Developing a Core Outcome Set for trials evaluating medication adherence interventions

One in two patients do not adhere to prescribed medication directions. This non-adherence has been identified by the World Health Organisation as an international priority as it presents a significant public health challenge that causes avoidable mortality and morbidity, and resource utilisation. Numerous strategies have been designed to address non-adherence and trials conducted to test their effects. There is, however, no agreed list of outcomes that should be measured in these trials resulting in large variation in the outcomes reported. This means that we are unable to easily compare the findings from different trials or combine them to provide higher quality evidence. This study aims to develop an agreed list of outcomes (Core Outcome Set) that should be measured in all adherence trials.

We will develop the Core Outcome Set by looking at previous trials related to medication adherence to create a list of all of the different measures that might be relevant to an adherence trial. We will narrow down this long list into those most important to measure using two rounds of online questionnaires with representatives of five stakeholder groups:

1. Patients
2. Informal carers
3. Healthcare practitioners whose role includes medicines management including general practitioners, clinical pharmacists, nurses and other practice staff such as allied health professionals
4. Primary care managers (e.g., medicines management lead and practice leads or managers)
5. Academic researchers with an interest in medication adherence

We will then convene an online workshop to agree on the most important outcomes to measure and understand the practicalities or how we might measure them in a trial.


Prof Debi Bhattacharya (Principal Investigator), University of Leicester
Dr Sion Scott (Principal Investigator), University of Leicester
Prof David Wright, University of Leicester
Katherine Murphy, PPI representative
David Turner, University of East Anglia
Kumud Kantilal, University of Leicester
Dr Allan Clark, University of East Anglia

Further Study Information

Current Stage: Ongoing
Date: April 2022 - January 2023
Funding source(s): National Institute for Health Research Programme Development Grants (award reference number NIHR203303)

Health Area

Disease Category: Other

Disease Name: Medication adherence

Target Population

Age Range: 18 - 120

Sex: Either

Nature of Intervention: Drug

Stakeholders Involved

- Clinical experts
- Consumers (caregivers)
- Consumers (patients)
- Patient/ support group representatives
- Policy makers
- Researchers
- Service commissioners
- Service providers
- Service users

Study Type

- COS for clinical trials or clinical research
- COS for practice


- Consensus meeting
- Delphi process
- Literature review
- Semi structured discussion
- Survey

The COS will be developed using a modified Delphi process, involving 3 phases:
Phase 1: Identify and review potentially relevant outcomes
Phase 2: Modified Delphi survey - 2 rounds
Phase 3: Stakeholder consensus workshop

Phase 1 will involve identifying all potential outcomes for medicines adherence from systematic reviews related to medicines adherence interventions and an existing COS for medication review trials. The list will be reviewed to identify all relevant outcomes, including definitions and organised into domains.

Phase 2 will involve reaching stakeholder consensus about which outcomes identified in phase 1 are the most important. We will conduct two Delphi rounds of stakeholder questionnaires. In round 1, for each outcome, participants will be asked to indicate whether an outcome is important on a 3-point scale: YES; NO and UNSURE/I DO NOT KNOW. Participants will be able to add comments for each outcome to explain their response. There will also be an opportunity to suggest any additional outcomes. Consensus will be met if the outcome is rated as important by 70% or more of participants of each stakeholder group. Outcomes reaching consensus to include or reject will be removed at round 1. Outcomes which fail to reach consensus and any new proposed outcomes will progress to round 2 for re-rating/rating. In round 2, for each outcome participants will be presented with the distribution of responses across the three options for each participant group and from all participant groups. They will be asked to re-rate whether the outcomes are important on a 2-point scale: YES or NO.

After round 2, the research team will collate responses from the two Delphi rounds. The outcomes that have reached consensus to include will progress to the workshop. Any outcomes that reached consensus to reject will be removed as well as those where all stakeholder groups failed to reach consensus. Outcomes will progress to the phase 3 workshop if a sub-group analysis demonstrates that at least one stakeholder group reached consensus to include (partial consensus). This is to ensure that no outcomes are removed that are important to one group e.g., patients, but are not considered important to the remaining groups.

Phase 3 will involve convening a 120-minute online consensus workshop with 2-4 representatives of each stakeholder group, up to a maximum of 20 participants. The aim of the workshop is to finalise the outcomes that should be included in the COS, explore the barriers and enablers to implementing the COS, and identify trial design features (e.g., using routinely collected data) and data collection tools and processes (e.g., patient follow-up) to facilitate this.

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