Randomization methods in emergency setting trials: a descriptive review.
BACKGROUND
Quasi-randomization might expedite recruitment into trials in emergency care settings but may also introduce selection bias.


METHODS
We searched the Cochrane Library and other databases for systematic reviews of interventions in emergency medicine or urgent care settings. We assessed selection bias (baseline imbalances) in prognostic indicators between treatment groups in trials using true randomization versus trials using quasi-randomization.


RESULTS
Seven reviews contained 16 trials that used true randomization and 11 that used quasi-randomization. Baseline group imbalance was identified in four trials using true randomization (25%) and in two quasi-randomized trials (18%). Of the four truly randomized trials with imbalance, three concealed treatment allocation adequately. Clinical heterogeneity and poor reporting limited the assessment of trial recruitment outcomes.


CONCLUSIONS
We did not find strong or consistent evidence that quasi-randomization is associated with selection bias more often than true randomization. High risk of bias judgements for quasi-randomized emergency studies should therefore not be assumed in systematic reviews. Clinical heterogeneity across trials within reviews, coupled with limited availability of relevant trial accrual data, meant it was not possible to adequately explore the possibility that true randomization might result in slower trial recruitment rates, or the recruitment of less representative populations.
Centre for Reviews and Dissemination, University of York, York, YO10 5DD, UK.
Mark Stephen
MS
Corbett
Centre for Reviews and Dissemination, University of York, York, YO10 5DD, UK.
Thirimon
T
Moe-Byrne
Centre for Reviews and Dissemination, University of York, York, YO10 5DD, UK.
Sam
S
Oddie
Centre for Reviews and Dissemination, University of York, York, YO10 5DD, UK.
William
W
McGuire
D002986:Clinical Trials as Topic / Q000379:methods*; D016206:Databases, Bibliographic; D004635:Emergency Medicine / Q000379:methods*; D006801:Humans; D011379:Prognosis; D011897:Random Allocation; D012306:Risk; D015983:Selection Bias
baseline imbalance; emergency setting; quasi-randomization; randomization; selection bias