Healthcare utilization predictors
We collected potential predictors by self-reported ques-
tionnaires at initial evaluation using an online study web-
site. Participants were directed back to the study website
4 weeks following initial evaluation to again complete
questions on pain intensity, disability, and pain-related
psychological distress. Change in pain intensity, disability,
and pain-related psychological distress from baseline to
4 weeks were modeled as treatment response variables
and included as potential predictors.
Sociodemographic and health-related information
Participants completed a standard intake questionnaire
form previously used in our clinical studies that assessed
age, sex, race, and insurance provider type. This ques-
tionnaire also assessed health-related variables included
anatomical region of primary pain complaint (low back,
neck, shoulder, or knee) and whether the patient had
undergone surgery for their primary pain complaints
(yes or no). Due to small cell sizes for certain categories,
race was dichotomized as white or non-white. For insur-
ance type, participants were asked to choose one of the
following options: private, public (Medicare and/or Me-
dicaid), uninsured/self-pay, worker ’s compensation, and
other/commercial insurance. Among the study sample,
we observed few with no insurance ( n = 7) or worker ’s
compensation ( n = 14). The study also included relatively
few with ‘other/commercial insurance ’ (n = 45). Within
this group, informal assessment of these various plans
suggested high heterogeneity of plan characteristics and
coverage. Due to the small number of subjects in these
individual insurance strata and to improve interpretabil-
ity of results, we collapsed those reporting no insurance,
worker’s compensation and other/commercial insurance
into a single category (i.e., ‘Other’). Therefore, insurance
type was categorized as private, public, or other (no in-
surance, worker ’s compensation, or other/commercial
insurance) for purposes of analysis.
Pain-related clinical variables
Pain status was determined using established definitions
that account for the duration of pain and activity limita-
tions [ 22, 23] using the following two questions: 1)
“How long have you been experiencing your current
painful symptoms? ” and 2) “Have you experienced ANY
pain and activity limitations every day for the past 3
months?” Responses to question 1 of “greater than 90
days” or responses to question 2 of “Yes” were used to
classify patients as having persistent pain at initial
evaluation.
Pain intensity
Pain intensity was assessed by the numerical pain rating
scale (NPRS) ranging from “0” (no pain) to “10” (worst
pain imaginable) [ 24– 26]. Participants rated their
current pain intensity, as well as their best (lowest) and
worst (highest) pain intensity over the past 24 h.
Current, best and worst pain ratings were averaged for
purposes of analysis.
Region-specific disability
Self-reported region-specific disability was assessed with
the Neck Disability Index [ 27, 28], Oswestry Disability
Questionnaire [29, 30], Quick Disability of Arm Shoulder
and Hand [ 31] or International Knee Documentation
Committee Subjective Knee Form [ 32] for cervical, low
back, shoulder and knee pain, respectively. Region-specific
disability measures were z-transformed for purposes of
analysis, consistent with our prior work involving multiple
anatomical regions [ 33].
Comorbidities
Charlson comorbidity index (CCI)
The Charlson Comorbidity Index was used to measure
the presence of chronic comorbid medical conditions
[34]. It lists 19 medical conditions that participants are
asked to indicate whether they “have ever been diag-
nosed with by a physician ”.C o n d i t i o n sa r ew e i g h t e d
and added for an overall measure of comorbidity
burden. The CCI has demonstrated good test-retest re-
liability (0.91) and positive but weak to modest correla-
tions with medication use, hospitalizations, length of