Clinical Trial to Evaluate One-to-one Peer Mentoring: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Clinical Trial to Evaluate One-to-one Peer Mentoring (NCT02274649), a randomized na study. The primary outcome is Self-efficacy Scale. It Includes an Adapted Self-efficacy Scale From Chronic Disease Literature Focused on Confidence in Managing Self-care Needs Plus Project-specific Items for Assessment of Confidence Regarding Integration Into Community Life..

2. Clinical Question

Participants were assigned randomly on admission to Shepherd Center. The clinical question therefore concerns the difference between the assigned peer-support approaches in this trial population, with self-efficacy as the primary measure. Rehospitalization was also recorded as a secondary outcome. The registry record does not report a more detailed definition of the population eligible for enrollment or the exact analysis population for each outcome.

3. Trial Design

The record describes a randomized, parallel-group trial with single masking. It lists an enrollment of 194 and a completed status. The study start is recorded as 2014-04, and primary completion as 2016-04. The phase is listed as NA. Shepherd Center, Atlanta GA, is the sponsor.

Assignment was to one of two groups: one-to-one peer mentoring or general peer support. The brief summary says assignment occurred randomly on admission to Shepherd Center. Injury level was the only stated stratifying criterion, grouped as C6 and above versus C7 and below. The record does not identify who was masked, how masking was maintained, or whether it was feasible to mask participants or mentors in this behavioral intervention.

The stated aim was to examine whether enhanced peer mentor interactions could facilitate successful transition to community living after traumatic spinal cord injury. The primary outcome was self-efficacy, assessed by telephone interview over the period beginning 3 days after rehabilitation discharge and ending 180 days post discharge. Rehospitalization measures were also registered as secondary outcomes. The record lists four secondary outcome entries, including cumulative rehospitalization days and the percentage of patients rehospitalized at specified follow-up periods.

The posted primary group summaries include 81 control participants and 77 intervention participants. Those outcome-group counts do not by themselves explain how the enrollment figure relates to the analysis population. Reasons for any difference, exclusions, withdrawals, and outcome-specific missingness are not reported in the registry record.

4. Participant Flow and Accounting

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

Before assignment: If planned discharge location was to non-community location, participants were not assigned to group and excluded from study

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 Self-efficacy Scale. It Includes an Adapted Self-efficacy Scale From Chronic Disease Literature Focused on Confidence in Managing Self-care Needs Plus Project-specific Items for Assessment of Confidence Regarding Integration Into Community Life., measured over 3 days post rehabilitation discharge through 180 days post discharge.

The primary endpoint is a self-efficacy score intended to capture confidence in managing self-care needs and integrating into community life after spinal cord injury. The registry describes an adaptation of the General Self-Efficacy scale for people with spinal cord injury. The adapted measure includes 6 items from the chronic-disease scale and 5 project-specific items focused on community navigation and accessibility, which were identified as a major focus of the peer-support program.

Respondents answered each of the 11 items during telephone interviews using a 10-point Likert scale, from 1, meaning not confident, to 10, meaning very confident. Item scores were averaged to form the total self-efficacy score. The stated total-score range is 11 to 110, with higher scores indicating greater self-efficacy to manage injury conditions.

This measure was selected to reflect confidence in activities relevant to the trial’s community-transition aim, rather than a clinical event alone. The endpoint timeframe runs from 3 days post rehabilitation discharge through 180 days post discharge. The registry describes growth curve analysis: initial status coefficients represent the first time point, and growth rate coefficients represent change over time. Numerical results from that growth curve model are not reported in the registry record; the posted group summaries instead give means and standard errors.

7. Results Posted in the Registry

• Intervention: mean 7.65 versus 7.64 on control; difference 0.01 (95% CI -0.71 to 0.73), standardized effect d = 0.00; z-test p = 0.978.

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.

Rehospitalization - Number of Days (Cumulative)

• 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:
  • Intervention: mean 0.99 versus 2.11 on control; difference -1.12 (95% CI -2.61 to 0.37), standardized effect d = -0.23; z-test p = 0.140.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Intervention and the control. The interval gives the range of effects that remain compatible with the data.

Rehospitalization - Percent of Patients Rehospitalized (90 Days)

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Intervention: 10.4% (8/77) versus 18.5% (15/81) on control; risk difference -8.1 percentage points (95% CI -19.0 to 2.7), risk ratio 0.56 (0.25–1.25); unadjusted two-proportion z-test p = 0.148.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Intervention and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes concern rehospitalization, an event-based measure distinct from the primary self-efficacy score. The posted summaries suggest lower rehospitalization burden in the intervention group in direction, both for days and for the percentage rehospitalized. However, the corresponding uncertainty intervals include the null values, and the unadjusted p-values do not provide a clear distinction between groups. The apparent direction therefore remains uncertain.

These secondary findings do not resolve the primary question about confidence and community integration. Rehospitalization may be relevant to transition after injury, but it measures a different aspect of participants’ experience. A pattern in secondary outcomes cannot substitute for the primary outcome or establish a mechanism linking peer support to self-efficacy.

The registry lists four secondary outcome entries, while numerical results are posted for two outcome entries. One listed item concerns the percentage of patients rehospitalized at 180 days, for which numerical results are not reported in the registry record. The record also repeats the cumulative rehospitalization-days title in its listed outcomes; a distinct additional result for that repeated listing is not reported.

Unadjusted secondary results generally carry less weight when several outcomes or time points are examined, because the chance of a seemingly notable result can increase across multiple comparisons. The registry record does not report a multiplicity adjustment, a hierarchy for secondary outcomes, or a confirmatory status for these analyses. The secondary comparisons should consequently be treated as descriptive and exploratory rather than as independent confirmation of the primary finding.

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

• Rehospitalization - Number of Days (Cumulative)
• Rehospitalization - Percent of Patients Rehospitalized (90 Days)
• Rehospitalization - Number of Days (Cumulative)
• Rehospitalization - Percent of Patients (180 Days)

9. Statistical Interpretation

10. Statistical Methods Explained

The primary comparison is a mean difference between intervention and control. The registry reports a mean and standard error for each group. A mean describes the average score in the group; a standard error describes the precision of that estimated average, rather than the spread of individual scores. The record does not provide standard deviations for the primary outcome.

What does the mean difference describe?

The reported mean difference is intervention minus control. A positive value would indicate a higher group mean in the intervention group, and a negative value would indicate a lower group mean. For the primary score, the posted difference is 0.01 units. This is an unadjusted comparison based on the posted summaries; it does not account for any model terms or repeated measurements unless those are incorporated in an analysis that is not reported.

What does the confidence interval add?

A confidence interval gives a range of estimates compatible with the observed data under the method used to calculate it. It shows the uncertainty around the point estimate, rather than guaranteeing that the true difference lies in the interval. For a difference, an interval containing zero is compatible with no group difference as well as with differences in either direction. A narrow interval indicates greater precision than a wide interval, all else being comparable.

How should the p-value be read?

The unadjusted p-value describes how unusual the observed result, or a more extreme result, would be under a statistical model in which there is no difference between groups. It is not the probability that the intervention is ineffective, nor does it measure the size or importance of an effect. The record does not state the trial’s original significance threshold or give a full analysis plan. The planning illustration separately specifies a two-sided significance level of 0.05; that planning assumption should not be mistaken for a reported primary-analysis rule.

What does the growth-curve description imply?

In general, growth curve analysis models outcomes measured over time. It can distinguish a group’s initial status from its rate or pattern of change, and can account for the fact that repeated observations on the same participant are related. The registry says this approach was used for self-efficacy, and describes initial status at 3 days post discharge and growth rate over time. It does not report the model form, covariance structure, covariates, coefficient estimates, or uncertainty for those coefficients. The posted mean comparison therefore should not be interpreted as a full report of the longitudinal model.

How do the secondary outcome measures differ?

Cumulative rehospitalization days is a continuous outcome summarized by group means and standard deviations. Days in hospital can be unevenly distributed across participants, so in general the mean and standard deviation may not fully describe the distribution. Over-dispersion occurs when the variability in a count outcome is greater than a chosen model expects; it can affect standard errors and inference if the model does not accommodate that variability. The registry does not report a model for the days outcome, so no particular distributional assumption can be attributed to its analysis.

The percentage rehospitalized is a binary outcome: each participant is classified according to whether rehospitalization occurred within the stated period. A risk difference compares the proportions directly; a risk ratio compares them as a ratio, while an odds ratio compares odds. These measures answer related but different questions and can have different numerical scales. The posted comparison includes a risk difference and also lists ratio estimates. The registry does not report a formal model or adjusted secondary analysis.

The figures identified as recalculated are simple unadjusted re-calculations from posted summary statistics. They should be distinguished from a trial’s prespecified analysis and from any adjusted or longitudinal model. Since the discrepancy indicator is false, the record does not flag a disagreement that would require precedence for the sponsor’s own analysis; however, sponsor analysis results are not reported. General statistical explanations of means, intervals, and outcome types do not establish which model the trial investigators used beyond the methods explicitly described in the record.

11. Confidence Intervals and Precision

The primary mean difference is 0.01 units, and its confidence interval extends from a negative value to a positive value. Because zero lies within that interval, the estimate is compatible with no difference as well as with effects in either direction. The interval is broad relative to the point estimate, so the observed near-zero difference should not be mistaken for a highly precise estimate of exactly zero.

Precision is distinct from the direction of the point estimate. The intervention group mean is slightly higher, but the interval indicates substantial uncertainty about the underlying difference. The unadjusted p-value of 0.978 likewise does not establish equivalence; it indicates that the posted summary does not provide evidence against a no-difference model under the recalculation used.

The secondary comparisons also have uncertainty intervals that include their respective null values: zero for the mean difference in days and the risk difference for rehospitalization. This limits how strongly the apparent direction of those point estimates can be interpreted. The registry does not report confidence intervals from adjusted analyses, from the described growth curve model, or for the unposted secondary outcomes.

In general, confidence intervals depend on the analysis method and assumptions. The registry record does not give enough detail to assess all such assumptions or the precision of repeated-measure estimates. The posted intervals are most appropriately read as uncertainty around the displayed unadjusted comparisons, not as a complete account of uncertainty for every planned analysis.

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 for these outcomes. The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The calculations use the stated fraction of the observed effect as the effect to detect. The trial’s own original design assumptions and sample-size justification are not reported in the registry record.

The 80% power column describes the planned number of participants per arm under those assumptions for a design with an 80% chance of detecting the specified effect if that effect is the true one. The 90% power column describes the corresponding number per arm for a design with a 90% chance under the same assumptions. These are design probabilities, not guarantees about what a particular trial will find.

The rows for 100%, 75%, and 50% of the observed effect illustrate how the planning requirement changes when the target effect is smaller than the observed estimate. Smaller effects require more participants to detect under otherwise unchanged assumptions. The observed effects can be unstable estimates, especially when uncertainty is substantial, so these illustrations should not be treated as a recommended design without additional clinical and statistical justification.

Time-to-event planning tables, if present, report total events using the Schoenfeld method; other tables report participants per arm. The outcomes in this trial’s planning illustrations are not described as time-to-event outcomes, so their figures are per arm. These numbers are planning illustrations based on observed effects, not observed power.

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 = 0.010; pooled standard deviation σ = 2.322.
2. n = 2 × (1.96 + 0.842)² × 2.322² / 0.010² = 846,545.2, rounded up to 846,546 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 <- 0.0100000000000007                      # observed difference in means
sigma <- 2.3222353289615                     # 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(2274649)
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 = 846,546 (80% power), 1,133,284 (90% power)
 75% of observed effect: n per arm = 1,504,970 (80% power), 2,014,727 (90% power)
 50% of observed effect: n per arm = 3,386,181 (80% power), 4,533,136 (90% power)
power.t.test: 846546.1 
Simulated power at n = 846,546 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.

14. Multiplicity, Missing Data and Analysis Populations

The registry record lists multiple secondary outcomes, including rehospitalization measures at different follow-up periods, but does not report how the investigators planned to control the risk of false-positive findings across outcomes or time points. No multiplicity adjustment, testing hierarchy, or designation of confirmatory versus exploratory secondary analyses is reported. This matters because interpreting each unadjusted comparison as if it were the only test can overstate the strength of a collection of findings.

The record lists no reported analyses. It does not provide a statistical analysis plan, the model specifications for the primary growth curve analysis, or details about which covariates were included. It also does not state whether the primary analysis followed intention-to-treat principles, whether participants were analyzed according to assignment, or how any per-protocol population was defined. The analysis population is not reported in the registry record.

Missing-data methods are also not reported. The record does not describe the amount or pattern of missing self-efficacy or rehospitalization data, reasons for missingness, imputation, or sensitivity analyses. Because the primary measure was collected by telephone over time, knowing how incomplete interviews or missed follow-up assessments were handled would be important for evaluating the longitudinal result; the registry does not give those details.

The posted primary group summaries list 81 control participants and 77 intervention participants, whereas the enrollment figure is 194. The registry record does not explain this relationship, and the figures should not be treated as a complete account of exclusions, follow-up, or analysis-set construction. Without these details, the available summaries cannot establish whether missingness or analysis-population choices affected the comparisons.

15. 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 adverse-event figures list 77 intervention participants and 81 control participants as at risk for serious adverse events, and the same group counts as at risk for other adverse events. The recorded number affected is 0 for both categories in each group. Deaths are also recorded as 0 in each group, and no serious adverse-event terms are listed.

These figures mean that the registry record reports no events in the displayed categories for the participants listed as at risk. They do not establish that no health events occurred outside the recorded categories, or that the intervention is free of risk. The record does not give further detail about how adverse events were defined, collected, graded, or attributed, nor does it explain whether follow-up completeness differed by group. The safety figures should therefore be read as the posted event counts, not as a comprehensive assessment of every possible harm.

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

The primary posted comparison is close to zero: the group means are 7.64 and 7.65, and the reported mean difference is 0.01 units. The unadjusted p-value is 0.978, and the uncertainty interval includes zero. These results do not demonstrate a clear difference in the primary self-efficacy summary between the assigned groups.

That conclusion is narrower than saying the peer-mentoring approaches are equivalent, that neither could have an effect, or that there is no effect over time. The registry describes growth curve analysis, but does not provide its model estimates. The summary means do not show the change trajectory or distinguish initial status from growth rate. The absence of a clear difference in the posted comparison is not proof of no difference.

The secondary rehospitalization comparisons point in a direction favoring fewer days or a lower percentage in the intervention group, but their uncertainty intervals include the null and the analyses are unadjusted. Those findings should not be taken as conclusive evidence of an effect, especially without a reported multiplicity plan and without numerical results for all listed secondary outcomes.

Interpretation is also limited by missing information about analysis populations, missing data, the original analysis plan, and the exact model used for the longitudinal endpoint. The posted results address this trial’s measures and follow-up period; they do not by themselves establish effects for other populations, peer-support programs, or care settings. They are statistical evidence to interpret in context, not medical advice or a basis for an individual treatment decision.

17. Why This Trial Matters Statistically

This trial raises a useful statistical question about how to evaluate a behavioral intervention whose goal is a successful transition to community living. The primary endpoint attempts to measure confidence in both self-care and community integration, rather than relying only on a clinical event. Connecting a measure to the intervention’s intended pathway can make an evaluation more informative, provided the construct and scoring are clearly described.

The registry’s description of growth curve analysis also highlights why a single group mean comparison may not capture the full longitudinal question. Initial status and change over time are different features of response. Reporting the model estimates, uncertainty, and handling of repeated observations would allow readers to assess the stated trajectory analysis rather than infer it from summary means.

The result is also a reminder that point estimates need to be read alongside their uncertainty. A near-zero estimate may look definitive at first glance, but the interval indicates that the comparison is not precise enough to establish exact equivalence. Conversely, directional secondary estimates are not persuasive simply because they point in a potentially favorable direction, particularly when they are unadjusted and several outcomes are listed.

Finally, complete reporting is part of statistical interpretation. Analysis populations, missing-data handling, outcome definitions, multiplicity decisions, and model specifications are needed to understand how results were obtained and how robust they may be. Their absence in the registry record limits the conclusions that can be drawn, even when the posted summaries are straightforward to describe.

18. 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 does not report the original sample-size justification, the planned primary analysis details, or a full statistical analysis plan. The description of growth curve analysis is not accompanied by its coefficients or uncertainty estimates, so the posted group summaries cannot answer the full longitudinal question stated for the endpoint.

The record identifies the trial as single-masked but does not say who was masked or how masking was implemented. The intervention involves peer interactions, but the record does not detail the practical procedures used to maintain masking. This limits assessment of possible influences on interviews or outcome reporting.

It is not reported how missing outcomes, withdrawals, or deviations from assigned intervention were handled. The registry also does not identify the analysis populations. The posted outcome-group counts and enrollment figure are not reconciled in the record, so the contribution of exclusions or incomplete follow-up cannot be assessed from the summaries alone.

Several secondary outcomes are listed, but numerical results are posted for only two entries, and no multiplicity strategy is reported. The record does not describe adverse-event collection in enough detail to determine the breadth of event capture. These reporting gaps do not establish that the study was conducted improperly; they constrain what can be evaluated from the registry record.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Clinical Trial to Evaluate One-to-one Peer Mentoring — NCT02274649.
• Registry record last updated 2019-02-04; status last verified 2019-01.
• Results first posted 2019-02-04.
• 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.

22. Record Summary

NCT02274649 is a completed randomized, parallel-group trial titled “Clinical Trial to Evaluate One-to-one Peer Mentoring.” The official title describes a patient-centered approach to community transition after catastrophic injury. The sponsor is Shepherd Center, Atlanta GA. The record lists an enrollment of 194, a study start of 2014-04, and primary completion of 2016-04. Phase is listed as NA.

The intervention was one-to-one peer mentoring, compared with general peer support, after traumatic spinal cord injury. The primary outcome was a self-efficacy score assessed from 3 days post rehabilitation discharge through 180 days post discharge. The posted primary mean difference was 0.01 units, with an unadjusted p-value of 0.978. Rehospitalization measures were registered as secondary outcomes; the posted secondary comparisons remain uncertain, and some listed secondary results are not reported in the registry record.