What are the barriers and facilitators to the implementation of pharmacogenomics in mental health settings? A theory-based systematic review
Authors: Jameson A , Tomlinson J , Medlinskiene K , Howard D , Saeed I , Sohal J , Dalton C , Sagoo G S , Cardno A , Bristow G C , Fylan B , McLean S L 
Published: April 2024

Abstract

Introduction
Prescribing of psychotropic medicines is largely led by a trial-and-error approach. Treatment inefficacy, side effects and poor adherence are common challenges.[1] Pharmacogenomics (PGx) studies how genetic variability influences medication response. PGx Testing (PGxT) can identify relevant gene variants and help tailor prescribing of medicines to individuals. Conducting PGxT has been demonstrated to improve treatment outcomes, including medication efficacy and tolerability. Yet, access to and adoption of PGxT in mental health settings is limited to date.[2]

Aim
To explore factors influencing PGx implementation in mental health settings, using Normalisation Process Theory (NPT) as a theoretical framework. NPT seeks to understand factors influencing the success of intervention implementation. This enabled us to:
-Identify barriers hindering the uptake of PGx.
-Determine facilitators helping the adoption of PGx prescribing practices.
-Map key barriers and facilitators to constructs of the NPT framework

Methods
The review was registered with PROSPERO (ID: CRD42023399926). Four literature databases were searched using synonyms for three terms (‘pharmacogenomics’, ‘mental health’ and ‘perspectives’), providing a total of 17499 records. Using pre-specified eligibility criteria, records were screened by four independent reviewers in three consecutive stages: title, abstract and full-text screening. Records were included if they contained data about relevant stakeholders (healthcare professional or patient) perspectives towards PGx implementation in mental health settings. Exclusion criteria included studies from non-mental health settings, review articles and clinical PGx studies. Data extraction and quality assessment were completed independently by a minimum of two reviewers. The QuADS tool was applied to enable quality assessment. Using an abductive approach, one reviewer utilised thematic analysis to map barriers and facilitators to the NPT framework, and then develop themes within and across NPT constructs.

Results
A total of 27 records with qualitative and/or quantitative data relating to PGx implementation in mental health were included. Major barrier themes included a PGx knowledge gap, in part due to a lack of education and training; a lack of top-down policy about PGx implementation; and uncertainty about the use of PGx. Major facilitator themes included interest in PGx as a new and improved approach to prescribing, a perception that PGx integration into electronic health records helps implementation, and a belief that PGx should be multidisciplinary.

Conclusion
PGx has the potential to improve prescribing in psychiatry, but integration of PGxT and realisation of its potential benefits has not been maximised. For the first time, by extracting data from a range of sources, barriers and facilitators to implementing PGx in mental health settings have been systematically reviewed, using a novel approach by adopting NPT as a theoretical framework. A limitation of the review was that some included studies had already implemented PGxT, so were potentially biased towards reporting positive perceptions about the uptake of PGxT. The review findings are useful to patients, policymakers, service providers and clinician stakeholders in designing pathways for PGx implementation, and health researchers to inform future research in the field of PGx implementation science. Future policy and research should aim to address identified barriers and use facilitators as leverage to enhance implementation.

References
1. Bousman CA, Bengesser SA, Aitchison KJ, Amare AT, Aschauer H, Baune BT et al. Review and Consensus on Pharmacogenomic Testing in Psychiatry. Pharmacopsychiatry. 2021;54(1):5-17.
2. Jameson A, Fylan B, Bristow GC, Sagoo GS, Dalton C, Cardno A et al. What Are the Barriers and Enablers to the Implementation of Pharmacogenetic Testing in Mental Health Care Settings? Frontiers in Genetics. 2021;12(1764).