Objective To evaluate the effectiveness of a rapid assessment zone (RAZ) to mitigate emergency department (ED) overcrowding.

Methods Electronic databases, controlled trial registries, conference proceedings, study references, experts in the field and correspondence with authors were used to identify potentially relevant studies. Intervention studies, in which a RAZ was used to influence length of stay, physician initial assessment and patients left without being seen, were included. Mean differences were calculated and reported with corresponding 95% CIs; individual statistics are presented as RR with associated 95% CI.

Results From 14 446 potentially relevant studies, four studies were included in the review. The quality of one study was appraised as moderately high; others were rated as weak. Two studies showed that a RAZ was associated with a reduction of 20 min (95% CI: −47.2 to 7.2) in the ED length of stay; in one non-randomised clinical trial (RCT), a 192 min reduction was reported (95% CI: −211.6 to −172.4). Physician initial assessment showed a reduction of 8.0 min; 95% CI: −13.8 to −2.2 in the RCT and a reduction of 33 min (95% CI: −42.3 to −23.6) and 18 min (95% CI: −22.2 to −13.8) respectively were found in two non-RCTs. There was a reduction in the risk of patient leaving without being seen (RCT: RR=0.93, 95% CI: 0.77 to 1.12; non-RCT: RR =0.68, 95% CI: 0.63 to 0.73).

Conclusions Although the results are consistent, and low acuity patients seem to benefit the most from a RAZ, the available evidence to support its implementation is limited.