46 CHAPTER 2.1 Discussion Main findings ADRs were highly prevalent in older patients with polypharmacy acutely admitted to the geriatric ward. The ADR trigger tool detected one or more trigger-drug combinations at admission in almost three quarters (73%) of all screened patients, and more than half (52%) of these patients had at least one confirmed ADR after causality assessment. The overall PPV of the ADR trigger tool was 41.8%, indicating that less than half of the trigger-drug combinations were considered to be ADRs. Usual care recognised the majority of ADRs (83.5%), increasing to 97.1% when restricted to possible and certain ADRs. Performance The performance of the ADR trigger tool recommended by the Dutch geriatric guideline was not previously studied. Using an ADR trigger tool may be a helpful and efficient strategy to increase ADR detection in older people, especially in cases of low recognition by usual care. A high PPV is important for a positive balance between reviewing signals and detecting actual ADRs. Although there is no generally accepted definition to distinguish ‘good’ from ‘poor’ trigger tool performance – which also depends on its intended use – a PPV ≥20% is often considered good [23,24]. In our study, the PPV per trigger of the investigated ADR trigger tool was highly variable, ranging from 0–100%. However, if triggers with a frequency of only one were excluded, all triggers had a PPV ≥ 20%, of which the PPVs for the triggers ‘fall/…/dizziness’ (PPV 28%) and ‘delirium/…/drowsiness’ (PPV 23%) were lowest. These clinical events often have multiple possible causes related to comorbidity, drugs and drug combinations, impeding the confirmation of a clear causal relationship. The mean number of drugs related to these two events at a patient’s level were highest. In contrast, trigger-drug combinations based on clinical events related to a single drug class (e.g. vitamin K antagonist – supratherapeutic INR) or for which a dechallenge usually results in a direct improvement (e.g. diuretics – hypokalaemia) were more likely considered to be ADRs. The low PPV for triggers related to fall and delirium are in line with other findings. Carnevali et al. found a PPV for the triggers ‘fall’ and ‘emergence of confused state’ of 19% and 9%, respectively, in hospitalised adults [12]. In addition, a French retrospective cohort study in acutely admitted geriatric patients investigated the triggers ‘fall’ and ‘delirium’ from the Global Trigger Tool [11,25]. The mean number of suspected drugs per patient related to these clinical events was comparable with our results, as well as the PPV for delirium (21% vs 23%). However, the PPV for falls was much higher (54% vs. 28%), which is likely due to differences in the
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