Examining Racial and SocioEconomic Disparities (ERASED) in Chronic Low Back Pain Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Examining Racial and SocioEconomic Disparities (ERASED) in Chronic Low Back Pain Study (NCT03338192), a registered phase not stated study. The primary outcome is Average Clinical Pain Severity.

2. Clinical Question

The central question is about describing and characterizing differences, rather than estimating the effect of a randomized treatment. The study summary says it remains unclear whether disadvantaged subgroups may be at heightened risk for poor chronic low back pain outcomes. Its stated aims are to incorporate a socioeconomic framework when characterizing racial differences in pain severity and disability, and to examine racial and socioeconomic differences in predictors of outcomes.

The primary outcome is average clinical pain severity. The registry specifies a baseline-to-one-week timeframe, but does not report group-level outcome values or an estimated difference. As a result, the study question can be described from the stated aims, but the magnitude or precision of any group contrast cannot be judged from the registry record.

3. Trial Design

ERASED is a study of chronic low back pain whose stated focus is racial and socioeconomic differences. The registry lists the study as completed and reports an enrollment of 281. The recorded start date is 2017-10-15, and the primary completion date is 2024-01-31. The sponsor is the University of Alabama at Birmingham.

The registry lists two groups: African American/Black QST and Caucasian/White QST. Each group description says it includes a full range of socioeconomic status within the named racial group. QST is listed as an intervention of type “OTHER,” but the record does not describe a treatment assignment or a randomized procedure. Allocation is not stated. Therefore, the group labels identify the populations being compared, not treatment and control conditions that can be presumed exchangeable.

The stated overall aim is to use a socioeconomic framework to characterize racial differences in chronic low back pain severity and disability. A further aim, guided by the theory of fundamental causes, is to examine racial and socioeconomic differences in biopsychosocial predictors of outcomes, particularly endogenous pain modulation. The listed outcomes include heat pain threshold and tolerance, mechanical temporal summation, pressure pain thresholds assessed using conditioned pain modulation, and several blood-based measures.

The primary outcome is average clinical pain severity, assessed with the Brief Pain Inventory Short-Form over the registry’s stated baseline-to-one-week timeframe. The record does not report a detailed statistical analysis plan, allocation method, or primary-outcome results. It reports 20 outcome measures and 0 analyses. These registry entries do not establish what analyses may have been conducted outside the record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Year One to Year Two

Reasons for not completing this period:

Year Two to Year Four

Reasons for not completing this period:

Year Four to Year Six

Reasons for not completing this period:

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Average Clinical Pain Severity, measured over Baseline to one week..

The primary endpoint is average clinical pain severity, measured using the Brief Pain Inventory Short-Form (BPI-SF). The registry describes four items assessing average, least, and worst pain over the past 24hours, as well as current pain. Each item uses a scale from 0, “no pain,” to 10, “pain as bad as you can imagine.” The four items are averaged to form a total score with a range of 0-10.

A mean is a way to describe the central level of a continuous measurement across participants. For this endpoint, a group mean would summarize the average reported pain severity in that group. The standard deviation, identified as the dispersion measure, describes how spread out individual scores are around the mean. A mean alone does not show how similar or varied participants’ scores were.

Pain severity is used as the primary endpoint because it directly addresses the study’s stated interest in chronic low back pain outcomes. The registry identifies the measurement timeframe as baseline to one week. It does not report the actual mean, standard deviation, group contrast, or uncertainty estimate. Thus, the endpoint and its measurement are specified, but the size and precision of the observed result are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary outcome as a continuous measure summarized by a mean and standard deviation. In general, a mean gives the arithmetic center of a set of measurements, while a standard deviation describes their dispersion. For the BPI-SF endpoint, the score is created by averaging four pain items, each rated from 0 to 10. That scoring description clarifies what the measure represents; it does not provide the observed group summaries.

What would a group contrast represent?

In general, comparing two group means describes how far apart their average measurements are. That contrast is an estimate based on the participants measured, not automatically a causal effect. A confidence interval, when reported, expresses uncertainty around an estimate under the analysis assumptions; it can help distinguish a precisely estimated contrast from one that remains uncertain. The registry record does not report a primary-outcome contrast or confidence interval, so neither the estimate nor its precision can be assessed.

The distinction between association and causation is especially relevant to the listed groups. The record describes racial groups spanning a full range of socioeconomic status, but it does not report random allocation. Randomization is one general method of balancing measured and unmeasured characteristics on average. Without a randomized comparison, differences in group composition can be intertwined with differences in outcome. Statistical adjustment can sometimes address measured characteristics, but the registry does not report an adjustment model or covariates.

Why does variability matter?

Standard deviations provide context for means. If individual values vary widely, a group average may conceal substantial variation among participants. Greater variability can also make estimates less precise. In some types of data, variability may differ across groups or the distribution may not fit assumptions of a simple normal model. Over-dispersion is a general term for variation greater than a model expects; it can make standard errors and inferential conclusions unreliable if the model does not account for it. The registry identifies standard deviation as the primary outcome’s dispersion measure, but reports no observed values or model diagnostics.

Continuous outcomes can be analyzed in several ways, depending on the design, distribution, and question. General options include estimating group means, modeling associations with relevant characteristics, or using methods suited to non-normal data. These options are explanations of statistical practice, not descriptions of analyses confirmed for this study. The registry records 0 analyses and does not report which model, test, covariates, or diagnostic checks were used outside the registry.

How should planning calculations be read?

Sample-size calculations are planning tools. The registry’s planning description specifies a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. It says that non-time-to-event planning values refer to participants per arm. Such calculations illustrate the sample size associated with assumptions; they are not observed results and do not show that a study had a particular probability of detecting an effect after completion. The record does not report the observed primary-outcome effect needed to evaluate the assumptions or resulting planning values.

Planning calculations should also be distinguished from retrospective “observed power.” In general, power is a design quantity defined using assumptions about the effect, variability, sample size, and significance threshold. Calculating power from an observed estimate after a study does not replace examination of the estimate and its confidence interval. Because the registry does not give the outcome estimates or their dispersion, it does not support a numerical assessment of precision based on the observed primary outcome.

What do the many outcome measures imply?

When a study assesses multiple outcomes or contrasts, multiplicity is a general concern: the more questions tested, the greater the chance that some results may appear noteworthy by chance if no plan accounts for the number of tests. Appropriate interpretation depends on which outcomes were prespecified, how many analyses were conducted, and whether any adjustment or hierarchy was used. The registry lists 20 outcome measures but records 0 analyses. It does not report a multiplicity strategy or clarify how results across measures were to be interpreted.

Finally, a registry’s outcome description, study status, and result record are different kinds of information. A completed status indicates the study is listed as completed; it does not itself provide results. The primary measure and time frame are specified, but the record does not report missing-data handling, analysis populations, or statistical estimates. These omissions limit what can be concluded from the registry entry.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("African American/Black QST", "Caucasian/White QST")
n   <- c(154, 96)
m   <- c(5.1, 3.9)
sp  <- c(2.1, 1.7)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  African American/Black QST  154  5.100  2.100  4.766  5.434
CARM  Caucasian/White QST  96  3.900  1.700  3.556  4.244

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 20 outcome measures, including the primary pain-severity endpoint and secondary measures of pain sensitivity, pain modulation, and blood-based markers. Considering several outcomes raises a general multiplicity issue: if many statistical tests are performed, some may appear statistically notable by chance. Interpretation depends on the prespecified outcome hierarchy, the analyses actually conducted, and whether any adjustment or other strategy was used. A multiplicity plan is not reported in the registry record.

The record reports 0 analyses. It does not describe whether analyses were performed outside the registry, whether the primary outcome was analyzed according to a prespecified plan, or how secondary outcomes were handled. No p-values or confidence intervals are reported. As a result, it is not possible to assess the number of comparisons underlying any reported claim or whether uncertainty was adjusted for multiple testing.

Missing-data handling is not reported in the registry record. The entry does not state how incomplete BPI-SF responses, missing follow-up measurements, or unavailable secondary measures were treated. It also does not describe an analysis population, such as who was included in each outcome analysis, or whether exclusions occurred. These details matter because the participants contributing to an estimate can affect its interpretation.

The registry’s enrollment figure does not establish how many participants contributed data to each outcome. Nor does the listed group information establish the completeness of measurements at each time point. Without participant flow, outcome-specific denominators, and a missing-data approach, the extent and possible consequences of missing observations cannot be assessed. No assumption about the cause or pattern of missingness is justified by the record.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists serious adverse events, other adverse events, and deaths separately for the two groups. For African American/Black QST, serious adverse events are recorded as 0 among 173 at risk, other adverse events as 15 among 173 at risk, and deaths as 0. For Caucasian/White QST, serious adverse events are recorded as 0 among 108 at risk, other adverse events as 1 among 108 at risk, and deaths as 0.

These are descriptive registry counts. The record does not provide event descriptions, timing, severity details for the other events, or an explanation of how events were collected. The groups are not described as randomized treatment arms, so the counts should not be interpreted as a causal comparison of treatment-related risk. They also do not establish that an event was caused by QST or by any particular exposure.

Zero recorded serious events or deaths means that none are listed in those categories for the groups in this record; it does not establish that risk is absent. The registry does not report an analysis comparing event rates, and no rate or percentage should be inferred from the counts. Safety interpretation is therefore limited to reading the recorded counts in their stated groups and categories.

13. What the Result Does, and Does Not, Mean

The study’s aims address an important descriptive question: whether racial and socioeconomic differences are associated with chronic low back pain severity, disability, and biopsychosocial predictors, particularly endogenous pain modulation. The registry identifies the population, group labels, primary pain measure, and additional outcomes relevant to those aims. It also records the study as completed.

However, the registry record does not report primary-outcome estimates, secondary-outcome results, or statistical analyses. It therefore does not show whether average clinical pain severity differed between the listed groups, in which direction any difference went, or how precisely it was estimated. It cannot support a conclusion about statistical significance or clinical importance. The stated research aims describe what the study sought to examine, not what its results demonstrated.

The group comparison also needs to be interpreted in light of the design information. The record does not state that participants were randomized, and it identifies the groups by race rather than by assigned treatment. Differences between groups, if reported elsewhere, would require careful consideration of socioeconomic and other group characteristics. The registry does not describe an adjustment plan, so the degree to which such characteristics were accounted for is unknown.

The adverse-event entries provide counts only. They do not establish a treatment effect or explain why events occurred. Likewise, the listed secondary outcomes indicate what was measured but do not establish findings about pain mechanisms or biological markers.

In short, the registry entry makes the study’s intended question and measurement approach clear, but leaves its quantitative answer unavailable. Conclusions about outcome differences or mechanisms require results and analysis details that are not reported in the registry record.

14. Why This Trial Matters Statistically

This study is statistically notable for framing chronic low back pain within a socioeconomic context rather than treating racial group labels as a complete explanation of differences. Its stated aim is to characterize racial differences in severity and disability while examining socioeconomic status and biopsychosocial predictors. That framing makes the distinction between group description and causal explanation central to interpretation.

For statistical analysis, the key challenge is that the named groups are not reported as randomized arms. Comparisons can describe patterns, but group differences may reflect multiple related characteristics. A careful analysis would need to make its estimand clear, define the role of socioeconomic status, and explain which factors are accounted for. The registry record does not report those analysis details, so readers cannot determine how the study addressed these challenges.

The primary endpoint also illustrates why both a point estimate and uncertainty matter. A mean BPI-SF score summarizes average reported pain severity, while the standard deviation describes variation among participants. Without the means, dispersion, and an uncertainty estimate, readers cannot assess the size, consistency, or precision of a possible group contrast.

The study’s breadth, including pain-processing measures and biological outcomes, creates a further need for transparent outcome prioritization and multiplicity handling. The registry lists 20 outcome measures, but does not report an analysis plan or multiplicity strategy. These are not minor technical details: they shape how confidently findings across several measures can be interpreted.

The registry record therefore supports understanding the study’s question and measurement choices, while also showing why complete reporting of estimates, uncertainty, missing-data methods, and analysis decisions is essential for evaluating observational research.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record leaves several limitations specific to interpretation of this study. First, it does not report results for the primary outcome or any of the listed secondary outcomes. The record therefore cannot establish the direction, magnitude, or precision of the differences the study aimed to examine.

Second, allocation is not stated, and the two groups are not a like-for-like randomized comparison. The entry does not explain how participants entered each group or report methods for addressing potential differences in socioeconomic status or other characteristics. This limits causal interpretation of any group contrast, even if estimates are available elsewhere.

Third, the primary outcome is described with a baseline-to-one-week timeframe, but the record does not explain the timing of individual assessments, how follow-up measurements were handled, or which participants contributed data at each assessment. Missing-data procedures and analysis populations are not reported. It is therefore not possible to evaluate attrition or the completeness of outcome data from this entry.

Fourth, the registry lists 20 outcome measures but does not provide a multiplicity plan, analysis hierarchy, or statistical model. It also records 0 analyses. These omissions prevent assessment of whether results were prespecified, how multiple comparisons were interpreted, or whether covariates were included.

Finally, the safety record provides counts without event descriptions or comparative analysis. These figures cannot identify causes or establish relative risk. Taken together, the available registry information is useful for identifying the study’s aims and measures, but it is insufficient for a full assessment of its quantitative findings or their robustness.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Examining Racial and SocioEconomic Disparities (ERASED) in Chronic Low Back Pain Study — NCT03338192.
• Registry record last updated 2025-03-30; status last verified 2025-03.
• Results first posted 2025-03-30.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry lists NCT03338192, Examining Racial and SocioEconomic Disparities (ERASED) in Chronic Low Back Pain Study, as completed. The study focuses on racial and socioeconomic differences in chronic low back pain. It lists African American/Black QST and Caucasian/White QST groups, and identifies average clinical pain severity measured by the Brief Pain Inventory Short-Form as the primary outcome.

The record reports enrollment of 281, a start date of 2017-10-15, and a primary completion date of 2024-01-31. It lists 20 outcome measures and 0 analyses. Primary and secondary outcome results, analysis methods, missing-data handling, and a multiplicity plan are not reported in the registry record. The entry therefore describes the research question and measurement framework but does not provide the results needed to quantify group differences.