Behavioral Treatments for Chronic Pain: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Behavioral Treatments for Chronic Pain (NCT00371865), a randomized na study. The primary outcome is Brief Pain Inventory.

2. Clinical Question

The trial record describes a comparison of two brief, group-administered psychosocial interventions for chronic pain. Its stated purpose was to assess pain interference with daily life, emotional distress, pain intensity, quality of life, and physical activity. The posted primary outcome is the Brief Pain Inventory, a continuous measure reported as a mean and standard deviation at 12 weeks post treatment.

The intervention descriptions specify 8 sessions for each treatment. The numeric outcome summaries identify the groups only as Arm 1 and Arm 2, while the treatment descriptions are named separately. The registry record does not explicitly connect those generic arm labels to the named treatment descriptions in the posted results. Accordingly, the numerical comparison can be described as Arm 2 relative to Arm 1, without assigning those numbers to a treatment name.

The main statistical question is whether the observed average scores differ and how precisely that difference is estimated. The posted group means are 4.5 for Arm 1 and 5.1 for Arm 2. The unadjusted re-calculation gives a mean difference of 0.6 for Arm 2 relative to Arm 1. The reported mixed-model analysis gives a p-value of .27. These results describe the data and the analyses recorded; they do not by themselves establish the size or practical importance of a treatment effect.

3. Trial Design

The registry describes a randomized, single-masked, parallel-group trial of behavioral treatments for chronic pain. It lists an enrollment of 114, the status as completed, a study start of 2006-10, and primary completion in 2008-12. The sponsor is the US Department of Veterans Affairs. The phase is listed as NA.

The two treatment descriptions are cognitive-behavioral therapy and acceptance-based therapy. Each is described as 8 group-administered sessions. The registry’s stated purpose was to test a brief group-administered psychosocial intervention in relation to pain interference, emotional distress, pain intensity, quality of life, and physical activity. The record lists Intractable Pain as the condition.

The posted results identify the outcome groups as Arm 1 and Arm 2. Each group has 57 participants in the primary outcome summary. Although the treatment descriptions are available, the record does not explicitly map the generic outcome-arm labels to those descriptions. The randomized comparison should therefore be read as Arm 2 versus Arm 1 when interpreting the numerical estimates.

The primary outcome was the Brief Pain Inventory at 12 weeks post treatment. Secondary outcomes listed in the record include the West Haven-Yale Multidimensional Pain Inventory - Activity Subscales, SF-12, Beck Depression Inventory, and Pain Anxiety Symptom Scale - 20. The posted results include comparative numeric summaries for three of those secondary measures; results for the Pain Anxiety Symptom Scale - 20 are not reported in the registry record.

The registry record does not report the randomization procedure, how masking was implemented, the participants or staff who were masked, the planned sample-size justification, or the original statistical analysis plan. It also does not provide detail about treatment adherence or delivery fidelity. Those omissions limit what can be inferred about implementation and the design rationale, beyond the stated randomized, single-masked, parallel-group structure.

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

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 Brief Pain Inventory, measured over 12 weeks (post treatment).

The primary endpoint is the Brief Pain Inventory, assessed at 12 weeks post treatment. The registry describes it as a questionnaire measuring pain severity and interference. Scores range from 0-10, with higher scores indicating more pain. The outcome is reported as a group mean with a standard deviation, so the comparison concerns average questionnaire scores rather than the proportion of participants crossing a threshold.

This measure is relevant to the trial’s stated purpose because the study aimed to reduce the interference of pain with daily life as well as pain intensity. A standardized questionnaire can provide a structured way to summarize participants’ reported pain severity and interference at a specified assessment time. The score’s direction is important for interpretation: a lower mean indicates less reported pain on this scale.

The posted endpoint summary gives a mean of 4.5 for Arm 1 and 5.1 for Arm 2, with standard deviations of 2.7 and 2.4, respectively. The unadjusted mean difference is 0.6 for Arm 2 relative to Arm 1. These are group-level summaries at one post-treatment timepoint. They do not show individual trajectories, changes from baseline, or how many participants experienced a particular degree of improvement. Baseline results and a change-from-baseline estimate are not reported in the registry record.

The endpoint is therefore best read as a comparison of average reported pain severity and interference at the specified assessment, with uncertainty around the estimated difference considered alongside the mean values.

7. Results Posted in the Registry

• Arm 2: mean 5.10 versus 4.50 on control; difference 0.60 (95% CI -0.34 to 1.54), standardized effect d = 0.23; z-test p = 0.210.

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.

West Haven-Yale Multidimensional Pain Inventory - Activity Subscales

• 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 deviations.
• Result:
  • Arm 2: mean 2.00 versus 2.30 on control; difference -0.30 (95% CI -0.59 to -0.01), standardized effect d = -0.37; z-test p = 0.045.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Arm 2 than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

SF-12

• 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 deviations.
• Result:
  • Arm 2: mean 41.00 versus 44.90 on control; difference -3.90 (95% CI -8.63 to 0.83), standardized effect d = -0.30; z-test p = 0.106.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Arm 2 and the control. The interval gives the range of effects that remain compatible with the data.

Beck Depression Inventory

• 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 deviations.
• Result:
  • Arm 2: mean 17.80 versus 13.20 on control; difference 4.60 (95% CI 0.32 to 8.88), standardized effect d = 0.39; z-test p = 0.035.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Arm 2 than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The secondary measures cover activity, general health-related status, depression symptoms, and pain anxiety. The registry lists four secondary outcomes, including the Pain Anxiety Symptom Scale - 20, but comparative numeric results for that measure are not reported in the registry record. Three secondary measures have posted group summaries and sponsor-reported mixed-model p-values.

Across those measures, the unadjusted re-calculations do not form a uniform pattern of clearly separated groups. Some estimated differences are closer to zero, while others are farther from zero; their uncertainty and the sponsor-reported analyses also matter. The primary Brief Pain Inventory result itself is inconclusive about a group difference. The secondary findings do not resolve that uncertainty or, on their own, establish a consistent overall treatment effect across outcomes.

Secondary outcomes can add context because they assess aspects of functioning and distress beyond the primary pain measure. However, they generally carry less confirmatory weight when a trial examines several measures and the registry record does not report a prespecified hierarchy or multiplicity adjustment. With repeated testing, some results can appear notable by chance. Unadjusted secondary comparisons should therefore be read as exploratory signals requiring cautious interpretation, not as independent confirmation of the primary result.

The record does not report whether the secondary analyses were planned as confirmatory, whether results were adjusted for multiple comparisons, or how missing secondary measurements were handled. It is also not possible to infer the direction or size of a result for the pain-anxiety measure from its listing alone. A balanced reading considers the full set of measures and the limits of the analysis record, rather than selecting individual p-values in isolation.

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

• West Haven-Yale Multidimensional Pain Inventory - Activity Subscales
• SF-12
• Beck Depression Inventory
• Pain Anxiety Symptom Scale - 20

9. Statistical Interpretation

10. Statistical Methods Explained

What does the mean difference describe?

The Brief Pain Inventory is reported as a continuous measure, so the group summaries are means and standard deviations. A mean describes the average score in a group; a standard deviation describes how spread out scores are around that average. The primary comparison is a mean difference, calculated in the posted re-analysis as Arm 2 minus Arm 1. A positive value means the average score was higher in Arm 2, and on this scale higher scores indicate more pain. The estimate of 0.6 is an unadjusted comparison based on the posted summary statistics.

“Unadjusted” means this re-calculation compares the group summaries without accounting for other variables or the repeated structure of any measurements. It is not a substitute for the trial’s reported analysis. The registry reports a mixed-model analysis for the primary comparison, but does not give its estimated difference or confidence interval. A mixed model is a general statistical approach that can represent dependence among observations, such as repeated measurements, and can incorporate specified explanatory variables. The registry record does not report the exact model specification, so the details of that analysis cannot be reconstructed from its description alone.

What does a confidence interval add?

A confidence interval expresses uncertainty around an estimated difference. In general, it describes a range of values that are reasonably compatible with the data and the statistical model used. It is not a guarantee that the true value lies inside the interval, nor does it measure the probability that a specific treatment effect is true. For the primary unadjusted comparison, the interval spans zero, so the summary-statistic analysis does not rule out no difference. The width also matters: a broad interval permits a wider range of possible differences than a narrow one.

A p-value addresses a related but different question. In general, it measures how incompatible the observed data are with a specified null hypothesis under the analysis assumptions. It does not measure the probability that the null hypothesis is true, and it does not indicate whether an observed difference is important to patients. The unadjusted primary p-value is 0.21; the registry’s mixed-model p-value is .27. Their interpretation depends on their respective analyses and assumptions.

Why distinguish the analyses?

The re-calculations use posted group means, standard deviations, and group sizes to produce simple unadjusted comparisons. The sponsor’s reported method is identified as Mixed Models Analysis. Those approaches may use information differently. For example, a model might account for repeated measurements or include covariates, but the record does not say which features were included. It would therefore be speculation to attribute the difference between p-values to any particular model choice. The sponsor’s reported analysis and the unadjusted re-calculation should be read as distinct analyses, not interchangeable estimates.

The registry reports one primary outcome and several secondary measures. In general, evaluating multiple outcomes increases the chance of finding at least one apparently notable result by chance if each is tested separately. Adjustment methods can change how evidence is assessed across a family of comparisons. No multiplicity adjustment or hierarchy for the outcomes is reported in the registry record, so the secondary p-values should be treated as unadjusted and exploratory rather than as confirmatory evidence.

What can be said about design and assumptions?

The registry identifies the trial as randomized, single-masked, and parallel-group. These descriptors establish the broad design, but do not specify how the sequence was generated, who was masked, or how allocation was concealed. The primary outcome summaries are available for the groups, but the record does not report the analysis population, missing-data methods, baseline adjustment, model details, or a full prespecified analysis plan. General statistical interpretation should not fill those gaps with assumptions.

The observed standard deviations are 2.7 for Arm 1 and 2.4 for Arm 2 on the primary measure. Standard deviations describe variability among scores; they are not confidence intervals and do not directly quantify the precision of the mean difference. Precision also depends on the amount of information in each group and on the analysis. The registry’s planning illustration is a separate calculation based on fractions of the observed effect and stated assumptions. It is not a report of the trial’s original design rationale or a measure of power after the study.

Finally, a statistically non-significant result is not evidence of equivalence, and a statistically significant result on a secondary measure would not by itself establish a robust treatment difference. Those conclusions require the relevant design, assumptions, outcome priorities, multiplicity handling, and uncertainty to be considered together. The information recorded supports a cautious reading of the estimated differences and their precision, not a definitive claim about comparative clinical effects.

11. Confidence Intervals and Precision

The primary unadjusted mean difference is 0.6 for Arm 2 relative to Arm 1. Its reported confidence interval extends from a negative value to a positive value and therefore includes zero. In general, an interval that includes zero is compatible with no average difference as well as with differences in either direction under the analysis. The unadjusted p-value is 0.21, while the registry’s mixed-model analysis reports p = .27. The model-based estimate and interval are not reported in the registry record.

The interval’s inclusion of zero is not evidence that the groups are exactly alike. The data are compatible with a range of possible differences, and the registry result does not narrow that range enough to exclude no difference using the simple unadjusted analysis. Nor does the confidence interval describe the range of individual participants’ scores; it concerns uncertainty around the estimated group difference.

The group standard deviations, 2.7 for Arm 1 and 2.4 for Arm 2, describe variation in the endpoint within each group. They should not be confused with the uncertainty around the between-group estimate. Precision of an estimate depends on the variability and amount of information available, along with the analysis method. The registry record does not provide the model-based confidence interval, so its precision cannot be compared directly with the unadjusted interval.

Confidence intervals are especially useful alongside p-values because they convey a range of estimates compatible with the data, rather than reducing interpretation to a threshold. In general, a narrow interval indicates greater precision than a wide interval, although clinical importance still depends on the scale and context. The registry record does not report a threshold for a clinically important Brief Pain Inventory difference, so the observed estimate cannot be classified against such a threshold from this record alone.

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 participants per arm, not total events. They are illustrations based on the observed effect, not the trial’s original sample-size justification. The assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; each scenario targets a stated fraction of the observed effect. The trial’s own design assumptions and sample-size justification are not reported in the registry record.

The 80% power column represents a planning target: under the listed assumptions and effect size, a study of the stated size would have an 80% chance of meeting the chosen statistical significance criterion if that effect were the true effect. The 90% power column uses a higher chance target under the same general planning framework. These are design concepts, not guarantees about the result of a future study; actual results depend on the data and whether the assumptions hold.

The rows illustrate planning for 100%, 75%, and 50% of the observed effect. A smaller effect is harder to distinguish from random variation, so the illustration requires more participants per arm for smaller target effects. This planning calculation is not observed power.

The curve should be interpreted as a planning aid tied to the same assumptions and effect-size choices, rather than as evidence about what the completed trial was designed to detect. The registry record does not report its original target, whether any sample-size re-estimation occurred, or an interim-analysis plan. These illustrations therefore cannot establish that the completed trial was adequately or inadequately sized for its original objectives.

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 = 0.600; pooled standard deviation σ = 2.554.
2. n = 2 × (1.96 + 0.842)² × 2.554² / 0.600² = 284.5, rounded up to 285 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 <- 0.6                      # observed difference in means
sigma <- 2.55440795488896                     # 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(371865)
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 = 285 (80% power), 381 (90% power)
 75% of observed effect: n per arm = 506 (80% power), 678 (90% power)
 50% of observed effect: n per arm = 1,139 (80% power), 1,524 (90% power)
power.t.test: 285.5 
Simulated power at n = 285 per arm: 0.799 (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 a Mixed Models Analysis for the primary outcome, with p = .27. It does not report the model’s estimated treatment difference, confidence interval, exact model specification, or the population included in that analysis. The unadjusted re-calculation from the posted group summaries gives a mean difference of 0.6 for Arm 2 relative to Arm 1 and p = 0.21. These are different analyses and should not be treated as if they were the same estimate.

The re-calculation is a simple comparison of the posted means and standard deviations. A mixed-model analysis may account for features not represented in that calculation, but the registry record does not describe its model sufficiently to identify which features were used or explain the difference in p-values. It would be inappropriate to infer a specific reason from the p-values alone.

The record does not flag a discrepancy between the sponsor’s analysis and the re-calculation. The sponsor’s reported method is the trial’s own analysis as recorded, while the unadjusted result offers a separate check based on the posted summaries. Because the model estimate and interval are absent, the numerical magnitude and precision of the sponsor’s modeled comparison cannot be assessed from the registry record.

15. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome and several secondary outcomes. When multiple outcomes are tested, the chance of at least one apparently unusual result can increase if each comparison is evaluated separately without adjustment. This is a general statistical concern, not evidence that any particular posted finding is false. Methods for addressing multiplicity include adjusting significance thresholds or defining a hierarchy of outcomes, but the registry record does not report such a strategy.

The secondary comparisons are therefore best treated as unadjusted. Their p-values should not be interpreted as if each were the sole planned test. The record also does not report whether a primary outcome was formally designated before analysis beyond identifying the Brief Pain Inventory as primary, or whether the analyses followed a complete prespecified statistical plan.

Missing-data handling is another important uncertainty. The record gives group sizes for the posted outcome summaries, but does not describe the amount or pattern of missing outcome data, reasons for missingness, or methods used to address it. It does not state whether the mixed model used all available repeated observations or how incomplete follow-up was handled. The primary outcome population field is blank. No analysis population, such as intention-to-treat or per-protocol, is reported in the record.

These omissions matter because methods for handling incomplete data rely on assumptions, and different assumptions can affect estimates and uncertainty. Without a description of follow-up and analysis populations, the extent to which the posted estimates represent all randomized participants cannot be assessed. The record also does not report sensitivity analyses examining alternative missing-data assumptions.

These limitations do not demonstrate that the analyses were inappropriate; they mean that the registry record does not contain the information needed to evaluate multiplicity control, missing-data handling, or the alignment between planned and reported analyses. Interpretation should remain focused on the estimates and uncertainty actually documented, without assuming unreported procedures.

16. Safety Results

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

Other (non-serious) adverse events

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

The adverse-event figures report zero serious adverse events among the 50 participants at risk in Arm 1 and among the 49 participants at risk in Arm 2. For other adverse events, the record likewise reports zero affected among 50 at risk in Arm 1 and zero affected among 49 at risk in Arm 2. These are the figures recorded for the specified groups and categories.

The at-risk counts shown for safety are not the same as the outcome group sizes reported for the primary efficacy measure. The registry record does not explain the difference, so the safety figures should be interpreted using their own listed denominators. It also does not provide serious-event terms in the listed results. Deaths are not reported in the registry record.

Zero recorded affected participants does not establish that no adverse events of any kind occurred, nor does it demonstrate equivalent safety between the groups. The record’s summary does not describe ascertainment methods, duration of safety follow-up, event definitions, or completeness of reporting. These figures are a limited description of the events recorded, not a comprehensive comparison of risk.

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

The posted results describe average scores at 12 weeks after treatment, not a complete account of how participants changed over time. On the Brief Pain Inventory, Arm 1 had a mean of 4.5 and Arm 2 had a mean of 5.1; higher scores indicate more pain. The unadjusted difference is 0.6 for Arm 2 relative to Arm 1, with an interval that includes zero. The sponsor-reported mixed-model analysis has p = .27, but its estimate and interval are not reported.

These results do not establish that the treatments are identical. A non-significant result can reflect uncertainty, and demonstrating equivalence would require an equivalence framework and a specified margin, neither of which is reported in the registry record. Conversely, the observed difference does not establish that one treatment is superior. The estimate’s uncertainty and the limitations of the available analysis details need to be considered.

The registry’s outcome is a questionnaire score, not a direct measure of every aspect of chronic pain or daily life. Although the study’s stated purpose includes emotional distress, quality of life, and physical activity, the primary result alone cannot answer all of those questions. Secondary outcomes add some information, but their interpretation is limited by the absence of a reported multiplicity strategy and incomplete results for one listed measure.

The record also does not report the original sample-size rationale, missing-data procedures, analysis population, or full statistical plan. These omissions restrict assessment of precision and potential analysis sensitivity. The results should therefore be understood as the recorded group summaries and analyses, rather than as a definitive estimate of comparative clinical benefit or harm.

18. Why This Trial Matters Statistically

This trial illustrates why a group mean, a p-value, and a confidence interval answer different questions. The primary group means describe the observed average scores. The unadjusted difference gives a direction and magnitude for the contrast, while its interval describes uncertainty. The p-value summarizes compatibility with a null hypothesis under a particular analysis, but it does not establish clinical importance or the probability that a treatment effect is real.

It also demonstrates the importance of distinguishing the trial’s reported model-based analysis from a simple re-calculation based on summary statistics. The sponsor’s mixed-model p-value is .27, whereas the unadjusted re-calculation gives p = 0.21. Without the model specification or its estimate and interval, the two analyses cannot be reconciled in detail. Reporting estimates and uncertainty for the model-based result would make its interpretation more complete.

The multiple secondary measures raise a further statistical issue: individual unadjusted results can be misleading when considered without the outcome family and analysis plan. A pattern across endpoints and an explicit multiplicity strategy are more informative than selective attention to one result. Missing-data and analysis-population details are also essential for judging how well a reported estimate represents the randomized groups.

Finally, planning illustrations based on observed effects are distinct from the original design justification and from post-study power. Keeping those concepts separate helps prevent retrospective calculations from being mistaken for evidence about what the completed trial could reliably detect. Together, these points make the record a useful example of reading effect estimates, uncertainty, sponsor analyses, and documentation gaps as parts of one statistical picture.

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.

Several trial-specific limitations affect interpretation. First, the outcome results label groups as Arm 1 and Arm 2, while the treatment descriptions are named separately. The registry record does not explicitly link each numeric arm label with a named intervention. The direction of the numerical comparison is clear as Arm 2 relative to Arm 1, but assigning that contrast to a treatment name from the record alone is uncertain.

Second, the registry reports a mixed-model p-value for the primary result but not its estimated difference or confidence interval. The model specification is also not reported. This prevents direct assessment of the effect size and precision under the trial’s reported analysis, and it limits comparison with the unadjusted re-calculation. The primary outcome population field is blank.

Third, the record does not report baseline outcome values, change-from-baseline estimates, missing-data procedures, analysis populations, or sensitivity analyses. It is therefore not possible to determine from the registry record how incomplete follow-up or analytic choices may have affected the primary comparison. The timing is given as 12 weeks post treatment, but longer-term outcomes are not reported in the posted results.

Fourth, the record lists four secondary measures, while comparative numeric results are not reported for the Pain Anxiety Symptom Scale - 20. It does not state whether secondary analyses were adjusted for multiple testing or prioritized in a hierarchy. The results for the other secondary measures should consequently be interpreted cautiously.

Finally, the registry does not report the original sample-size justification, the randomization procedure, details of masking, or treatment adherence and fidelity. These are limitations of the information recorded; they do not establish that the trial lacked those procedures.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Behavioral Treatments for Chronic Pain — NCT00371865.
• Registry record last updated 2015-04-10; status last verified 2015-03.
• Results first posted 2015-04-10.
• 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

NCT00371865 is a completed randomized, single-masked, parallel-group trial titled Behavioral Treatments for Chronic Pain. The registry lists an enrollment of 114 and describes 8 group-administered sessions of cognitive-behavioral therapy and 8 sessions of acceptance-based therapy. The sponsor is the US Department of Veterans Affairs.

The primary endpoint was the Brief Pain Inventory at 12 weeks post treatment. Its mean was 4.5 in Arm 1 and 5.1 in Arm 2; the unadjusted mean difference was 0.6 for Arm 2 relative to Arm 1, with an interval spanning zero. The reported mixed-model analysis gives p = .27, but its estimate and confidence interval are not reported in the registry record.

Secondary outcomes include activity, SF-12, depression, and pain anxiety measures. Comparative numeric results for the pain-anxiety measure are not reported in the registry record. The registry does not report the original sample-size justification, multiplicity strategy, missing-data methods, or analysis population. The posted results support a cautious interpretation of the observed group differences and their uncertainty, rather than a definitive conclusion about comparative treatment effects.