Table 1 Changes made to trial recruitment strategies

De-coupling baseline assessment from allocation

Before recruitment began, including at pilot sites.

Participants assessed at baseline and allocated to FC or usual care group immediately afterwards.

Baseline assessment was conducted first and at a later date participants were remotely allocated to group.

The change allowed a greater run-in time within which to conduct recruitment. Formerly all recruitment had to occur over a short period of time immediately prior to groups starting.

Adjusting the allocation ratio from 1:1 to 2:1

After the pilot phase and before the second wave of recruitment.

Participating carers allocated in equal numbers across the two study groups, maximising statistical power.

Allocation ratio changed to 2:1 to FC and usual care and usual care only group. This design had less power, meaning that the overall sample size was increased.

A minimum number was required in the trial arm to reach the required group size of 12 foster carers. Changing the allocation ratio increased the likelihood of filling an intervention group where total numbers of participants at a site are restricted (i.e. a group of twelve could be formed with only 18 recruited participants in this approach, whereas, 24 would be required using a conventional 1:1 allocation).

Increase the period of time during which recruitment could be undertaken prior to groups running

After the pilot phase and before the second wave of recruitment.

During the pilot service providers and foster carers were approached approximately 6 weeks before the programme was due to start.

Approach time was increased to up to 4 months.

This allowed more time for service providers and Trial team to contact foster carers and for foster carers to respond. It also gave foster carers more notice of the possibility of attending the 12-week programme.

Improved participant materials

The materials used in the initial approach were revised between the pilot phase and before the second wave of recruitment.

The original documents were designed to fit the established processes for clinical trials

The first approach letter was amended after piloting to contain less text and to be more reader-friendly in the formatting. A reminder leaflet was introduced designed to be posted out to foster carers 1 week after the initial approach letter to remind them of the Fostering Changes Programme and the Confidence in Care evaluation.

The aim was to produce a simpler, briefer and more accessible document set. This may reduce a barrier to engaging initially with the study. The original documents were designed to fit the established processes for clinical trials where often participation risks can be higher (e.g. new drug treatments) and coercion possible so they are designed to protect patients. However in the present trial, we considered that some streamlining was possible without compromising individual’s ability to form an informed decision to participate.

Service providers’ selection of foster carers as well as all foster carers invited (change from all foster carers invited only)

After the pilot phase and before the second wave of recruitment.

For each site/wave, at least 50 foster carers were randomly selected by the trial team to receive a study pack from the LA. Foster carers registered their interest by responding to this.

In addition to the original process, service providers (LAs and Independent Fostering providers (IFP)) provided a subset of at least 18 eligible foster carers considered to be both interested in and eligible for the trial, and who had provided permission to be contacted by the trial team. Provider agencies selected participants to nominate based on locally determined criteria, including perceived needs of a foster carer, or apparent availability based on absence of competing commitments.

To better target eligible foster carers who might be interested.