Testing of a Tool to Elicit Patient Preferences for CTS
Phase: NA
Conditions: Carpal Tunnel, Carpal Tunnel Syndrome, Carpal Tunnel Syndrome Left, Carpal Tunnel Syndrome Right, Carpal Tunnel Syndrome Bilateral
Sponsor: Stanford University

 
 
 
 
 
Testing of a Tool to Elicit Patient Preferences for CTS 
Study Protocol and Statistical Analysis Plan 
NCT03532373 
April 30, 2018 
 
 
 

 
Title: Does a preference elicitation tool improve decisional conflict for the diagnosis 
of carpal tunnel syndrome? A randomized controlled trial 
 
Study purpose:  
To test a novel preference elicitation tool at the point of care for patients with suspected 
carpal tunnel syndrome to aid in the decision to obtain a diagnostic nerve test.  
 
 
Primary null hypothesis:  
• There will be no difference in decisional conflict score between the intervention 
and control groups 
 
 
Subjects 
Inclusion criteria:  
All new patients (>18 years) visiting the Orthopaedic Hand Service 
English fluency and literacy 
Able to take informed consent 
Patient is suspected for carpal tunnel syndrome by a provider in clinic 
 
Exclusion criteria: 
Prior diagnostic testing for carpal tunnel (nerve test, ultrasound) 
Prior carpal tunnel release 
Diagnosis of C5/6 radiculopathy (double crush) 
Peripheral neuropathy (ex: diabetic) (general bilateral numbness/tingling in extremities) 
Worker Compensation/EMG Required 
Cubital (symptoms in all fingers) 
 
Statistical Analysis 
Response variables:  
• Primary: Decisional Conflict scale 
 
Explanatory variables:  
• Primary: Group assignment (intervention vs control group) 
Age 
Sex 
Site 
Treating physician 
Clinical diagnosis of carpal tunnel Y/N 
Number of months since onset of symptoms 
Laterality of symptoms (left/right/both) 
CTS-6 Score 
Preference for diagnosis method 
Received diagnostic method 
Socioeconomic elements: 

• Race/ethnicity (White, Black, Hispanic, other) 
• Primary health insurance (Medicare, Medicaid, private, uninsured, workers’ 
compensation) 
• Years of education 
• Work status (Working, retired, disabled, unemployed) 
• Marital status 
• Annual salary 
 
Methodology: 
We will measure decisional conflict in 150 new patients being evaluated for CTS with the 
tool compared to 150 patients being evaluated for CTS with standard care. Inclusion 
criteria will include new, adult patients (>18 years) with a clinical diagnosis of carpal 
tunnel syndrome who will undergo further diagnosis and treatment (or both). This will 
include women and minorities that are able to give written consent. Exclusion criteria 
will include patients who have already been seen by the recruiting surgeon for CTS, who 
have undergone prior carpal tunnel release, or who have a diagnosis of C5/6 
radiculopathy (double crush). Those patients randomized to receiving the tool will use it 
to identify their preferences for certain attributes of care. Patients will then be presented 
with their preference data and the surgeon will have a discussion with the patient 
regarding CTS. Surgeons will have their standard discussion with the patients 
randomized to the standard care group (no tool).  
 
Statistical Analysis: We will use descriptive statistics techniques to describe the 
sociodemographic profile and characteristics of the total sample and individual study 
centers. We will test the hypothesis that patients randomized to use the tool will have 
lower decisional conflict compared to standard care using a linear mixed-effects 
regression model, with a fixed and random effect for site to account for the clustering of 
patients within sites and within site randomization (blocking).  
Power Analysis: Although this aim is primarily about feasibility and generating pilot data 
for a larger grant, we based our power analysis on number of sites J = 6, Cohen’s effect 
size for the Decisional Conflict Scale total score δ = 0.5 (i.e. 8 points), alpha = 0.05, 
effect size variability = .20, proportion of variance explained by the blocking variable 
(site) - .20, and power = 0.80 yields a site-level sample size of 50. Prior studies using 
choice experiments have included similar sample sizes.  
 
 
 

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