Background identifying drug-related hospital admissions (DRAs) in older people is difficult. A standardised chart review procedure has recently been developed. It includes an adjudication team (physician and pharmacist) screening using 26 triggers and then performing causality assessment to determine whether an adverse drug event (ADE) occurred (secondary to an adverse drug reaction, overuse, misuse or underuse) and whether the ADE contributed to hospital admission (DRA). Objective to assess the performance of those triggers in detecting DRA. Design retrospective study using data from the OPERAM (OPtimising thERapy to prevent Avoidable hospital admissions in Multimorbid older people) trial. Settings four European medical centres. Subjects multimorbid (≥ 3 chronic medical conditions) older (≥ 70 years) inpatients with polypharmacy (≥ 5 chronic medications) were enrolled in the OPERAM trial (N = 2,008) and followed for 12 months. We included patients with ≥1 adjudicated hospitalisation during the follow-up. Methods the positive predictive value (PPV; number of DRAs identified by trigger/number of triggers) was calculated for each trigger and for the tool as a whole. Results of 1,235 hospitalisations adjudicated for 832 patients, 716 (58%) had at least one trigger; an ADE was identified in 673 (54%) and 518 (42%) were adjudicated as DRAs. The overall PPV of the trigger tool for detecting DRAs was 0.66 [0.62–0.69]. Conclusions this tool performs well for identifying DRAs in older people. Based on our results, a revised version of the tool was proposed but will require external validation before it can be incorporated into research and clinical practice.