Appendix.

Reasons for Being Willing or Unwilling to Participate—Codebook

Code	Description
1. Benefit
1.1 Clinical benefit	Direct clinical benefit to self or other research participant or motivation to receive benefit on own behalf. Must include use of “my” or “me” or “I” or, for family member questions, be specifically about benefit to family member.
1.2 Curiosity	Self-knowledge, understanding, curiosity, knowledge, information, discovery, etc.
1.3 Others, society, general support for research	Altruism or general support for research (e.g., “I support research”) or results of research (e.g., “I want to help find the best treatment”). May reference helping family members, patients, the disease group, society, the future; improving treatments; finding the best drug; the word “help”; or help or benefit for “all.”
2. Risk
2.1 Safety	Safety, including both high risk and low or no risk (e.g., “doesn’t seem too risky”). Includes mention of or concerns about side effects.
2.2 Ability to switch medications, leave study	Ability, or perceived lack of ability, of self or doctor to switch or control medications or to leave the study.
2.3 No added risk beyond usual care	Additional risk from the study as compared to the general risk of clinical care.
2.4 Drug similarity	Similar or dissimilar effectiveness of all of the drugs in the study.
3. Trust or relationships
3.1 Physician or specific institution	Trust or mistrust in personal doctor or specific health care institution, belief that physician will manage or filter risk, or other reference to a clinical relationship. Includes wanting doctor to choose treatments for you.
3.2 General or institutional	Trust or mistrust (including extreme mistrust of system) in medical system, pharmaceuticals, researchers, research and development, drugs, results, method, etc.
4. Privacy or confidentiality
4.1 Privacy, confidentiality	Concerns about release or sharing of medical records, protected health information, data sharing, etc.
5. Informed consent
5.1 Active patient choice	Importance of patient’s having the choice to participate or not participate; personal control in consent process.
5.2 Transparency, information	Needs more information before deciding, wants to know that research is happening, wants to talk to someone else before deciding, etc.
6. Research
6.1 Randomization	Specific mention of positive or negative aspects of randomization as a methodological approach. May include sound or unsound research method, sample size, reduced bias, dangers of randomization, concerns about study design (must clearly address randomization, either by name or proxy [i.e., “gold standard”]).
6.2 Experimentation	Dislike of being “experimented” on, including mention of being a “guinea pig” or wanting control over health care or medications. Includes desire for personalized medicine as a reason not to participate.
6.3 Misunderstandings	Misunderstandings or confusions about research design or approach, specifically about placebos, testing new treatments, or other clear misunderstandings of ROMP or randomization.
7. Specific surrogate issues
7.1 Specific family-member issues	Explicit comments about differences when making decisions for a family member.
8. Specific “more serious” issues
8.1 Specific “more serious” issues	Explicit comments about differences in the context of a more serious condition.
9. Vague, irrelevant, other
9.1 Vague, irrelevant, other	Answers that are too vague to interpret, are irrelevant, or do not fit in any of the above categories. Apply only if nothing else fits.