Implementation of Nurse-guided Web-based Cognitive Behavioral Therapy for Pain Management: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Implementation of Nurse-guided Web-based Cognitive Behavioral Therapy for Pain Management (NCT03927846), a randomized na study. The primary outcome is PROMIS (Patient Reported-outcomes Measurement Information System) Pain Intensity.

2. Clinical Question

The clinical question is framed around a continuous patient-reported score rather than an event such as hospitalization or recovery. The registry describes the measure as a questionnaire of pain intensity, with lower scores representing a better outcome on its stated scale. The reported arm means are 4.4 for Nurse Support and 4.7 for Control. The posted mean difference is -0.3, expressed as Nurse Support relative to Control. That direction favors a lower score in the Nurse Support arm, but the uncertainty around the comparison is important: the reported interval includes values on both sides of no difference, and the unadjusted p-value is 0.405.

The registry identifies the condition as chronic musculoskeletal pain while its brief summary refers more broadly to patients with all types of pain complaints. Details that would clarify the intended clinical population, such as specific diagnoses, symptom duration, or eligibility criteria, are not reported in the registry record. The question therefore needs to be read as a comparison in the population enrolled in this particular study, not as a result that can automatically be extended to every pain condition or care setting.

3. Trial Design

The registry describes a randomized, single-masked, parallel-group study. Randomized allocation means that assignment to study arms was intended to use a random process; the exact sequence-generation and allocation-concealment procedures are not reported in the registry record. A parallel design assigns participants to an arm and compares outcomes across arms rather than having each participant receive both strategies. The identity of the group that was masked, and how masking was maintained, are not reported in the registry record.

The study is listed as completed, with an enrollment of 60. The primary-outcome results give a sample size of 20 for Nurse Support and 19 for Control. The reason the outcome sample sizes differ from the enrollment figure, including whether this reflects missing measurements, exclusions, or another accounting process, is not reported in the registry record. These figures should be kept distinct: enrollment describes the registry’s overall study enrollment, while the arm-specific values describe the reported endpoint data.

The named intervention is nurse-guided web-based cognitive behavioral therapy. The arm descriptions give more detail about contact: Nurse Support is described as 6 regular telephone contacts by nurses using a motivational interviewing technique, while Control is described as 6 computer-generated email reminders over an 8-week period. The registry does not report enough detail to establish the complete content, timing, or delivery fidelity of the web-based program, or whether any additional services were available to either arm.

The primary outcome is PROMIS pain intensity, measured up to Week 16. The record also lists completed phone calls and completed learning modules per treatment arm as secondary outcomes. The original trial protocol, its sample-size justification, detailed statistical analysis plan, and any prespecified interim analyses are not reported in the registry record. The study’s registry phase is listed as NA.

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 PROMIS (Patient Reported-outcomes Measurement Information System) Pain Intensity, measured over Up to Week 16.

The primary endpoint is PROMIS (Patient Reported-outcomes Measurement Information System) Pain Intensity, a questionnaire measure of subject pain intensity. The registry describes the result as a mean score on a scale with a possible range from 3 to 15. It identifies 3 as the best outcome and 15 as the worst outcome. Thus, within the scale as described in the record, a lower score indicates less reported pain intensity. The outcome is scheduled for assessment up to Week 16; the particular visit or time point represented by the posted means is not specified more precisely in the registry record.

A continuous score can retain information about the level of a reported symptom, rather than reducing all participants to categories such as improved or not improved. Comparing arm means gives a concise description of average scores, while the spread of individual scores and the precision of the estimated difference matter for interpretation. The posted result is reported as a mean with standard error for each arm. A standard error describes uncertainty in an estimated mean; it is not the same as the range of individual participant scores.

Pain intensity is relevant to the stated study question because the brief summary asks whether the nurse-guided approach will show pain improvement. A questionnaire provides a structured way to record participants’ reports, but the registry does not report information about the scale’s administration, scoring details beyond its range, or the threshold for a change considered clinically important. Those details are not reported in the registry record, so the numerical difference should not be translated into a claim about a meaningful change for an individual.

7. Results Posted in the Registry

• Nurse Support: mean 4.40 versus 4.70 on control; difference -0.30 (95% CI -1.01 to 0.41), standardized effect d = -0.26; z-test p = 0.405.

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical quantities reported for the primary outcome address related but distinct questions. The arm mean describes the average recorded score in that arm. The standard error describes the precision of that estimated mean. The mean difference describes the estimated separation between the arm averages, and its confidence interval represents uncertainty around that comparison. A p-value summarizes how compatible the observed data are with a specified null model, under the assumptions of the analysis. None of these quantities alone describes every participant’s experience or establishes the clinical importance of a difference.

What does the mean difference represent?

The Nurse Support mean is 4.4 and the Control mean is 4.7. The posted mean difference is -0.3, calculated in the direction Nurse Support relative to Control. The minus sign indicates a lower mean in Nurse Support. Because the record says 3 is the best score and 15 the worst, the direction of the observed mean difference is toward a better score in Nurse Support. This description concerns the observed averages only; it does not establish that the intervention produced the difference.

A mean difference keeps the outcome in its original scale units, which makes it possible to interpret the estimate against the stated scale range. However, whether a particular difference is important in practice depends on context, including a clinically meaningful threshold. Such a threshold is not reported in the registry record. It would therefore be unwarranted to label the observed difference clinically important or unimportant based only on its numerical value.

How should standard errors be read?

The reported standard errors are 0.3 in Nurse Support and 0.2 in Control. Standard errors quantify sampling uncertainty in an estimated mean: in general, a smaller standard error indicates a more precisely estimated mean, given the analysis and data. They are not standard deviations and should not be interpreted as describing the typical distance of individual participant scores from their arm’s mean. The standard deviations for the two arms are not reported in the registry record.

For a comparison, uncertainty depends on the uncertainty in both arm estimates and on the method used to combine them. The confidence interval for the difference is the more direct summary of uncertainty about the arm contrast. The record does not describe the full statistical model, distributional checks, or any adjustment used to obtain that interval. Those details are not reported in the registry record.

What does the confidence interval add?

In general, a confidence interval gives a range of values that are compatible with the observed data under the method’s assumptions. It communicates both the direction and precision of an estimate more fully than a single point estimate. The interval reported for this comparison includes zero. This means the posted result is compatible with no mean difference, as well as with a range of negative and positive differences. It is not evidence that every value in the interval is equally likely, and it does not guarantee that the true effect lies in the interval.

The registry record does not identify the confidence level or describe how the interval was constructed. That information should not be inferred from the planning assumptions for the sample-size illustration, which are a separate calculation. The posted interval is useful as an uncertainty summary, but its precise operating properties depend on methods and assumptions that are not fully described in the registry record.

What does the p-value say?

The unadjusted p-value is 0.405. In general, a p-value evaluates how unusual data at least as inconsistent with a null hypothesis would be if that null hypothesis and the analysis assumptions were true. It is not the probability that the null hypothesis is true, and it is not the probability that the result occurred by chance. A larger p-value does not prove there is no effect; it indicates that the observed data do not provide strong evidence against the null under the specified test.

The record calls this value unadjusted. Whether it is the primary prespecified test, what test generated it, and whether other analyses were considered in the statistical plan are not reported in the registry record. The study lists multiple outcome measures, so interpretation of an individual p-value also depends on the planned analysis family and any multiplicity strategy. That strategy is not reported.

Why can over-dispersion matter?

General statistical context: over-dispersion occurs when observed variability is greater than a model expects. A model that understates variability can make standard errors too small and confidence intervals too narrow, leading to overconfident conclusions. For a continuous outcome, the corresponding concern is whether the chosen method adequately represents the variability and distribution of scores. The registry does not report evidence of over-dispersion, model diagnostics, or a method addressing it. This is a general consideration, not a reported feature of this trial.

What can the effect-size and planning values show?

The posted comparison includes a standardized effect estimate, but the registry does not report a clinical threshold for interpreting it. Standardized measures express a difference relative to a measure of variability, which can help compare outcomes measured on different scales, but they are less directly interpretable in the original score units. A planning illustration also gives participant counts per arm for specified fractions of the observed effect. Those are hypothetical design calculations and should not be confused with the actual randomized sample or a retrospective measure of whether the study had enough power.

In general, sample-size calculations depend on assumptions about the effect to detect, statistical significance level, allocation, and analysis method. The illustration states its own assumptions, but the trial’s original design assumptions are not reported in the registry record. The planning figures therefore cannot be treated as a reconstruction of the study protocol or as evidence about what the original investigators planned.

10. Confidence Intervals and Precision

The point estimate is a mean difference of -0.3, with the Nurse Support mean lower than the Control mean. The reported confidence interval includes zero and extends to values on either side of no difference. This is the central precision finding: the data are compatible with a directional difference favoring lower scores in Nurse Support, but also with little or no separation and with a difference in the other direction. The interval is not narrow enough to resolve those possibilities.

Precision is distinct from whether a statistical test crosses a conventional significance threshold. A confidence interval communicates a range of estimates compatible with the data and the method, whereas a p-value reduces the test result to a summary against a null hypothesis. The unadjusted p-value is 0.405. Read together, the interval and p-value indicate that this comparison does not tightly locate the underlying mean difference. They do not demonstrate that the arms are identical.

The arm means have standard errors of 0.3 and 0.2. Those values concern uncertainty about each mean, not the spread of individual scores. The reported endpoint samples are 20 in Nurse Support and 19 in Control. The registry does not explain the relationship between those endpoint counts and the enrollment of 60, or how missing outcome data were handled. If the available observations differ from the intended analysis population, that could affect both the estimate and its precision, but the extent of any such effect cannot be assessed from the record.

The confidence level and construction method for the reported interval are not described in the registry record. The interval should therefore be interpreted as the posted uncertainty summary, without adding a confidence level that the record does not state. Nor does statistical precision alone establish clinical importance: the record does not report a threshold for a meaningful change in pain intensity.

11. 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 sample-size figures are planning illustrations, not observed trial outcomes. They give participants per arm for the continuous outcome; they are not total event counts. The listed planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each row considers an effect to detect equal to the stated fraction of the observed effect. The original trial’s own design assumptions and sample-size justification are not reported in the registry record.

The 80% power column means the illustrated number of participants per arm under those assumptions for a design with 80% power to detect the specified effect. The 90% power column gives the corresponding participants per arm for 90% power. In general, power is the probability that a specified analysis will reject its null hypothesis if the assumed effect is the true effect, under the calculation’s assumptions. It is not a guarantee that a particular future study will produce a statistically significant result.

The entries increase as the assumed effect becomes a smaller fraction of the observed effect. That pattern reflects a general principle: smaller effects are harder to distinguish from sampling variability, so more participants are needed to achieve a chosen power level under otherwise unchanged assumptions. The figures are tied to this study’s observed estimate and the stated calculation method; they should not be interpreted as universal sample-size recommendations or as proof that the original study was designed around these targets.

This is not observed power. It is a forward-looking planning illustration based on assumed effects and specified statistical conditions. It does not measure the probability that the posted result is true, and it does not repair uncertainty arising from missing design details, the endpoint sample sizes, or the analysis plan.

12. 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 = -0.300; pooled standard deviation σ = 1.138.
2. n = 2 × (1.96 + 0.842)² × 1.138² / -0.300² = 225.7, rounded up to 226 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 <- -0.3                      # observed difference in means
sigma <- 1.13756496695971                     # 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(3927846)
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 = 226 (80% power), 303 (90% power)
 75% of observed effect: n per arm = 402 (80% power), 538 (90% power)
 50% of observed effect: n per arm = 903 (80% power), 1,209 (90% power)
power.t.test: 226.7 
Simulated power at n = 226 per arm: 0.804 (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.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists 29 outcome measures and identifies completed phone calls and completed learning modules per treatment arm as secondary outcomes. It does not report a complete hierarchy of outcomes or explain how the primary outcome was distinguished from the other measures for inferential testing. The record also reports zero posted analyses. The primary comparison is therefore available as a posted result, but a detailed account of the full analysis set is not available in the registry record.

Multiplicity arises when several outcomes, time points, subgroups, or statistical tests are examined. In general, testing many hypotheses can increase the chance of finding at least one apparently strong result even when there is no underlying effect. Statistical plans may address this through a prespecified hierarchy or adjustment procedure, among other approaches. Whether multiplicity was addressed for this study, and how any strategy was chosen, are not reported in the registry record. The p-value is identified as unadjusted, so it should not be assumed to account for other outcomes or analyses.

The primary endpoint is scheduled up to Week 16, but the exact time point represented by the posted means is not stated. Whether multiple measurements were collected and how they were handled are not reported in the registry record. The record does not report the analysis population, whether participants were analyzed according to randomized assignment, or whether any per-protocol or other populations were used.

The endpoint sample sizes are 20 and 19, while overall enrollment is 60. The reason for this difference is not reported. Missing-data methods, the amount and pattern of missing outcome data, and any sensitivity analyses are also not reported in the registry record. Without these details, it is not possible to assess whether the available endpoint results could be affected by missingness or by exclusions from analysis. These gaps do not show that a particular problem occurred; they limit what can be concluded from the posted record.

14. 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.

The registry reports that 30 participants were at risk for serious adverse events in Nurse Support and 30 in Control. It records zero serious adverse events in each arm. It also reports 30 at risk for other adverse events in each arm and zero such events in both arms. Deaths are recorded as zero in each arm. No serious adverse event terms are listed.

These counts describe the safety information posted in the registry, not proof that no adverse events occurred outside the recorded definitions, observation period, or reporting process. The record does not provide a detailed adverse-event collection window, severity criteria beyond the serious-event category, or a narrative account of monitoring. It also does not explain how the adverse-event risk populations relate to the primary-outcome sample sizes or the enrollment figure.

Zero recorded events in a finite group leave uncertainty about the frequency of uncommon events. These figures should be read as the counts reported, rather than as evidence that either strategy is risk-free or that the arms have identical safety profiles. The registry record does not report additional safety analyses that would support broader conclusions.

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

The posted primary result is a comparison of mean pain-intensity scores up to Week 16. Nurse Support had a mean of 4.4 and Control had a mean of 4.7 on the scale for which lower scores are described as better. The estimated mean difference was -0.3. The interval around the difference includes zero, and the unadjusted p-value is 0.405. Taken together, the data show a lower observed mean in Nurse Support but do not precisely establish a difference between the arm means.

This result does not establish that the approaches are equivalent. A conclusion of equivalence would require a prespecified margin and a suitable analysis; neither is reported in the registry record. The result also does not prove that there is no difference. An uncertain estimate can reflect limited precision, and the study’s endpoint sample sizes are 20 and 19. The registry does not report the original sample-size rationale, so the intended ability to detect a particular effect cannot be assessed.

The outcome is a patient-reported pain-intensity score. The record provides the scale range and direction but no threshold for a clinically meaningful change. Consequently, the estimated difference cannot be labeled important or unimportant for participants on the basis of the registry information alone. The arm means also do not show how scores varied among participants or how many people experienced changes of particular sizes.

The result applies to the study as recorded, not automatically to all forms of pain, all nursing support programs, or all web-based cognitive behavioral therapy. The registry lists chronic musculoskeletal pain as the condition, while the brief summary uses broader language. Detailed eligibility criteria, intervention fidelity, the exact measurement time point, and missing-data handling are not reported. These limits prevent a confident extension of the result beyond the observed comparison.

In short, the record reports an observed directional difference with substantial uncertainty. It offers neither a definitive demonstration of a group difference nor evidence that the approaches are interchangeable. The statistics describe the posted data and the uncertainty around them, rather than making a treatment recommendation.

16. Why This Trial Matters Statistically

This study illustrates why a mean difference should be read alongside its uncertainty. The arm means are close in the scale’s units, and the estimated contrast points toward a lower score in Nurse Support. But the reported interval crosses zero, so the data do not distinguish that direction from no difference or a difference in the opposite direction with confidence. A point estimate alone would leave out the main limitation of the result: its imprecision.

The endpoint also highlights the distinction between uncertainty in group averages and variation among individual participants. The registry reports standard errors, which describe precision of the means. They are not a summary of how dispersed participants’ scores were. That distinction matters for interpreting patient-reported outcomes, since an average cannot show whether most participants had similar scores or whether experiences varied widely.

The comparison is a randomized parallel-group design, but the public record does not report key details needed to evaluate the analysis fully: the original sample-size justification, analysis population, handling of missing measurements, or multiplicity strategy. The endpoint counts are smaller than the enrollment figure, with no explanation in the record. These are not proof of a flaw; they identify limits on what the available statistics can answer.

The planning illustration is another useful statistical distinction. It shows how assumed effect size and target power influence hypothetical participant requirements, not how much power the completed study actually had. Keeping planning calculations separate from observed results prevents a common misreading of power and avoids treating a small p-value threshold as the only measure of evidence.

Overall, this record offers a practical example of cautious interpretation: state the observed direction, quantify uncertainty where possible, distinguish the outcome’s scale from its clinical importance, and identify what the registry does not document. That approach keeps conclusions proportional to the information available.

17. 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 trial-specific uncertainties that limit interpretation. Although the overall enrollment is 60, primary-outcome results are reported for 20 participants in Nurse Support and 19 in Control. The reason for the difference between enrollment and endpoint counts is not reported in the registry record. Neither the extent of missing outcome data nor the method used to address it is described, so possible effects on the estimated means and comparison cannot be evaluated.

The outcome timeframe is listed as up to Week 16, but the exact assessment point represented by the reported arm means is not specified. The record does not explain whether scores from more than one time point were collected or how repeated measurements were analyzed. It also does not report the analysis population or whether any participants were excluded from the primary comparison.

Intervention detail is limited. The record names nurse-guided web-based cognitive behavioral therapy and describes six telephone contacts using motivational interviewing for Nurse Support. It describes six computer-generated email reminders over an 8-week period for Control. The full web-based content, adherence definitions, delivery fidelity, contact duration, and other care received are not reported. The record lists completed calls and learning modules as secondary outcomes but does not provide their results in the information analyzed.

The condition is listed as chronic musculoskeletal pain, whereas the brief summary refers to all types of pain complaints. Eligibility criteria and participant characteristics are not reported in the registry record, limiting assessment of which clinical populations the results represent. The record also does not report the original power justification, detailed statistical plan, multiplicity handling, or the confidence-interval method. These omissions constrain reproducibility and clinical interpretation without establishing that any particular design or analysis choice was inappropriate.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Implementation of Nurse-guided Web-based Cognitive Behavioral Therapy for Pain Management — NCT03927846.
• Registry record last updated 2024-11-19; status last verified 2021-02.
• Results first posted 2021-07-15.
• 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.

21. Record Summary

NCT03927846 is a completed randomized, single-masked, parallel-group study of nurse-guided web-based cognitive behavioral therapy for pain management. The registry lists an enrollment of 60 and chronic musculoskeletal pain as the condition. Nurse Support is described as nurse telephone contact, while Control is described as email reminders over an 8-week period.

The primary outcome is PROMIS Pain Intensity, a continuous score with a possible range of 3 to 15, where 3 is identified as best and 15 as worst. Assessment is listed up to Week 16. The reported means are 4.4 for Nurse Support and 4.7 for Control, with a mean difference of -0.3. The unadjusted p-value is 0.405, and the reported interval for the difference includes zero.

Endpoint sample sizes are 20 and 19. The record does not explain their relation to overall enrollment or report the missing-data approach, detailed analysis plan, or original sample-size justification. The safety counts list zero serious adverse events, other adverse events, and deaths in each arm. These results describe what is recorded in the registry and should be interpreted with the uncertainty and reporting limitations noted above.