Efficacy of the Quell Wearable Device for Chronic Low Back Pain
Phase: NA
Conditions: Low Back Pain
Sponsor: Brigham and Women's Hospital

Title: Efficacy of the Quell Wearable Device for Chronic Low Back Pain 
NCT# 02944513 
Date: July 1, 2016 
 
STUDY PROTOCOL - METHODS 
This trial is registered at ClinicalTrials.gov (NCT02944513). The Human Subjects 
Committee of Brigham and Women’s Hospital (BWH) will approve the study procedures 
and written informed consent will be obtained from every participant. Flyers will be 
distributed about this trial and subjects will be recruited consecutively as they respond 
to the flyers. We will recruit patients with a primary complaint of chronic low back pain 
and randomize each of the subjects to one of two treatment conditions: 1) the hfTENS 
device or 2) treatment-as-usual control (no device) using a random number table 
(https://www.graphpad.com/quickcalcs/randomize1.cfm). All participants will be adults 
age 21 or older and diagnosed with axial musculoskeletal or discogenic back pain with 
or without radiculopathy. There will be a number of other inclusion criteria: (1) 
participants will need to own a compatible smartphone, either Android or iPhone, (2) 
they will have to have evidence of chronic pain for over 6 months and average ≥4 on a 
0-10 pain intensity scale, and (3) they will need to understand and speak English. Study 
exclusion criteria will include (1) diagnosis of cancer, (2) evidence of osteomyelitis, (3) a 
psychiatric disorder judged to interfere with the study (e.g., psychosis or delusional 
disorder), (4) an active substance abuse disorder (e.g., cocaine or heroin use), (5) 
surgery scheduled within 3 months, (6) pregnancy, (7) an implanted device (e.g., 
pacemaker), and (8) any unstable systemic illness judged to interfere with treatment. 

During the 3-month study period all participants will be discouraged from making 
changes in their pain management regimen.  
We will employ the use of a smartphone pain app in this study,16,17 which was 
designed to collect daily assessment data as well as demographic and medical 
information. It was devised to help monitor daily patient progress over the period of the 
trial.  All subjects will be informed how to find the apps (‘Quell Relief’ and ‘BWH 
Painapp’ either on the App Store or Google Play) and will be assisted in downloading 
the apps, if assistance is needed. The pain app has built-in daily reminders for the user 
with push notification to complete daily assessments as well as 2-way messaging to 
connect with study staff.   
Patients will be randomized to either the Experimental group with use of a 
hfTENS or Control group with treatment as usual. Both groups will be asked to use the 
smartphone pain app to monitor their daily assessments. All subjects will complete a 
packet of validated questionnaires and will be followed for 3 months. All participants will 
sign an informed consent form and will be given assistance in downloading the apps by 
a research assistant (RA) who will answer any questions and help to manage any 
problems that the individuals might encounter. All participants will be also administered 
QST at baseline.11,12  
Patients randomized to the experimental group (hfTENS) will be encouraged to 
use the device at least two hours every day. Tracking of use of the device will be 
available electronically through the hfTENS app. All demographic and daily pain 
assessment data will be stored on a secure server (Veracode tested) and messages will 
be sent via the 2-way messaging pain app program to help track use of the device and 

to address any problems that the subjects might encounter. All subjects will be also 
asked to complete post-intervention mailed assessments after 3 months and return the 
completed assessments in pre-addressed stamped envelopes. Each subject will be 
compensated $25 at baseline and $50 at study completion upon receipt of their 
completed assessments. All subjects will be allowed to keep their hfTENS device at the 
end of the study. Those subjects assigned to the Control condition will be offered a 
hfTENS device at the end of the 3-month trial period.  
Brief Quantitative Sensory Testing 
Pressure pain thresholds (PPThs) will be assessed using a standard manual pressure 
algometer (Wagner Force Ten Digital Force Gage; www.wagnerinstruments.com). 
PPThs will be evaluated at the trapezius muscles bilaterally and at the wrists bilaterally 
(four sites) by a trained and experienced RA.  A 0.5 cm2 probe covered with a 
rubberized pressure-transducing material will be applied twice to each site to measure 
PPThs. Mechanical force will be gradually increased until the subject verbally indicates 
to the tester that the pressure is “painful.” Temporal summation of mechanical pain will 
be assessed using weighted pinprick stimulators at each of the metacarpophalangeal 
joints of the middle fingers with a Touch-Test Sensory Evaluator 
(www.ncmedical.com).14 The subjects will be instructed to indicate which of the probes 
produced a painful sensation (usually the 128 or 256 mN gauge) and this stimulator will 
be used to apply a series of 10 sequential stimuli at the rate of 1 per second to the 
dorsum of the hand. The RA will ask the subjects to indicate their perceived level of 
painfulness of the first, fifth, and tenth stimulus. The degree of mechanical temporal 
summation will be determined by the increase in pain (as rated by the subject) between 

the first and last stimulus. We and other groups have frequently employed these QST 
procedures in prior studies among patients with a broad array of musculoskeletal 
chronic pain conditions.11,12,18 
Patient Measures 
Participants will complete measures recommended by the Initiative on Methods, 
Measures, and Pain Assessment in Clinical Trials (IMMPACT)19 as primary outcomes.  
All participants will be asked to complete a series of baseline questionnaires. Identical 
questionnaires will be mailed to the subjects for completion after 6 weeks and again 
after 3 months.  All subjects will be supplied with self-addressed stamped envelopes to 
mail back their completed questionnaires. The following measures will be administered 
to the study patients: (1) The Brief Pain Inventory (BPI).20,21 It has been shown to have 
excellent reliability and validity among samples of chronic pain patients; (2) The Pain 
Disability Inventory (PDI).22 This is a 7-item questionnaire designed to assess activity-
related disability in performing household chores, recreational and social activities, 
work-related and sexual activities, general activities of daily living, and life-supporting 
behavior.  It has been shown to have excellent reliability and validity; (3) The Pain 
Catastrophizing Scale (PCS).23,24 This is an instrument that examines the propensity for 
recurring intrusive ruminating thoughts. Persons scoring high on this scale tend to 
magnify and amplify their pain and show signs of helplessness. It has good 
psychometric properties with adequate reliability and validity; (4) The Hospital Anxiety 
and Depression Scale (HADS).25,26 This is a valid and reliable measure of anxious and 
depressive symptoms over the past week. The HADS has been used extensively in 

clinics to assess mood and has been shown to have an optimal balance between 
sensitivity and specificity.  
Once a week the subjects will be called by the RA and asked to rate their current 
progress on a 0=no pain/no interference to 10=worse possible pain/extreme 
interference on the following items: 1) current pain intensity, 2) average pain intensity, 
3) pain interference on activities of daily living, social activities, outdoor and recreational 
activities, sleep, appetite, work ability, and 4) anxiety, depression and irritability from 
0=stable mood to 10=worse possible mood. All questions were developed and 
standardized from a previous study.27 All subjects will be asked about their current pain 
medications and all changes in prescription pain medications will be noted. Participants 
assigned to the Experimental group will be also asked which leg they used the hfTENS 
on over the past week and all subjects will be given the opportunity to share any 
additional thoughts about the study.  
 At 3-month post-treatment all patients will be sent a packet of the baseline 
questionnaires to complete again and return by self-addressed stamped envelopes. 
Those in the Experimental group will be also asked to respond to a 14-item helpfulness 
questionnaire designed to investigate the perceived benefit of the hfTENS. Those in the 
Control group will complete helpfulness questions only about the study and perceived 
helpfulness of the pain app. All items, which were developed in a prior study,18 and 
adapted from a previously validated measure,28 will be rated on a 0 to 10 scale (e.g., not 
at all helpful to very helpful) and assessed helpfulness, bothersomeness, ease of use, 
how often they used the device, and whether the user was willing to use the hfTENS in 
the future.  

Statistical Analysis Plan 
The aim of this study is to establish the safety, efficacy, feasibility, and tolerability of the 
hfTENS device for use among chronic back pain patients. We will use an intent-to-treat 
analysis and all variables will be assessed using univariate and multivariate analyses to 
establish group differences at baseline and follow-up. Although this will be designed as 
a preliminary study, power calculations, as outlined by Cohen,29 will be performed to 
determine the probability of detecting clinically significant differences between treatment 
groups in the primary area of measurement: pain intensity.  These calculations will 
assume a two-tailed test and alpha level of 0.025 confirming the hypotheses that the 
Quell would be associated with general overall improvement (e.g., more pain relief). A 
more rigorous p<0.025 significance level will be established rather than p<0.05 because 
of the multiple observations. The power analyses is expected to reveal that a sample 
size of 60 subjects (30 per treatment group), gives the study a >80% probability of 
detecting a 1.5-point group difference on a 0-10 rating scale. Depending on the nature 
of the variables, chi-square, t-tests, and logistic regression analyses will be conducted. 
We also will examine and report on the qualitative responses of the participants in using 
the hfTENS. Group differences will be assessed using repeated measures ANOVA and 
preliminary mixed linear regression model analyses, as appropriate.