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

Table 2 Patient characteristics, preferences, or values which influenced decisions to participate in placebo-controlled surgical trials

Potential attribute	Potential levels	References
Demographics
Gender	Male Female Other	[41]
Education	Did not finish high school High school/equivalent University level	[33, 39, 42]
Disease characteristics
Level of disability	No impact on functional activities Some impact on functional activities Severe impact on functional activities	[33]
Level of pain/functional status	No pain/functional impairment Some pain/functional impairment Severe pain/functional impairment	[33]
Stage of disease	Early (< 6 months) Medium term (6–24 months) Long term (> 24 months)	[46]
Perception of requiring immediate treatment (e.g. due to work or age)	Believe I require immediate treatment Do not believe I require immediate treatment	[33]
Individual characteristics
Perceptions of risk (associated with experiment/surgery)	Low High	[33, 39, 41, 42, 44, 46]
Individual tolerance of risk/risk appetite	Low High	[42, 46]
Altruism (as an individual characteristic)/able to see benefits to society	Altruistic Not altruistic	[37, 39, 40, 42, 44, 47]
Trial preferences
Perceived therapeutic benefit associated with trial participation	Therapeutic benefit No therapeutic benefit	[42, 43, 46]
Preference for a treatment arm (e.g. due to concerns about the effectiveness or adverse events)	Placebo arm Active treatment arm	[33, 35, 38, 41, 45, 46, 48]

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