Title: Incentives in Diabetic Eye Assessment by Screening (IDEAS) Trial
Funder: Department of Health (England)

Abstract: Reducing inequalities in health is a central part of government health policy. Deprived sections of our communities are known to suffer increased levels of significant disease in many areas and are less likely to attend screening opportunities. Evidence from diabetic retinopathy screening programmes in particular supports this (Scanlon et al 2008) highlighting the fact that in areas with the greatest socioeconomic deprivation diabetic prevalence is highest and attendance is poorest. As a result screening programmes in general have the potential to exacerbate existing inequalities in outcomes. A challenge for screening programmes therefore is to find effective simple and inexpensive population wide strategies to recruit hard to reach individuals. One such strategy gaining prominence is finding ways to incentivise these populations to better align their behaviour with underlying intentions. Our interventions will use cutting-edge theory from the interdisciplinary field of behavioural economics to design incentives that encourage people to utilise screening opportunities. Behavioural economics integrates lessons from psychology into the laws of economics (Kahneman 2003). Psychological phenomena from behavioural economics can allow us to design more effective incentive-based interventions. We will employ the following prominent insights into the design of our interventions because those are the three most established phenomena in behavioural economics embodied in the well-known Prospect Theory for which Daniel Kahneman was awarded the 2002 Nobel prize in economics (see Kahneman & Tversky 2000): - Reference Points. Offering a very small incentive can get people to pick up their HIV Result but increasing the value of the incentive has little effect (Thornton 2008). We will offer an incentive of £10 (equivalent to minimal hourly wage for UK workers >21) to assess whether this leads to an increase in participation. - Overweighting of Small Probabilities. People are known to overvalue small probabilities which explains the popularity of lotteries and insurance (see Kahneman & Tversky 2000). In the review of the effect of incentives on smoking cessation one of the reasons given for the lack of effectivenes shown is the low level of incentives on offer in most of the programmes (Cahill & Perera 2008). It follows that if an incentive programme only has limited resources it may be more effective to offer a lottery based programme rather than smaller individual rewards. We will offer lotteries where the expected value matches the incentive level offered in the other arms It may be that overweighting of small probabilities will make a lottery offering eg 1% chance for £1000 more attractive than £10 for certain so the former should be more effective incentive for participation in screening. - Loss Aversion. We dislike financial losses twice as much as we like financial gains of an equivalent amount (Kahneman 1979). Incentives may be more powerful where individuals lose a reward rather than gain one for screening. In our intervention participants will either receive a fake banknote (such as Monopoly money) that can be exchanged for cash at after screening or a lottery ticket which expire at the date of the screening.The study proposed is a randomised controlled trial conducted within the Kensington Chelsea and Westminster Diabetic Eye Screening Programme of London. Patients aged 16 or older who were invited to screening the in the last 12 months and failed to attend or contact the screening service to rearrange an appointment will be studied. Study participants will be identified from the Diabetic Eye Screening Programme prior to commencement of the study. Data from the screening programme for the year 01/04/2011 to 31/03/2012 suggests that 12 months worth of screening activity will provide the required study size. All invitees during the study period will be randomised prior to invitation between the three study groups: Group 1 – Control Group: subjects will be sent documentation on diabetic eye screening and the standard screening programme invite only.Group 2 – Fixed Incentive: subjects will be sent a £10 fake banknote which they can exchange for cash at the clinic after attending for screening in addition to the documentation on diabetic eye screening and the standard screening programme invite.Group 3 – Probabilistic Incentive: subjects will be sent a lottery ticket offering a 1% chance to win £1000 if they attend for screening in addition to the documentation on diabetic eye screening and the standard screening programme invite.It will be stated on the £10 fake banknote and the lottery ticket that they will lose their value if the patient does not attend the scheduled or the rescheduled screening appointment which is expected to trigger loss aversion in groups 2 and 3.The incentive schemes were designed in conjunction with patient representatives and a survey of diabetic patients (see the Detailed Project Description for more information). The study group will comprise patients who have never attended for screening so attendance in the study group should be very low (a nominal 1%). Evidence (Scanlon 2008) and consultation with the Diabetic Eye Screening Service informs us that the study group have the greatest risk of losing their sight so an increase in attendance of 10% is worthwhile. With 2 intervention groups each being compared to the control group for maximum statistical efficiency we should randomise 1.4:1:1. This would give 412 controls and 294 in each of the intervention groups (1000 in total) and the study would have at least 95% power to detect an increase in attendance of 10% from 1% in the control arm to 11% in an intervention arm and 85% power to detect a smaller increase from 1% to 7.5% (should attendance in the control arm turn out to be 5% the study would still have approximately 85% power to detect an increase in attendance of 10% with an intervention to 15%).Demographic data will allow us to explore whether inequalities in screening may be addressed by an incentive scheme. The proposed trial has been discussed at the local Diabetic Eye Screening board meeting and has support. The trial also is aligned with the National agenda to encourage research achieving higher attendance rates at screening.


Research activity codes: 4.3 INFLUENCES AND IMPACT
Health categories: EYE;METABOLIC AND ENDOCRINE