A Study of VIVITROL in the Prevention of Re-arrest and Re-incarceration: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of VIVITROL in the Prevention of Re-arrest and Re-incarceration (NCT01453374), a na phase 4 study. The primary outcome is Incidence of Subject Re-arrest.

2. Clinical Question

In statistical terms, this is a feasibility-focused question in a particular setting, not a controlled estimate of treatment effect. A single-group study can describe events observed among participants receiving the intervention, but it cannot separate an intervention-associated change from other influences over the same period. The study also listed secondary outcomes concerning re-incarceration, opioid use, overdose, treatment entry, community retention, craving, opioid dependence, and cocaine use. Their inclusion indicates a broad set of outcomes of interest, but does not substitute for a concurrent comparison group or establish what those outcomes showed.

3. Trial Design

The registry describes a phase 4, pilot, open-label study with a single-group model. Enrollment was 27, and the study status is completed. The listed intervention was VIVITROL 380 mg by intramuscular injection. The stated aim was to evaluate the feasibility of initiating participants on VIVITROL in prison and continuing VIVITROL in the community after release. The registry lists opioid dependence as the condition.

Because this is a single-group study, participants were not assigned to parallel intervention and control arms. Allocation is recorded as not applicable, and masking is listed as none. There is therefore no randomized, like-for-like control comparison in the design. Any observed re-arrest or safety events describe the enrolled group during the study; they do not by themselves show what would have occurred in a comparable group without the intervention.

The primary outcome was incidence of subject re-arrest over 7 months, expressed as the number of participants re-arrested. The definition included a new crime or probation or parole violation, using official criminal justice records and/or self-report. Secondary outcomes covered several additional criminal justice, substance use, treatment, and community-retention measures. The registry lists 10 outcome measures and 4 analyses, but further details of the analysis procedures are not reported in the registry record.

The study began in 2011-01, reached primary completion in 2014-05, and is marked completed. The registry record does not report details such as the exact recruitment process, treatment duration, injection schedule, follow-up procedures beyond the primary timeframe, or a protocol for handling departures from treatment. These omissions limit how fully the implementation and analysis can be reconstructed from the record alone.

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: Eligible subjects had a diagnosis of opioid dependence, were seeking treatment, and were eligible for release from prison within 30 days from screening.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All subjects with non-missing data who received at least 1 injection of VIVITROL; 1 subject did not have any outcome data

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.

Population: All subjects who received at least 1 injection of VIVITROL

6. Primary Endpoint

The registry lists the primary outcome as Incidence of Subject Re-arrest, measured over 7 months.

The primary endpoint counts participants who experienced re-arrest during a 7-month timeframe. The registry defines re-arrest as an arrest for any new crime or probation or parole violation, identified through official criminal justice records and/or self-report. The unit is participants re-arrested, so the endpoint is a count rather than a continuous measurement or a time-to-event estimate as described in the registry.

Re-arrest is relevant to the study’s stated purpose because the intervention was intended to be initiated in prison and continued after release, and the study title identifies prevention of re-arrest and re-incarceration as its focus. Counting re-arrests offers a direct way to describe how many participants in the study group had a recorded or self-reported qualifying event during follow-up. The registry’s definition also makes clear that more than one information source could contribute to classifying an event.

The primary endpoint result is not reported in the registry record. Thus, the available record does not state the observed number re-arrested or provide an estimate of the frequency of re-arrest in the outcome population. Nor does it report an uncertainty interval for that endpoint. Without those details, the endpoint’s observed value and its precision cannot be assessed from the posted information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Several statistical ideas help clarify what this study can and cannot estimate. The registry describes a count endpoint and a single-group design. General statistical explanations below are not claims about an unreported analysis plan; the specific planned methods are not reported in the registry record.

What does a count endpoint represent?

In general, a count endpoint records how many people or events meet a defined condition. Here, the stated unit is participants re-arrested, and the qualifying condition is a re-arrest during the 7-month timeframe. A count is easiest to interpret when the number of participants whose outcomes were assessed is also clear. The registry says the primary population includes subjects with non-missing data who received at least 1 injection, and notes that 1 subject had no outcome data. It does not report the primary outcome count itself.

Counts can be analyzed with methods that account for how event frequencies vary, but an analysis method must match the exact endpoint and data structure. The registry record does not report a model for the re-arrest endpoint, an estimate of uncertainty, or a statistical test. It is therefore not possible to identify from the record whether the sponsor used a count model, a direct descriptive summary, or another approach.

Why does the single-group design matter?

In general, a control group helps estimate what might have happened to similar participants under a different intervention or circumstance. Random allocation, when used, can help balance measured and unmeasured characteristics across groups on average. This study is listed as single-group, with allocation not applicable and no masking. It therefore supplies no direct randomized contrast. A count observed in the intervention group would be a description of that group, not an estimate of the difference between VIVITROL and a comparator.

Because the study is open-label, participants and study personnel were not masked to the intervention according to the registry. In general, lack of masking can affect reporting, follow-up, or outcome assessment, depending on the endpoint and procedures. The primary definition draws on official records and/or self-report, but the registry does not explain how those sources were reconciled or whether assessors were otherwise independent.

How should uncertainty be understood?

In general, a confidence interval describes a range of values compatible with the data under a specified statistical method and assumptions. It communicates precision, not the probability that a particular treatment effect is true. No confidence interval for the primary re-arrest endpoint is reported in the registry record. Without an observed endpoint estimate and its uncertainty, readers cannot assess how precisely the study characterizes re-arrest in its outcome population.

Statistical significance, when reported, is also not a measure of clinical importance or proof of causation. The record does not report a primary-outcome p-value or a hypothesis test. The absence of these details should not be filled by assuming a conventional testing procedure. The statistical plan, including any planned adjustment or model specifications, is not reported in the registry record.

What do planning assumptions mean?

In general, a sample-size calculation is a prospective planning exercise: it asks how many participants might be needed under specified assumptions to detect an effect with a chosen probability. It is not an outcome of the trial and is not “observed power.” The planning illustration associated with this record is described as using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect expressed as a fraction of the observed effect. Those are illustration assumptions, not evidence that the study itself used a two-arm design. The study is single-group, and the registry does not report its own sample-size justification. The sponsor’s original planning assumptions and any corresponding design calculation are therefore not reported in the registry record.

General considerations also apply to over-dispersion. In count data, over-dispersion means that observed variability exceeds what a chosen simple count model expects; ignoring it can make uncertainty estimates too narrow. Whether over-dispersion is relevant depends on the outcome definition and model. The registry does not report a count model or a dispersion estimate for re-arrest, so no conclusion about over-dispersion in this analysis can be drawn.

Finally, a statistical analysis needs a defined population and explicit handling of incomplete observations. The stated endpoint population excludes subjects without non-missing data and requires at least 1 injection. One subject is recorded as having no outcome data. The registry does not report whether additional analyses used a different population, how missingness was assessed, or whether sensitivity analyses were conducted. These details affect how far any result could be generalized beyond participants with observed outcomes.

10. Multiplicity, Missing Data and Analysis Populations

The record lists 10 outcome measures and 4 analyses, including a primary re-arrest outcome and multiple secondary outcomes. When several outcomes or analyses are examined, general statistical practice recognizes a multiplicity issue: the chance of at least one apparently notable result can rise if many tests are performed. Prespecified priorities and adjustment procedures can help readers interpret such findings. The registry record does not report whether multiplicity was addressed, which outcomes were included in each analysis, or whether the analyses were prespecified. No claims about adjustment should therefore be inferred from the number of listed outcomes or analyses.

Missing data are relevant to the primary endpoint. Its stated population includes subjects with non-missing data who received at least 1 injection, and the record notes that 1 subject did not have any outcome data. The reason for the missing outcome, the timing of loss to follow-up, and any efforts to obtain the information are not reported in the registry record. The record also does not describe imputation, sensitivity analyses, or assumptions about how missing outcomes relate to re-arrest.

The analysis population is consequently only partly described. The registry names the primary outcome population, but does not report a broader intention-to-treat definition or additional analysis populations. It is not possible to determine from the record whether all enrolled participants were included in other analyses or whether participants were excluded for reasons beyond missing primary outcome data. In a single-group study, these details are important for interpreting the description of observed outcomes and judging whether the analyzed participants represent the enrolled group.

11. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: anaphylactic reaction (3.7%), hypersensitivity (3.7%), abscess limb (3.7%), depression (3.7%), psychotic disorder (3.7%).

The safety summary lists 6 participants with serious adverse events among 27 at risk and 26 participants with other adverse events among 27 at risk. These are descriptive counts for the VIVITROL group. They do not provide a comparison with an untreated or alternative-treatment group, so they cannot establish whether the intervention increased or decreased adverse events relative to another condition. The record does not report deaths for this group.

The listed serious adverse event terms are anaphylactic reaction, hypersensitivity, abscess limb, depression, psychotic disorder, and schizophrenia, paranoid type. Each term is accompanied by a reported frequency of 3.7%. These entries identify reported event categories; the registry does not clarify from this summary whether categories could overlap within participants or how repeated events were counted. The percentages should therefore be read as registry-reported term frequencies, not as evidence of comparative risk.

Serious adverse events and other adverse events are separate summary categories in the record. The counts do not indicate severity distribution beyond that classification, event timing, duration, relatedness assessment, or whether events led to treatment discontinuation. Those details are not reported in the registry record. These safety figures describe what the registry reports for this study group and should not be interpreted as causal estimates.

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

The study’s central question is whether VIVITROL could be initiated in prison and continued in the community after release, with re-arrest designated as the primary endpoint. Its phase 4 pilot, open-label, single-group structure is suited to describing experience in the studied group, but it does not create a randomized estimate of what the same participants would have experienced under a control condition.

The primary result is not reported in the registry record. Consequently, the record does not show how many participants were re-arrested during the 7-month timeframe, and it does not provide an estimate or uncertainty interval for that endpoint. No conclusion about the observed frequency of re-arrest can be drawn from the posted information. The stated purpose and outcome definition are not substitutes for the missing result.

The safety summary does report adverse-event counts and serious-event terms for the VIVITROL group. These are descriptions, not comparisons or causal findings. The study has no like-for-like control arm, and the registry does not provide further detail on event attribution or analysis. The recorded counts should not be taken as proof that VIVITROL caused or prevented any listed event.

More broadly, the findings that could be obtained from a pilot study do not automatically generalize to other populations or settings. The registry record does not provide detailed eligibility criteria, implementation procedures, or a statistical analysis plan. It also notes 1 subject without outcome data, with no explanation of the missingness. These gaps limit assessment of representativeness and precision.

The defensible interpretation is therefore narrow: the registry records a completed study designed to assess feasibility and a primary re-arrest outcome, but does not report the primary outcome result. It also provides a descriptive safety summary. Neither the design nor the posted data support a controlled treatment-effect conclusion.

13. Why This Trial Matters Statistically

This study is statistically informative as an example of the distinction between feasibility-oriented work and comparative efficacy estimation. The intervention was studied in a setting where treatment was intended to begin in prison and continue in the community after release. A single-group pilot can document whether such a study was conducted and can collect outcome and safety information in that context. It cannot, on its own, separate intervention effects from the many other factors that may influence re-arrest or other outcomes.

The choice of re-arrest as the primary endpoint also highlights the importance of precise outcome definitions. The registry specifies qualifying events and the information sources used to identify them: official criminal justice records and/or self-report. This makes the endpoint’s intended meaning clearer, while also leaving practical questions about source reconciliation and outcome ascertainment unanswered in the registry record.

Another statistical lesson is that a registered outcome and a reported outcome are not the same thing. The primary endpoint and its timeframe are described, but the result is not reported. Without the observed count and a measure of uncertainty, readers cannot evaluate the magnitude or precision of the primary finding. This is true even though the record includes a completed status, enrollment information, and a safety summary.

The study also illustrates why missing-data and multiplicity details matter. One subject lacked outcome data, and multiple outcomes and analyses are listed. The record does not explain how missing outcomes or multiple analyses were handled. Such information is important for judging robustness, especially in a small pilot where each participant’s outcome can materially affect descriptive summaries.

These considerations make the record valuable for understanding the design and its interpretive boundaries, while underscoring that the available information cannot answer the primary outcome question numerically. The distinction between what was planned, what was measured, and what was reported is central to transparent statistical interpretation.

14. 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 limitations specific to this study affect interpretation. First, the registry record does not report the primary endpoint result, despite specifying re-arrest over 7 months as the primary outcome. The number of participants re-arrested and any associated uncertainty are therefore unavailable in the record.

Second, the study is single-group and open-label, with no randomized comparator. As a result, outcome and adverse-event descriptions cannot be interpreted as treatment effects relative to a control. The registry specifically notes that the study is not a randomized comparison and that arms are not a like-for-like control comparison.

Third, the primary outcome population requires non-missing data and at least 1 injection. One subject did not have any outcome data. The reason for missingness and its treatment in analysis are not reported. Details on other possible analysis populations are also not reported in the registry record.

Fourth, although several secondary outcomes are listed, their results and the relationship between the 10 outcome measures and 4 analyses are not reported in the registry record. The statistical plan, multiplicity handling, sample-size justification, interim analyses, and analysis methods are not reported. Thus, no assumptions about these procedures should be made.

Finally, the record provides limited detail about eligibility, treatment implementation, follow-up, and safety-event assessment. The adverse-event summary is descriptive and does not report a comparator, event attribution, or further clinical detail. These limitations restrict both the precision of interpretation and the extent to which results, if available elsewhere, could be generalized beyond the studied group and setting.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study of VIVITROL in the Prevention of Re-arrest and Re-incarceration — NCT01453374.
• Registry record last updated 2015-07-13; status last verified 2015-06.
• Results first posted 2015-07-13.
• 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.

18. Record Summary

NCT01453374 is a completed phase 4 pilot, open-label, single-group study of VIVITROL in people with opioid dependence. Enrollment was 27. The intervention is described as a 380 mg intramuscular injection, with a stated aim of evaluating initiation in prison and continuation in the community after release. The primary endpoint was the number of participants re-arrested during a 7-month timeframe, with re-arrest defined using official records and/or self-report.

The primary outcome population included subjects with non-missing data who received at least 1 injection; 1 subject did not have outcome data. The primary re-arrest result is not reported in the registry record. Safety information includes 6 participants with serious adverse events and 26 with other adverse events among 27 at risk. The design has no randomized control group, and the registry does not report the statistical analysis plan, sample-size justification, or handling of missing outcomes.