Mixed methods co-design and evaluation of a Decision Support Tool to enable shared decision making for people who are considering cascade screening for Thoracic Aortic Disease: The DECIDE TAD Programme.

Research Question: Will implementation of a Decision Support Tool improve detection of latent Thoracic Aortic Disease (TAD) through increased uptake of cascade screening in people at risk compared to current standards of care? Background: TAD causes more deaths every year than road accidents.

TAD has a long latent phase characterised by asymptomatic aneurysm formation followed by presentation with an acute aortic syndrome, most commonly an acute aortic dissection, which has >70% mortality. Improving outcomes in acute aortic dissection is a priority for the National Cardiac Transformation Programme.

Over 20% of TAD is caused by a single genetic mutation.

Up to 30% of first- and second-degree relatives of people with TAD will also have recognised mutations or aortic aneurysms.

Cascade screening, where relatives undergo genetic tests and imaging significantly reduces mortality through detection of latent disease, effective secondary prevention, and early treatment. Over 80% of TAD is non-syndromic (NS-TAD).

Our preliminary work identified multilevel organisational and individual barriers to screening in people at risk of NS-TAD.

Fewer than 1/6 dissection survivors report being involved in shared decisions about cascade screening, and only 1/3 of relatives offered cascade screening agree to testing although >2/3 of those screened have positive results or require further treatment. Health inequalities are evident for underserved groups.

We hypothesise that the intervention most likely to overcome these barriers is implementation of a Decision Support Tool (DST) to enable effective shared decision making. We further hypothesise that this intervention will increase uptake of screening, and the detection of latent TAD.

Objectives: To co-develop, refine, evaluate, and implement a DST that will improve shared decision for all people at risk of Non-Syndromic TAD who are considering cascade screening.

Methods: An Equality Diversity and Inclusion Toolkit developed with the Leicester Centre for Ethnic Health will be applied across all WP to reduce health inequalities in the research process. Work Package 1: Co-develop the DST and Implementation Toolkit, addressing inequalities in under-served groups.

Create the content of the DST in formats likely to be most effective and integrate it with existing care pathways.

Work Package 2: Feasibility study of the DST and Implementation Toolkit in 2 centres, with linked qualitative work to address key uncertainties related to the intervention and the RCT procedures, then refinement. Work Package 3: Cluster RCT, where centres are randomly assigned to implement the DST or the current standard of care.

Outcomes will include detection rates in at risk relatives, the quality of decision making, and cost effectiveness. A linked process evaluation will address how context, mechanisms of action, and implementation affect outcomes.

Work Package 4: Develop an Implementation Plan that provides key information to support prioritisation by national and regional commissioners and providers of TAD services. Timelines for WP delivery: WP1 Month 16, WP2 Month 28, WP3 Month 63, WP4 Month 66.

Anticipated Impact and Dissemination: If effective, the DST should be incorporated into the Aortic Dissection Prevention Toolkit.

Dissemination will capitalise on partnerships with the national patient charity and specialised and regional commissioners.