Table 1 Potential mechanisms for introducing contamination bias within the FinCH trial

Detail of the intervention in the study documentation

FinCH trial study documentation outlined that the trial was evaluating the guide to action tool as a way of reducing falls for care homes residents. This documentation was discussed with care home managers to allow informed consent. Care home managers could review their existing falls management strategies and consider using the Guide to Action tool.

NHS clinicians delivering training package to care home staff

Falls specialists had access to the confidential training manual which formed the intervention. Clinicians could share this with other colleagues and care home staff considering this as best practice. Clinicians may have changed their behaviour and practice in their day to day clinical practice following their involvement in the FinCH trial. This might not be a conscious process.

Care home staff and managers move between homes

Care home staff that received the FinCH intervention training may move to a care home in the control arm and share their knowledge and skills. Conversely skills in the intervention homes could be lost following the training if care staff leave the home.

Publishing the development of the FinCH intervention and the feasibility trial

There has been a growing trend to publish trial protocols and development work to allow transparency in the research process [12]. The development of the Guide to Action tool was published by the research team and available to access online. The feasibility trial which established the trial procedures for the FinCH trial was also published and indicated a positive trend for the intervention.

Unable to blind therapists, care staff and care home residents to whether they are allocated to the intervention or control arm

Awareness of the group allocation could influence the response to subjective outcomes such as the quality of life measures completed by care home staff and residents.

Promotion of the study findings throughout the duration of the trial

Researchers are encouraged to engage with a wide range of stakeholders throughout the research process to maximise impact and to prepare for impact at the end of the study. The FinCH study was discussed in a wide variety of forums which included Enabling Research in Care Home (EnRICH) forums, TV news bulletins, and national conferences, care home communities of practice, commissioning groups and patient and public involvement groups.