Cluster randomized trials (CRTs) is the concept of grouping individuals for randomization into a treatment or control group. The design is increasingly becoming more common when randomizing large groups. It also reduces bias as there are less decision making required from clinicians or nurses.

A study to compare the effects of a patients head position after suffering a stroke (HeadPost) is currently ongoing and has implemented the CRT design. The study has been designed to resolve the uncertainty of which head position is best suited for patients who have suffered acute stroke; and provide evidence to support a policy regarding the ideal head position in the acute phase of stroke. HeadPost is the largest nursing care trial to be conducted with the target sample size of over 19,000 patients.

Although CRTs may seem complicated to treat/randomize, the nurses participating in HeadPost were able to minimize errors that would disrupt the study by applying simple, yet effective procedures on-site.

Previously, a HeadPost pilot study was conducted which clustered patients by months. Nurses participating in the pilot study were required to memorize the month and position their patients were positioned in. This was difficult to manage, so in the current full-scale HeadPost study, the cluster was changed to sites rather than months – with an objective to reach 120 sites around the world for the trial to be effective.

The crossover from one head position to the next was at 50 ischemic stroke patients, and this had to be managed tightly. Once 48 ischemic stroke patients were achieved, the project team and sites would receive an alert to prepare for crossover. With the implementation of this new design, the patients head position remains the same until the next crossover – thus all patients had the same head position at any one time. Nurses only had to look at another patient in the ward to determine which head position was current. Nurses would also simplify the crossover procedure by placing posters above the patient’s bed-heads to assist them in identifying the patients current head position for the trial. At this stage the crossover process has worked fluently with minimal late crossovers (approximately 3 out of 1900).

One of the challenges in HeadPost was the consecutive recruitment in the trial. Typical CRTs have washout periods to minimize contamination between clusters; however, in HeadPost, subjects were recruited consecutively so that the momentum for recruitment was not lost. This resulted in an average recruitment rate of 7 subjects/site/month. Approximately 50% of patients in HeadPost begun their head positioning in the emergency department. To alleviate this, subjects positioned in the emergency department were accepted into the study, resulting in a larger and more diverse population of the included disease group. Strong inter-departmental collaboration was required between wards and emergency departments to effectively manage this challenge.

The study protocol also allowed nurses to move patients and place them out of position for 30 mins, three times within 24 hours; then reverted back to the position they were in based on the poster above the patient’s bed-head. This practical solution in the study design allowed for day to day activities in the ward to still be completed as they normally would.

The team on-sites were provided with extensive training to familiarise themselves with the CRT process. The study team and sites were provided with many training materials and events, such as multiple Investigator meetings, videos, face-to-face meetings with study team, and interaction with local leaders or champions. Feedback groups were also created from nurses and clinicians so that gaps in training were identified and actioned.


CRTS are increasingly being utilised in health services and primary care research. Although the design is quite novel, pragmatic solutions in the study design and study conduct process allowed site personnel to implement the study successfully. As CRTs are often large trials in practical settings, such easy-to-implement solutions are key. The posters placed above the patients head in HeadPost is an example of simple, yet effective method that made the crossover process seamless.