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The CLOQS trial protocol: a cluster-randomized trial evaluating a simple, low-cost intervention to reduce treatment times in acute stroke


  • Conflict of interest: The authors declare no potential conflict of interest.
  • Funding: This trial is funded by the Sunnybrook Academic Health Sciences Centre ‘Alternate Funding Plan Innovation Fund’. A research grant in aid has been received from Hoffmann-La Roche Limited to support city wide trial expansion.



In acute stroke, time is brain: faster tissue plasminogen activator treatment improves patient outcomes. Published guidelines for door-to-scanner time are <25 minutes, and for door-to-needle time <60 minutes. These benchmarks are rarely met. Paradoxically, the earlier a stroke patient arrives to hospital, the longer treatment takes. There is an urgent need to shift focus away from the 4·5 hour time window, towards treatment times <60 minutes.


The objective of the Countdown Lights to Optimize Quality in acute Stroke (CLOQS) trial is to determine whether a simple, low-cost organizational behavior intervention, a large, red stopwatch timer attached to the stretcher upon arrival, will decrease door-to-scanner and door-to-needle treatment times for tissue plasminogen activator-treated patients.


A multicenter, time-clustered randomized control trial. The stopwatch timers will be used in Emergency Departments for all acute stroke patients across the University of Toronto Stroke Program. The order of intervention (ON) and control (OFF) blocks will be randomly assigned in a 1:1 ratio over an 18 month period. Blocks will be weighted in a 2:1 ratio of ON/OFF using a permuted block design (ON blocks last two weeks; OFF blocks last one week).

Study Outcomes

The primary end-point is percentage of patients achieving best-practice guidelines (door-to-needle treatment time <60 minutes). Secondary end-points are median time intervals for 1) door-to-scanner and 2) door-to-needle times during ON versus OFF blocks. Tertiary end-points are in-hospital mortality and time series analysis to determine change in treatment times from prior to study onset through study completion.