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Table 4 Trial characteristics and information/consent procedures associated with differences in recruitment rates

From: Patient and clinician characteristics and preferences for increasing participation in placebo surgery trials: a scoping review of attributes to inform a discrete choice experiment

Potential attribute

Potential levels

References

Trial characteristics

Involvement of other clinicians

Surgeons only are involved in trial

Surgeons and physicians (e.g. neurosurgeon and neurologist) work collaboratively on trial

[45]

Patient involvement in the trial design

Trial has been designed based on patient perspectives

Trial has not had patient input into the design

[45]

If usual clinician is involved in trial

Usual clinician involved in trial

Different clinician involved in trial

[44]

Study arm allocation

Random allocation to study arm

Patient preference for study arm informs allocation

[33, 35, 39, 45]

Number and type of arms

Two – intervention and placebo

Three – intervention and placebo and treatment as usual/non-surgical (e.g. physiotherapy)

Three – intervention, placebo one [incision only], and placebo two [more invasive placebo surgery]

[34]

Randomisation ratio

1:1 placebo and active intervention

1:2 placebo and active intervention

[37]

Invasiveness of procedure

Invasive procedure (e.g. joint replacement)

Less invasive procedure (e.g. arthroscopy)

[34]

Invasiveness of placebo arm (including anaesthetic use)

Use of local/regional (with sedation) or general anaesthetic; and size of placebo incision (1-10 cm)

[34, 37]

Novelty of procedure (including availability outside the trial)

Procedure available outside of the trial

Procedure not available outside of the trial (novel)

[38, 48]

Crossover (availability of procedure if initially assigned to placebo)

Crossover not offered

Crossover offered if treatment shown to be effective

Crossover offered if desired by patient/ no improvement in symptoms

[41, 47]

Time to follow up and/or crossover

3 months

6 months

12 months

[33, 46, 48]

Financial costs of placebo procedure

Some cost to patient or health system

No cost to patient/health system

[37]

Information and consent procedures

Information about benefits (and likelihood of them)

No benefit to self – benefit to future patients and research/society

Possible benefit due to placebo effect – and benefit to future people/research/society

Possible benefit to you because of extra care during study visits

[33, 35, 44, 47]

Patient understanding about procedure and/or study details

Information about the randomisation process, the study arm(s), and their risks will be included in a standard information sheet for patients to read prior to consenting, with patient understanding not checked prior to consent.Information about the randomisation process, the study arm(s), and their risks will be included in an information sheet for patients to read, and then their understanding will be checked to ensure it is sufficient, prior to consenting.

[33, 41, 44, 47, 48]

Definition/terminology of placebo provided to patient

Use of sham vs placebo

Standard definition of placebo provided to patient

Placebo defined in patient-centred terms, with opportunity for questions

[36]

Comprehensive provision of information about all possible outcomes (including risks)

Patients are informed of possible outcomes and risks through standard discussion with surgeon prior to surgery

Patients are informed of possible outcomes and risks through a discussion with a research coordinator in addition to the standard discussion with surgeon prior to surgery

[39, 41, 46, 47]

Patient involvement in the consent process (e.g. writing consent in own hand, pre-agreed discussions, formal decision aids)

Standard information and consent form only

Information and consent forms accompanied by patient-centred discussion & formal decision aids

[36]

Surgeon involvement in the consent process (and format)

Surgeon involved in consent procedure

Surgeon not involved in consent procedure

[40]