Trial Outcomes & Findings for Examining Racial and SocioEconomic Disparities (ERASED) in Chronic Low Back Pain Study (NCT NCT03338192)

NCT ID: NCT03338192

Last Updated: 2025-03-30

Results Overview

The Brief Pain Inventory Short-Form (BPI-SF) was used to assess clinical pain severity. Four items assessed participants' average, least, and worst pain over the past 24hours, as well as current pain (0=no pain, 10=pain as bad as you can imagine). These 4 items were averaged for a total score (range: 0-10).

• Recruitment status: COMPLETED
• Target enrollment: 281 participants
• Primary outcome timeframe: Baseline to one week.
• Results posted on: 2025-03-30

Participant Flow

Participant milestones

Measure	African American/Black QST This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Year One to Year Two STARTED	173	108
Year One to Year Two COMPLETED	165	107
Year One to Year Two NOT COMPLETED	8	1
Year Two to Year Four STARTED	165	107
Year Two to Year Four COMPLETED	162	107
Year Two to Year Four NOT COMPLETED	3	0
Year Four to Year Six STARTED	162	107
Year Four to Year Six COMPLETED	160	106
Year Four to Year Six NOT COMPLETED	2	1

Reasons for withdrawal

Measure	African American/Black QST This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Year One to Year Two High Blood Pressure	7	1
Year One to Year Two HIV +	1	0
Year Two to Year Four High Blood Pressure	1	0
Year Two to Year Four HIV +	2	0
Year Four to Year Six High Blood Pressure	2	1

Baseline Characteristics

Examining Racial and SocioEconomic Disparities (ERASED) in Chronic Low Back Pain Study

Baseline characteristics by cohort

Measure	African American/Black QST n=173 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=108 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Total n=281 Participants Total of all reporting groups
Age, Categorical <=18 years	0 Participants n=93 Participants	0 Participants n=4 Participants	0 Participants n=27 Participants
Age, Categorical Between 18 and 65 years	165 Participants n=93 Participants	99 Participants n=4 Participants	264 Participants n=27 Participants
Age, Categorical >=65 years	8 Participants n=93 Participants	9 Participants n=4 Participants	17 Participants n=27 Participants
Sex: Female, Male Female	98 Participants n=93 Participants	62 Participants n=4 Participants	160 Participants n=27 Participants
Sex: Female, Male Male	75 Participants n=93 Participants	46 Participants n=4 Participants	121 Participants n=27 Participants
Race (NIH/OMB) American Indian or Alaska Native	0 Participants n=93 Participants	0 Participants n=4 Participants	0 Participants n=27 Participants
Race (NIH/OMB) Asian	0 Participants n=93 Participants	0 Participants n=4 Participants	0 Participants n=27 Participants
Race (NIH/OMB) Native Hawaiian or Other Pacific Islander	0 Participants n=93 Participants	0 Participants n=4 Participants	0 Participants n=27 Participants
Race (NIH/OMB) Black or African American	173 Participants n=93 Participants	0 Participants n=4 Participants	173 Participants n=27 Participants
Race (NIH/OMB) White	0 Participants n=93 Participants	108 Participants n=4 Participants	108 Participants n=27 Participants
Race (NIH/OMB) More than one race	0 Participants n=93 Participants	0 Participants n=4 Participants	0 Participants n=27 Participants
Race (NIH/OMB) Unknown or Not Reported	0 Participants n=93 Participants	0 Participants n=4 Participants	0 Participants n=27 Participants
Region of Enrollment United States	173 Participants n=93 Participants	108 Participants n=4 Participants	281 Participants n=27 Participants
Brief Pain Inventory-Short Form (BPI) pain severity scale	5.1 units on a scale STANDARD_DEVIATION 2.1 • n=93 Participants	3.9 units on a scale STANDARD_DEVIATION 1.7 • n=4 Participants	4.7 units on a scale STANDARD_DEVIATION 2.1 • n=27 Participants

PRIMARY outcome

Timeframe: Baseline to one week.

The Brief Pain Inventory Short-Form (BPI-SF) was used to assess clinical pain severity. Four items assessed participants' average, least, and worst pain over the past 24hours, as well as current pain (0=no pain, 10=pain as bad as you can imagine). These 4 items were averaged for a total score (range: 0-10).

Outcome measures

Measure	African American/Black QST n=154 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=96 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Average Clinical Pain Severity	5.1 units on a scale Standard Deviation 2.1	3.9 units on a scale Standard Deviation 1.7

SECONDARY outcome

Timeframe: Baseline

Pain threshold refers to the intensity at which a stimulus is first perceived as painful. Heat stimuli will be delivered using a computer-controlled thermal stimulation system with a 30 millimeter X 30 millimeter probe. From a baseline of 32 degrees Celsius, the probe temperature will increase at a rate of .5 degrees Celsius/second until the participant responds by pressing a button on a handheld device. For heat pain threshold, participants will be instructed to press the button when the sensation "first becomes painful". Heat pain threshold was assessed at the lumbar spine. On a scale of 32 degrees Celsius to 51 degrees Celsius, with 51 being the hottest temperature.

Outcome measures

Measure	African American/Black QST n=159 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=99 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Average Pain Threshold (Heat)	39.96 degrees Celsius Standard Deviation 13.87	40.54 degrees Celsius Standard Deviation 14.45

SECONDARY outcome

Timeframe: Baseline

Pain tolerance refers to the maximum amount of pain produced by a stimulus that a person is able/willing to tolerate. Heat stimuli will again be delivered using the computer-controlled thermal stimulation system. From a baseline of 32 degrees Celsius, the probe temperature will increase at a rate of .5 degrees Celsius/second until the participant responds by pressing a button on a handheld device. For heat pain tolerance, participants will be instructed to press the button when they are "no longer willing to tolerate" the painful sensation. Heat pain tolerance was assessed at the lumbar spine. Scale range from 32 degrees Celsius to 51 degrees Celsius with 51 being the hottest.

Outcome measures

Measure	African American/Black QST n=159 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=99 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Average Pain Tolerance (Heat)	42.50 degrees Celsius Standard Deviation 13.79	44.61 degrees Celsius Standard Deviation 14.80

SECONDARY outcome

Timeframe: Baseline

Temporal summation of pain refers to a form of endogenous pain facilitation characterized by the perception of increased pain despite constant or even reduced peripheral afferent input. Temporal summation is presumed to be the psychophysical manifestation of wind-up. Wind-up is a phenomenon where repetitive stimulation of C primary afferents at rates greater than 0.3 Hertz produces a slowly increasing response of second-order neurons in the spinal cord. Temporal summation was assessed at the lumbar spine using a 512 milliNewton punctate probe. Participants are stimulated once with the punctate probe and asked to provide a pain rating from 0-100 whereby 0 = no pain and 100 = most intense pain imaginable. They are then stimulated 10 consecutive times with the punctate probe and asked to provide another pain rating from 0-100. Temporal summation is the difference between these two ratings, such that positive scores indicate pain facilitation and negative scores indicate pain inhibition.

Outcome measures

Measure	African American/Black QST n=157 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=98 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Difference in Temporal Summation of Pain (Mechanical)	20.16 units on a scale Standard Deviation 27.64	12.68 units on a scale Standard Deviation 18.08

SECONDARY outcome

Timeframe: Baseline

Pressure was manually applied and increased at a rate of 30 kPa/s. Participants indicated when the pressure was first perceived to be painful (pressure pain threshold) via button-push. Three applications of a handheld algometer were used to determine baseline pressure pain thresholds (PPTs). Following this, participants underwent two trials of cold pressor immersion. Participants placed their entire hand, up to the wrist, into 12 °C water for 60 s. Immediately following withdrawal of the hand from the cold pressor, the algometer was re-applied at the lumbar region. Participants again indicated when they first perceived the pressure as painful (conditioned PPT). The trial was repeated following a two-minute rest period. The baseline PPTs were averaged, as were the two conditioned PPTs. Conditioned pain modulation was calculated as the difference between Conditioned PPT - Baseline PPT. Positive difference scores indicate pain inhibition and negative scores indicate facilitation.

Outcome measures

Measure	African American/Black QST n=160 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=97 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Difference in Pressure Pain Thresholds Assessed Using Conditioned Pain Modulation	-7.82 Difference in kiloPascals of pressure Standard Deviation 30.05	-10.80 Difference in kiloPascals of pressure Standard Deviation 27.43

SECONDARY outcome

Timeframe: One week follow up

A single blood draw was collected from each participant during their one week follow up visit. The blood was processed and serum was used to quantify C-reactive protein, which is a marker of systemic pro-inflammation. Increasing levels of C-reactive protein are suggestive of greater inflammation.

Outcome measures

Measure	African American/Black QST n=155 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=95 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Total Level of C-reactive Protein	6394.52 nanograms per milliliter Standard Deviation 12828.45	5040.71 nanograms per milliliter Standard Deviation 5309.51

SECONDARY outcome

Timeframe: One week follow up

Fibrinogen is a protein that plays a crucial role in blood clotting. It is produced by the liver and is present in the blood plasma. Fibrinogen is considered a key player in inflammation, acting as a pro-inflammatory molecule by directly interacting with immune cells and promoting their migration to the site of injury, essentially serving as a "scaffold" for the inflammatory response, and its levels significantly increase during inflammatory conditions, making it a marker for inflammation in the body; high fibrinogen levels often indicate an ongoing inflammatory process.

Outcome measures

Measure	African American/Black QST n=131 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=81 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Total Level of Fibrinogen	1656.55 nanograms per milliliter Standard Deviation 1052.78	1417.26 nanograms per milliliter Standard Deviation 1046.08

SECONDARY outcome

Timeframe: One week follow up

Serum amyloid A (SAA) is considered a key marker of inflammation, as its levels significantly increase in the blood during an inflammatory response, acting as an "acute phase reactant" produced by the liver when stimulated by pro-inflammatory cytokines like interleukin-6 (IL-6); essentially, high SAA levels indicate the presence of active inflammation in the body.

Outcome measures

Measure	African American/Black QST n=131 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=81 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Total Level of Serum Amyloid A	12224.88 nanograms per milliliter Standard Deviation 17436.72	9109.35 nanograms per milliliter Standard Deviation 12349.25

SECONDARY outcome

Timeframe: One week follow up

Vitamin D (also referred to as calciferol) is a fat-soluble vitamin that is naturally present in a few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet (UV) rays from sunlight strike the skin and trigger vitamin D synthesis. We quantified Vitamin D from blood serum. Lower levels of Vitamin D have been associated with greater musculoskeletal pain severity and worse bone and muscle health.

Outcome measures

Measure	African American/Black QST n=97 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=59 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Total Level of Vitamin D	20.5 nanograms per milliliter Standard Deviation 11.1	26.9 nanograms per milliliter Standard Deviation 10.3

SECONDARY outcome

Timeframe: One week follow up

Oxytocin is a hormone that plays a crucial role in various physiological and behavioral processes, particularly in reproduction, social bonding, and emotional well-being.

Outcome measures

Measure	African American/Black QST n=51 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=38 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Total Level of Oxytocin	181.54 nanograms per milliliter Standard Deviation 69.39	192.71 nanograms per milliliter Standard Deviation 87.92

SECONDARY outcome

Timeframe: Between baseline and one week follow-up

Insomnia Severity Index (ISI) was used to measure sleep quality. The ISI is a seven-item questionnaire used to evaluate the severity and impact of insomnia. Participants used a 5-point Likert scale to rate severity of difficulties with sleep onset and sleep maintenance as well as problems with early morning awakenings, sleep dissatisfaction, and interference of sleep difficulties with daytime functioning within the last month. Items are summed to calculate a total score ranging from 0 to 28, thus, indicating absence of insomnia (0-7), subthreshold insomnia (8-14), moderate insomnia (15-21) and severe insomnia (22-28).

Outcome measures

Measure	African American/Black QST n=155 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=97 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Sleep Quality	12.08 units on a scale Standard Deviation 7.10	12.12 units on a scale Standard Deviation 7.40

SECONDARY outcome

Timeframe: One week follow up

Self-reported disability was assessed using the Graded Chronic Pain Scale (GCPS) - interference scale. A higher score on the interference section indicates a greater level of disruption to daily life due to pain. The GCPS scale ranges from 0-100 and higher scores are indicative of greater self-reported disability.

Outcome measures

Measure	African American/Black QST n=155 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=96 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Self-reported Disability	53.40 units on a scale Standard Deviation 29.49	41.96 units on a scale Standard Deviation 26.39

SECONDARY outcome

Timeframe: One week follow up

The Short Physical Performance Battery was used to assess movement-evoked pain. Participants completed three movements (balance, chair stands, and walking). After completion of each movement task, participants were asked to provide a pain intensity rating for any movement-evoked pain experienced during completion of the balance, chair stands, and walking tests. The 0-100 numeric rating scale was utilized for this purpose, whereby: (0 = no pain and 100 = most intense pain imaginable). Average pain intensity was calculated across the three movements.

Outcome measures

Measure	African American/Black QST n=159 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=99 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Evoked Pain With Movement	31.01 units on a scale Standard Deviation 31.00	13.33 units on a scale Standard Deviation 18.88

SECONDARY outcome

Timeframe: One week follow up

The Short Physical Performance Battery (SPPB) is an objective measurement instrument of balance, lower extremity strength, and functional capacity in adults. The test includes three different domains (walking, sit-to-stand and balance) to assess functional mobility. Scores range from 0 to 12 with higher scores suggest of better functional performance.

Outcome measures

Measure	African American/Black QST n=159 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=99 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Functional Performance	8.95 units on a scale Standard Deviation 1.81	9.82 units on a scale Standard Deviation 1.75

OTHER_PRE_SPECIFIED outcome

Timeframe: Baseline

The 20-item Center for Epidemiological Studies- Depression (CES-D) scale was used to measure depressive symptoms over the past week (0=rarely or none of the time [less than 1 day], 3=most or all of the time [5-7days]). All items were summed, such that higher scores suggest greater depression severity (range: 0-60).

Outcome measures

Measure	African American/Black QST n=154 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=96 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Depressive Symptoms	16.0 units on a scale Standard Deviation 10.0	17.6 units on a scale Standard Deviation 11.8

OTHER_PRE_SPECIFIED outcome

Timeframe: Baseline

The Injustice Experience Questionnaire (IEQ) was used to assess perception of pain-related injustice in this sample. Participants rated the frequency with which they experienced each of 12 thoughts/feelings when reflecting on their chronic pain condition. Items are rated on a scale of 0 (never) to 4 (all of the time). Injustice Experience Questionnaire items broadly reflect the associated factors of "severity/irreparability of loss" and "blame/unfairness." Representative severity/irreparability items include "Most people don't understand how severe my condition is, and "My life will never be the same." Blame/unfairness items include "I am suffering because of someone else's negligence, and "It all seems so unfair." The total score was used and it ranges from 0 to 48 with higher scores representing greater perceived injustice.

Outcome measures

Measure	African American/Black QST n=159 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=95 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Average Perceived Injustice (Pain-related)	15.69 units on a scale Standard Deviation 12.68	13.85 units on a scale Standard Deviation 11.50

OTHER_PRE_SPECIFIED outcome

Timeframe: Baseline

The Experiences of Discrimination (EOD) scale was used to assess lifetime occurrences of racial discrimination across 9 different domains (eg, at work, getting medical care). Participants rated the frequency with which they perceived experiencing discrimination in each situation (0=never, 1=once, 2.5=2-3 times, 5=4 or more times). Responses across all items were summed and higher score suggest greater perceived discrimination (range: 0-45).

Outcome measures

Measure	African American/Black QST n=154 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=96 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Perceived Discrimination	10.3 units on a scale Standard Deviation 9.6	4.1 units on a scale Standard Deviation 8.1

OTHER_PRE_SPECIFIED outcome

Timeframe: Baseline

Measured using the Multidimensional Survey of Perceived Social Support Scale (MSPSS). This scale consisted of 12 items that measure the extent of social support received from 3 specific sources: friends, family, and significant others. Types of social support assessed by the MSPSS included emotional (eg, "I get the emotional help and support I need from my family"), tangible (eg, "There is a special person who is around when I am in need"), informational (eg, "My family is willing to help me make decisions"), social network support (eg, "I can count on my friends when things go wrong"), and esteem (eg, "I have a special person who is a real source of comfort to me"). Each item was scored on a scale ranging from 1 (very strongly disagree) to 7 (very strongly agree). Summation of the 12 item scores provided a possible total score ranging from 12 to 84 for overall social support, with higher scores corresponding to higher levels of social support.

Outcome measures

Measure	African American/Black QST n=154 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=95 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Social Support	64.62 units on a scale Standard Deviation 15.60	65.88 units on a scale Standard Deviation 15.01

OTHER_PRE_SPECIFIED outcome

Timeframe: Baseline

The Pain Resilience Scale (PRS) is a 14-item assessment of resilience in the presence of intense or prolonged pain. The assessment has 2 subscales to measure specific domains of resilience: behavioral perseverance and cognitive/affective positivity. The behavioral perseverance subscale examines an individual's ability to continue engaging in behaviors or activity when experiencing pain. The cognitive/affective positivity subscale examines an individual's ability to maintain positive thoughts and manage negative thoughts or emotions while in pain. Each item is scored from 0 (not at all) to 4 (all the time) to determine the degree to which individuals engage in resiliency resources. The total Pain Resilience Scale (PRS) ranges from 0 to 56, calculated as the sum of all 14 items. Higher scores suggest greater pain resilience.

Outcome measures

Measure	African American/Black QST n=159 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=96 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Total Psychological Pain Resilience	39.49 units on a scale Standard Deviation 10.41	38.82 units on a scale Standard Deviation 10.13

OTHER_PRE_SPECIFIED outcome

Timeframe: Between baseline and one week follow up

Measured using a daily diary of dietary intake across seven days. The value presented represents the average daily caffeine consumption.

Outcome measures

Measure	African American/Black QST n=31 Participants This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=31 Participants This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Average Dietary Caffeine Consumption	165.12 milligrams per day Standard Deviation 208.10	219.13 milligrams per day Standard Deviation 208.49

Adverse Events

African American/Black QST

Serious events: 0 serious events

Other events: 15 other events

Deaths: 0 deaths

Caucasian/White QST

Serious events: 0 serious events

Other events: 1 other events

Deaths: 0 deaths

Serious adverse events

Adverse event data not reported

Other adverse events

Measure	African American/Black QST n=173 participants at risk This group will consist of a full range of socioeconomic status in African American/Black individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.	Caucasian/White QST n=108 participants at risk This group will consist of a full range of socioeconomic status in Caucasian/White individuals with chronic low back pain. QST: All participants will undergo quantitative sensory testing for assessment of endogenous pain modulation using painful heat, mechanical, and cold stimuli in a laboratory session lasting approximately 1 hour.
Cardiac disorders High Blood Pressure	6.9% 12/173 • Number of events 12 • 6 weeks We had no adverse events linked to this protocol.	0.93% 1/108 • Number of events 1 • 6 weeks We had no adverse events linked to this protocol.
Immune system disorders HIV +	1.7% 3/173 • Number of events 3 • 6 weeks We had no adverse events linked to this protocol.	0.00% 0/108 • 6 weeks We had no adverse events linked to this protocol.

Additional Information

Burel Goodin

Washington University Pain Center in St. Louis

Phone: 3142736403

Email: burel@wustl.edu

Results disclosure agreements

• Principal investigator is a sponsor employee
• Publication restrictions are in place