Pharmacogenomic Medicine Use and Adverse Outcomes in Hospitalised Older Patients: A Retrospective Cross-Sectional Study

Abstract This study aimed to assess the prevalence of pharmacogenomic medicine usage upon hospital admission in patients aged 65 and over and evaluate its association with adverse outcomes, including length of stay, unplanned admissions, and repeat hospital admissions. A retrospective cross-sectional study was conducted using hospital admissions data from 2018-2019 in one NHS hospital trust in England, focusing on patients aged 65 and over. Pharmacogenomic medicine usage was examined, and comparisons were made between the prevalence of pharmacogenomic use in unplanned and planned admissions. Multivariable models assessed whether pharmacogenomic medicine use was associated with adverse outcomes, considering frailty status. Analysis of 59,973 admissions revealed 67 pharmacogenomics medicines as per the Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines, with 11 classified as high-risk among 1,438 unique medicines identified from 560,179 recorded medications. Notably, unplanned admissions exhibited a higher prevalence of pharmacogenomic medicine use (84% versus 64%, p<0.001) compared to planned admissions. The models demonstrated that pharmacogenomic medicine usage was associated with adverse outcomes (length of stay in hospital, unplanned admission and repeat hospital admission) with substantial evidence (Delta_AICc < 2) particularly in patients with high frailty status. This study highlights the association between pharmacogenomic medicine usage for adverse outcomes, particularly among patients with high frailty. The findings emphasise the importance of integrating pharmacogenomic-guided care into the management of older individuals with frailty to mitigate adverse outcomes and enhance medication safety.