Enhanced Enrollment in the National Diabetes Prevention Program for the Underserved: a Randomized Control Trial
Phase: NA
Conditions: Prediabetic State, Obesity, Gestational Diabetes
Sponsor: Denver Health and Hospital Authority

COMIRB Protocol 
 
Protocol #: 18-2542  
 
Project title: Enhanced enrollment in the National Diabetes Prevention Program for the underserved: a 
randomized control trial  
 
 
Principal Investigator: Natalie Ritchie, PhD 
Version Date: 7/21/20 
 
I. Hypotheses and Specific Aims 
Type 2 diabetes affects 9.4% of US adults with higher rates among racial/ethnic minorities and individuals of 
low socioeconomic status.1 The Diabetes Prevention Program was a successful clinical trial demonstrating that 
intensive lifestyle support for weight loss reduced diabetes incidence by 58%.2 The intervention was translated 
into the National Diabetes Prevention Program (NDPP) and disseminated by the Centers for Disease Control 
and Prevention as a yearlong group-based program since 2012.3 Despite successes, a 2017 report found that 
retention in the NDPP is problematic and leads to suboptimal weight loss.4 Attendance and weight loss are 
especially low among Hispanic, non-Hispanic black, and low-income non-Hispanic white participants.4-6 
Strategies to improve NDPP outcomes among these disadvantaged populations are urgently needed.  
We previously developed and pilot-tested a novel NDPP enrollment protocol, the Pre-NDPP, that 
provides a “pre-session” with three components: 1) education about diabetes risks, 2) motivational interviewing 
(MI) to encourage participation in the NDPP and, 3) problem-solving of barriers to engagement.7 In a 
longitudinal cohort study among a diverse and underserved population, outcomes of 75 Pre-NDPP participants 
who enrolled in the NDPP were compared to 1,065 prior participants using ANCOVA and multivariable logistic 
regression. Pre-session participants stayed in the NDPP 99.8 days longer (p<.001) and attended 14.3% more 
sessions (p<.001) on average than those without a pre-session. Pre-session participants lost 2.0% more 
weight (p<.001) and were 3.5 times more likely to achieve the 5% weight loss target (p<.001). Sensitivity 
analyses were consistent. These findings suggest pre-sessions may be a promising and pragmatic strategy to 
improve NDPP retention and effectiveness and mitigate disparities in program outcomes. We now propose a 
large, pragmatic, intent-to-treat randomized controlled trial (RCT) to test effects of the Pre-NDPP enhancement 
on NDPP attendance and weight loss among a diverse, predominately underserved population with elevated 
diabetes risks. A RCT is necessary to determine whether Pre-NDPP reliably improves NDPP outcomes. Power 
calculations based on pilot results indicate that a RCT of 500 participants will allow for a robust test of Pre-
NDPP on the primary outcome of percent weight loss.  
Aim 1: To evaluate clinical effectiveness of the Pre-NDPP intervention. We will recruit 500 diverse, 
predominately low-income patients with elevated diabetes risks (e.g., prediabetes) in the Denver Health safety 
net healthcare system. We will conduct a RCT to compare NDPP attendance and weight loss outcomes 
between participants randomized to receive the Pre-NDPP enhancement vs. direct enrollment into the NDPP 
(usual care). Pre-sessions, led by trained Lifestyle Coaches, will focus on providing information on diabetes 
risks and locally available resources to reduce risk, including the NDPP. Coaches will use MI techniques to 
help participants identify an actionable plan to reduce risk, such as attending NDPP sessions, and guide 
participants in identifying barriers and possible solutions that would enable participation. Pre-NDPP 
participants and usual care NDPP participants will be assigned to separate NDPP classes to prevent 
contamination of Pre-NDPP effects. We will collect data on demographics, NDPP outcomes (primary outcome 
is percent weight loss), potential mediators, implementation factors, and cost. We hypothesize that Pre-NDPP 
participants will have greater engagement and weight loss compared to those who are directly enrolled into the 
program (usual care).  
Aim 2: To examine mediators and moderators of Pre-NDPP outcomes. We will explore potential 
mediators (perceived risk for developing diabetes and self-efficacy and readiness for weight control) and key 
sociodemographic variables (race/ethnicity and income level) as potential moderators of intervention 
effectiveness that are important to understand for future uptake by stakeholders. We hypothesize that a) Pre-
NDPP will increase perceived risk, self-efficacy, and readiness, which will mediate relationships between pre-
session treatment and NDPP outcomes, and that b) race/ethnicity and income level will moderate Pre-NDPP 
effectiveness. 
Aim 3: To evaluate the implementation factors of Pre-NDPP. In preparation for potential future 
dissemination, we will evaluate implementation factors following a RE-AIM framework8, including a qualitative 
evaluation of pre-sessions from a Lifestyle Coach, clinic provider/personnel, and patient perspective. We will 

also evaluate the cost of adding pre-sessions to NDPP delivery and projected return on investment (ROI). We 
hypothesize that Pre-NDPP will be implementable and yield sufficient projected ROI to justify its cost.  
Our future goal is to disseminate a scalable, evidence-based strategy to improve success of the NDPP 
and reduce disparities in NDPP effectiveness. If found to be effective, this approach can be disseminated to all 
NDPP providers, including more than 1,700 suppliers9, and may be supported by current NDPP payers such 
as Medicare, commercial insurers, and employer groups.10-12 Thus, this approach has potential for high impact 
on the burden of type 2 diabetes and related health disparities across the country.  
 
II. Background and Significance 
Diabetes in the US. Type 2 diabetes (T2D) affects 9.4% of US adults, imposing a significant public health and 
economic burden.13,14 Diabetes prevalence is higher among Hispanics (12.1%) and non-Hispanic blacks 
(NHBs; 12.7%) than among non-Hispanic whites (NHWs; 7.4%).13 Low socioeconomic status is also 
associated with higher prevalence.1,15 An additional 33.9% of US adults are estimated to have prediabetes,13 
an intermediary condition of elevated blood glucose that is likely to progress to diabetes without intervention. 
Individuals with impaired fasting glucose experience annual rates of diabetes incidence of 5.6%.16 Yet only 1 in 
10 individuals with prediabetes are estimated to be aware of their risk.13 Interventions to prevent T2D have 
been developed and widely disseminated by the Centers for Disease Control and Prevention (CDC), but gaps 
in participation and effectiveness need to be addressed to improve population health and diabetes-related 
disparities. 
The National Diabetes Prevention Program: Strengths and areas for improvement. The Diabetes 
Prevention Program clinical trial was highly successful in demonstrating that intensive lifestyle support for 
weight loss reduced diabetes incidence by 58% over an average of three years.2 Longitudinal follow up 
showed that lifestyle intervention benefits can persist up to 15 years.17,18 The National Diabetes Prevention 
Program (NDPP), a lower cost translation of the program, has achieved scalability with over 1,700 suppliers9 
and 106,000 participants served19 since dissemination began in 2012. Successful outcomes have led to health 
policy change, including reimbursement from payers like Medicare, which began coverage of the NDPP as of 
April 2018.10 The NDPP promotes ≥5% weight loss through diet and physical activity, with 16 weekly to 
biweekly sessions, plus ≥6 monthly sessions, over 12 months. Greater duration and intensity of participation 
are associated with better weight loss.4 Incrementally greater weight loss is important to prevent diabetes as 
each kilogram of weight loss has been associated with a 16% reduction in incidence.20 Delivering the NDPP in 
healthcare settings also appears optimal given: 1) access to a provider referral network bolsters initial 
enrollment of at-risk patients,21 2) greater weight loss is achieved when delivered in healthcare vs. community 
sites,22 and 3) clinic settings have existing infrastructure for insurer reimbursement. At the same, the CDC has 
approved of remotely-conducted NDPP sessions (or combined in-person and remotely-conducted classes) 
since 2018, which has shown promise for improving participant retention with its more flexible approach,23  and 
is expressly encouraged in the era of COVID-19.  
The NDPP has numerous strengths, yet limitations include suboptimal engagement and weight loss 
rates,4,24 that are further disparate among racial/ethnic minorities and low-income NHW participants.4,5,25 
Specifically, a national evaluation showed that Hispanic and NHB participants have similar weight loss 
(medians of 2.5% and 2.2%, respectively among participants with ≥2 recorded weights), but less than the 
weight loss achieved by NHW participants (median=4.1%).4 Low-income NHWs have also been shown to 
achieve less than half as much weight loss as higher-income NHWs.25 It is important to develop cost-effective 
strategies to improve NDPP attendance and weight loss among these disadvantaged populations.  
Theoretical model to improve NDPP 
effectiveness. The Health Belief Model26 
(Fig. 1) is a widely used theory of health 
behavior change that offers insights toward 
developing strategies to improve NDPP 
outcomes. The model posits that perceived 
risk, benefits of, barriers to and cues to 
action, and self-efficacy, are factors 
determining health behavior that can be 
addressed in targeted interventions. Based on the Health Belief Model, interventions to prevent T2D must 
focus on increasing risk awareness and exploring pros/cons of available interventions, including the NDPP. 
Studies have demonstrated that increasing awareness of diabetes risks may lead to risk-reduction behavior. 
For example, being told of having prediabetes by a healthcare professional was associated with self-reported 
Fig. 1: Health Belief Model, adapted from Champion & Skinner, 2008

weight loss efforts among 52-68% of at-risk individuals in national surveys.27,28 Motivational interviewing (MI)29 
may also facilitate action-oriented decision-making about NDPP engagement with its empathic coaching style 
and evocation of “change talk”. Multiple systematic reviews support the proposed use of MI in a brief, group-
based intervention to improve NDPP effectiveness: A broad review found MI was effective in brief doses as low 
as 10 minutes (although greater duration appears beneficial), when delivered in group settings (3 of 3 studies 
showed positive effects), and to support weight loss behavior and outcomes (8 of 10 had positive results).30 
More specifically, a 2001 review found brief MI was particularly effective at enhancing engagement in weight 
loss interventions.31 A more recent 2014 review noted overall positive results of MI for weight management.32 
Good evidence was also found for MI as a necessary component for interventions to prevent diabetes.33 
Pre-NDPP: A theory-driven, pragmatic solution to improve NDPP effectiveness. Implementing a “pre-
session” prior to NDPP enrollment (Pre-NDPP) may be a pragmatic strategy for delivering a theory-driven 
educational and motivational intervention to bolster the NDPP’s effectiveness. Pre-sessions have been 
recommended to increase NDPP engagement,34 without supporting evidence prior to our recently published 
pilot study.35 In brief, we developed and pilot-tested a novel strategy to improve attendance and weight loss in 
the NDPP in which diverse and predominately underserved participants attended a pre-session that provided 
1) education about diabetes risks, 2) brief MI to participate in the NDPP, and 3) problem-solving of barriers to 
participation, based on well-known findings that sufficient engagement in the NDPP generally yields good 
weight loss4,22. Our pre-session strategy pilot study was highly successful (see Preliminary Data below) but 
results require confirmation from an adequately powered randomized trial to justify dissemination efforts. 
Research gap and scientific rationale of proposed study. NDPP outcomes are suboptimal, especially for 
disadvantaged populations, which risks further widening of health disparities if not addressed. Pilot data show 
feasibility and promising results of Pre-NDPP among diverse, underserved patients with elevated diabetes 
risks, but are limited by small sample size of the intervention group and no concurrently randomized control 
group. To address the research gap, we propose a randomized controlled trial (RCT) to compare NDPP 
attendance and weight loss among diverse, predominately underserved participants who receive Pre-NDPP 
vs. direct enrollment into NDPP (usual care). The primary hypothesis generated by pilot data and above-cited 
literature is that pre-sessions improve NDPP engagement and weight loss, which will be confirmed if those 
randomized to Pre-NDPP have better outcomes than those receiving usual care NDPP. A secondary analysis 
will examine whether only Pre-NDPP participants who go on to NDPP benefit (vs. no benefit for those declining 
NDPP), which would suggest that pre-sessions screen for individuals likely to participate adequately, and thus 
benefit from, the NDPP. Screening via pre-sessions may yet be an efficient population health strategy to a) 
increase risk awareness for the estimated one-third of US adults with prediabetes,1 b) offer informed decision-
making, and c) maximize performance-based reimbursement for suppliers, which supports access36. In either 
case, a brief group model may be optimal as: 1) Individual pre-sessions appear cost-prohibitive, while longer 
sessions may also be more taxing on vulnerable populations; 2) Uptake by NDPP suppliers likely depends on 
establishing efficacy in a low-cost, high-reach model; 3) A key goal is supporting engagement in the yearlong 
NDPP for continued intervention, and thus increasing familiarity with its hour-long, group class format may be 
important (held remotely and/or in-person as allowable in the era of COVID-19). If effective, greater uptake is 
expected if NDPP providers and payers can understand how Pre-NDPP achieves an effect and whether their 
populations are likely to benefit, which will be addressed via mediation and moderation analyses. To prepare 
for future dissemination, we will also evaluate implementation factors, including cost of adding pre-sessions to 
NDPP delivery and estimated return on investment (ROI). If effective, this approach may reduce disparities in 
NDPP effectiveness. It can also be disseminated to all NDPP providers, including more than 1,700 suppliers9, 
and may be supported by current NDPP payers such as Medicare, commercial insurers, and employer 
groups.10-12 Thus, Pre-NDPP has potential for high impact on the burden of T2D and related health disparities 
across the country.  
 
III. Preliminary Studies/Progress Report 
Preliminary data. Our pilot study was conducted at Denver Health (DH), a safety net healthcare system and 
early NDPP adopter, offering the program since March 2013 per CDC-established guidelines.7 Bilingual lay 
health educators received CDC-approved training to serve as NDPP coaches. New NDPP classes began 
every 3-6 months in DH primary care clinics, in English and Spanish. We used CDC-established NDPP 
eligibility criteria (e.g., A1c 5.7-6.4).37 Eligible individuals were identified from medical records and referrals and 
enrolled through outreach calls, without fees or financial incentives to participate. Following standard NDPP 
delivery to 1,065 participants through July 2016 cohorts, we found disconcerting evidence of disparities in 
outcomes, consistent with national data4 (e.g., only 27% of NHBs with ≥2 recorded weights achieved the ≥5% 

weight loss goal in national data, comparable to 23% of NHBs at DH). Thus, we aimed to develop a cost-
effective NDPP adaptation by adding an educational and motivational “pre-session” before enrollment. NDPPs 
launched in September 2016 and January 2017 were preceded by these group-based meetings. In brief, 
participants received education on diabetes risks and information about locally available resources to reduce 
risk, including the NDPP. Coaches used MI techniques to help participants identify their preferred plan of 
action to reduce risk, such as attending the NDPP, and guided participants in identifying barriers and possible 
solutions to enable participation. Seventy-five participants completed a pre-session before NDPP enrollment. 
Another 15 individuals (17%) attended a pre-session, but did not enroll, and no further data were collected.  
Analysis. Pilot study outcome measures were duration (days) and intensity (percentage of sessions 
attended) of NDPP participation, percent weight change (based on weight at first/last NDPP sessions 
attended), and achievement of ≥5% (vs. <5%) weight loss at any point in the program (per Centers for 
Medicare and Medicaid Services [CMS] performance standards10). The primary analysis for this longitudinal 
cohort study compared outcomes of 75 participants who received a pre-session prior to the NDPP to 1,065 
previously enrolled DH participants who did not. We also conducted a sensitivity analysis comparing outcomes 
of the 75 pre-session participants to outcomes of 42 participants who began the NDPP during the immediately 
preceding June 2016 cycle, but were not offered a pre-session. This group was selected for the sensitivity 
analysis to reduce potential influences of differences over time in coaching staff, other modifications in NDPP 
implementation (e.g., incorporating the revised 2016 NDPP curriculum3), and general time trends. Differences 
in characteristics between intervention groups were assessed using chi-square and t-tests. Differences in 
NDPP outcomes were analyzed with ANCOVA and multivariable logistic regression. Covariates included age, 
gender, race/ethnicity, and income (≥/< 133% of federal poverty level).  
Results. The majority of participants were female (77.5%), low-income (61.8%), and Hispanic (58.9%). 
An additional 21.5% of participants were NHW and 19.8% were NHB. Mean age was 48.4 (SD=12.7). There 
were no significant differences in demographic characteristics between participants who received a pre-
session and those who did not, facilitating comparisons of between group outcomes. In adjusted models, pre-
session participants attended more sessions (49.3% vs. 35.0%; p<.001) and stayed in the program longer 
(196.3 vs. 96.5 days; p<.001) on average than participants who were not offered a pre-session. Pre-session 
participants also achieved more weight loss (3.4% vs. 1.5%; p<.001), and were 3.5 times more likely to 
achieve ≥5% weight loss (p<.001, 95% CI [2.1-6.1]). Sensitivity analysis results were fully consistent. Pre-
NDPP cohorts also met full CDC accreditation criteria,37 important to both fidelity and reimbursement.38,39 For 
example, participants attending the NDPP for ≥9 months exceeded the 5% average weight loss goal (M=5.9%; 
SD=6.2). The Pre-NDPP group also performed well compared to national data4 (e.g., only 31% of Hispanic 
participants with ≥2 recorded weights achieved the ≥5% weight loss goal in national data, vs. 51% of Hispanic 
participants who received a pre-session before NDPP enrollment at DH).  
Summary. A pre-session enhancement to the NDPP showed highly successful results upon initial 
dissemination in a diverse, predominately low-income population and may be a viable strategy to address 
suboptimal NDPP outcomes. Our pilot work was an award-winning abstract at the 2018 American Diabetes 
Association meeting40 and is now published in the American Journal of Health Promotion.35 Pilot work also 
highlights our ability to 1) implement both Pre-NDPP and NDPP, 2) recruit a large underserved population of 
at-risk patients, and 3) conduct analyses and publish findings.  
 
IV. Research Methods 
A. Outcome Measure(s).   
Data collection for Aims 1 and 2. This RCT focuses on comparing NDPP outcomes between 
participants who receive Pre-NDPP vs. direct enrollment into the NDPP. The assessment schedule is shown in 
Table 1 below. Demographic characteristics will be extracted from EHR databases and verified as needed 
during the first study visit, including age, gender, race/ethnicity, preferred language, income (above/below 
133% of federal poverty level), and education (highest level completed). Body weight will be measured on a 
high-capacity medical-quality scale at study visits and NDPP sessions. We will also provide study participants 
with a commercial-grade scale for in-home use (e.g., Inevifit’s Premium Bathroom Scale I-BS002; 
https://www.inevifit.com/product/inevifit-premium-bathroom-scale-w-led-display-silver/) so that they can send 
us a picture of their weight via text message or email when not meeting in-person. The primary outcome is 
percent weight change from baseline to 12-months by ITT analysis (without regard to whether participants 
declined NDPP or had early dropout). We will also calculate percent weight change from the first to last NDPP 
sessions attended (i.e., last observation carried forward), per CDC guidelines.37 CMS standards for NDPP 
reimbursement also emphasize achieving ≥5% weight loss at any point in the program,10 assessed as a 

dichotomous outcome. Attendance in the NDPP will be measured as ≥1 session attended, total number of 
NDPP sessions attended (including make-up sessions), and duration of participation in the yearlong program. 
We will also record how many sessions were attended remotely vs. in-person. Rates of completing between-
session support calls will also be assessed as an additional indicator of engagement and treatment dose. Per 
the CDC’s NDPP curriculum, participants will self-report weekly minutes of moderate to vigorous physical 
activity since the last session.3 Baseline BMI will also be assessed at the initial study visit as kg/m2. If the initial 
study visit is held remotely (i.e., due to restrictions to meeting in-person per COVID-19), we will collect BMI by 
confirming height from a participant’s medical record, and mailing a scale to participants for them to send us a 
picture of their weight within 1-2 weeks.  
We will assess potential mediators of perceived risk and self-efficacy, key constructs of the Health 
Belief Model,26 as well as readiness for weight loss as an indicator of motivation. Perceived risk for developing 
diabetes will be assessed with the Risk Perception Survey for Developing Diabetes, a 53-item Likert scale 
measure with four subscale scores on Comparative Disease Risk, Environmental Risk, Personal Control, and 
Optimistic Bias.41,42 Self-efficacy for weight control will be measured with the Weight Efficacy Lifestyle 
Questionnaire, a 20-item measure of confidence (on a 10-point scale) managing five situational factors related 
to weight management behavior: negative emotions, availability, social pressure, physical discomfort, and 
positive activities.43 We will use validated Spanish-language versions of both measures.42,44 Weight loss 
readiness will be assessed with the Stages of Change in Overweight and Obese People (S-Weight), a 5-item 
survey developed concurrently in English and Spanish by expert consensus.45,46 Mediators will be measured 
during an initial assessment at the time of enrollment and 1-2 weeks prior to the first NDPP session (i.e., about 
one week after pre-sessions are completed for the Pre-NDPP arm, and shortly before NDPP classes begin for 
both arms). This will determine whether Pre-NDPP results in increased perceived risk, self-efficacy, and 
readiness compared to the usual care NDPP, and whether changes in these variables mediate outcomes. 
Data collection for Aim 3. RE-AIM is a planning and evaluation framework for implementation 
research that will guide our evaluation of Pre-NDPP delivery and effectiveness.8 RE-AIM constructs will be 
assessed through a combination of recruitment data, intervention outcomes, staff logs, observations, and 
interviews with Lifestyle Coaches, clinic personnel, and patients, as well as cost records (Table 1). Dr. Holtrop 
holds expertise in implementation research and will lead qualitative data collection with Ms. Connelly 
(Qualitative Research Assistant; QRA), first developing semi-structured interview guides47, surveys, and a 
structured observation template. Health economist Dr. Gritz will lead cost-related data collection. 
Observations and interviews with Lifestyle Coaches and clinic personnel will focus on how Pre-NDPP 
implementation works in practice and where gaps in care processes may be. Semi-structured interview and 
observation guides will be used. Interviews will seek to understand the context of intervention delivery and 
mindsets and belief systems that drive thoughts and actions regarding Pre-NDPP. External influences such as 
financial demands and staff turnover will also be explored as potential challenges. Both Lifestyle Coaches and 
3 personnel per each of 8 clinics (focusing on high- and low-referring providers and clinic directors) will be 
interviewed. The QRA will shadow pre-sessions using the observation template and field notes to determine 
fidelity to core features of the Pre-NDPP protocol. Patient interviews will focus on discerning similarities and 
differences in perspectives about the Pre-NDPP and NDPP across 6 groups: those 1) randomized to Pre-
NDPP and 2) randomized to usual care, and within these groups, those a) who initially decline to enroll in the 
NDPP, b) who enroll but complete <6 months of the NDPP, and c) who complete ≥6 months. We will begin 
with 5 interviews per group and continue until thematic saturation is achieved (i.e., not eliciting new 
information). Key interview questions include to what extent Pre-NDPP sessions increase motivation, relieve 
uncertainty about participating in the NDPP, address practical barriers to engagement, support autonomy, and 
other emergent factors that may influence participation. Patients and clinic personnel will be provided gift-card 
incentives. Interviews will be recorded with consent and transcribed. Interviews may be completed in-person or 
by phone/video-conference. 
We will measure Pre-NDPP costs using principles of time-driven activity based costing,48,49 accounting 
for Lifestyle Coach and supervisor time (including salaries and benefits), supplies and other direct costs, and 
indirect costs (e.g., facilities and general administrative expenses). To focus on Pre-NDPP, we will exclude 
other costs associated with standard NDPP delivery and research-related costs (e.g., data collection solely for 
research purposes). To facilitate accurate estimates of personnel costs, coaches and their supervisor will track 
time spent on Pre-NDPP activities (e.g., training, outreach, preparing for and conducting Pre-NDPP) and report 
total hours for each Pre-NDPP activity quarterly. Supplies and other direct costs will also be reported quarterly. 
Standard cost collection guides will be used by study staff.  
Table 1: Measures* 

Measure 
Description 
Method of Collection  
Timeframe 
Characteristics 
Demographics  
Age, gender, race/ethnicity, 
primary language, income, 
education, household 
composition, etc 
Collected from EHR and during 
first study visit 
BL 
Body mass index 
Baseline body mass index 
(kg/m2) 
Collected during first study visit 
(or within 1-2 weeks of remotely- 
conducted initial study visits) 
Main outcomes 
Initial NDPP 
attendance 
≥1 NDPP session attended 
Collected during NDPP delivery; 
Note weight is also measured at 
an initial study assessment and 
at a final 12-month study visit 
(we are setting up a time for all 
randomized individuals to have 
their weight measured at these 
study visits, for which they will 
receive gift cards). Participants 
may also text/email a picture of 
their weight using a study-
provided scale for in-home use if 
not meeting in-person for weight 
collection. 
Ongoing 
collection 
# of sessions attended  
1-25 NDPP sessions attended 
(including virtual vs. in-person 
sessions) 
Duration in NDPP  
1-365 days of NDPP 
participation  
# of between-session 
calls completed 
1-25 between-session support 
calls completed 
Physical activity  
Average self-reported weekly 
minutes at each NDPP session 
Percent weight change  
Based on a) BL to 12 months 
(primary outcome), and b) first 
to last NDPP sessions attended  
≥5% weight loss  
Achieved at any point in the 
NDPP 
Mediators 
Risk perception  
Risk Perception Survey for 
Developing Diabetes42 
Administered by Lifestyle 
Coaches during first study visit 
and repeated prior to start of 
NDPP classes to assess pre-
post change 
BL and 1-2 
weeks prior 
to start of 
NDPP 
classes 
Self-efficacy 
Weight Efficacy Lifestyle 
Questionnaire43  
Readiness 
Stages of Change in Overweight 
and Obese People45,46  
Implementation factors using RE-AIM 
Reach – Absolute 
number, proportion, 
and representativeness 
of individuals who 
participate 
# and characteristics of patients 
referred, outreached, and 
express interest, consent, 
complete Pre-NDPP (intervention 
group), and attend NDPP (both 
groups); Reasons for not 
enrolling or dropout  
Demographics and referral data 
from EHR; enrollment and 
participation data collected by 
coaches; reasons for 
participating or declining 
collected by QRA interviews with 
select participants 
Ongoing 
collection 
Effectiveness- 
Intervention impact on 
key outcomes 
Based on main outcomes listed above 
Adoption – Absolute 
number, proportion, and 
representativeness of 
settings and agents 
willing to initiate 
intervention 
# and characteristics of 
participating DH clinics; NDPP 
referrals; Lifestyle Coach 
participation 
Study documentation; EHR data 
Monthly 
abstraction 
analysis 
Factors influencing adoption 
QRA interviews with Lifestyle 
Coaches and select clinic 
personnel  
BL (for 
coaches 
and clinic 
personnel); 
6 months 
after start of 
Pre-NDPP 
(for coaches 

only) 
Implementation – 
Fidelity to intervention 
protocol, including 
consistency of delivery 
(e.g., bias) and time 
and cost of intervention 
Completion of Pre-NDPP and 
NDPP protocol components  
Coach documentation; Pre-
session shadowing by QRA; 
Fidelity checks 
Ongoing 
collection 
Acceptability of Pre-NDPP 
components, processes and 
tools; any adaptations made by 
coaches 
Interivew by QRA with Lifestyle 
Coaches  
6 months 
after start of 
Pre-NDPP  
Process, barriers, facilitators to 
implementing Pre-NDPP 
QRA interviews with select 
participants, select clinic 
personnel and Lifestyle Coaches 
12 months 
after start of 
Pre-NDPP 
(for clinic 
personnel 
and 
coaches); 1-
2 months 
after last 
intervention 
session 
attended 
(for 
participants) 
Pre-NDPP cost 
Lifestyle Coach time and 
resources survey 
Quarterly 
after each 
pre-session 
Maintenance (potential) 
– Extent to which 
intervention becomes 
routine practice and 
long-term participant 
benefits  
Plans and intent to continue, or 
modify/adapt, Pre-NDPP after 
study; ROI as an indicator of 
potential sustainability; 12-
month weight loss outcomes 
QRA interviews with Lifestyle 
Coaches and select clinic staff; 
Document review and 
abstraction of NDPP payment 
schedules (e.g., Medicare); 
Above outcome data 
Study 
completion 
*EHR=electronic health record; BL=baseline; QRA=qualitative research assistant; ROI=return on investment 
 
B. Description of Population to be Enrolled.  As a pragmatic trial, we will recruit English- and Spanish-
speaking adults who meet CDC-established NDPP eligibility criteria, including BMI≥25 (≥23 if Asian) and 
history of recent prediabetes or former GDM diagnosis.37 Prediabetes is based on a laboratory test within the 
past year indicating a fasting blood glucose of 100-125, blood glucose of 140-199 measured 2 hours after a 
75gm glucose load, or hemoglobin A1c of 5.7-6.4. GDM is based on past diagnosis in the medical record or 
self-reported. Patients without known prediabetes or past GDM may also be eligible based on a risk screening 
tool50, as administered by Lifestyle Coaches during recruitment. Participants are excluded if pregnant at 
enrollment or known to have T2D.  
 
C. Study Design and Research Methods.  
Recruitment. We will identify potential participants through referrals from healthcare providers at DH, which is 
known to support initial enrollment in the NDPP.21 Providers refer through the electronic health record (EHR) 
per usual practice. Since 2013 over 7,000 at-risk patients were referred by providers to the DH NDPP. If 
needed to meet recruitment goals, we will also identify participants from a risk registry based on EHR data, 
which has previously identified over 10,000 NDPP-eligible patients annually. The enrollment process after 
initial identification will be as follows: 1) Lifestyle Coaches pre-screen via medical record review and contact 
referrals by phone to verify interest, eligibility, and schedule eligible individuals for an initial screening visit (held 
in-person or remotely as needed), 2) consenting individuals are randomized to receive Pre-NDPP or usual care 
NDPP  (note we will use Denver Health’s e-consent process for any virtually-conducted recruitment visits), and 
3) complete an initial assessment (behavioral and anthropometric assessments), 4) the Pre-NDPP group 
completes a pre-session 1-2 weeks before NDPP classes start, 5) both groups complete a follow up behavioral 

assessment 1-2 weeks before NDPP classes start (collected in-person or remotely as needed), and 6) both 
groups commence yearlong NDPP classes (held in-person or remotely as needed).  
We will initially enroll 500 participants, with a goal of 400 randomized participants across both groups 
attending ≥1 NDPP session as based on statistical power estimates (see Sample Size and Power Calculations 
below). From previous experience, we expect approximately 50% of referred patients to express interest in 
participating upon initial outreach. Then after initial assessment, we expect early attrition of approximately 20% 
of consenting participants. We will seek to recruit 50 individuals every 3 months, for a total of 500 participants 
recruited over 2.5 years (i.e., 200 participants annually). From 2013-2017, we recruited 300 NDPP participants 
on average each year. Thus, we expect to fully meet RCT recruitment goals. Demographic characteristics of 
individuals in this study are expected to approximately match characteristics of all previous NDPP participants 
at DH: 78.0% female, 58.2% Hispanic, 19.5% NHB, 21.0% NHW, 61.4% low-income (including a majority of 
low-income individuals within each racial/ethnic group), and a mean age of 48.4 (SD=12.7) years.  
Randomization. We will randomize eligible, consenting participants to receive either the enhanced 
intervention (Pre-NDPP + standard NDPP) or usual care control group (standard NDPP only) in a 1:1 ratio. 
After defining our randomization parameters, including allocation by varying block sizes and stratification by 
demographic characteristics, we will use the Randomization Module of the Research Electronic Data Capture 
system (REDCap) to manage random assignment of participants. 
Retention. We aim to have 400 randomized participants across arms attending ≥1 NDPP session. We 
established initial retention rates during our 2013-2017 NDPP delivery and Pre-NDPP pilot as described above 
and in Preliminary Data (e.g., 83% [n=75] of participants attended the NDPP after completing a pre-session). 
We expect similar rates of early retention following the initial assessment in this study. Note dropout does not 
impede our ability to test main effects of Pre-NDPP on NDPP attendance and weight loss as: 1) NDPP 
engagement is a main outcome of interest; 2) The primary outcome of percent weight loss from baseline to 12 
months will be assessed by intent-to-treat (ITT) analysis. Imputation methods for missingness will be used as 
appropriate (see Analysis Plan). For generalizability, we will deliver NDPP with only customary retention 
methods: offering classes at clinics where participants receive their primary care (with an option to join classes 
remotely, as allowable by the CDC since 201823), facilitating transportation as needed (e.g., providing free 
parking and information about insurance-provided transportation benefits), offering make-up sessions as 
needed, and updating participant contact information often. To reduce both participant and study staff burden, 
make up sessions will be offered primarily as a pre-recorded audio and/or video of the Lifestyle Coach talking 
through the session content (without other participants present). Coaches will seek to follow up briefly (e.g., 10-
15 minutes) with participants via phone to ensure comprehension and address remaining questions.  To 
accommodate additional data collection required of participants in both arms of the trial (above and beyond 
routine care in the NDPP), we will provide compensation of $25 for completing each of two 30-minute research 
assessments at the time of initial recruitment and immediately prior to attending the NDPP. We will also 
provide an additional $25 for all participants to complete a final study visit for weight measurement at 12 
months (which may be collected via an in-home, study-provided scale as needed).  
Description of the National Diabetes Prevention Program (for both conditions). The yearlong NDPP 
promotes modest weight loss through diet and physical activity. The curriculum is published by the CDC.3 We 
will follow CDC guidelines for implementing the standard group-based NDPP,37 including 16 weekly to biweekly 
sessions, followed by ≥6 monthly sessions over a total of one year. The objective of NDPP is achieving ≥5% 
weight loss. Attending more sessions is associated with greater weight loss,4,22 and guidelines allow NDPP 
sites to offer more than the minimum 22 sessions to support this goal. We will offer 25 total NDPP sessions (16 
in months 1-6; 9 in months 7-12), held at the same time, day, and location in group visit rooms available at 8 
neighborhood primary care clinics. There will also be an option to attend classes virtually via phone or video-
conference. In light of COVID-19, in-person group classes will be offered when allowable by public health 
entities and Denver Health, although a virtual attendance option will remain for participants who prefer to join 
remotely. Two new NDPP classes will commence quarterly over 2.5 years. To minimize potential 
contamination, participants in the two study arms will be enrolled in separate NDPP classes. Trained, bilingual 
lay health educators will lead NDPP classes as Lifestyle Coaches and provide make-up sessions as needed. 
They will be observed by the research coordinator and/or qualitative research assistant  for fidelity and to 
assess for potential bias in NDPP delivery. Weight is measured at each session on a high-capacity, medical-
grade scale, or by reporting their weight from a study-provided in-home scale. As required by the NDPP 
curriculum, participants are encouraged to achieve a weekly goal of ≥150 minutes of moderate to vigorous 
intensity physical activity (beginning gradually as needed). Participants are instructed to track start and stop 
times and report total weekly activity minutes at the following session. The most recent CDC curriculum also 

encourages a low-fat diet, but does not require monitoring of dietary adherence.3,32 Lifestyle Coaches conduct 
support calls between sessions to support engagement and health behavior change, address individual 
questions and concerns, and remind participants about upcoming sessions. 
Description of the Pre-NDPP protocol. The Pre-NDPP protocol was previously developed in a pilot study 
funded by the Colorado Department of Public Health and Environment. The protocol is based on the Health 
Belief Model26 and extensive stakeholder engagement, including feedback from previous NDPP participants 
and Lifestyle Coaches. Pre-sessions are intended to increase motivation and readiness to engage in the 
NDPP, while helping participants become comfortable with the group class format. Content was developed for 
a 4th grade reading level. Pre-sessions focus on 1) education on diabetes risks, 2) MI to participate in the 
NDPP, and 3) problem-solving of barriers to engagement. Pre-sessions are scheduled for 1 hour to minimize 
burden, but are flexible in practice, lasting 60-90 minutes to address individual questions and needs. Pre-
sessions will be held 1-2 weeks before NDPP classes start, at the same day, time, and location to facilitate 
transitions to the NDPP. We will hold pre-sessions remotely when needed per COVID-19 restrictions on in-
person meetings. To minimize bias, Lifestyle Coaches will be assigned each quarter to deliver one Pre-NDPP 
and one usual care NDPP classes, with accompanying fidelity observations. Moreover, there have been no 
significant differences in NDPP outcomes among coaches (e.g., 1.5% vs. 1.6% mean weight loss among 
participants attending ≥1 session with Ms. Covarrubias and Ms. Amaro, respectively, p=.475). The research 
coordinator is also a trained Lifestyle Coach and will assist in all pre-sessions.  
Pre-NDPP participants will first receive education on diabetes risks and information about available 
resources to reduce risk, including a description of the NDPP. Education is informed by the Health Belief 
Model26 in which perceived risk, severity, benefits of and barriers to action, and cues to action determine health 
behavior. Topics include: a) an overview of T2D (e.g., prevalence, common complications) and risks for 
developing T2D (e.g., prediabetes, sedentary lifestyle, overweight/obesity), b) rates of T2D onset, c) guidance 
that modest weight loss can reduce risk, and d) evidence-based resources to prevent T2D, including a detailed 
overview of the NDPP. Guidance is intended to normalize the experience of being at-risk for T2D to reduce 
anxiety, while focusing on instilling hope that T2D is preventable and making calls to action.   
Coaches will then use MI techniques (e.g., reflective listening, evoking ambivalence, rolling with 
resistance, and eliciting change talk)29 to help participants identify their preferred plan of action to reduce risk, 
encouraging participation in NDPP sessions. For example, to create discrepancy, coaches will acknowledge 
the difficulty of making changes in health behavior and probe for typical experiences of weight loss followed by 
weight regain or other similar challenges. To counter-balance these challenges, coaches will encourage 
participants to describe why preventing T2D is important to them (e.g., wanting to live a long and healthful life 
or setting a positive example for their children and grandchildren). Coaches will also non-judgmentally 
acknowledge that while the NDPP works well for those who attend regularly, it may be challenging for some 
individuals to attend a yearlong class, and that it is okay to opt out or choose other risk reduction resources.  
Finally, to plan behavior to reduce diabetes risk, participants will be guided toward developing a 
personalized SMART (Specific, Measurable, Achievable, Realistic, and Time-bound) strategy for attending the 
NDPP. Coaches will help participants identify their anticipated barriers to attendance (e.g., need for childcare) 
and possible solutions that would enable participation (e.g., finding other caregivers or bringing children to 
class on occasion if needed). Participants will also be encouraged that more frequent attendance is associated 
with greater weight loss, but overall benefits can be achieved despite missing some sessions: attending ≥15 
sessions is associated with achieving the ≥5% weight loss goal on average (i.e., each session is associated 
with 0.31% weight loss4). Scaling questions will be used to help individuals identify an appropriate initial goal. 
For example, although some participants may have limited confidence to make a commitment to attend the 
yearlong NDPP without having tried it before, they may report a 10 of 10 in confidence to attend at least the 
first NDPP session. Lastly, participants will complete an individualized action plan that includes their SMART 
goal and anticipated problem-solving strategies.  
Observations and interviews. Observations and interviews with Lifestyle Coaches and clinic personnel will 
focus on how Pre-NDPP implementation works in practice and where gaps in care processes may be. 
Interviews will seek to understand the context of intervention delivery and mindsets and belief systems that 
drive thoughts and actions regarding Pre-NDPP. External influences such as financial demands and staff 
turnover will also be explored as potential challenges. Both Lifestyle Coaches and 3 personnel per each of 8 
clinics (focusing on high- and low-referring providers and clinic directors) will be interviewed. The QRA will 
shadow pre-sessions using the observation template and field notes to determine fidelity to core features of the 
Pre-NDPP protocol. Patient interviews will focus on discerning similarities and differences in perspectives 
about the Pre-NDPP and NDPP across 6 groups: those 1) randomized to Pre-NDPP and 2) randomized to 

usual care, and within these groups, those a) who initially decline to enroll in the NDPP, b) who enroll but 
complete <6 months of the NDPP, and c) who complete ≥6 months. We will begin with 5 interviews per group 
and continue until thematic saturation is achieved (i.e., not eliciting new information). Key interview questions 
include to what extent Pre-NDPP sessions increase motivation, relieve uncertainty about participating in the 
NDPP, address practical barriers to engagement, support autonomy, and other emergent factors that may 
influence participation. Patients and clinic personnel will be provided gift-card incentives. Interviews will be 
recorded with consent and transcribed.  
We will measure Pre-NDPP costs using principles of time-driven activity based costing,48,49 accounting 
for Lifestyle Coach and supervisor time (including salaries and benefits), supplies and other direct costs, and 
indirect costs (e.g., facilities and general administrative expenses). To focus on Pre-NDPP, we will exclude 
other costs associated with standard NDPP delivery and research-related costs (e.g., data collection solely for 
research purposes). To facilitate accurate estimates of personnel costs, coaches and their supervisor will track 
time spent on Pre-NDPP activities (e.g., training, outreach, preparing for and conducting Pre-NDPP) and report 
total hours for each Pre-NDPP activity quarterly. Supplies and other direct costs will also be reported quarterly.  
 
D. Description, Risks, and Justification of Procedures and Data Collection Tools.   
 
1) Pre-NDPP and NDPP classes 
a. Description (see above description in section C) 
b. Risks: Discussing diabetes risks may also be emotionally stressful. Muscle soreness or minor 
injury may occur from engaging in physical activity as recommended in the NDPP. To be safe, we 
encourage starting slowly with physical activity and checking with a doctor as needed. 
Participants may experience anxiety or distress related to answering personal questions or having 
weight collected. The National Diabetes Prevention Program classes are held in groups of other 
participants. We will ask the class to not share sensitive personal information outside of the 
group, but privacy cannot be guaranteed. 
a. Why necessary: The one-time Pre-NDPP classes are being studied to see if they increase 
engagement in NDPP classes. 
2) Study visits for survey completion and weight assessment 
a. Description: Study visits will occur for 1) an initial eligibility and baseline assessment held in 
person (or remotely when needed due to restrictions on in-person meetings), 2) a follow up 
assessment in person, electronically, by mail, or by phone 1-2 weeks prior to the start of NDPP 
classes, and 3) a 12-month weight assessment in person (or collected remotely when needed).   
b. Risks: Participants may experience anxiety or distress related to answering personal questions or 
having weight collected. The study investigators will make every effort to keep records private 
but it cannot be guaranteed. 
c. Why necessary: Quantitative data collected from these visits will be used to answer research 
questions about the effectiveness of Pre-NDPP.  
3) Interviews 
a. Description: Observations and interviews with Lifestyle Coaches and clinic personnel will focus 
on how Pre-NDPP implementation works in practice and where gaps in care processes may be. 
Interviews will seek to understand the context of intervention delivery and mindsets and belief 
systems that drive thoughts and actions regarding Pre-NDPP. External influences such as 
financial demands and staff turnover will also be explored as potential challenges. Both Lifestyle 
Coaches and 3 personnel per each of 8 clinics (focusing on high- and low-referring providers 
and clinic directors) will be interviewed. Patient interviews will focus on discerning similarities 
and differences in perspectives about the Pre-NDPP and NDPP across 6 groups: those 1) 
randomized to Pre-NDPP and 2) randomized to usual care, and within these groups, those a) 

who initially decline to enroll in the NDPP, b) who enroll but complete <6 months of the NDPP, 
and c) who complete ≥6 months. We will begin with 5 interviews per group and continue until 
thematic saturation is achieved (i.e., not eliciting new information). Key interview questions 
include to what extent Pre-NDPP sessions increase motivation, relieve uncertainty about 
participating in the NDPP, address practical barriers to engagement, support autonomy, and 
other emergent factors that may influence participation. Patients and clinic personnel will be 
provided gift-card incentives. Interviews will be recorded with consent and transcribed. 
b. Risks: Interviewees may experience anxiety or distress related to answering personal questions. 
The study investigators will make every effort to keep interview records private but it cannot be 
guaranteed. 
c. Why necessary: Qualitative data collected from interviews will be used to answer research 
questions about the effectiveness of Pre-NDPP and inform future implementation and 
dissemination.  
Please note that a Spanish-language translation of the updated English-language consent form will be 
submitted pending approval.  
 
E. Potential Scientific Problems. This study is powered on percent weight loss; more limited power is 
expected to evaluate Pre-NDPP effectiveness among demographic subgroups and mediators/moderators. 
Although we do not anticipate difficulty meeting recruitment goals via provider referrals, we can identify more 
eligible participants as needed from an EHR-derived patient registry. Regarding implementation, delivery is 
limited to a single healthcare system, yet in a variety of different clinics and following CDC standards for NDPP 
delivery. Economic analysis limitations include reliance on literature-derived estimates of projected cost 
savings and the relationship between weight loss and T2D incidence. It is possible there will be limited or no 
effect of Pre-NDPP in an RCT, but pilot results are strong and any clinically meaningful benefit may be 
worthwhile given Pre-NDPP is expected to be a relatively low-resource intervention. Financial incentives may 
in fact lead to better outcomes than obtained in previous observational study, but are only offered for study-
related assessments and appropriately sized.  
 
F. Data Analysis Plan.   
General quantitative approaches. Differences in characteristics between study groups will be assessed 
using chi-square and t-tests to examine potential sampling bias. Percent weight change is the primary 
outcome, which has a well-documented association with T2D incidence.2,20 ITT analyses will include all 
randomized participants regardless of NDPP participation, including those lost to follow up. Weight loss data 
for women who become pregnant during the study will be excluded from analyses. Patient-level covariates will 
be screened in bivariate analyses and included in multivariate analysis if related to the outcome at p<.2, differ 
between treatment arms, or associated with dropout. Covariates and potential moderators will include age, 
gender, race/ethnicity, primary language, comorbidities, and other demographic and clinical variables. 
Although primary analyses examine a single outcome per patient (e.g., percent weight loss), for longitudinal 
analyses (e.g., perceived risk) we will determine whether missingness patterns are ignorable or non-
ignorable.51-54 If so, we will employ likelihood-based methods that use all available data, adjusting for 
covariates associated with missingness. If missingness is non-ignorable we will use pattern mixture models.55 
If normality assumptions are not met, we will use transformations to normalize distributions, ordinal or Poisson 
regression where appropriate, and/or the appropriate link function and distribution (e.g., logit link, gamma 
distribution). We will use general (generalized) linear mixed models to incorporate data structures that may be 
both hierarchical (patients within groups) and longitudinal (repeated observations over time).56,57 Hypothesis 
tests will be two-sided with α=.05 or p values reported. Goodness of fit statistics and model fitting diagnostics 
will be used to assess for influential points, outliers, overdispersion, and heteroscedasticity and to evaluate 
alternative model specifications.57 SAS version 9.4 (SAS Institute Inc., Cary, NC) will be used for analyses.  
Aim 1: To evaluate clinical effectiveness of the Pre-NDPP intervention. 
Hypothesis 1.1. Pre-NDPP participants will experience greater weight loss than those directly enrolled 
into NDPP. The primary outcome for this analysis will be percent weight change among all randomized 
participants. As study participation includes groups of individuals in the same study arm, the data structure will 
be hierarchical, with patients nested within groups. Statistical models are shown in hierarchical notation below. 

Likelihood of achieving ≥5% weight loss in the NDPP will also be evaluated (using generalized linear mixed 
models with logit link), as well as percent weight change from first to last NDPP sessions attended. 
Level 1 model. Individual outcomes will be modeled as a function of patient characteristics (fixed effects), such 
as sociodemographic variables, baseline BMI, and comorbid conditions: Yij = β0j + β1j X1ij + β2j X2ij + … + βpj Xpij  
Level 2 model. Group level models specify relationships between group-level predictors and coefficients in the 
Level 1 model. The intervention effect is included as 0 if control, 1 if intervention: β0j= γ00 + γ01(intervention)+ u0j.  
Thus, for a standardized model, γ00 is adjusted mean weight loss for patients in the standard condition (i.e., no 
pre-session intervention), γ01 represents the average increment (decrement) from the mean for groups with 
intervention patients, and u0j is a group level random effect that reflects between-group variance and is the 
difference between group means and the predicted mean based on the model, and u0j ∼ N(0,τ00). Thus, 
Hypothesis 1.1 can be tested as H0: γ01=0 vs H1: γ01≠0.  
Hypothesis 1.2. Pre-NDPP participants will have greater engagement in the NDPP than those who are 
directly enrolled into the program. The outcome variables, number of sessions attended and days of 
participation, will be analyzed using similar approaches. If the distribution of outcomes is non-normal we will 
use generalized linear mixed models with the appropriate distribution and link function, as described above. 
We will also examine the dichotomous outcome of ≥1 NDPP session attended using multilevel logistic 
regression (generalized linear mixed model with logit link and random effect for group). 
Aim 2: To examine mediators and moderators of Pre-NDPP outcomes. 
Hypothesis 2.1. The Pre-NDPP intervention will increase perceived risk for developing diabetes and 
self-efficacy and readiness for weight management. Outcomes for these analyses will be patients’ perceived 
risk, self-efficacy, and readiness scores over time. We will use longitudinal models to determine if trajectories 
differ for patients in control vs. intervention groups, shown below in mixed model notation:  
     
Ytij = γ000 + γ010 (intervention) + γ100 (time) + γ110 (intervention x time) + u00j + r0ij + εtij,  
where γ000 represents the initial status for control groups; γ010 represents the baseline difference between 
intervention and control groups (should be close to 0); γ100 is the change in scores for groups of control 
patients; γ110 is the difference in change for control vs. intervention groups. rtij is a patient random effect and 
U00j is a group random effect, independent of rtij and assumed to have a bivariate normal distribution over 
practices;  εtij is residual variance. Thus, the Pre-NDPP effect can be tested as H0: γ110=0 vs H1: γ110≠0.  
Hypothesis 2.2. Perceived risk, self-efficacy, and readiness will mediate relationships between Pre-
NDPP treatment and outcomes. Outcomes will be weight loss and session attendance, using similar 
approaches as described above for Hypotheses 1.1 and 1.2. We will include baseline perceived risk, self-
efficacy, and readiness as covariates and change in these constructs as primary independent variables to 
determine if the intervention effect is partially or fully explained by these hypothesized mediators.58 
Hypothesis 2.3. Pre-NDPP effects will differ for participants with the moderator condition (e.g., 
Hispanic; low-income) compared to those without the moderator (non-Hispanic; higher income). The effects of 
moderator analyses involve inclusion of an intervention x moderator fixed effect for models that are not 
longitudinal (e.g., percent weight loss, number of sessions attended). For longitudinal models (e.g., self-
efficacy over time) models will include a main effect for time, arm, moderator variable, time x arm, time x 
moderator, arm x moderator, and time x arm x moderator interaction term. The 3-way interaction term tests for 
differential intervention effectiveness in subgroups identified by the moderator variable.    
 Sample size and power. Pre-NDPP pilot data indicate a 0.36 effect size for percent weight change in 
the NDPP with an intraclass correlation coefficient (ICC) of 1.44%. To be conservative for our primary outcome 
of percent weight loss among all randomized participants regardless of NDPP participation, we estimate 
minimum effect sizes detectable for various sample sizes and ICCs (Table 2), with effect sizes of 
approximately 0.28 to 0.35 for analyses of the primary outcome with a type-1 error rate of .05. Consequently, 
we expect that 500 randomized participants will provide adequate power while accounting for expected 
attrition. Note that mediation and moderation analyses are considered exploratory, as estimated power is 
unknown. 
Table 2: Estimated power to detect treatment differences in 
percent weight loss.  
Groups 
per arm 
Patients per 
group 
ICC 
Effective 
sample 
size 
Detectable 
difference 
(effect size) 
Power 
10 
18 (180 per arm) 
1% 
154 
.32 
80% 
10 
18 (180 per arm) 
2% 
134 
.35 
82% 

10 
20 (200 per arm) 
1% 
168 
.31 
81% 
10 
20 (200 per arm) 
2% 
145 
.33 
80% 
12 
20 (240 per arm) 
1% 
201 
.28 
80% 
12 
20 (240 per arm) 
2% 
174 
.31 
82% 
 
Aim 3: To evaluate the implementation factors of Pre-NDPP. Qualitative analyses will evaluate Pre-
NDPP implementation from a Lifestyle Coach, clinic provider/leadership, and patient perspective. Interviews 
and observation data will be cleaned and entered into the qualitative software program ATLAS.ti (version 8; 
Scientific Software Development GmbH, Berlin, Germany) for analysis. Analyses will begin as a small group 
process for data triangulation to occur and use a grounded hermeneutic editing approach.59 Dr. Holtrop and 
Ms. Connelly will read 5-10 interviews and together determine key themes and their definitions and labels 
(“codes”). Codes will be vetted with the larger study team and stakeholder representatives. After establishing 
initial codes, analysts will code the data (first together, then independently) as outlined by Addison59, and will 
compare and reconcile coding until a high degree (≥80%) of conceptual inter-rater reliability is achieved. 
Specifically, data from interviews with Lifestyle Coaches and clinic personnel will examine themes related to 
adoption, feasibility, and acceptability of Pre-NDPP. Did the presence of Pre-NDPP affect referral processes in 
any way? Did they perceive differences in patients who participated in Pre-NDPP or not? This analysis will 
determine key underlying characteristics, such as belief systems or mindsets, and/or practical reasons that 
make Pre-NDPP effective or not, and to what extent. We expect data from patient interviews will more 
thoroughly explain engagement in the NDPP. We will examine emergent codes across study groups by 
comparing group-level quotations to determine differential experiences. Did Pre-NDPP availability address 
practical concerns? Did Pre-NDPP change mindsets about the importance of diabetes prevention? Did it alter 
participants’ experience in the NDPP? Finally, perceived reasons for participation (or non-participation) will be 
examined alongside actual engagement data to corroborate and explain quantitative results. In ongoing 
meetings with the larger study team, we will further consider existing literature and associated experiences for 
corroboration, and seek out additional data as needed to confirm or refute results. After initial analysis has 
identified data to support one theme or interpretation, effort will be devoted to finding negative or disconfirming 
evidence. Clinic personnel and Lifestyle Coaches will be selected for member checking and revision of 
thematic groupings prior to final coding. The final phase consists of preparing interpretive summaries detailing 
the findings of prior phases. All phases of data processing and analysis will be cross-checked to ensure 
consistency in application of coding and classification procedures. Observation data will be similarly analyzed. 
Pre-NDPP cost and ROI. We will first calculate Pre-NDPP cost as the average expense of each pre-
session delivery based on personnel time, supplies and other direct costs, and indirect costs. We will then 
determine the projected ROI of Pre-NDPP from both provider and payer perspectives. For NDPP providers, 
ROI will be calculated as the additional payment expected from payers as a result of potentially improved 
retention and weight loss of Pre-NDPP participants minus the average pre-session cost and divided by pre-
session cost. For common reference, payments will be based on the Medicare reimbursement schedule for 
achievement of NDPP attendance and weight loss milestones.10 We will compare the average expected 
reimbursement for participants in both study arms to measure additional payments that may be attributed to 
Pre-NDPP. We will also conduct a sensitivity analysis by calculating the projected ROI for varying numbers of 
Pre-NDPP participants with varying demographic characteristics (e.g., race/ethnicity, income), and with other 
available NDPP payment schedules (e.g., Maryland Medicaid60). Sensitivity analysis results will inform Pre-
NDPP sustainability by identifying the number of participants needed per pre-session to achieve a positive 
ROI, the extent to which moderators identified in Hypothesis 2.3 affect ROI, and the extent to which different 
payment models affect ROI. From the perspective of NDPP payers, ROI will account for the expected 
reduction in direct healthcare expenditures as a result of covering Pre-NDPP through an additional payment to 
NDPP providers, as calculated over a 3-year horizon. ROI will be the reduction in projected expenditures 
minus the average pre-session cost and divided by pre-session cost. Estimates of change in direct healthcare 
expenditures will be based on the impact of Pre-NDPP on weight loss from Hypothesis 1.1, the known 
relationship between weight loss and T2D incidence20, and the difference in expenditures for individuals with 
prediabetes or T2D over a 3-year horizon.61 This timeline requires discounting of expected reductions in years 
2 and 3 expenditures for which we will apply a standard 3% discount rate. We will also conduct a sensitivity 
analysis by varying the number of Pre-NDPP participants, their characteristics, and the discount rate. To be 
conservative, cost and ROI is based on all Pre-NDPP participants, regardless of NDPP attendance. 
 

G. Summarize Knowledge to be Gained.  In summary, this proposed RCT of Pre-NDPP may lead to future 
dissemination of a scalable, evidence-based strategy to improve success of the NDPP, reduce disparities in 
NDPP effectiveness, and help prevent T2D across the country.  
 
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Dunn C, Deroo L, Rivara FP. The use of brief interventions adapted from motivational interviewing 
across behavioral domains: a systematic review. Addiction. 2001;96(12):1725-1742. 

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Christie D, Channon S. The potential for motivational interviewing to improve outcomes in the 
management of diabetes and obesity in paediatric and adult populations: a clinical review. Diabetes, 
obesity & metabolism. 2014;16(5):381-387. 
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Greaves CJ, Sheppard KE, Abraham C, et al. Systematic review of reviews of intervention components 
associated with increased effectiveness in dietary and physical activity interventions. BMC Public 
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Ritchie ND, Kaufmann P, Gritz RM, Sauder K, Holtrop JS. Presessions to the National Diabetes 
Prevention Program May be a Promising Strategy to Improve Attendance and Weight Loss Outcomes. 
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CDC. Diabetes Prevention Recognition Program: Standards and Operating Procedures. 2018; 
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38. 
Ritchie ND, Kaufmann P, Sauder KA. Comment on Ely et al. A National Effort to Prevent Type 2 
Diabetes: Participant-Level Evaluation of CDC's National Diabetes Prevention Program. Diabetes Care 
2017;40:1331-1341. In: Diabetes Care. Vol 40. United States2017:e161-e162. 
39. 
Ritchie ND, Havranek EP, Moore SL, Pereira RI. Proposed Medicare Coverage for Diabetes Prevention: 
Strengths, Limitations, and Recommendations for Improvement. American journal of preventive 
medicine. 2017;53(2):260-263. 
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ND R, PG K, RM G, JS H. Pre-sessions to the National Diabetes Prevention Program are a Promising 
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2017. 
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Walker EA, Caban A, Schechter CB, et al. Measuring comparative risk perceptions in an urban minority 
population: the risk perception survey for diabetes. The Diabetes educator. 2007;33(1):103-110. 
43. 
Clark MM, Abrams DB, Niaura RS, Eaton CA, Rossi JS. Self-efficacy in weight management. Journal 
of consulting and clinical psychology. 1991;59(5):739-744. 
44. 
Ruiz VM BC, López AE, Rivas T. Factor analysis of the Spanish version of the Weight Efficacy Life-
style Questionnaire. Educational and psychological measurement. 2002;62(3):539-555. 
45. 
Andrés A, Saldaña C, Gómez-Benito J. Establishing the stages and processes of change for weight loss 
by consensus of experts. Obesity (Silver Spring, Md). 2009;17(9):1717-1723. 
46. 
Andrés A. Stages and processes of change questionnaires in weight management (S-Weight and P-
Weight). 2016; https://www.researchgate.net/publication/299845622_S-Weight_and_P-
Weight_questionnaires_Spanish_and_English_version. Accessed August 6, 2018. 
47. 
Gilchrist V, Williams RL,. Key informant interviews. In: Crabtree B, Miller WL, ed. Doing Qualitative 
Research. Thousand Oaks, CA: Sage Publications; 1999:71-88. 
48. 
Kaplan RS, Porter ME. How to solve the cost crisis in health care. Harv Bus Rev. 2011;89(9):46-52, 54, 
56-61 passim. 
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Kaplan RS, Witkowski M, Abbott M, et al. Using time-driven activity-based costing to identify value 
improvement opportunities in healthcare. J Healthc Manag. 2014;59(6):399-412. 
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51. 
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algorithm. Journal of the Royal Statistical Society. 1977;Series B(39):1-38. 
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53. 
Diggle P, Kenward M. Informative drop-out in longitudinal data analysis. Appl Stat. 1994;43:49-93. 
54. 
Fairclough DL. Design and analysis of quality of life studies in clinical trials. 2nd ed. Boca Raton: CRC 
Press; 2010. 

55. 
Hedeker D, Gibbons R. Application of random-effects pattern-mixture models for missing data in 
longitudinal studies. Psychological Methods. 1997;2:64-78. 
56. 
Bryk, AS, SW R. Hierarchical Linear Models: Applications and Data Analysis Methods. Second ed. 
Newbury Park: Sage Publications; 2000. 
57. 
Littell R, Milliken GA, Stroup WW, Wolfinger RD, eds. SAS System for Mixed Models. Cary, NC: SAS 
Institute Inc; 1996. 
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randomized clinical trials. Arch Gen Psychiatry. 2002;59(10):877-883. 
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Addison R. A Grounded Hermenuetic Editing Approach. In: Crabtree B, Miller W, eds. Doing 
Qualitative Research. 2nd ed. Thousand Oaks, CA: Sage; 1999:145-161. 
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Maryland MCO National DPP Demonstration – Codes for DPP Services. In:2016. 
61. 
Francis BH, Song X, Andrews LM, et al. Progression to type 2 diabetes, healthcare utilization, and cost 
among pre-diabetic patients with or without comorbid hypertension. Current medical research and 
opinion. 2011;27(4):809-819.