Brief Cognitive Behavioral Therapy for Chronic Pain to Improve Functioning Among Veterans: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Brief Cognitive Behavioral Therapy for Chronic Pain to Improve Functioning Among Veterans (NCT04724694), a randomized na study. The primary outcome is Brief Pain Inventory -- Interference Subscale (BPI-I) to Assess 12 Week Follow-up.

2. Clinical Question

3. Trial Design

This was a completed randomized, parallel-group trial sponsored by the VA Office of Research and Development. The registry records the allocation as randomized and the masking as single; it does not specify who was masked. The phase is recorded as NA. The trial start date is 2021-10-01, and the primary completion date is 2025-01-27.

The two groups were Brief CBT for Chronic Pain plus treatment as usual, and treatment as usual only. The intervention description specifies six 30-minute sessions over 6-12 weeks. The brief summary says assessments were planned at baseline, mid-treatment, post-treatment, and 6-month follow-up. The primary outcome listed in the results is assessed at 12 weeks. The record does not explain whether the 12-week outcome corresponds to a particular named assessment point, or how the other scheduled assessments were used in the analysis.

The registry lists 184 enrolled. Its brief summary describes 178 eligible participants as intended for randomization, whereas the primary outcome results report 71 participants in the combined-treatment arm and 84 in the usual-care-only arm. These are distinct figures from the record; it does not explain their relationship or give a flow of participants from enrollment through follow-up. The analysis population and the number of randomized participants contributing to each outcome are not fully described in the posted record.

The registry reports a mixed models analysis for the primary outcome and several secondary outcomes. The model specification, covariates, assumptions, missing-data handling, and analysis population are not reported in the registry record. An original sample-size justification and the trial's planned power assumptions are also not reported in the registry record. The planning illustrations based on observed effects are separate from the trial's own design information.

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.

Overall Study

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 Brief Pain Inventory -- Interference Subscale (BPI-I) to Assess 12 Week Follow-up, measured over 12-weeks.

The primary endpoint is the Brief Pain Inventory Interference Subscale (BPI-I) at 12 weeks. It is a validated seven-item measure of the extent to which pain interferes with daily activities and social and occupational functioning. Its average score ranges from 0 to 10; higher scores indicate greater pain-related interference. The endpoint focuses on the functional consequences of pain rather than pain intensity alone.

A continuous score preserves information across the instrument's range, so the group means describe average recorded interference rather than the number of participants who crossed a particular threshold. The registry reports the endpoint as a mean with standard error. The standard error describes the precision of an estimated mean, rather than the spread of individual participants' scores.

This measure is relevant to the trial's stated aim of assessing functional outcomes among primary care Veterans with chronic pain. It does not, on its own, describe every dimension of functioning or establish why scores differ. The registry also lists pain intensity, psychological distress, quality of life, and social participation as related outcomes. Those measures address other domains and should not be treated as interchangeable with the primary interference score.

The comparison is between the two randomized groups at the recorded follow-up. The posted arm means are 4.58 for Brief CBT for Chronic Pain plus usual care and 5.35 for usual care alone. The re-calculated unadjusted mean difference, expressed as usual care alone minus combined treatment, is 0.77. In that direction, a positive difference corresponds to a higher average interference score in the usual-care-only group. The registry's mixed models result is a separate analysis of final values.

7. Results Posted in the Registry

• Treatment as Usual Only: mean 5.35 versus 4.58 on control; difference 0.77 (95% CI 0.15 to 1.39), standardized effect d = 0.39; z-test p = 0.016.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Brief Pain Inventory -- Pain Intensity Subscale (BPI-P) to Assess 12 Week Follow-up

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard errors.
• Result:
  • Treatment as Usual Only: mean 5.43 versus 5.01 on control; difference 0.42 (95% CI -0.07 to 0.91), standardized effect d = 0.27; z-test p = 0.090.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Treatment as Usual Only and the control. The interval gives the range of effects that remain compatible with the data.

Patient Health Questionnaire -- 9 (PHQ-9) to Assess 12 Week Follow-up

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard errors.
• Result:
  • Treatment as Usual Only: mean 8.10 versus 6.75 on control; difference 1.35 (95% CI -0.19 to 2.89), standardized effect d = 0.28; z-test p = 0.086.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Treatment as Usual Only and the control. The interval gives the range of effects that remain compatible with the data.

World Health Organization Quality of Life - BREF (WHOQOL-BREF) to Assess Physical Health at 12 Week Follow up

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard errors.
• Result:
  • Treatment as Usual Only: mean 12.10 versus 13.02 on control; difference -0.92 (95% CI -1.75 to -0.08), standardized effect d = -0.35; z-test p = 0.031.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Treatment as Usual Only than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The registry lists seven secondary outcomes spanning pain intensity, psychological distress, quality of life domains, and participation in social roles and activities. In broad terms, these outcomes extend the primary question from pain-related interference to other aspects of symptoms and well-being. The secondary findings should be read as complementary evidence rather than as replacements for the primary endpoint.

The secondary results do not present a single uniform statistical pattern across the outcomes with numerical summaries in the record. The posted results include both smaller and larger p-values, and not every secondary analysis aligns in statistical strength with the primary result. This means the secondary outcomes should be considered individually and in the context of the trial's overall testing plan, rather than combined into a claim that all measured domains changed in the same way.

The registry record does not report a multiplicity adjustment or specify a hierarchy for testing secondary outcomes. General statistical explanation: when many outcomes are tested, interpreting each unadjusted p-value as if it were the only test can overstate the evidence. An isolated nominally small p-value may be less persuasive when considered among many comparisons. Conversely, a non-small p-value does not establish that there is no difference; it may reflect uncertainty, limited information, or an effect that is not readily detected.

The secondary outcome patterns can help assess whether the primary result is accompanied by findings in related domains, but they do not establish a mechanism or explain why the primary scores differ. The record does not report a prespecified multiplicity strategy, and the observed results should not be treated as independent confirmations of the primary finding. The primary endpoint remains the central registered outcome for the trial's main question.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Brief Pain Inventory -- Pain Intensity Subscale (BPI-P) to Assess 12 Week Follow-up
• Patient Health Questionnaire -- 9 (PHQ-9) to Assess 12 Week Follow-up
• World Health Organization Quality of Life - BREF (WHOQOL-BREF) to Assess Physical Health at 12 Week Follow up
• World Health Organization Quality of Life - BREF (WHOQOL-BREF) to Assess Psychological Quality of Life at 12 Week Follow up
• World Health Organization Quality of Life - BREF (WHOQOL-BREF) to Assess Social Relationships at 12 Week Follow up
• World Health Organization Quality of Life - BREF (WHOQOL-BREF) to Assess Environmental Health at 12 Week Follow up
• Ability to Participate in Social Roles and Activities - Short Form (APSRA) to Assess 12 Week Follow up

9. Statistical Interpretation

10. Statistical Methods Explained

Clinical trial results can be described in several complementary ways. A group mean gives the average score among the participants included in that outcome result. For the primary BPI-I outcome, the posted means are 4.58 and 5.35, with standard errors of 0.23 and 0.22. The mean difference places those means on a common scale and makes the direction of the comparison explicit. In the unadjusted calculation, the difference is 0.77 for usual care alone minus combined treatment.

What does an unadjusted comparison represent?

General statistical explanation: an unadjusted comparison uses the posted group summary statistics without accounting for additional variables or a model for repeated measurements. It is useful as a transparent description of the observed group means, but it need not match an analysis that uses more of the trial's data structure. The re-calculated p-value of 0.016 and the corresponding interval are based on the summary statistics, not a reconstruction of the sponsor's mixed models analysis.

The registry reports that the sponsor used mixed models analysis and gives a final-values mean difference of 0.69 with p = 0.026. General statistical explanation: mixed models can be used to account for correlations among repeated measurements from the same participant and to represent time or other model terms. The exact model and terms used in this trial are not reported in the registry record, so the general purpose of the method should not be mistaken for a description of its precise implementation.

What does a standard error describe?

General statistical explanation: a standard error describes the sampling precision of an estimated quantity, such as a group mean. It is not the standard deviation of individual scores. A standard deviation describes how participant values vary around a mean; a standard error describes how precisely the mean has been estimated. The registry reports standard errors for the arm means. The posted summary statistics also support a simple unadjusted comparison, but they do not reveal the distribution of individual outcomes.

A p-value describes how compatible the observed result is with a specified null model, under the assumptions of the analysis. It is not the probability that the null hypothesis is true, nor does it measure the probability that the result will replicate. The re-calculated primary p-value is unadjusted. The sponsor's reported p-value comes from the mixed models analysis. Neither p-value, by itself, communicates the range of effect sizes compatible with the data; that is why an interval estimate is also useful when available.

Why can estimates differ across analyses?

General statistical explanation: an unadjusted endpoint comparison and a model-based analysis can produce different estimates because they can use different information, assumptions, and weighting. A model may use observations across assessment times or incorporate terms not present in a comparison of final-value summaries. The registry identifies the sponsor's method but does not report enough detail to determine which specific features account for the difference between 0.77 and 0.69. The discrepancy flag is false, so the posted result does not identify a discrepancy requiring the sponsor's analysis to take precedence over the re-calculation.

Care is also needed when interpreting the secondary results. The registry lists seven secondary outcomes, including pain intensity, psychological distress, physical, psychological, social and environmental quality of life, and participation in social roles and activities. Separate tests across multiple outcomes create multiple opportunities for a small p-value to arise by chance. General statistical explanation: multiplicity procedures can control or otherwise address this issue, but the registry record does not report a multiplicity adjustment or an overall testing strategy.

What is not specified?

The registry does not report the original statistical analysis plan, the model formula, covariates, assumptions checks, treatment of repeated observations, analysis population, missing-data methods, or whether any interim analyses occurred. These are not details that can be inferred from the outcome summaries. General statistical explanation: complete reporting of these choices helps readers distinguish a pre-specified primary analysis from exploratory analyses and assess sensitivity to analytic decisions. The absence of these details does not invalidate the posted estimates, but it limits independent evaluation of how they were obtained.

The enrollment information also needs to be kept distinct from outcome analysis counts. The registry lists 184 enrolled, while the brief summary describes 178 eligible participants as intended for randomization. The primary results list 71 and 84 participants in the two arms. These values describe different registry entries; without a participant flow or analysis-population description, they should not be combined into a single count or treated as interchangeable.

11. Confidence Intervals and Precision

Precision concerns the range of effect sizes that remain compatible with the observed data under a stated analysis. For the primary unadjusted mean difference, the re-calculated interval excludes zero and includes positive values. With the difference defined as usual care alone minus combined treatment, that direction corresponds to higher BPI-I scores in the usual-care-only group. An interval is more informative than a point estimate alone because it reflects uncertainty around the estimated difference.

The registry reports standard errors for the two primary arm means, 0.23 and 0.22. These quantify uncertainty in the estimated means, not the variability among individual participants. The posted registry result for the mixed models analysis gives a mean difference of 0.69 and p = 0.026, but no confidence interval is reported for that analysis. Consequently, the precision of the sponsor's model-based difference cannot be assessed from a reported interval in the registry.

General statistical explanation: a confidence interval is constructed by a method that, over repeated studies under its assumptions, would capture the underlying quantity at the stated confidence level at the stated frequency. It is not a range containing a known fixed proportion of individual outcomes, and it does not assign probabilities to each possible effect after observing the data. The interval's width reflects both the amount of information and the variability represented by the analysis.

The interval from the unadjusted calculation should not be treated as a substitute for an interval from the mixed models analysis. The analyses answer closely related but not necessarily identical statistical questions, and the model details are not reported. Precision also concerns the effect on the BPI-I scale; the registry does not report a threshold that would classify a particular difference as clinically important. Statistical uncertainty and practical importance are related questions, but they are not the same question.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are illustrations based on the observed effect, not the trial's original design justification. All figures in this case are participants per arm; they are not total event counts. The calculation assumes a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each row uses a stated fraction of the observed effect as the effect to detect.

The 80% power column gives the estimated number of participants per arm for a hypothetical study to have an 80% chance of detecting the specified effect under those planning assumptions, if that effect and the calculation assumptions were correct. The 90% power column gives the corresponding number per arm for a 90% chance. Power is a design property calculated under assumptions; it is not the probability that a particular result is true.

The rows consider planning for 100%, 75%, and 50% of the observed effect. The required number rises as the target effect gets smaller: a subtler difference is harder to distinguish from random variation and generally requires more participants. For this primary outcome, the displayed figures range from 104 to 416 participants per arm for 80% power and from 140 to 557 participants per arm for 90% power, depending on the effect fraction used. Those are hypothetical planning quantities, not observed enrollment or a statement about the actual power of this completed trial.

This is not observed power. The original sample-size justification and design assumptions are not reported in the registry record. The illustrations do not incorporate unreported features of the trial's own design or analysis, and should be read as conditional planning calculations rather than as evidence that the study was adequately or inadequately sized.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 0.770; pooled standard deviation σ = 1.981.
2. n = 2 × (1.96 + 0.842)² × 1.981² / 0.770² = 103.9, rounded up to 104 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 0.77                      # observed difference in means
sigma <- 1.98088545593694                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(4724694)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 104 (80% power), 140 (90% power)
 75% of observed effect: n per arm = 185 (80% power), 248 (90% power)
 50% of observed effect: n per arm = 416 (80% power), 557 (90% power)
power.t.test: 104.9 
Simulated power at n = 104 per arm: 0.797 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

The registry reports the sponsor's primary analysis as a mixed models analysis of final values, with a mean difference of 0.69 and p = 0.026. The sign convention or direction for that reported difference is not specified in the analysis entry. The posted arm means are 4.58 for combined treatment and 5.35 for usual care alone; the simple unadjusted difference, defined as usual care alone minus combined treatment, is 0.77, with p = 0.016 and an interval that excludes zero.

These are related but distinct analyses. The re-calculation uses the posted summary statistics and is not a reproduction of the sponsor's mixed model. The registry does not provide the model specification, covariate adjustments, or the participant-level observations needed to recreate that analysis. The difference between the reported estimates therefore cannot be attributed to a particular model feature from the record alone.

The discrepancy flag is false. There is no registry indication that the re-calculation conflicts with the sponsor's result in a way that calls for the sponsor analysis to take precedence. The sponsor's result remains the trial's own reported analysis, while the re-calculation is a simple, unadjusted check based on the posted summaries. No confidence interval for the sponsor's estimate is reported in the registry record.

15. Multiplicity, Missing Data and Analysis Populations

Multiplicity refers to the interpretive problem created when several statistical tests are conducted. This trial lists a primary outcome and seven secondary outcomes. The secondary domains include pain intensity, depressive symptoms, several quality-of-life dimensions, and participation in social roles and activities. If each result is evaluated separately, the chance of encountering at least one apparently unusual result can increase as the number of tests grows.

The registry record does not report whether the trial used a multiplicity adjustment, a prespecified order for testing, or another strategy to distinguish confirmatory from exploratory comparisons. It also does not report the detailed statistical analysis plan. Therefore, the posted secondary p-values should not be interpreted as though each were the sole planned test. This limitation is especially relevant when selecting individual secondary findings for emphasis.

The record also does not describe missing-data handling, the analysis population, or the number of participants with observed outcomes at each assessment. The primary outcome results list 71 participants in the combined-treatment group and 84 in the usual-care-only group. The registry separately lists 184 enrolled and describes 178 eligible participants as intended for randomization, without a participant flow explaining those figures. It is not possible from the posted information to determine why the numbers differ or how missing outcome values were treated.

General statistical explanation: missing observations can affect estimates if the probability of missingness is related to participant characteristics or outcomes. Methods such as likelihood-based modeling or imputation require assumptions, and reporting those methods helps readers assess their plausibility. The registry's use of mixed models does not by itself establish how missing data were handled. The specific approach is not reported in the registry record.

Interim analyses, stopping rules, and the original sample-size justification are also not reported in the registry record. Their absence should be described as an information gap rather than evidence that a particular procedure was or was not used. These details matter for judging the planned analysis and the context in which the reported estimates were selected.

16. 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 serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: evaluation for cva (1.1%), rib fracture (1.1%), admitted for persistent cough and sore throat (1.1%), admitted for evaluation of syncope (1.1%), admitted for abdominal pain (1.1%).

The registry reports serious adverse event counts for 92 participants at risk in each group. There were 2 participants with serious adverse events in the Brief CBT for Chronic Pain plus usual-care group and 4 in the usual-care-only group. The registry reports zero deaths in both groups. These are counts as recorded; they should be read alongside the fact that the number at risk differs from the primary outcome participant counts.

Other adverse events were reported for 12 participants in the combined-treatment group and 10 in the usual-care-only group, each among 92 participants at risk. The registry lists serious-event terms including evaluation for CVA, rib fracture, admission for persistent cough and sore throat, admission for evaluation of syncope, and admission for abdominal pain. Each listed term is recorded as 1.1%. The record does not provide information to attribute these events to a particular treatment or to assess their causes.

Adverse-event counts are descriptive safety information. They do not, by themselves, establish whether an event was caused by the intervention, and they do not capture severity, timing, or context beyond what the registry entry states. The registry record does not provide additional detail on event relatedness or how the safety comparisons were analyzed.

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

The posted primary result describes lower average pain-related interference scores in the group assigned to Brief CBT for Chronic Pain plus usual care than in the group assigned to usual care alone at 12 weeks. The unadjusted difference is 0.77 points on a 0-to-10 measure, expressed as usual care alone minus combined treatment. The registry's mixed models analysis also reports a statistical difference, with a mean difference of 0.69 and p = 0.026.

This result is about group averages and the specific outcome measured. It does not mean that every participant improved, that the score changed by the same amount for everyone, or that an individual participant's experience can be predicted from the group mean. It also does not directly answer whether a difference is important to participants, because the registry does not report an interpretation threshold for the BPI-I.

The trial compared an added behavioral program with usual primary care alone. It does not isolate which component of the six-session intervention, if any, accounts for the group difference. The record also does not provide enough information to determine how the model handled repeated assessments or missing observations. Those gaps limit interpretation of the precise estimand represented by the sponsor's mixed models result.

Secondary outcomes address other areas, but several outcomes create a multiplicity concern when their results are interpreted together. No multiplicity strategy is reported. Safety counts are also descriptive and do not establish that events were caused by either treatment assignment. The findings therefore need to be understood as a set of reported outcome comparisons, not as a complete account of benefit, risk, or how treatment might perform in every setting.

The evidence applies most directly to the randomized comparison as recorded for Veterans with chronic musculoskeletal pain and pain-related functional impairment identified in primary care. The registry does not describe enough participant characteristics to judge how closely the analyzed sample resembles other populations. The findings should not be generalized beyond the studied comparison without considering those limits.

18. Why This Trial Matters Statistically

This trial addresses a statistical question about delivering a behavioral intervention within primary care rather than comparing two medicines or testing pain intensity alone. Its primary endpoint captures interference with daily, social, and occupational functioning, a distinct outcome from pain severity. The design therefore makes the interpretation of the measure's scale and direction central: higher BPI-I scores indicate more interference.

The trial also illustrates why a reported analysis and a simple re-calculation should be distinguished. The registry's mixed models analysis and the unadjusted comparison both report a difference, but their estimates and p-values are not identical. Model details are needed to understand precisely how repeated measurements, covariates, or incomplete data may contribute. Publishing enough information to reproduce the planned analysis would make the result easier to evaluate independently.

For biostatisticians and clinical researchers, the record also highlights the importance of reporting participant flow, analysis populations, missing-data methods, and multiplicity plans. Enrollment and outcome counts appear in different entries without an explanation of their relationship. The outcome list includes multiple secondary domains, but the record does not describe a hierarchy or adjustment strategy. These are not merely administrative details; they shape how confidently a result can be interpreted and how secondary findings should be weighed.

Finally, the observed-effect planning illustrations show how sample-size needs depend on the effect selected for detection. Smaller target effects require larger per-arm planning numbers under the stated assumptions. Such illustrations can inform future study planning, but they cannot substitute for the original design justification or be interpreted as the completed trial's observed power.

19. 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 has several reporting limitations relevant to this trial. It does not explain the difference between 184 enrolled, the 178 eligible participants described as intended for randomization, and the 71 and 84 participants listed in the primary outcome arms. A participant flow showing eligibility, allocation, follow-up, and analysis counts is not reported in the registry record. The analysis population for the primary and secondary outcomes is also not specified.

The registry identifies mixed models analysis but does not report the model formula, covariates, repeated-measures structure, assumptions, or missing-data approach. It gives no confidence interval for the sponsor's primary analysis. The original sample-size justification, interim analysis procedures, and multiplicity plan are not reported in the registry record. These gaps make it harder to assess the planned-versus-reported analysis and the precision of the sponsor's model-based estimate.

The record says masking was single but does not identify who was masked. It does not provide details on adherence, intervention receipt, or variation in usual care. The brief summary describes the intervention and the assessment schedule, but the registry does not explain how the 12-week primary assessment relates to the stated pre-treatment, mid-treatment, post-treatment, and 6-month follow-up assessments.

Some limitations are inherent in what is reported: the primary endpoint is a self-report measure, and its mean does not show individual trajectories or the distribution of participant experiences. The record does not report a threshold for clinical importance. The safety results are counts and listed terms, without causal attribution or additional event context. These omissions call for cautious interpretation; they do not, on their own, establish that the reported estimates are biased.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Brief Cognitive Behavioral Therapy for Chronic Pain to Improve Functioning Among Veterans — NCT04724694.
• Registry record last updated 2026-03-17; status last verified 2026-02.
• Results first posted 2026-01-28.
• 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.

23. Record Summary

NCT04724694 is a completed randomized, parallel-group trial sponsored by the VA Office of Research and Development. It compared Brief CBT for Chronic Pain plus usual primary care with usual care alone among Veterans with chronic musculoskeletal pain and pain-related functional impairment. The registry lists 184 enrolled and records the primary completion date as 2025-01-27.

The primary outcome was BPI-I at 12 weeks, a 0-to-10 measure on which higher scores indicate greater interference. The posted means were 4.58 for combined treatment and 5.35 for usual care alone. The unadjusted comparison and the sponsor's mixed models analysis both report a statistical difference, though with different estimates. Missing-data methods, the original design assumptions, and a multiplicity strategy are not reported in the registry record.

Secondary outcomes cover pain intensity, psychological distress, quality of life, and social participation. Safety entries report serious and other adverse-event counts and zero deaths in both groups. The secondary findings and safety counts should be interpreted with the trial's reporting limitations in mind.