Stated versus revealed preferences: An approach to reduce bias

Stated preference (SP) survey responses may not predict actual behavior, leading to hypothetical bias. We developed an approach that harnesses large-scale routine data to help SP surveys provide more accurate estimates of revealed preferences (RPs), within a study which elicited preferences for alternative changes to the blood service in England. The SP survey responses were used to predict the mean number of annual whole blood donations. Ex ante, the iterative survey design estimated hypothetical bias by contrasting pilot SP survey responses (N = 1254), with individually linked data on RPs, to inform the main SP survey design (N = 25,187). Ex post, the analysis recognized mediation of the relationship between SP and RP when blood donation is deferred. The pilot survey reported that donors' intended donation frequency of 3.2 (men) and 2.6 (women) times per year, exceeded their actual frequency by 41% and 30% respectively. Choice scenario attributes for the main SP survey were then modified, and over-prediction subsequently decreased to 34% for men and 16% for women. The mediating effect of deferrals explained 29% (men) and 86% (women) of the residual discrepancy between SP and RP. Future studies can use this approach to reduce hypothetical bias, and provide more accurate predictions for decision-making.

A systematic review and network meta-analysis of incentive- and non-incentive-based interventions for increasing blood donations

BACKGROUND AND OBJECTIVES

Blood services are tasked with efficiently maintaining a reliable blood supply, and there has been much debate over the use of incentives to motivate prosocial activities. Thus, it is important to understand the relative effectiveness of interventions for increasing donations.

MATERIALS AND METHODS

This systematic review used a broad search strategy to identify randomized controlled trials comparing interventions for increasing blood donations. After full-text review, 28 trials from 25 published articles were included. Sufficient data for meta-analysis were available from 27 trials. Monetary incentives were assumed to be equivalent regardless of value, and non-monetary incentives were assumed to be equivalent regardless of type. Non-incentive-based interventions identified included existing practice, letters, telephone calls, questionnaires, and the combination of a letter & telephone call. A network meta-analysis was used to pool the results from identified trials. A subgroup analysis was performed in populations of donors and non-donors as sensitivity analyses.

RESULTS

The best performing interventions were letter & telephone call and telephone call-only with odds ratios of 3·08 (95% CI: 1·99, 4·75) and 1·99 (95% CI: 1·47, 2·69) compared to existing practice, respectively. With considerable uncertainty around the pooled effect, we found no evidence that monetary incentives were effective at increasing donations compared to existing practice. Non-monetary incentives were only effective in the donor subgroup.

CONCLUSION

When pooling across modes of interventions, letter & telephone call and telephone call-only are effective at increasing blood donations. The effectiveness of incentives remains unclear with limited, disparate evidence identified.

Options for possible changes to the blood donation service: health economics modelling

Background

Evidence is required on the cost-effectiveness of alternative changes to the blood collection service.

Objectives

(1) To estimate the cost-effectiveness of alternative minimum interdonation intervals between whole-blood donations. (2) To investigate donors’ frequency of whole-blood donation according to alternative changes to the blood collection service. (3) To estimate the cost-effectiveness of alternative strategies for maintaining the supply of whole blood.

Methods

We undertook a within-trial cost-effectiveness analysis (CEA) of the INTERVAL trial, stated preference (SP) surveys to elicit donor preferences and a CEA of different strategies for blood collection. The strategies considered were reduced minimum intervals between whole-blood donations, introduction of a donor health report and changes to appointment availability and opening times at blood collection venues. The within-trial CEA included 44,863 donors, with men randomly assigned to 12- versus 10- versus 8-week interdonation intervals, and women to 16- versus 14- versus 12-week interdonation intervals. We undertook a SP survey of non-INTERVAL donors (100,000 invitees). We asked donors to state the frequency with which they would be willing to donate blood, according to the service attribute and level. The CEA compared changes to the blood service with current practice by combining the survey estimates with information from the NHS Blood and Transpant database (PULSE) and cost data. The target population was existing whole-blood donors in England, of whom approximately 85% currently donate whole blood at mobile (temporary) blood collection venues, with the remainder donating at static (permanent) blood collection centres. We reported the effects of the alternative strategies on the number of whole-blood donations, costs and cost-effectiveness.

Results

The reduced donation interval strategies had higher deferral rates caused by low haemoglobin (Hb), but increased frequency of successful donation. For men in the 8- versus 12-week arm of the INTERVAL trial [Di Angelantonio E, Thompson SG, Kaptoge S, Moore C, Walker M, Armitage J,et al.Efficiency and safety of varying the frequency of whole blood donation (INTERVAL): a randomised trial of 45 000 donors.Lancet2017;390:2360–71], the Hb-related deferral rate was 5.7% per session versus 2.6% per session, but the average number of donations over 2 years increased by 1.71 (95% confidence interval 1.60 to 1.80). A total of 25,187 (25%) donors responded to the SP survey. For static donor centres, extending appointment availability to weekday evenings or weekends, or reduced intervals between blood donations, increased stated donation frequency by, on average, 0.5 donations per year. The CEA found that reducing the minimum interval, extending opening times to weekday evenings and extending opening times to weekends in all static donor centres would provide additional whole blood at a cost per additional unit of £10, £23 and £29, respectively, with similar results for donors with high-demand blood types.

Limitations

The study did not consider the long-term rates at which donors will leave the donation register, for example following higher rates of Hb-related deferral.

Conclusions

Extending opening hours for blood donation to weekday evenings or weekends for all static donor centres are cost-effective ways of increasing the supply of high-demand blood types.

Future work

To monitor the effects of new strategies on long-term donation frequency.

Funding

The National Institute for Health Research Health Services and Delivery Research programme.

The effects of feedback and incentive-based insurance on driving behaviours: study approach and protocols

Background

Road injury is the leading cause of death for young people, with human error a contributing factor in many crash events. This research is the first experimental study to examine the extent to which direct feedback and incentive-based insurance modifies a driver's behaviour. The study applies in-vehicle telematics and will link the information obtained from the technology directly to personalised safety messaging and personal injury and property damage insurance premiums.

Methods

The study has two stages. The first stage involves laboratory experiments using a state-of-the-art driving simulator. These experiments will test the effects of various monetary incentives on unsafe driving behaviours. The second stage builds on these experiments and involves a randomised control trial to test the effects of both direct feedback (safety messaging) and monetary incentives on driving behaviour.

Discussion

Assuming a positive finding associated with the monetary incentive-based approach, the study will dramatically influence the personal injury and property damage insurance industry. In addition, the findings will also illustrate the role that in-vehicle telematics can play in providing direct feedback to young/novice drivers in relation to their driving behaviours which has the potential to transform road safety.