Bastiaan Sallevelt

37 Performance of a trigger tool for detecting adverse drug reactions Screening for trigger-drug combinations For this study, the original ADR trigger tool from the Dutch guideline was explicated to reduce undesirable variations in interpretation when applied to EHRs. Modifications to the original ADR trigger tool were implemented at three levels prior to screening for trigger-drug combinations: 1. Triggers were specified if they represented clinical events which could be linked to different drug classes (e.g. specification of ‘disturbed serum glucose levels’ into ‘hypoglycaemia’ and ‘hyperglycaemia’). 2. Drug classes were further specified following the ATC classification system (e.g. specification of ‘diuretics’ into ‘thiazide diuretics’, ‘loop diuretics’ and ‘potassium sparing diuretics’). 3. Triggers were merged for clinical events that are difficult to distinguish and are used interchangeably in clinical practice. For instance, ‘fall’ was merged with the triggers ‘collapse / (orthostatic) hypotension / dizziness / syncope’. Especially in older patients, it is difficult to distinguish falls and syncope, because falls can be preceded by temporarily loss of consciousness due to cerebral hypoperfusion [19]. Modifications to the original ADR trigger tool were performed by two researchers with clinical experience in medical practice (WL, NN) and reviewed by a senior geriatrician/clinical pharmacologist (WK) with the intention to follow the original ADR trigger tool as closely as possible. Table 1 illustrates the original ADR trigger tool as published in the Dutch national geriatric guideline and the explicated ADR trigger tool used for this research. Two researchers (WL, NN) screened EHRs for the presence of trigger-drug combination. The trigger had to be either documented as a symptom, or listed by the physician as a diagnosis or health problem. Trigger-drug combinations were regarded as discrete events if the prescribed drugs were related to different drug classes according to the explicated trigger tool. However, if multiple drugs from the same drug class were linked to the same trigger, this was counted as one triggerdrug combination. For example, oxycodone and morphine linked to constipation were considered as one trigger-drug combination (constipation-opioids), while hydrochlorothiazide (thiazide diuretics) and furosemide (loop diuretics) linked to hyponatraemia were considered as two separate trigger-drug combinations. 2