36 CHAPTER 2.1 drugs) admitted to the emergency department for potential ADRs by using this ADR trigger tool. However, the recommendation has not been substantiated by evidence supporting the use of such a trigger tool in clinical practice. Hence, evaluation of the performance of the ADR trigger tool in the above-mentioned guideline is warranted. This study aimed to investigate the performance of the ADR trigger tool recommended by the Dutch geriatric guideline and the recognition by usual care of ADRs detected with the tool in patients with polypharmacy acutely admitted to our geriatric ward. Methods Setting and study population The study population consisted of patients aged 70 years and older with polypharmacy acutely admitted to the geriatric ward at a 1,000 bed tertiary university hospital in the Netherlands (University Medical Centre Utrecht). Admissions of patients to the geriatric ward through the emergency department (ED) in the period between 01-01-2011 and 01-08-2017 were extracted with SAS enterprise guide v7.1 from a pseudonymised hospital database. Based on the consecutive order of randomly assigned numbers for each patient, admission letters were manually screened to include approximately 350 patients aged ≥70 years with polypharmacy. Polypharmacy was defined as the chronic use of at least five prescription drugs excluding dermatological preparations at admission . For patients with multiple hospital admissions during the study period, the first admission that met the inclusion criteria was selected. A patient’s first admission was selected to minimise interference of consecutive hospital admissions with the study outcomes. Patients with an incomplete record (i.e. no admission or discharge letter available) were excluded. Study procedures Electronic health records (EHRs) from the ED on the day of admission were screened for trigger-drug combinations listed in the ADR trigger tool of the Dutch national geriatric guideline ‘polypharmacy optimisation in hospitalised older people’ (first publication 2017, last revision 2020) . This consensus-based trigger tool was developed in accordance with literature listing ten clinical events (i.e. triggers) and their associated drug classes frequently resulting in ADR-related admissions in older people [16–18]. Next, a causality assessment was performed for all detected triggerdrug combinations. The admission and discharge letters were also screened for ADR recognition by the attending physicians.