Correlation of Trust and Outcomes Following Physical Therapy for Chronic Low Back Pain
Conditions: Trust, Chronic Low Back Pain, Physical Therapy
Sponsor: University of South Dakota

Title: Correlation of Trust and Outcomes Following Physical Therapy for Chronic Low Back Pain 
NCT#: NCT03443401 
Date: 6/10/24 
 

 
Study protocol 
This dissertation was a non-experimental correlational quantitative analysis of multi-
clinic site locations of consecutive patients referred to or coming via direct access for physical 
therapy care related to chronic low back pain. It was a collection of trust surveys, TA 
questionnaires, and patient reported outcomes related to their low back pain and function 
completed by the patient participant through an interrupted time-series of prior to initial 
evaluation, post-initial evaluation, and at discontinuation of the current episode of care. The 
physical therapist participants completed a patient connection and engagement questionnaire 
after the second visit and at discharge along with outcomes measurement data collect at the 
completion of the current episode of care. Data collection was at multiple outpatient physical 
therapy sites with multiple physical therapists and wide patient demographics to improve 
generalizability of the study findings. 
The research project was conducted according to the Declaration of Helsinki. All the 
participants were fully informed of the study content before their participation in this study and 
completed informed consent. Institutional Review Board (IRB) at the University of South 
Dakota served as the IRB of record with joint approval from Nova Southeastern University IRB.  
3.3 Procedures 
3.3.1 Participant recruitment 
Various clinic sites (AZ, CA, RI, VA, WA, and WI) were approached through email, 
phone, and direct contact and were provided general study protocol to investigate their interest in 
serving as a data collection site. Clinic sites interested in participating completed an IRB 
Location Site Application along with a clinic site consent agreement (Appendix A). Each clinic 
site had a point of contact person appointed, and that contact person ensured that all informed 

consent forms were signed for those physical therapists willing to consent to participate in the 
study protocol. Once each clinic site and participating physical therapists at those sites were set 
up, new patients potentially meeting inclusion criteria of chronic low back pain (pain greater 
than 3 months) coming to the clinic were identified by front office staff scheduling the 
appointment. Upon arrival at the clinic, potential patient participants were handed regular clinic 
site new patient paperwork, but they were also given a participant recruitment flier. If the patient 
verbally expressed interest in participation, they were provided with an introductory letter with a 
PsychData link. This link had the informed consent and the participant was given a Health 
Insurance Portability Accountability Act (HIPAA) form as part of the IRB process. This method 
of recruitment was utilized to minimize any potential coercion.  
Once patient participants completed the informed consent process they were directed to a 
second PsychData link in order from them to complete a participant demographics form 
(Appendix B) that further verified their eligibility into the study. Inclusion criteria consisted of 
greater than 18 years of age, able to read, speak, and write in English, and presence of low back 
pain for at least 3 months. Exclusion criteria were current pregnancy or active cancer diagnosis. 
Patient participants were also excluded from the study if at any point during the episode of care 
they required different medical attention beyond physical therapy and needed to be referred out 
for medical reasons and had to discontinue their physical therapy prior to achieving goals. Any 
patient participant that did not receive at least 80% of the treatments from the initial physical 
therapist participant were excluded from primary data collection. Physical therapist participant 
inclusion criteria were having a physical therapy license to treat patients and employed at a clinic 
site approved for the study. 

The initial a priori was set for a total of 64 patient participants with the primary 
complaint of chronic low back pain that had lasted a minimum of 3 months prior to initiating the 
current physical therapy episode of care. The patient were consecutively enrolled in the study at 
the various clinic sites. An a priori achieves 79% power to detect a Pearson correlation of 0.400 
using a two-sided hypothesis test with a significance level of 0.05 with an included 20% dropout 
rate. These results are based on 1000 samples from the bivariate normal distribution under the 
alternative hypothesis. The number of physical therapist participants was determined by the 
clinic site enrollment and treating at least one patient participant during the course of the study.  
3.3.2 Instruments – Predictor variables 
 
Various instruments were used to measure trust during the encounter. For the purpose of 
this study, three of the most well studied provider-specific trust measurement scales (Trust in 
Physician Scale,29 Primary Care Assessment Survey (PCAS),28 and Wake Forest Scale38) used in 
the physician and psychology literature were chosen that have items written that could easily 
translate to physical therapy practice and patient care. To date, none of these provider-specific 
trust measurement scales had been studied for use in physical therapy practice. General trust in 
the medical profession and physical therapy was assessed by the General Trust in Physician 
Scale.37 A TA measurement scale (Working Alliance Inventory – Short Revised) was used and 
was the only predictor instrument previously used in the physical therapy literature.126 The final 
instrument was developed as part of the dissertation process to assess the physical therapist’s 
perception of their patient’s connection and engagement (PT Survey of Patient Connection and 
Engagement) within the therapeutic process during the physical therapy encounter.  
Trust in Physician Scale: The Trust in Physician Scale29 is one of the first instruments 
developed to assess a patient’s interpersonal trust in their physician. The original published work 

of Anderson and Dedrick in 1990, detailed the development and validation of the Trust in 
Physician Scale. Three different dimensions of trust were assessed: dependability of the 
physician, confidence in the physician’s knowledge and skills, and confidentiality and reliability 
of information between the physician and patient. The Trust in Physician Scale is a patient self-
report tool with 11-items scored on a 5-point Likert scale. The labels for the Likert scale 
followed the later modified version by Thom, et al.53 (1 = totally disagree, 2 = disagree, 3 = 
neutral, 4 = agree, 5 = totally agree). Raw scores can range from 11 to 55 with higher scores 
demonstrating higher trust. The scale was modified for the purposes of this study with the words 
“physical therapist” inserted any place the original version had the word “doctor”. It has a 
combination of positively (questions #2, 3, 4, 6, 8, 9, and 10) and negatively (questions #1, 5, 7, 
and 11) worded questions. The Flesch reading ease score equates to 52.3 to provide a Flesch-
Kincaid grade level at 9.6 according to Microsoft® Word 365 for Office (Redman, WA).  This 
scale has been used in research in primary care physicians and specialty medical practice with a 
variety of patient populations.29,53,59 (Appendix C) 
Primary Care Assessment Survey: The PCAS28 was developed to measure seven different 
domains of care through 11 different summary scales. The trust summary scale assesses the 
physician’s integrity, competence, and role as the patient’s agent. The trust summary scale is 
measured with eight different item questions with a lowest score of 8 and maximal score of 40, 
with the higher score demonstrating more trust. Seven of the item questions (questions #1-7) are 
measured by a five-point Likert scale (1 = strongly agree, 2 = agree, 3 = not sure, 4 = disagree, 5 
= strongly disagree). Question #8 is scored on a 11-point scale with anchors (0 = not at all, 10 = 
completely) it requires recalibration to align with questions #1-7 (1 = 0-2 precoded item value, 2 
= 3-4 precoded item value, 3 = 5-6 precoded item value, 4 = 7-8 precoded item value, 5 = 9-10 

precoded item value). Four of the seven Likert scale items (questions #1, #3, #5, #8) are reverse 
score items and must be recoded for final scoring (5 = precoded item value 1, 4 = precoded item 
value 2, 3 = precoded item value 3, 2 = precoded item value 4, 1 = precoded item value 5). For 
purposes of this study, the word “doctor” was replaced with “physical therapist” from the 
original scale. The PCAS scoring algorithms calculate a score if a respondent answers at least 
50% of the items on the scale (4 items on the trust scale), the missing whole values are inputted 
as the respondent’s average score across all completed items for the scale. A transformed scale 
score can be computed as the product of the actual raw scale score minus the lowest possible raw 
scale score (8 on the trust scale) that is divided by the possible raw scale score range (32 on the 
trust scale) multiplied by 100. The Flesch reading ease score is 62.6, which equates to an 8.4 
Flesch-Kincaid grade level according to Microsoft® Word 365 for Office (Redman, WA). The 
scale was originally developed and tested on Massachusetts state employees on their level of 
trust with their primary care physician. (Appendix D)  
Wake Forest Scale: The third provider specific trust measurement scale used was the 
Wake Forest Scale38 developed by Hall, et al. The Wake Forest Scale was developed to improve 
on the various trust measurement scales that currently had been published at that time 
(Anderson/Dedrick29 with the Thom modification53, Safran28, and Kao39,118) and to be more 
generalized to other care providers, not just physicians. The Wake Forest Scale development was 
done by retaining or modifying questions from the existing scales that fit their conceptual model 
of trust measurement. To address areas of the trust domain that the study team did not think 
where fully covered, they, along with a group of experts developed additional items. After initial 
testing and screening of questions, it produced 26 candidate items for further testing, which 
ultimately produced the final 10-items that were accepted for the scale. The 10 items reflect 

dimensions of trust (fidelity = #1-2, competence = #3-4 and #8, honesty = #6, global = #5, #7, 
and #9-10). The items cover question format consisting of a mixture of positive (#1, #4-7, and 
#9-10) and negative (#2, #3, and #8) statements in Likert categories (1 = strongly disagree, 2 = 
disagree, 3 = neutral, 4 = agree, 5 = strongly agree). Trust is measured with a sum of the 10 item 
scores, with reverse scoring for negative items, to produce a range of scores from 10 to 50, with 
higher scores demonstrating higher levels of trust. For purposes of this study the questions with 
the words “your doctor” were replaced with “your physical therapist”. The final Flesch reading 
ease is 54.0, demonstrating a Flesch-Kincaid grade level of 9.6 according to Microsoft® Word 
365 for Office (Redman, WA).  (Appendix E) 
General Trust in Physician Scale: Patient general trust in healthcare providers has been 
shown to be different than interpersonal healthcare provider trust.37 Thus general trust potentially 
has a strong influence on the formation of interpersonal trust and was measured prior to the 
initial visit for the purpose of this study with the General Trust in Physician Scale.37 This scale 
was developed to test general trust in physicians in contrast to other scales that assess individual 
physician trust. An 11-item scale was formulated from the initial 25 candidate items that were 
based on five domains (fidelity, competence, honesty, confidentiality, and global trust). Five-
point Likert scale categories were utilized for each question (1 = strongly disagree, 2 = disagree, 
3 = neutral, 4 = agree, 5 = strongly agree). The final 11-items have both positive (#1, #3-6, and 
#8-10) and negative (#2 and #7) worded questions, with reverse scoring for negative items. 
Scores can range from 11 to 55, with higher scores demonstrating higher trust. If one or two 
scores were left out, the missing values were imputed with the average score, if three or more 
scores were missing the total score was not be calculated and left out. The words “physical 
therapists” were inserted for the word “physician” for use with this study. The General Trust in 

Physician Scale according to Microsoft® Word 365 for Office (Redman, WA) has a Flesch 
reading ease of 42.4 providing a Flesch-Kincaid grade level of 10.8. (Appendix F) 
Working Alliance Inventory-Short Revised: The Working Alliance Inventory-Short 
Revised (WAI-SR)127 is one of the most commonly used instruments to measure the alliance 
between patients and therapists in physical rehabilitation.55 A 12-item short form was originally 
developed in 1989128 from the original 1986 36-item Working Alliance Inventory129 and revised 
in 2006127 into the current WAI-SR. The WAI-SR has been developed to assess Bordin’s Task, 
Goal, and Bonds dimensions.18 The scale is measured on a 5-point Likert scale (1 = never, 2 = 
rarely, 3 = sometimes, 4 = often, 5 = always). All items are positively worded and higher scores 
reflect higher levels of therapeutic alliance. Flesch reading ease score is at 63.0, producing a 
Flesch-Kincaid grade level of 8.0 according to Microsoft® Word 365 for Office (Redman, WA).  
(Appendix G) 
PT Survey of Patient Connection and Engagement: This survey questionnaire was 
developed for use during this dissertation study. An original 10-question survey was developed 
and created based on current literature48,52,93,130,131 in the area of TA along with personal 
conversation with experts in the field of physical therapy and patient care management. After 
original survey item creation was completed, it was sent to a panel of five clinicians throughout 
the US that have experience in research and the study of patient involvement and psychosocial 
aspects of clinical care from both practice and academic settings. After review of the 
questionnaire and the comments made by the panel, it was revised into its current consensus 
form. This questionnaire is aimed to evaluate the physical therapist’s perceptions of the patient’s 
engagement and connection with their physical therapist during the therapeutic encounter. No 
measurement tool such as this exists based on the review of the current literature. The scale 

contains 10 positively worded items scored on a 5-point Likert scale (1 = very poor, 2 = below 
average, 3 = average, 4 = above average, 5 = excellent). The score contains two sub-scores 
connection (questions 1, 3, and 7) and engagement (questions 2, 4-6, and 8-10). The 
questionnaire scores a 62.0 on the Flesch reading ease scale, making it at an 8.5 Flesch-Kincaid 
grade level according to Microsoft® Word 365 for Office (Redman, WA). (Appendix H) 
3.3.3 Instruments – Outcome measurement variables 
 
The outcome measurements chosen for this study assessed the patients’ progress during 
their physical therapy episode of care on various levels. Patient reported outcomes assessed 
clinical pain and functional progress by utilizing the Oswestry Disability Index 2.0 (ODI), 
Numeric Pain Rating Scale (NPRS), and a Global Rate of Change Scale (GROC) as these have 
been shown to be more responsive than physical impairment measurements.132,133  
 
Oswestry Disability Index 2.0: Improvement in function is a key outcome measurement 
for clinical conditions and the ODI has shown to have some of the best responsiveness when it 
comes to patients with low back pain.134 The ODI has been an extensively used measurement 
tool to evaluate function and how back pain affects an individual’s ability to do daily 
activities.135-138 The ODI assesses function in 10 categories (pain intensity, personal care, lifting, 
walking, sitting, standing, sleeping, sexual activity, social life, and traveling). Version 2.0135 was 
utilized for the purposes of this study. Each of the 10 categories has six statements that are 
scored from 0 to 5, the statement with the least disability is scored a 0 and the greatest disability 
scored with a 5. If more than one statement is marked, then the highest score is recorded. The 
overall score (index) is calculated by taking the total points added up for items answered and 
dividing by the total possible score (number of categories answered x 5). This number is then 
multiplied by 100 and rounded to a whole number. Overall index scores can be interpreted for 

the range of 0-20% for minimal disability, 21-40% for moderate disability, 41-60% for severe 
disability, 61-80% for crippled, and 81-100% for individuals bed bound or exaggerating their 
symptoms.139,140 (Appendix I) 
Numeric Pain Rating Scale: The NPRS is a unidimensional measurement of pain 
intensity in adults.132,141-147 It consists of an 11-point ordinal scale measuring pain from “0” = no 
pain to “10” = worst pain imaginable. The respondents were asked to report on current, best and 
worst pain in the last 24 hours. All three scores (current, best, and worst) were recorded along 
calculation of the average of all three being reported. This scale has been used across various 
diagnoses and age ranges.132,143-145,148 (Appendix J)  
Global Rate of Change scale: The GROC scale, as stated in its name, is global rating of 
improvement and satisfaction over the course of treatment.149 It does not measure a specific 
dimension such as pain or function, but allows the patient to decide what they consider 
important. The GROC is a commonly used outcome tool in clinical research, especially as it 
relates to musculoskeletal care.150,151 The most common formats of the GROC is typically a 7, 
11, or 15 point scale on a number line with 0 in the middle and moving out one integer in the 
positive and negative numerical direction. The end anchors also contain the negative and positive 
words of “very much worse” and “very much improved” or ”completely better” with “no 
change” being in the middle at the zero.152 Evidence shows that scales with 7 or 11 points offer 
the best mix of patient preference, appropriate discrimination ability, and test-retest 
reliability.153,154 For purposes of this study the recommended 11-point scale was used (-5 = very 
much worse, 0 = unchanged, 5 = completely recovered).152 (Appendix K) 
3.3.4 Instruments – Demographic collection 

 
Demographic data was collected on both the patient along with the treating physical 
therapists involved in providing care. Each patient provided information regarding age, gender, 
race, and educational level. The patient’s birth order was recorded, as first born or only child 
have been shown to accept treatment more readily and stayed in treatment longer.155 Questions 
related to whether the patient had been seen in physical therapy previously, at this specific site, 
or by this specific therapist was enquired upon during the initial demographics screening. Lastly, 
the choice of why the patient participant selected physical therapy, the specific clinic, and 
physical therapist was asked. (Appendix B) Each of the participating physical therapists also 
completed a demographics form providing their age, gender, race, level of physical therapy 
education, specialty certifications (if any), and years practicing as a physical therapist. 
(Appendix L) 
3.3.5 Procedural process 
 
Clinical sites across the US were recruited to be data collection sites. These sites were 
chosen based on interest in participating with research design and availability to be a data 
collection site. Physical therapists at each location were given the option to opt in or out as a 
participating physical therapist. If the physical therapist opted in, they signed an informed 
consent and completed a physical therapist participant demographic information form and were 
provided a coded ID#.  
At each clinical site, front office staff that recognized potential patients for the study 
(patients being seen for initial evaluation of low back pain or equivalent diagnosis by a physical 
therapist that had consented to partake in the study) gave the patient a research study recruitment 
flier. Those patients interested in participating were provided a link to an online PsychData link 
to complete the informed consent and a HIPAA form. Once the patient participant provided 

informed consent, they progressed to additional PsychData questionnaires to be filled out by the 
patient participant prior to their initial evaluation with their physical therapist. Information 
collected consisted of: baseline demographic information sheet, General Trust in Physician 
Scale, Trust in Physician Scale, PCAS, Wake Forest Scale, ODI, and NPRS. The online 
participant data collection allowed for blinding of the physical therapist throughout the study to 
the trust measurement scores. Patient participants received normal physical therapy evaluation 
and treatment as directed by the physical therapist. Upon completion of the initial visit, the 
patient participant completed the WAI-SR, Trust in Physician Scale, PCAS, and Wake Forest 
Scale through a second PyschData link. After completion of the second physical therapy visit, 
the participating physical therapist completed the PT Survey of Patient Connection and 
Engagement. Patient participants were blinded to the physical therapist’s responses on this 
instrument. Patient participants continued to receive normal physical therapy as directed by the 
physical therapist working toward discontinuation of the current episode of care. The majority of 
the physical therapy encounters (80%) needed to have the initial physical therapist directly 
involved with the care of the patient participant to be eligible for data collection. If less than 80% 
of the visits have the direct care delivered by someone other than the initial physical therapist, 
that data was excluded from primary analysis. Upon discontinuation of the current episode of 
care or the end of 6 months of care, the patient participant completed the Trust in Physician 
Scale, PCAS, Wake Forrest Scale, WAI-SR, ODI, NPRS, and GROC. The participating physical 
therapist completed a second PT Survey of Patient Connection and Engagement at the 
conclusion of care. (Figure 1) Patient participants that complete all three series of forms (pre-
initial visit, post-initial visit, and discontinuation episode) were eligible for a total of $25 in 
Walmart gift cards to be mailed to an address of their choice. 

Statistical Analysis Plan (SAP) 
All data was coded and entered into SPSS version 27.0 (IBM Corp., Armonk, N.Y., USA) for statistical 
analysis. Patient participant and physical therapist participant demographic data was reported with 
means, ranges, and standard deviations. The primary correlational statistics was the Spearman rho to 
assess the various individual trust measurement scores and changes in scores over time and individual 
scores with the primary outcome measurements of pain, function, and global change. The individual 
trust measurement scores, that have not been used in physical therapy, were be analyzed for 
correlation to WIA-SR, which has been used in physical therapy research, with Spearman’s rho. 
Friedman’s analysis of variance looked at changes in individual trust measurement scores over time 
from pre-initial visit, post-initial visit, and discharge. The non-parametric analysis was used due to the 
ordinal nature of the outcome variables. The PT Survey of Patient Connection and Engagement was 
analyzed for correlation with outcomes and the individual trust measurement scales with the Spearman 
rho. Linear regression analysis was done with the individual trust measurement scales and outcomes 
variables for predictive modeling of trust and outcomes assessment.