adverse events were recorded during the trial.
DISCUSSION
An informed choice invitation for diabetes screening
did not significantly reduce rates of attendance com-
paredwith a standard letter.No interactionwas present
between type of invitation and levels of deprivation.
Table 2 | Characteristics of non-attenders and attenders pooled over trial arms
Variable
Overall
P value*Non-attenders (n=551) Attenders (n=721)
% (No) women 42.8 (236) 47.6 (343) 0.092
Mean (SD) age (years) 53.0 (7.9) 57.4 (7.8) <0.001
Mean (SD) body mass index† 34.8 (6.3) 32.7 (5.6) <0.001
% (No) prescribed drugs‡ 46.2 (150) 53.0 (286) 0.052
% (No) prescribed antihypertensives 39.7 (129) 47.0 (254) 0.035
Mean (SD) index of multiple deprivation 2007 score 21.6 (10.6) 18.8 (9.9) <0.001
*Unpaired t test for age, body mass index, and index of multiple deprivation 2007 score; Pearson χ2 test for other variables.
†Based on 513 non-attenders and 669 attenders.
‡Based on 325 non-attenders and 540 attenders.
RESEARCH
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Social deprivation did, however, strongly predict
attendance. Regardless of invitation type, those from
more deprived areas were less likely to attend for
screening. Among those attending for screening, the
type of invitation did not affect their intentions to
change their behaviour to reduce risks were diabetes
subsequently diagnosed. Among both groups inten-
tions were strong. Similarly, satisfaction with the deci-
sion to attend for screening was high in both groups.
Meaning of the study results
We considered several possible explanations for our
main finding. Firstly, although the informed choice
invitation was longer and contained more information
than the standard one, recipients may have treated the
two invitations as similar. If, for example, they had
gone no further than the opening paragraph, they
would have read the same information as that pre-
sented in the standard invitation. Secondly, the provi-
sionof a prearranged screening appointmentmayhave
been regarded as an implicit recommendation for
screening, over-riding any influence of different invita-
tions. Thirdly, recipients may have gained more infor-
mation from the informed choice invitation, but this
knowledge did not affect attendance. This may be
because they perceived the harms associated with
screening to be negligible or the benefits to be very
good. In support of this, in our pilot study we found
that the informed choice invitation increased knowl-
edge about screening for diabetes but did not affect
attitudes, which were consistently positive, or inten-
tions to attend for screening.27 Other studies have
found knowledge about screening to be a weak predic-
tor of attendance and to have little or no association
with attitudes towards attending for screening.27 28 In
contrast, attitudes towards screening have been found
to be moderately strong predictors of attendance.6
The gradient in uptake with social advantage has
been observed previously.29 30 This gradient may
reflect differences in people’s attitudes or differences
in their enactment of similar positive intentions accord-
ing to their different social circumstance. In our pilot
study, individual attitudes and intentions to attend for
diabetes screening were positive regardless of social
deprivation,27 a finding supported by other studies.31
This suggests a social patterning not to intentions but
to the enactment of intentions, perhaps reflecting prac-
tical barriers to keeping appointments.
Implications for clinicians and policy makers
Taken together the evidence from this trial and other
studies suggests that providing information to support
choice does not adversely affect attendance for screen-
ing: written information can increase knowledge about
screening but this does not necessarily alter uptake or
increase the likelihood that choices are more value
consistent—that is, informed.27 28 32 33 But although we
found no evidence of harm, there was little to suggest
any quantitative benefit. The informed choice invita-
tions may have resulted in people being better
informed which, from the perspective of individual
autonomy, is a benefit. People with better knowledge
are less anxious when recalled for further tests,34 so
such invitations may be preferred, although anxiety is
not a major concern in screening for diabetes.13
Importantly, our findings raise further questions
about the equity of programmes that fail to engage
those who are more socially deprived and therefore
with lower health and life chances. Overall attendance
was low, albeit similar to a national pilot screening pro-
gramme in deprived areas in England.35 Compared
with attenders, non-attenders were not only more
likely to be from more deprived areas but also to
have a higher bodymass index, despite being younger,
and less likely to be prescribed antihypertensive drugs.
A mix of opportunistic approaches to screening (for
example, during planned reviews of drugs for hyper-
tension) combined with a range of systematic
approaches that go beyond repeated invitation letters,
however elaborate, may be most effective in creating
environments that enable people to enact their choices.
These include visiting patients at home36 and training
receptionists to telephone and talk to patients.37 The
effectiveness and appropriateness of these and other
interventions merit further consideration given the
large gap in screening uptake between the most and
least deprived groups, which is not accompanied by
evidence of a difference in motivation or preference,
both of which are uniformly high.
Strengths and limitations of the study
The trial design was rigorous for several reasons. We
defined a real world at risk population through pri-
mary care, and 87.3% of the eligible population were
randomised and participated. Both invitations were
delivered in the same way and were similar for read-
ability. Attendance was measured reliably for every
participant, and those recording it were blind to the
Table 3 | Attendance at diabetes screening after receipt of informed choice invitation or standard invitation, grouped by
social deprivation thirds. Values are percentages (numbers) unless stated otherwise
Deprivation* Overall (n=1272)
Informed choice invitation
(n=633)
Standard invitation
(n=639)
% difference in uptake
between arms
Overall 56.7 (721) 55.8 (353) 57.6 (368) −1.8 (−7.3 to 3.6); P=0.51
Lowest third (<13.7) 64.3 (272) 64.3 (133) 64.4 (139) −0.1 (−9.2 to 9.0)
Middle third (13.7-23.5) 58.5 (244) 55.8 (116) 61.2 (128) −5.5 (−14.9 to 4.0)
Highest third (>23.5) 47.5 (205) 47.7 (104) 47.2 (101) 0.5 (−8.9 to 9.9)
P=0.50 for interaction between arm and index of multiple deprivation 2007 on uptake.
*Index of multiple deprivation 2007 third.
RESEARCH
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