Table 2

Longitudinal assessment of measures and constructs used to evaluate the efficacy of the PREPARE study

Construct	Measure	Number of items	English reliability/validity	Spanish reliability/validity	Screener	Baseline	1 week	3 months	6 months	12 months
	Eligibility screening
Cognitive impairment	SPMSQ 0–2=eligible 3–7 moderate impairment → Mini-Cog ≥8 severe impairment=ineligible	7	Sensitivity 86.2%, specificity 99.0%53	–	X
Cognitive impairment (participants scoring 3–7 errors on SPMSQ)	Mini-Cog (3-item recall as needed, if SPMSQ screen+for cognitive impairment) If recall ≥2 words=eligible	3	Sensitivity 76%, specificity 89%32	Sensitivity 99%, specificity 93%54	X
Vision	Ability to see words on a newspaper52	1		–	X
Health literacy screen for block randomisation (inadequate vs adequate)	‘How comfortable are you filling out medical forms by yourself?’ ‘Qué tan seguro(a) se siente al llenar formas usted solo(a)’	1	AUROC 0.80 (95% CI 0.67 to 0.93) for inadequate health literacy55	C-index=0.82, (0.77 to 0.87) for inadequate health literacy56	X
	Primary outcome
ACP documentation	ACP Engagement Survey:27 self-report: ACP documentation	1	ICC*=0.8727	–		X	X	X	X	X
ACP documentation	Chart review: ACP documentation					X				X
	Secondary outcomes
The full ACP Process	ACP Engagement Survey:27 behaviour change process measures (knowledge, contemplation, self-efficacy, readiness) Action measures: values identification and discussions	108	Process measures: Cronbach's α=0.94 (0.91 to 0.96), ICC=0.70 (0.54 to 0.82)27 Action measures: ICC*=0.87 (0.79 to 0.92)27	–		X	X	X	X	X
Communication quality	CAHPS (eg, Did this provider explain things in a way that was easy to understand?)	13	Comparative Fit Index=0.98, Tucker Lewis Index=0.98 Cronbach's α≥0.70 for constructs39	Cronbach's α ≥0.70 for constructs and associated with global physician rating40		X	X
Satisfaction with communication	(i.e, How satisfied are you that you could share your most important concerns with X/that X understood what was most important to you?)	8	–	–		X	X	X	X	X
Care consistent with current goals	Care consistent with goals: comparing 10-point scales of patient ratings about aggressiveness of care desired and care currently receiving	4	–	–		X			X	X
Satisfaction with decision-making	Decisional Conflict Scale	20	Test–retest coefficient=0.81 Cronbach's α: 0.78–0.92 for total scale41	Cronbach's α=0.8057			X	X	X	X
Depression	Patient Health Questionnaire-8	8	Scores ≥10 100% sensitive and 95% specific for major depressive disorder42 43	Scores ≥10 77% sensitive and 100% specific for major depressive disorder58		X	X	X	X	X
Anxiety	GAD-744	7	Cronbach's α=0.9244 ICC*=0.83	Cronbach's α=0.8845 ICC*=0.64		X	X	X	X	X
Barriers to ACP	Checkbox of common barriers and one open-ended question	13	Associated with ACP59	Associated with ACP59		X				X
Attitudes about ACP	Processes of change for ACP31	34	Responsive to an ACP intervention27	–		X	X	X	X	X
Implementation: acceptability	Acceptability and usability (1) Ease of use and understanding (2) Usefulness in decisions and discussions (3) Attitudes about norms or expectations	8 6 6	1 factor explained 81–85% of variance/scale. Kuder-Richardson >0.758	1 factor explained 81–85% of variance/scale. Kuder-Richardson >0.758		X
Implementation: feasibility	Feasibility (both arms) (eg, when and where to review ACP materials) Feasibility (PREPARE only) (eg, when/where to review and which materials did you use and would recommend to others)	7 34	–	–					X	X
Surrogate reports of patient engagement in ACP	Modified from the ACP Engagement Survey,29 knowledge of patient's wishes, and confidence making decisions, 5-point Likert	47	–	–						X
	Moderator variables
Health literacy assessment	s-TOFHLA scores 0–3660 Continuous and dichotomised to limited=0–22 and adequate=23–36	36	Cronbach's α=0.97 Correlation coefficient with other literacy tests >0.8060	Cronbach's α >0.9561		X
Patient–clinician language concordance	To clinicians: ‘How well do you speak Spanish?62 Fluently, very well (concordant) vs well, fair or poor’	1	AUROC† 94% (CI 90% to 98%)62	AUROC† 94% (CI 90% to 98%)62		X
Desired role in decision-making	CPS with clinicians and family63	2	Correlation between preferred and actual roles in decision-making12 64 65	Correlation between preferred and actual roles in decision-making66		X				X
US acculturation	Based on acculturation scale (USAS) ‘How many years have you lived in the USA?’	1	Cronbach's α=0.98 Associated with desire to know prognosis67	–		X
	Mediator variables‡
Baseline knowledge	Knowledge subscales of the ACP Engagement Survey27	6	Cronbach's α=0.84 (0.76–0.90), ICC*=0.70 (0.50–0.82)27	–		X
Baseline self-efficacy	Self-efficacy subscales of the ACP Engagement Survey27	6	Cronbach's α=0.83 (0.75–0.89), ICC*=0.60 (0.41–0.76)27	–		X
Baseline readiness	Readiness subscales of the ACP Engagement Survey27	10	Cronbach's α=0.92 (0.88–0.95), ICC*=0.60 (0.53–0.81)27	–		X
Baseline ACP barriers	Checkbox of 13 comment barriers59	13	Associated with ACP59	–		X
Baseline attitudes about ACP	Processes of change for ACP31	34	Responsive to ACP intervention27	–		X
	Potential confounders
Functional status	ADL and IADL measure (13-item)68 69	13	Morbidity/mortality correlation68 69	Cronbach's α=0.9470		X
Self-rated health status	How would you rate your health? (5-point Likert)71 72	1	Cronbach α=0.8072	–	X
Self-rated quality of life	How would you rate your quality of life? (5-point Likert)72 73	1	Test–retest coefficient=0.8173	–	X
Comorbid illness	Charlson comorbidity score74 75 Elixhauser comorbidity score76 77	0	Mortality c-stat:78 Charlson=0.704 Elixhauser=0.793	– –		X
Prior ACP experience	Prior ACP experiences (eg, (Ever had to make life-threatening medical decisions?)8	5		–		X
Social support	mMOS-SS79	11	Cronbach's α=0.88–0.9379	Cronbach's α=0.9480		X
Major life changes	For example, ‘In the past 12 months, have you or someone close to you been faced with a serious medical problem or diagnosis?’	4	–	–						X
	Demographic information
Demographic information	Age, gender, race/ethnicity,81 income, marital status and education				X	X
Religion/spirituality	Self-reported extent of how spiritual/religious (five-point Likert) and role play in decision-making82	4	Spirituality associated with quality of life. Religiosity associated with wanting all measures to extend life82	–		X
Finances	‘In general, how do your finances usually work out at the end of the month?’	1	Associated with functional impairment and comorbidity83	–		X
Socioeconomic status and social standing	Social standing ladder (ie, place an ‘x’ where you think you stand relative to other people in society)	1	Associated with functional decline84	–		X

If a validated Spanish version of a survey was not available, we translated the English version into Spanish.
*ICC=intraclass correlation.
†Area under the receiver operating curve (AUROC).
‡While mediator variables, measured at baseline, may explain how or why a particular effect or relationship occurs, these variables may also be affected by the intervention and are therefore also considered secondary outcome variables measured over time (ie, knowledge, self-efficacy and readiness, as well as barriers and attitudes).
ACP, advance care planning; ADL, activities of daily living; CAHPS, Consumer Assessment of Healthcare Providers and Systems; CPS, Control Preference Scale; GAD-7, Generalized Anxiety Disorder 7-Item Scale; IADL, instrumental activities of daily living; mMOS-SS, modified Medical Outcomes Study Social Support; SPMSQ, Short Portable Mental Status Questionnaire; s-TOFHLA, Short form Test of Functional Health Literacy in Adults; USAS, US Acculturation Scale.