48 Chapter 3 Methods We planned and reported this systematic review in accordance with the guideline for performing and reporting systematic reviews and meta-analyses (PRISMA) [21]. The protocol of this review is accessible on the PROSPERO website (registration number: CRD42017075575). Data sources and searches We searched for studies published between January 1990 and March 2017 in the following databases: PubMed (including MEDLINE), Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Cochrane Library, EMBASE and PsychInfo. Our search strategies comprised a combination of key search terms related to the ‘emergency department’, ‘elderly patients’, ‘(quasi) experimental studies’, and ED crowding measures. Supplement 1 provides a detailed listing of the search terms. References of the selected publications were manually checked to identify additional relevant studies that were missed in the database search. We also searched for additional relevant studies in the online archives/bibliographies of three high-impact journals in the field of emergency care (i.e., Annals of Emergency Medicine, Injury, Academic Emergency Medicine). Study selection Studies were included if they were: 1) published with an abstract in English language; 2) used an experimental or quasi-experimental design (i.e., RCT, non-RCT, CBA, time-series); 3) evaluated an intervention targeting older adults (≥ 60years of age); and 4) reported outcome effects on ambulance diversion, waiting time or count, patient leaves before treatment, ED occupancy level, time to consultation or ED room/bed placement, ED LOS, ED boarding time or count, ED return visits or ED staff stress level. We defined these ‘direct’ outcome measures based on the input-throughput-output model for ED crowding by Asplin et al. [22], the outcomes of a systematic review on ED crowding measures [23], expert opinions of circumstances that define ED crowding [24], and the consensus definition of crowding by Boyle et al. [2]. Table 1 shows the definitions for each type of measure. ED return visits and the ED staff stress level are considered to be important ‘indirect’ indicators for ED crowding [22, 23]. ED revisits may indirectly contribute to an increase of the ED input that is higher than the ED staff can handle. We also included intervention studies with a different aim (e.g., improving patient health outcomes following an ED visit) as long as we could identify that crowding reduction was a secondary study aim and if effectiveness was assessed on one or more of the above mentioned relevant outcome measures.
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