Mediating variables and covariates
| Construct | Specific measure | Source | Timing |
| Variables mediating patient engagement | |||
| Family member present | Observation: Was a family member present during clinic visit? | Audio recording | Clinic visit |
| MD endorsement of QPL | Observation: no endorsement, any endorsement, extensive endorsement | Audio recording | Clinic visit |
| QPL intervention penetrance | To patient: ‘Did you receive information in the mail to prepare you for your appointment with the surgeon?’ (yes/no/uncertain) | Patient | First questionnaire |
| Variables mediating psychological well-being | |||
| Surgical complications | National Surgical Quality Improvement Project definition (yes/no) | Chart review | Third questionnaire |
| Advance directive | New advance directive completed or prior advance directive documented in patient chart (yes/no) | Chart review | Third questionnaire |
| DNR | New DNR order placed or existing DNR order documented in patient chart (yes/no) | Chart review | Third questionnaire |
| Covariates | |||
| Comorbid illness | Charlson comorbidity score | Chart review | Clinic visit |
| Indication for surgery | Patient’s presenting problem | Chart review | Clinic visit |
| MD subspecialty | Oncology or vascular subspecialty | Surgeon | Clinic visit |
| MD practice intensity | Average number of operations surgeon performs monthly | Operative log | 3-month lead-in |
| Patient insurance status | Medicare, Medicare + Supplemental, Medicare+Medicaid, other | Chart review | Clinic visit |
| Patient demographics | Age, gender, race/ethnicity, educational attainment, health literacy | Patient | First questionnaire |
| MD demographics | Languages spoken, age, gender, race/ethnicity | Surgeon | Clinic visit |
DNR, do not resuscitate; MD, medical doctor; QPL, question prompt list.