According to new research from the University of East Anglia in collaboration with Boots UK and Leiden University, four million UK patients could benefit annually from pharmacogenetic testing prior to being prescribed common medicines.
Pharmacogenetic testing
Pharmacogenetics (PGx) refers to how variants within an individual’s DNA sequence can affect drug metabolism, transport and response. Application of these drug-gene interactions can help guide personalisation of drug prescription. This is important for both drug safety and effectiveness.
The rate at which aberrant phenotypes occur in the general population is high. Estimates indicate that over 95% of the population carry a genetic variant that affects the prescribing of at least one drug. In addition, a recent study exploring phenotype frequencies for 14 pharmacogenes from participants in the UK Biobank, found that 99.5% of individuals had a predicted atypical response to at least one drug.
Implementation of PGx testing in the NHS has become a source of particular interest to policymakers, clinicians and pharmacists. In the UK, PGx is currently implemented in secondary care for a small group of high-risk medicines. However, most prescribing takes place within primary care. NHS England hope to implement pre‐emptive pharmacogenomic testing within the next 10 years. Experts will record these PGx test results within a patients’ medical records in order to support clinicians and pharmacists in all sectors to make therapeutic decisions.
The impact of PGx testing
In this study, published in the British Journal of Clinical Pharmacology, researchers aimed to estimate the impact of PGx testing annually on primary care within a UK context. To do this, the team calculated quantitative estimates of the volumes of medicine dispensed annually with a Clinical Pharmacogenetics Implementation Consortium (CPIC) and/or Dutch Pharmacogenetic Working Group (DPWG) recommendation and affected by aberrant phenotypes. They also calculated estimates for the volumes of medicine requiring dose or drug change, increased monitoring or change in long-term management.
The team utilised a large community pharmacy database to estimate the national incidence of first prescriptions for 56 PGx drugs used in the UK. They then combined the estimated prescription volumes with phenotype frequency data to estimate the occurrence of actionable drug-gene interactions in daily practice.
The researchers found that between 19.1-21.1% (n = 5,233,353–5,780,595) of all new prescriptions for 56 drugs, an actionable drug-gene interaction was present. For these cases, the interaction resulted in either increased monitoring or a change of drug or dose. The team found that four pharmacogenes (CYP2C19, CYP2D6, SLCO1B1, HLA‐B) were responsible for >95% of all drug–gene interactions.
These findings emphasise that actionable drug-gene interactions frequently occur within UK primary care. This represents a large opportunity to optimise prescribing. As a result, these findings can help inform policymakers looking to implement PGx testing in UK primary care.
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