Bastiaan Sallevelt

35 Performance of a trigger tool for detecting adverse drug reactions Introduction Older people are more susceptible to adverse drug reactions (ADRs) due to comorbidity, polypharmacy, frailty and age-related changes in pharmacokinetics and -dynamics [1–3]. It is estimated that ADRs account for approximately 10% of all acute hospital admissions in older people [4,5]. Despite this high frequency of hospital admissions due to ADRs in older people, studies show that drug related problems, including ADRs, are missed or misdiagnosed by physicians at the emergency department in approximately 40–60% of the cases [6–8]. Consequently, methods to improve detection and management of ADRs are needed [9]. Polypharmacy is one of the most important risk factors for developing ADRs [10]. It is known that a few commonly used drug classes account for the majority of ADRs leading to or developed during hospital admission in the older population [1,3–5,9]. A meta-analysis found that ADR-induced hospital admissions were most frequently related to nonsteroidal anti-inflammatory drugs (NSAIDs) causing upper gastrointestinal bleeding, hypertension, coronary events and renal failure. Other ADRs frequently associated with hospitalisations were hypotension due to betablockers, angiotensin-converting enzyme (ACE) inhibitors or calcium antagonists; hypoglycaemia due to oral antidiabetics; bleeding due to oral anticoagulants and bradycardia due to digoxin [4]. The use of a trigger tool focusing on clinical events and drugs frequently associated with such events may therefore reduce the problem of undiagnosed ADRs. Several trigger tools have been developed to increase ADR detection in patient care. The most commonly known trigger tool is the Global Trigger Tool [11,12], but other trigger tools targeting ADR detection, especially in the older population, have been investigated [13–15]. These trigger tools have in common that they comprise lists of either clinical events (e.g. ‘hypotension’), the use of specific drugs or antidotes (e.g. ‘naloxone use’) or abnormal drug or laboratory values (e.g. ‘potassium <2.9 mEq/L’, ‘digoxin level >2 ng/L’). However, the positive predictive values (PPVs) of such triggers were generally low, which impedes their implementation in clinical practice to improve ADR detection in older people [12–15]. Consequently, no ‘gold standard’ to improve ADR detection in older people has yet been established. The performance of trigger tools in detecting clinically relevant ADRs in older people may be improved by combining clinical events with drug classes frequently associated with such events. The Dutch national geriatric guideline on ‘polypharmacy optimisation in hospitalised older people’ provides a consensus-based trigger tool listing combinations of certain clinical events and associated drugs that frequently result in ADR-related hospital admissions in older people [16]. The guideline strongly recommends screening each patient aged 70 years and older with polypharmacy (≥5 2