Our PhD projects cover both methodological and applied research.
- Beyond the diagnosis: the value of genome-wide sequencing for the diagnosis of rare conditions in Scotland
Rare conditions collectively affect approximately 8% of the Scottish population. Patients and families with rare conditions often undergo a long, costly and stressful ‘diagnostic odyssey’ of clinical and genetic testing in search of a diagnosis. Novel developments in genomic medicine, namely whole genome and exome sequencing, may offer an opportunity to shorten or end the diagnostic odyssey. However, the costs and benefits of introducing genome-wide sequencing in clinical practice remain unclear. As part of a wider economic evaluation of genome sequencing to inform the development of a genomic testing strategy in Scotland, this thesis aims to value the benefits of genomic medicine.
Typically, the benefits of genomic testing are quantified in clinical terms, such as the chance of diagnosis, within a cost-effectiveness analysis comparing the incremental cost per additional diagnosis offered by different testing strategies. However, there is evidence to suggest that patients and families with rare conditions value a wide range of factors beyond the chance of diagnosis alone. This includes: non-health factors such as the value of information about the risk of passing on the rare condition; process factors such as waiting times for results; and psychological factors such as peace of mind, closure, regret and disappointment. To broaden the valuation space beyond the chance of diagnosis for rare genetic conditions, this thesis will use two economic valuation methods, a discrete choice experiment and contingent valuation. The broader value of genome-wide sequencing will be incorporated into a user-perspective cost-benefit analysis economic model, with policy recommendations compared to the standard cost-effectiveness analysis.
PhD Student: Michael Abbott
- Incorporating preference heterogeneity in economic evaluation: informing "realistic medicine"
This is a cross-theme PhD project, within the Assessment of Technologies and the Preference And ValuE themes.
The Chief Medical Officer in Scotland recently outlined her vision for realistic medicine, with key objectives to: (1) build a personalised approach to care; (2) promote shared decision making between patients and their doctors; (3) reduce unnecessary variation in practice and outcomes; (4) reduce harm and waste; (5) improve risk management; and (6) promote improvement and innovation. Some key aspects of this vision are shared decision-making and personalized care, where patients are guided to the treatment that provides the most value to them. This could potentially reduce healthcare costs by avoiding wasteful treatments that patients might not value.
Traditional economic evaluation methods focus on the costs and benefits of different alternatives treatment, using a measure of benefit that reflects population-averaged preferences for health outcomes. The aim of this thesis is to examine the effect of incorporating preference heterogeneity into the economic evaluation of health care interventions, and to see how policy recommendations might differ from those based on traditional evaluation methods. Incorporating preference heterogeneity into treatment choice could then lead to a more beneficial and more efficient allocation of healthcare resources.
PhD student: Divya Mohan
Supervisors: Graham Scotland, Sebastian Heidenreich
- Public and patient preferences for social prescribing
Social prescribing is a means to enable healthcare professionals to refer patients to the voluntary, community and social enterprise sector. Patients are referred to a link worker and together they co-design a non-clinical ‘social prescription’ to improve the patient’s health and wellbeing. Social prescribing is new and varied, and its value for money to the NHS and acceptability to patients and the public is unknown:
Social prescribing is only worthwhile if patients value the outcomes it provides. Patients’ preferences for social prescribing may depend on the health condition it is prescribed for. Knowledge about the variation in patient preferences can identify those who most value social prescribing. Furthermore, the public acceptability and willingness to pay for social prescribing is unknown. Variation in the willingness to pay across health conditions would undermine the ideal of equal care for equal need and have implications for the use of public preferences for decision making. To address these issues, the thesis will be split into three questions and discrete choice experiment methods will be used to answer these:
- Do patients’ preferences for social prescribing differ across mental and physical health conditions?
- Do public preferences for social prescribing differ across health conditions?
- Do public and patient preferences for social prescribing differ?
PhD student: Mélanie Antunes
- Using existing data to incorporate broader measures of benefit in economic evaluation
This is a cross-theme PhD project, within the Assessment of Technologies and the Preference And ValuE themes.
The quality-adjusted life year (QALY) is the predominantly used measure of health benefit in economic evaluation. The QALY has many advantages, including readily available generic preference based instruments (e.g. EQ-5D) and its applicability across disease areas. However, these advantages are somewhat traded off by its narrow, health-oriented viewpoint and inability to capture benefits of health and healthcare outwith these generic instruments. For example, the QALY framework fails to adequately capture patient preferences for non-health attributes or the process of care.
A popular approach used in health economics to value all relevant benefits is the use of stated preference methods, where benefits can be measured in terms of willingness-to-pay (WTP). Despite their growing application in health economics, WTP measures of benefit are rarely used in economic evaluations. One reason is that measuring WTP is resource intensive (in terms of time and finances) because a new valuation study is required for each economic evaluation.
There are now many published monetary valuation studies that provide enough data to test if pre-existing WTP measures of benefit can be combined using benefit transfer (BT) as an alternative to conducting a new study. BT synthesises results from previously published studies and with adjustment, using all available and relevant information, predicts an estimate in a new study setting that is different in type, location or time from the original studies. This PhD will conduct two case studies to test the transferability of values. The first case study will focus across clinical areas (e.g. are values of the process of care the same across chronic and acute care settings?) while the second will focus within a clinical area (e.g. can values collected in perinatal care be transferred to post-natal care?).
To date, original monetary valuation studies have been conducted to value specific interventions, but the transferability of valuation results has not been explored. If BT can be successfully achieved in a healthcare setting, accessible methods to broaden the valuation space beyond the current QALY approach will be established.
PhD student: Emma Tassie
Recently Completed Projects
- Assessment of the external validity of discrete choice experiments: an application in pharmacy
The discrete choice experiment (DCE) technique has been applied extensively in the valuation of healthcare benefits to capture preferences. A key methodological question is if external validity i.e. the extent to which respondents’ choices made in a hypothetical DCE context, truly reflect their actual preferences. This thesis explored the external validity of DCEs within a pharmacy context. The thesis compared what respondents said they would do in a DCE survey with what they actually did when presented with the same scenario in real life. The thesis also explored the roles of uncertainty and attitudes in explaining discrepancies and uised qualitative research to provide insight.
The DCE correctly predicted 42.1% of participants’ actual choices. Calibration of the DCE with certainty questions and incorporation of the TPB into DCE improved DCE-prediction. Reasons for discrepancies in stated choice and actual behaviour included differences in decision-making processes in DCE and real life, attitudinal and other contextual factors (e.g. timing, location).
Outcome and Translation
Calibration methods should be considered to improve external validity. The development of DCEs, and the modelling of choice responses, should mimic as closely as possible the decision-making process individuals face in reality. This thesis extends the limited pool of empirical studies assessing external validity of DCEs.
PhD student: Gin Nie Chua
Supervisors: Mandy Ryan (HERU); T Porteous (HSRU, University of Aberdeen) and C Bond (Academic Primary Care, University of Aberdeen)
- Broadening the valuation space in health technology assessment: the case of monitoring individuals with ocular hypertension
The economic evaluation (EE) component of health technology assessments (HTA) often defines value in terms of health related quality of life, with many HTA agencies requiring the use of EQ-5D based quality adjusted life years (QALYs). These approaches do not capture value derived from patient experience factors and the process of care. This thesis widened the valuation space beyond this limited perspective, taking account of such factors, using monetary values generated from a DCE, incorporating these into a discrete event simulation (DES) and conducting a cost–benefit analysis (CBA).
The case study monitored individuals with ocular hypertension (Project Number B2.21). Five strategies were compared using a DES: (1) ‘treat all’ at ocular hypertension diagnosis with minimal follow-up; (2), (3) biennial monitoring (either in primary or secondary care) with treatment according to predicted glaucoma risk; and monitoring and treatment according to the UK National glaucoma guidance (either (4) conservative or (5) intensive).
Outcome and Translation
DCE based WTP estimates for health outcomes (e.g. risk of developing or progressing glaucoma and treatment side-effects), patient experience factors (e.g. communication and understanding with the healthcare professional) and process of care (e.g. monitoring setting) were obtained. Conditional logit, mixed logit preference space and mixed logit WTP-space (rarely used within health economics) econometric specifications were used. These WTP valuations were aggregated in the DES, as fixed mean values or allowing variation between simulated individuals.
While the standard cost–utility analysis (CUA) using EQ-5D implied that ‘treat all’ was most likely cost-effective, CBA with broadened valuation space identified, consistently across different econometric specifications, ‘biennial hospital’ as the best choice.
This thesis proposed an approach to broaden the valuation space that can be promptly used for EE-HTA. Researchers should be attentive of the valuation space considered in their EE and choose wisely the EE approach to be used (e.g. CUA and/or CBA).
PhD student: Rodolfo Hernández
Supervisors: Mandy Ryan (HERU), Jen Burr (St Andrews University) and Luke Vale (Newcastle University)
- Do I care or do I not? An empirical assessment of decision heuristics in discrete choice experiments
Discrete choice experiments (DCEs) are widely applied by health economists to elicit individuals’ preferences for healthcare services. The analysis of DCE data assumes that respondents consider and trade all attributes of the healthcare service under valuation when completing the hypothetical choice tasks. Over the last ten years, this assumption has been questioned and several studies suggest that respondents may ignore attributes as a simplifying choice heuristic. This PhD (1) investigates the presence of such decision heuristics in DCE responses, (2) explores causes of such behaviour and (3) evaluates methods to determine if a respondent used a particular heuristic.
Outcome and translation
Respondents are found to ignore DCE attributes and accounting for such behaviour may improve the validity of estimates. Current approaches assume that ignoring attributes is a heuristic to simplify choices. However, this PhD demonstrated that attributes may be ignored because they are not valued. Approaches that do not distinguish between non-valuation and heuristic are found to be potentially misleading. Furthermore, whilst respondents had difficulty reporting their information processing strategy, statistical methods could not distinguish between preference and heuristic. Future research could use process tracking techniques (e.g. eye-tracking and think aloud), pre-piloting and other qualitative methods (e.g. interviews) to better understand decision-making heuristics. The PhD also found that respondents’ use of heuristics may be caused by either a ‘too simple’ or ‘too difficult’ DCE design.
PhD Student: Sebastian Heidenreich
- External validity of DCEs: a case study of dental care
This was a cross-theme PhD project, within the Assessment of Technologies and the Preference And ValuE (then Methods of Benefit Valuation) themes.
Stated preference methods in health are sometimes criticised due to concerns over the external validity of the results. Most of these concerns relate to hypothetical bias, where respondents to a survey may not follow through on their stated choices if offered an identical choice in reality. The implication of hypothetical bias may be incorrect predictions of service uptake or biased estimates of WTP, leading to incorrect policy recommendations from cost–benefit analysis. The thesis focused on the challenge of hypothetical bias, and investigated several different mitigation techniques.
Ex ante mitigation methods focus on addressing hypothetical bias a priori, before respondents complete the choice task. Three different methods: oath scripts, consequentiality scripts and cheap talk scripts with an opt-out reminder were compared with a standard approach.
Ex post mitigation methods aim to calibrate choice responses, often based on certainty scales, to recode or statistically calibrate stated and revealed preferences based on the assumption that more certain responses are less likely to suffer from hypothetical bias. The thesis compared the use of different calibration approaches (recoding and elimination of uncertain responses) using quantitative and qualitative certainty scales.
Predictions of service uptake (scale and polish and dental check-ups) from two DCEs were compared with revealed preference data, collected using retrospective questionnaires, to determine the methods generating the best predictive validity. Willingness to pay was estimated across groups.
Outcome and Translation
DCEs can be reliably used in dentistry. They generate accurate service opt-in predictions for scale and polish and dental check-ups. However, it is less clear how accurately DCEs predict the uptake of specific dental care service configurations, especially check-up recall intervals.
Ex-ante corrections (cheap talk, consequentiality scripts and honesty oaths) have little effect on WTP or data quality. However, it should be acknowledged that scope to show benefit is limited because the magnitude of hypothetical bias in the binary decision to consume a dental care service (i.e. the opt-in decision) was small. Consequentiality scripts and honesty oaths may have the greatest potential to address hypothetical bias, should it exist, and further research is required.
It is encouraging that ex-ante corrections can be used without adversely impacting on DCE data quality, with no evidence to preclude their use in future studies.
Ex-post certainty corrections however should not be used routinely in DCEs to mitigate hypothetical bias in their current, most widely used (recoding) form. Ex-post calibrations require selection of arbitrarily selected threshold values to determine which responses are valid and which are not. The approach does not improve congruence between stated and real preferences but has serious implications for data quality and theoretical validity and raises equity concerns for using the method to inform policy recommendations.
Recently published, and ongoing research is striving to find a better way to use certainty in DCEs (Beck, et al., 2016; Regier, et al., 2017). It is likely that these new and emerging approaches may pave a more positive way for the use of certainty in future DCEs, though this area of research is only in its infancy.
Papers arising from this work are currently being prepared for submission to peer reviewed journals.
PhD Student: Dwayne Boyers
- Investigating willingness to pay for low emission public transportation
In this thesis, we investigated how much bus users’ are willing to pay to reduce emissions that cause air pollution from buses using a Discrete Choice Experiment (DCE). We considered two different types of emissions separately: global emissions that cause climate change and local emissions that impact on health. The context of the study is an existing low emission bus (LEB) scheme – the Aberdeen Hydrogen Bus Project. The thesis addressed three research questions:
Whether bus users value reduction in emissions from buses and determine if people distinguish between different types of emissions?
If experience from regularly using a hydrogen bus has as an effect on the value users place in different characteristics of the bus service?
- Exploration of asymmetries in the preferences for attributes using a reference-dependent (pivoted) experimental design.
This is the first study to investigate the effect of the introduction of a low emission public transport scheme on its users’ valuations using a DCE. The results provide us with insight to better inform how to implement LEB schemes.
Outcome and Translation:
Aberdeen bus users value buses that are cheaper, more frequent, more punctual and reduced emissions. Respondents seem to place a higher value in reducing local pollutant emissions than greenhouse gas emissions, thus suggesting they care more about emissions which have local consequences (i.e. poorer local air quality) than those that have global consequences (i.e. climate change). There was evidence of preference heterogeneity across the sample, specifically when splitting the sample based on the level of experience of using a hydrogen bus. Bus users with more experience using a hydrogen bus as their main service placed a higher value on reduced emissions and improved comfort inside the bus when compared to users with no or little experience using the hydrogen bus. Reduced emissions and increased comfort are the most salient differences between a hydrogen bus and a diesel bus, thus this was interpreted as experience of using the hydrogen buses having an effect in preferences. Finally, bus users’ preferences were consistent with prospect theory. Preferences for frequency, punctuality and fare exhibited loss aversion (loses loomed larger than gains), reference dependence and diminishing marginal utilities. This has policy implications, as the allocation of resources for a bus service should not assume linearity of preferences. For example, an improvement in frequency in one service will not make up for a similar deterioration in another service.
PhD Student: Luis Loría
Supervisors: Verity Watson (HERU); Kiso, T., Phimister, E. (Economics, UABS)
- Our values or mine? A philosophical and empirical critique of deliberative and stated preference elicitation techniques in health economics
The thesis evaluates to what extent health economic stated preference methods and deliberative approaches towards health preference elicitation allow participants to express normative considerations that are related to the well-being of others, register preferences that take the social status of beneficiaries into account, and express normative evaluations that go beyond a consequentialist focus on outcomes. In addition, the thesis assesses to what degree participants are afforded the opportunity for peer interaction and peer discussion, evaluates the sensitivity of elicitation methods towards participants undergoing preference transformation, and assesses to what degree health economic preference elicitation methods are compatible with the concept of collective moral authorship.
For the assessment, the thesis combines a philosophical analysis of the theoretical paradigms of neoclassical health economics and deliberative democratic theory with an evaluation of how both approaches relate to the practice of health preference elicitation. To the latter end, the thesis presents the findings of a literature review of health-related stated preference studies and discusses the results of qualitative interviews with the participants of two deliberative Community Juries on the topic of disinvestment in breast cancer screening.
Outcome and Translation
The thesis argues for the increased utilization of deliberative methods in health economic preference research alongside preference elicitation methods.
PhD Student: Ruben Sakowsky
Supervisors: Mandy Ryan (HERU) and V. Entwistle (Health Services Research Unit, University of Aberdeen)
- The gift of time: how do I use it and how should I use it?
There is extensive evidence on the relationship between a cancer diagnosis and labour market outcomes. However, there is limited evidence on the relationship between a cancer diagnosis and non-labour market outcomes, such as household work and leisure. Understanding time allocation on daily activities may imply the recovery journey post a cancer diagnosis.
The PhD explored the ‘trajectories’ of time allocation following a breast cancer diagnosis; the causal impact of time allocation on wellbeing among women diagnosed with a breast cancer; and preferences of time allocation, and the monetary value of time on non-labour market activities, such as household work, leisure and sleeping.
The PhD was part of the Aberdeen Curtin Alliance, combining the strengths of two of the world’s leading Universities.
PhD Student: Ni Gao
Supervisors: Mandy Ryan (HERU); R. Norman, S. Robinson (Curtin University, Western Australia) and N. Krucian (Evidera)