Don't Throw Your Heart Away: Medical Student Study 2
Phase: NA
Conditions: Cardiac Transplant Disorder
Sponsor: Carnegie Mellon University

Don’t Throw Your Heart Away: Medical Student Study 2 
NCT04176796 
Last IRB Approval Check-in: January 10 2024 
 
 

Study Information 
Title 
Heart Transplant Tradeoff Study: 2-Condition Medical Student Study 
Authors 
  
Description 
Publicly available outcome assessments for transplant programs do not make salient that some 
programs tend to reject many of the hearts they are offered, whereas other programs accept a 
broader range of donor offers. We use empirical studies to test whether transplant center 
performance data (i.e. transplant and waitlist outcome statistics) that reflect center donor 
acceptance rates influence laypersons to evaluate centers with high organ decline rates less 
favorably than centers with low organ decline rates. 125 medical student participants will be 
recruited from University of Pittsburgh School of Medicine and randomized to one of two 
different information presentation conditions. Participants will be given an introduction to the 
donor organ match process, then asked to view the table of transplant outcomes 
corresponding to the condition they were randomized to. Each participant is asked to choose 
which hospital is higher performing upon being given a choice between two hospitals: one 
hospital with an non-selective, "accepting" strategy (takes all donor heart offers), and one 
hospital with a more selective, "cherrypicking" strategy (tends to reject donor offers that are 
less than “excellent” quality). In order to identify the decision process that underlies this choice 
pattern, we will examine a putative mediator. Specifically, participants will be asked to rate the 
extent to which they considered patients' chances of getting an excellent heart, avoiding a less-
than-optimal heart, and getting any type of heart when making their choice between the two 
hospitals. 
 
Hypotheses 
Hypothesis 1 When centers must present information on their transplant success rate only, lay 
evaluators will respond by selecting hospitals with higher transplant success. However, if 
information presented on transplant outcomes is stratified by the number and quality of 
donors used, or displayed in addition to total survival rates, then participants will respond by 
selecting hospitals with higher organ acceptance rates rather than the hospital with higher 
transplant outcomes. Hypothesis 1a: Preference for the non-selective transplant center will be 
lower (than for the selective center) in condition 1 (baseline: combined transplant survival only), 
compared to condition 2. That is, a higher proportion of participants will prefer the non-
selective center over the selective center in condition 2, relative to condition 1. Hypothesis 1b: 
There will be a main effect of viewing stratified transplant survival, such that in condition 2 
(when transplant survival is stratified by number and quality of donor hearts accepted at each 
center) participants will prefer the non-selective center over the selective center, relative to the 
baseline condition 1. Hypothesis 2 There will be an indirect (mediated) effect of providing 
participants with information about stratified transplant survival; this information will lead to 
higher preference for the non-selective hospital by leading participants to think that the 
chances a patient at either hospital will "get a heart at all" is a more important factor in their 
decision (about which hospital is a better choice for patients). Specifically ratings of importance 

(0-100 continuous scale) for the item "likelihood of getting any heart” will differ across 
conditions 1-2 such that “getting any heart” will be rated lower in condition 1 than in condition 
2. Furthermore, ratings on this item will be associated with choice, such that higher ratings will 
be associated with choice of the non-selective center.  
Design Plan 
Study type 
Experiment - A researcher randomly assigns treatments to study subjects, this includes field or lab 
experiments. This is also known as an intervention experiment and includes randomized controlled trials. 
Blinding 
• 
For studies that involve human subjects, they will not know the treatment group to which 
they have been assigned. 
Is there any additional blinding in this study? 
n/a 
Study design 
We have a between-subjects design in which participants are randomized to one of two 
information conditions (independent variable). In each condition, they make a choice 
(dependent variable) between two hospitals (one with a non-selective donor acceptance 
strategy, and another with a more selective donor acceptance strategy). Independent variables: 
(1) Condition 1 ("baseline" condition): view only combined transplant survival (e.g. transplant 
survival rate not stratified by number and quality of donor hearts accepted at each center) (2) 
Condition 2: view only stratified transplant survival (e.g. transplant survival rate stratified into 
patients who received excellent donor organs and patients who received less than optimal 
donor organs) These two conditions will be analyzed for our primary analysis: a 1x2 design with 
2 arms (control arm or combined transplant survival, and experimental arm or stratified 
transplant survival).  
 
Randomization 
We will use simple randomization, where each participant will be randomly assigned to one of 
the two predetermined conditions. The Qualtrics randomizer function will be used for 
randomization into a condition. 
Sampling Plan 
Existing Data 
Registration prior to creation of data 
Explanation of existing data 
n/a 
Data collection procedures 
125 medical student participants will be recruited from University of Pittsburgh Medical School. 
Participants will be recruited via (1) an email to the Class of 2020, Class of 2021, and Class of 
2022 listserv pages, and (2) a Facebook post on the class Facebook pages for the classes 

corresponding to the listservs described. Inclusion criteria: Participants who are 2nd, 3rd, or 4th 
year medical students at University of Pittsburgh School of Medicine will be asked to participate 
if they confirm the following inclusion criteria in the consent form. (1) 18 years of age or older 
(2) must read and understand the information in the consent form (3) must want to participate 
in the research and continue with the survey (4) must live in United States Payment: 
Participants will be entered into a lottery for completing the survey and providing an email (the 
latter is optional). The lottery gives a 1 in 60 chance of winning a $50 Amazon gift card and a 1 
in 10 chance of winning a $5 Starbucks gift card.  
 
Sample size 
Our target sample size is 125 participants. We expect that this will amount to approximately 60 
participants per condition, although due to the nature of the randomization technique used 
(Qualtrics randomizer function), we may end up with slightly more or slightly less than 60 per 
condition.  
Sample size rationale 
A sample size of 61 per group was calculated to yield at least 90% power to detect a 30 
percentage point difference between conditions (e.g., 35% vs. 65%) with α=0.05 (GPower 
3.1.9.4). 
 
Stopping rule 
We will stop data collection after the first of the following three scenarios is achieved: (1) 125 
responses collected (2) January 20, 2020 and at least 100 responses collected (3) March 31, 2020 
Variables 
Manipulated variables 
We will manipulate how transplant center outcomes are presented. Different components of 
the same outcome statistics for two transplant centers will be varied over two different 
conditions. (1) Condition 1 ("baseline" condition): view only combined transplant survival (e.g. 
transplant survival rate not stratified by number and quality of donor hearts accepted at each 
center) (2) Condition 2: view only stratified transplant survival (e.g. transplant survival rate 
stratified into patients who received excellent donor organs and patients who received less 
than optimal donor organs) The two conditions will be included in our main analysis, which is a 
2x1 design with 1 factors (transplant survival) and 2 levels per factor: "combined": reference 
level, in which transplant survival rate is not stratified by number and quality of donor hearts 
accepted at each center "stratified": transplant survival rate stratified into patients who 
received excellent donor organs and patients who received less than optimal donor organs 
 
Measured variables 
The outcome variable will be a binary choice between two hospitals: one with a selective donor-
heart acceptance strategy and one with a non-selective donor heart acceptance strategy. 
Participants will respond to the question "Which Hospital do you consider to be higher 
performing? Please click on one of the two tables below to indicate which hospital is the better 

choice." Participants will choose been two outcome tables featuring the selective and non-
selective hospital (counterbalanced, such that each of the two choices is equally likely to be 
presented at top of the choice scenario in each condition). The number of participants that 
choose each hospital will be the measured outcome variable used in analyses. On the next 
page of the survey, participants will respond to three mediator questions: "There are many 
reasons why one transplant hospital might outperform another. Which reasons were most 
important in your decision? Please move the slider to indicate how much you considered each 
of the reasons below (0=reason was not important, 100=reason was extremely important)." 
Participants will then move a slider bar (0-100) to indicate the importance of the following three 
items: (1) Patients were more likely to receive an excellent donor heart at the hospital I picked. 
(2) Patients were less likely to receive a marginal donor heart at the hospital I picked. (3) 
Patients were more likely to receive any kind of heart at the hospital I picked. The third item 
(more likely to receive any kind of heart) will be the only variable that is included in the planned 
mediation analysis. 
 
Indices 
No response 
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Analysis Plan 
Statistical models 
To test Hypotheses 1a /1b, we will use a binomial logistic regression analysis. The categorical 
independent variable will be 'stratified transplant survival'; the dependent variable is binary 
choice of hospital. -We will test whether the main effect of "stratified transplant survival" is 
statistically significant and in the predicted positive direction. To test Hypothesis 2, we will 
conduct a causal mediation analysis to determine whether information display had a 
mechanistic effect on hospital choice through our proposed mediator. We will estimate the 
average causal mediation effect (ACME), average direct effect (ADE), and the total effect. The 
ACME is the effect of the experimental information display condition (stratified) on the outcome 
of hospital choice (selective vs. non-selective), mediated through the hypothesized mediator 
(the importance of "getting any heart" at each hospital when considering the choice). The 
remaining effect of information display on hospital choice that is not mediated through the 
hypothesized mediator represents the ADE. The entire effect of the information display on 
hospital choice via the hypothesized mediator and the direct effect is the total effect. The 
proportion of the total effect that is accounted for by the ACME is called the proportion 
mediated.{Imai, 2010}. Analyses will be performed using the “mediation” package in R (The R 
Foundation for Statistical Computing).{Tingley, 2014}. We will generate 95% confidence intervals 
by using 1000 bootstrap simulations. The unstandardized point estimate of the ACME and its 
95% confidence intervals will be interpreted. -A significant ACME for "stratified transplant 
survival" would suggest that stratifying transplant survival by number and quality of accepted 
donors works via increasing the perceived importance of "getting any heart" to increase 
preference for the non-selective hospital. If the ACME is non-significant, we will identify where 
the causal path breaks down.  

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Transformations 
Logistic regression analysis: The categorical predictor "transplant survival stratified" will be 
dummy coded (0=not stratified, 1=stratified), with 'stratified' as the reference category. The 
outcome variable "choice of hospital" will be dummy-coded (0=selective hospital, 1=non-
selective hospital). The reference category is 'selective hospital'. Mediation analysis: The 
categorical predictor "transplant survival stratified" will be dummy coded (0=not stratified, 
1=stratified), with 'stratified' as the reference category. The continuous mediator variable "get 
any heart" will be mean-centered for each analysis. The outcome variable "choice of hospital" 
will be dummy-coded (0=selective hospital, 1=non-selective hospital). The reference category is 
'selective hospital'. 
Inference criteria 
We will use the standard p=0.05 criteria for determining if the results are significantly different 
from those expected if the null hypothesis were correct. 
Data exclusion 
Two attention checks will be used. The data will be analyzed with all participants, and with only 
the participants who pass both of these attention checks.  
Missing data 
If a participant does not complete the entire survey, they will not be included in the analysis. 
Exploratory analysis 
No response 
Other 
Other 
No response