SMART Trial: Intrapersonal and Interpersonal Stigma Reduction: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for SMART Trial: Intrapersonal and Interpersonal Stigma Reduction (NCT04693416), a non-randomized phase 2 study. The primary outcome is Enacted Stigma (Intrapersonal).

2. Clinical Question

3. Trial Design

The SMART Trial: Intrapersonal and Interpersonal Stigma Reduction is recorded as a phase 2 study sponsored by the University of Tennessee. Its status is completed, and the registry lists enrollment of 71. The listed study dates are 2021-03-08 for the start and 2021-08-30 for primary completion. The design fields describe the study as nonrandomized, unmasked, and single-group.

The record names an intrapersonal stigma-reduction intervention and an interpersonal stigma-reduction intervention. The intrapersonal intervention is directed at individuals and includes substance use disorder education, goal setting, and decisional balance. The interpersonal intervention is intended for family members and support persons of enrolled intrapersonal participants, and includes education about substance use disorders, stigma reduction, and ways to support someone with a substance use disorder. The available description of the intrapersonal intervention ends mid-sentence, so further details about its content are not reported in the registry record.

The listed design features need to be read together. Although the record names two intervention groups, it classifies the model as single-group and allocation as nonrandomized. The groups also consist of different kinds of participants and receive different intervention content. The registry explicitly cautions that the arms are not a like-for-like control comparison. Their outcomes therefore cannot be interpreted as if participants had been randomly assigned to comparable treatment and control conditions.

The primary outcome is restricted to the intrapersonal arm. Engagement in treatment is listed as a secondary outcome, but its definition and results are not reported in the registry record. The record lists seven outcome measures and six analyses; it does not report a detailed protocol or statistical analysis plan.

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:

Analysis population for the primary outcome, as defined in the registry: Intrapersonal arm only

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 Enacted Stigma (Intrapersonal), measured over Immediately before and 2-weeks post-intervention delivery.

The primary endpoint is the change in the Enacted Stigma subscore from the Substance Use Stigma Mechanisms Scale, measured before and after the intervention in the intrapersonal arm. The record specifies an assessment immediately before and 2-weeks post-intervention delivery. The subscore is formed by averaging responses to six items, each recorded on a 5-point Likert-type scale. The described score range is from 6 to 30, with higher scores indicating greater endorsement of substance use stigma.

The reported change is defined as the pre-intervention score minus the post-intervention score. Under that convention, a positive mean change corresponds to a lower post-intervention score and is described by the registry as a reduction in stigma using average scores. A mean change near zero would indicate little average movement on the measured scale, while a negative mean would indicate a higher post-intervention score. These interpretations concern the scale scores and do not, by themselves, establish changes in behavior or treatment engagement.

Using a defined, repeated measure gives the study a way to describe whether average enacted-stigma scores changed over the specified assessment interval. However, the registry record does not report the observed mean change, its standard deviation, a confidence interval, or a significance test. It is therefore not possible to assess the size or precision of the measured change from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary measure is continuous: it is a score with a reported mean and standard deviation. For a continuous endpoint, a mean summarizes the average score or average change in a group, while a standard deviation describes how much individual values vary around that mean. The registry identifies the primary parameter as a mean and the dispersion measure as a standard deviation, but does not provide the observed values.

How should the change score be read?

The registry defines change as the pre-intervention score minus the post-intervention score. This order determines the sign. A positive value indicates that the post-intervention average was lower than the pre-intervention average; a negative value indicates that it was higher. This is a within-participant change concept, but the record does not explain the exact calculation procedure for handling participants with incomplete assessments or whether the reported mean uses paired observations.

General statistical explanation: a mean change describes the average movement in scores, but it can conceal variation in individual responses. The standard deviation helps describe that variability. A confidence interval, if reported, would describe the uncertainty around an estimated mean under the assumptions of the analysis. It would not show the range of changes for all individual participants, nor would it establish that the intervention caused the change. No confidence interval is reported for the primary result.

What can the design establish?

The registry lists a nonrandomized allocation and a single-group model. It also cautions that the two named arms are not a like-for-like control comparison. General statistical explanation: random assignment can help make groups comparable with respect to measured and unmeasured characteristics, while a suitable control group can help distinguish intervention-related change from change that would have occurred over time. In a nonrandomized or single-group design, those protections are limited. Pre-to-post differences can be described, but causal attribution requires additional design or analysis support.

Here, the arms have different intended participants: the intrapersonal intervention concerns enrolled individuals, while the interpersonal intervention is for family members and support persons. Their content also differs. A contrast between their outcomes would therefore mix intervention differences with differences in participant roles and other group characteristics. The record does not describe a randomized comparison or a statistical method for estimating a comparative treatment effect.

Why can over-dispersion matter?

General statistical explanation: over-dispersion occurs when the observed variability in data is greater than a statistical model assumes. If a model understates variability, standard errors can be too small and uncertainty can appear less than it is. For a continuous score, the observed standard deviation is one direct description of spread; model-based methods may also rely on assumptions about how scores or residuals vary. The registry does not report a model specification, diagnostics, or an assessment of distributional assumptions, so it is not possible to determine what methods were used or whether over-dispersion was relevant to the analyses.

What does the sample-size planning language mean?

The registry describes sample-size figures as planning illustrations based on the observed effect, rather than as the trial’s original design justification. The stated illustration assumptions include a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The target effect is described as a stated fraction of the observed effect. For non-time-to-event outcomes, the stated convention is participants per arm; time-to-event planning is described in terms of total events. The record does not report the numerical planning outputs or a trial-specific sample-size justification.

General statistical explanation: a planning calculation estimates the sample size that would be required under selected assumptions, such as a target effect and variability. It is not an observed trial result, and it is not observed power. If the assumed effect is derived from an observed estimate, the calculation is conditional on that estimate and may not reflect the effect that would be expected in a new study. The planning assumptions also include equal allocation, which should not be confused with the actual study design; the registry identifies this trial as single-group and nonrandomized.

What can be inferred from a p-value?

General statistical explanation: a p-value describes how compatible the observed data are with a specified null hypothesis under a statistical model. It is not the probability that the null hypothesis is true, does not quantify the size of an effect, and does not measure clinical importance. Interpretation depends on the analysis, its assumptions, and the broader set of outcomes examined. No primary-outcome p-value or inferential procedure is reported in the registry record, so no significance conclusion can be drawn.

The record lists six analyses and seven outcome measures, but those counts do not specify the methods used. The registry does not report the test or model for the primary outcome, covariate adjustment, treatment of repeated observations, missing-data methods, or the analysis population. Those details are necessary to evaluate whether the estimate and its uncertainty were calculated appropriately.

10. Confidence Intervals for Each Arm

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

R code and output

arm <- c("Intrapersonal Stigma Reduction")
n   <- c(37)
m   <- c(0.73)
sp  <- c(3.813)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Intrapersonal Stigma Reduction  37  0.730  3.813  -0.541  2.001

11. Multiplicity, Missing Data and Analysis Populations

The registry lists seven outcome measures and six analyses. It does not report how the primary and secondary outcomes were prioritized for statistical testing, whether multiple comparisons were made, or whether any adjustment for multiplicity was planned or applied. When several outcomes or analyses are examined, the chance of obtaining at least one apparently notable result can increase. General statistical explanation: multiplicity procedures are used in some settings to control that risk, but the appropriate approach depends on the questions and analysis plan. No adjustment method is reported in the registry record, so multiplicity cannot be assessed.

Missing-data handling is also not reported in the registry record. The primary endpoint requires pre-intervention and post-intervention scores, but the record does not state how many participants contributed to each assessment, how incomplete item responses were handled, or whether participants missing a follow-up measurement were included in the analysis. It does not describe imputation, complete-case analysis, or sensitivity analyses. These omissions matter because the available paired observations may differ from all enrolled participants.

The primary outcome is defined for the intrapersonal arm only. The registry does not identify an intention-to-treat, per-protocol, or other analysis population, nor does it report deviations from intervention or assessment procedures. The listed enrollment of 71 does not establish the denominator for the primary analysis. Without those details and the outcome results, the completeness and representativeness of the analysis cannot be judged.

The registry record also does not report a statistical analysis plan, interim analyses, or a sample-size justification for the actual trial. The separate planning illustration is not evidence of the study’s original design rationale. These unreported details limit assessment of prespecification, selective analysis, and the relationship between study planning and the results.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

The safety record lists the intrapersonal group with 50 participants at risk and the interpersonal group with 21 participants at risk. For each group, the registry records zero participants affected by serious adverse events, zero affected by other adverse events, and zero deaths. The serious-event terms list is empty. These are the posted safety figures; they should be read as counts in the registry record, not as evidence about outcomes that were not recorded there.

General statistical explanation: a count of zero observed events does not prove that an event is impossible or that risk is absent. The interpretation of safety counts depends on the number of participants observed, the length and completeness of follow-up, and how events were collected and classified. The registry record does not report additional detail about safety surveillance, event definitions, follow-up duration for safety, or missing safety data.

The participant counts at risk are safety denominators and should not be treated as the number analyzed for the primary stigma endpoint. The registry does not report the primary endpoint’s analysis denominator. Nor do the safety counts provide evidence about whether the stigma intervention changed scores or treatment engagement. They address reported adverse-event counts, a separate question from the trial’s primary outcome.

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

The record establishes that the SMART Trial was designed to develop a multicomponent approach to stigma related to opioid use disorder, addressing intrapersonal and interpersonal levels. It identifies intervention components and specifies a primary measure of enacted stigma in the intrapersonal arm. The endpoint uses a pre-minus-post score, with positive mean change defined as a reduction in the measured stigma score.

The posted results do not include the observed primary change, its variability, or an uncertainty interval. As a result, the record does not establish whether the average score rose, fell, or stayed similar. It also does not quantify how consistently individual participants changed. The intervention rationale and outcome definition cannot be treated as evidence that the intended result occurred.

Even if a pre-to-post estimate were available, the nonrandomized, single-group classification would constrain what it could mean. Such a change would describe score movement over the assessment period, but would not alone separate intervention effects from other possible explanations. The registry explicitly warns that the named arms are not like-for-like controls, and they involve distinct participants and intervention content.

The trial record therefore does not support a conclusion about intervention efficacy, a comparative advantage between the intrapersonal and interpersonal interventions, or a change in treatment engagement. Engagement in treatment is listed as a secondary outcome, but its measurement details and results are not reported in the registry record. The safety entries report no serious adverse events, other adverse events, or deaths in the listed groups; those counts do not answer the efficacy questions.

In statistical terms, the record describes a research question and measurement framework, but leaves the key estimate and its precision unavailable. A careful reading separates what was planned and measured from what was observed and from what can be causally attributed. The available information supports the former, but not the latter.

14. Why This Trial Matters Statistically

This trial is statistically notable for the distinction between an outcome definition and an outcome result. The registry gives a detailed direction convention for the primary score: pre-intervention minus post-intervention, with a positive mean change representing a lower stigma score. But without the observed estimate and its uncertainty, that convention cannot answer whether the measured scores changed or how precisely any change was estimated.

The design labels also matter. The record names interventions at intrapersonal and interpersonal levels, while classifying the study as nonrandomized and single-group. The two arms are not described as comparable control conditions: they target different participants and include different intervention content. This makes it important not to interpret arm labels as a controlled treatment contrast. A statistical comparison between groups, if one were reported, would need to account for these design differences and could not be assumed to isolate an intervention effect.

The score is a continuous measure derived from multiple Likert-type responses. Reporting its mean change and standard deviation would help describe average movement and observed variability. Confidence intervals and clear analysis methods would further help readers evaluate precision and assumptions. Those result details are not reported in the registry record.

Finally, the registry’s planning language needs to be kept distinct from the study’s observed evidence. Planning illustrations based on an observed effect are conditional calculations, not observed power and not a substitute for an original sample-size rationale. The record’s counts of outcomes and analyses, without a reported multiplicity plan or missing-data approach, also leave important inferential context unresolved. These distinctions are useful well beyond this trial: they help readers separate design intent, descriptive findings, statistical uncertainty, and causal interpretation.

15. Limitations

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

The largest limitation for interpreting the primary outcome is that the registry record does not report its numerical result. The mean change, standard deviation, confidence interval, and p-value are not reported in the registry record. Without those quantities, neither the direction nor magnitude nor precision of the observed score change can be evaluated.

The design is described as nonrandomized and single-group. The record cautions that the intervention arms are not like-for-like control conditions. The intrapersonal and interpersonal interventions have different intended participants and content, limiting direct comparison. These features make causal attribution difficult even if pre-to-post changes were reported.

The primary endpoint applies to the intrapersonal arm only. The available description of that intervention is incomplete, ending mid-sentence, and the registry record does not report the actual delivery details or adherence. It also does not provide participant demographic characteristics, so the extent to which the enrolled participants reflect the intended population facing intersecting stigma related to opioid use disorder and African American race cannot be assessed.

Several analysis details are unreported: the statistical test or model, whether estimates were adjusted, the analysis population, the number contributing paired scores, and the approach to missing items or follow-up data. The record also does not describe a multiplicity strategy, protocol deviations, or a trial-specific sample-size justification. These gaps prevent a full assessment of model assumptions and risk of biased estimates.

The record lists engagement in treatment as a secondary outcome but does not report its definition or results. Safety counts are available, but further details about event ascertainment and follow-up are not reported in the registry record. Together, these limitations mean the registry supports description of the study framework but not a comprehensive evaluation of efficacy, precision, or generalizability.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: SMART Trial: Intrapersonal and Interpersonal Stigma Reduction — NCT04693416.
• Registry record last updated 2023-03-09; status last verified 2023-03.
• Results first posted 2023-03-09.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT04693416, titled SMART Trial: Intrapersonal and Interpersonal Stigma Reduction, is recorded as a completed phase 2 study sponsored by the University of Tennessee. The registry lists enrollment of 71, a start date of 2021-03-08, and primary completion on 2021-08-30. Its design is classified as nonrandomized, unmasked, and single-group.

The project describes an intrapersonal stigma-reduction intervention for individuals and an interpersonal intervention for family members and support persons. The primary outcome is change in the Enacted Stigma subscore in the intrapersonal arm, measured immediately before and 2-weeks post-intervention delivery. Positive mean change is defined as a reduction in the score.

The primary outcome result and key statistical analysis details are not reported in the registry record. Engagement in treatment is listed as a secondary outcome without a reported result. The safety record lists zero serious adverse events, other adverse events, and deaths in each intervention group.