Nicotine Dependence, Withdrawal and Replacement Therapy Assessed by PET Imaging: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Nicotine Dependence, Withdrawal and Replacement Therapy Assessed by PET Imaging (NCT01664741), a randomized phase 4 study. The primary outcome is Change in Mu-opioid Receptor Binding Potential (BP) Between Baseline and Post-patch Scans.

2. Clinical Question

3. Trial Design

The registry identifies this as a randomized, triple-masked, parallel phase 4 trial sponsored by Johns Hopkins University. The recorded enrollment is 127. The study began in 2012-04, reached primary completion in 2018-05 and has completed status. Those record dates describe the trial timeline; they do not provide the dates on which individual participants were scanned or treated.

The intervention descriptions identify a 21 mg transdermal nicotine patch and a matching placebo patch. The record also describes a healthy non-smoker comparison group, made up of demographically matched women and men who have never smoked. It does not state how this comparison group was assigned, whether it was randomized, or how it was incorporated into the primary treatment contrast. The record's randomization designation should therefore be read as a design feature, not as a complete account of allocation procedures.

Triple masking indicates that the registry classifies the study as masked at three levels, but it does not identify which people were masked or explain how masking was maintained. Allocation concealment, randomization sequence generation, and masking assessment are not reported in the registry record. Nor are participant flow details or the number contributing to the primary endpoint reported in the registry record for this analysis.

The stated primary outcome is a continuous mean change in binding potential, reported in ratio units with standard error as the dispersion measure. The listed timeframe is 90 minutes. The record additionally names relationships between changes in binding potential and craving and withdrawal scale scores as secondary outcomes. It reports 0 analyses, so the design description cannot be treated as evidence of a completed statistical comparison.

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: 102 of the participants who passed the on-phone screen came in and signed the consent form to be enrolled in the study. Baseline characteristics data was collected from them but they however failed an assessment done prior to getting the PET scan and so could not start the 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.

Population: 102 of the participants who passed the on-phone screen came in and signed the consent form to be enrolled in the study. Baseline characteristics data was collected from them but they however failed an assessment done prior to getting the PET scan and so could not start the study.

6. Primary Endpoint

The registry lists the primary outcome as Change in Mu-opioid Receptor Binding Potential (BP) Between Baseline and Post-patch Scans, measured over 90 minutes.

The primary endpoint is the change in mu-opioid receptor binding potential between baseline and post-patch scans. Binding potential is reported in ratio units. The registry description says it estimates the product of the density of available receptors and receptor affinity, expressed as 1/equilibrium dissociation constant. The available receptor density is described as Bmax less receptors occupied by endogenous transmitters. Regional values are obtained using reference tissue graphical analysis, with the occipital lobe as the reference region.

This measure is used to characterize receptor binding in brain regions under the study's imaging approach. It is not described as a direct count of receptors: it reflects a combination of available receptor density and affinity. The endpoint's change score compares the post-patch measure with baseline, rather than describing a single scan in isolation. The registry defines the sign convention: a negative change means a decrease in binding potential, while a positive change means an increase.

The outcome is summarized as a mean, with standard error listed as the dispersion measure. In general, a mean describes the average observed change, while its standard error describes the precision of that estimated average; it is not the spread of individual measurements. No mean change, standard error, confidence interval or treatment comparison is reported in the registry record. Thus, the endpoint definition explains what would be measured, but not what the study found.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the endpoint estimate?

The primary outcome is a continuous measure: mean change in mu-opioid receptor binding potential from baseline to post-patch scans. A continuous endpoint can take values across a range rather than being restricted to categories such as event or no event. Here, the unit is a ratio, and the registry lists standard error as the dispersion measure. The timeframe recorded for this outcome is 90 minutes.

The registry describes binding potential as an estimate based on available receptor density and receptor affinity. Its imaging method is reference tissue graphical analysis, using the occipital lobe as the reference region. These details explain how the measure is defined, but the record does not provide enough information to independently assess image acquisition, processing, quality control or the derivation of participant-level values. Those procedures are not reported in the registry record.

What do mean and standard error tell a reader?

In general, the mean summarizes the average change in the analyzed observations. The standard error describes the precision of that estimated average under the analysis; it does not describe how much individual participants' measurements vary. A standard deviation, when reported, is more directly about variation among individual observations. The registry names standard error, but it reports no primary mean or standard error estimate.

In general, a confidence interval combines an estimate with an uncertainty range under a specified method. Its interpretation depends on the method and assumptions. It is not reported for the primary endpoint in the registry record. Without a group contrast and its uncertainty, readers cannot assess whether the data are consistent with a range of potentially different effects.

Why does the analysis structure matter?

A randomized comparison is intended to make groups comparable on average with respect to factors that could affect the outcome, subject to the way randomization and analysis are conducted. The registry labels the study randomized and parallel, but does not report sequence generation, allocation concealment, the exact analysis contrast or an analysis population. It also describes a healthy non-smoker comparison group without explaining how its observations enter the analysis. Those missing details constrain interpretation.

Masking can reduce the influence of expectations on care, measurement or assessment, depending on who is masked and how outcomes are collected. The registry calls the study triple-masked but does not identify the masked roles or give implementation details. It is therefore possible to report the masking designation, but not to assess its success from the record.

How should planning calculations be read?

The record describes planning illustrations based on an observed effect, using a two-sided significance level of 0.05, equal allocation between the treatment arms and a normal approximation. It says the effect to detect is a stated fraction of the observed effect, and that non-time-to-event calculations are expressed as participants per arm. Such illustrations are conditional calculations: they show what a planning scenario implies under its assumptions, not what happened in the trial.

In general, a sample-size calculation depends on the assumed effect, variability, significance level, power target and analysis method. A planning illustration is not observed power and does not establish that a study can detect every effect of interest. The record does not report the trial's own sample-size justification, so the planning assumptions should not be mistaken for the original design rationale. No planning value is reproduced in this explanation.

What cannot be inferred from a missing estimate?

No primary estimate is reported, and the registry identifies 0 analyses. A completed-trial designation does not supply missing statistical results. It is not possible to reconstruct an unadjusted comparison, standard error, interval or significance test from the outcome definition alone. Nor is it possible to infer an analysis model or covariate adjustment. General statistical principles can explain what such methods would mean, but the registry record does not identify which, if any, were used for the primary analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome and two named secondary outcomes: relationships between change in mu-opioid receptor binding potential and visual analog craving scores, and between binding potential change and Minnesota Nicotine Withdrawal Scale scores. It also records 3 outcome measures and 0 analyses. The primary outcome has several categories or time points and was not reduced to one comparison in the registry record. This means the record does not provide a single primary contrast suitable for a results interpretation.

When a study evaluates multiple outcomes or comparisons, the chance of at least one apparently notable result can increase if each is assessed separately. In general, a prespecified multiplicity strategy can address that issue, but the registry record does not report whether any adjustment or hierarchy was planned or applied. The statistical analysis plan, prespecified contrasts, interim analyses, and any strategy for controlling multiplicity are not reported in the registry record. No particular procedure should be assumed.

Missing-data handling is also not reported in the registry record. The record does not state how incomplete scans, unavailable measurements, withdrawal from follow-up, or missing questionnaire scores were handled. It does not report the analysis population, whether participants were analyzed according to randomized assignment, or the number contributing to each outcome. These details matter because exclusions or missing observations can affect which participants an estimate represents and how robust it is.

Accordingly, the registry supports description of the planned outcome topics but not assessment of selective outcome reporting, missing-data bias, or multiplicity control. No adjustment or missing-data method can be inferred from the completed status or the endpoint definitions.

11. 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 registry safety figures list 6 participants at risk for serious adverse events in the nicotine patch group and 6 in the placebo group. Serious adverse events are recorded as 0 in each group. The figures also list 6 at risk for other adverse events in each group, with 0 recorded as affected, and 0 deaths in each group.

These counts describe the safety information recorded for the listed groups; they should not be read as covering all 127 enrolled participants. The registry entries do not explain why the at-risk counts are limited to 6 per group, how safety follow-up was defined, or whether the reported counts cover the full study period. They also do not give event definitions, severity categories beyond the serious-adverse-event distinction, or exposure duration.

In general, observing no events in a reported group does not establish that an intervention carries no risk. The strength of a safety conclusion depends on the number observed, the period of observation, the completeness of reporting and the nature of the events monitored. Here, the registry's limited safety counts should be interpreted narrowly as recorded counts, not as proof of absence of adverse events across the whole trial or in other settings.

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

The registry record establishes that this completed study was designed to examine nicotine dependence, withdrawal and replacement therapy using mu-opioid receptor binding potential. It identifies a randomized, triple-masked, parallel phase 4 design, nicotine patch and matching placebo interventions, and a healthy non-smoker comparison group. It also defines the primary measure and names craving- and withdrawal-related secondary outcomes.

Those design details do not establish an efficacy result. The record reports 0 analyses and gives no primary outcome estimate, treatment contrast, uncertainty interval or secondary-outcome analysis. As a result, the direction and magnitude of any difference are not reported in the registry record. No conclusion about whether nicotine patch changed binding potential relative to placebo, or whether binding potential change was associated with craving or withdrawal scores, can be drawn from the posted results.

The research rationale proposes gender-specific scientific and clinical questions, including possible differences in nicotine craving, withdrawal and response to nicotine replacement therapy. A rationale identifies why researchers undertook a study; it does not demonstrate that the study confirmed those ideas. The registry entries do not report subgroup estimates or results by gender, so gender-specific effects cannot be assessed.

The endpoint itself also requires careful interpretation. Binding potential is described as reflecting both available receptor density and receptor affinity, with the occipital lobe used as a reference region. A change in this imaging measure should not be treated as a direct receptor count or as a direct measure of clinical benefit. The registry record does not report evidence connecting an estimated change to a patient-centered outcome.

Overall, the record supports an account of the study question, design and measurement approach, but not a conclusion about treatment effects, clinical outcomes or safety beyond the limited adverse-event counts recorded.

13. Why This Trial Matters Statistically

This trial is statistically notable for combining a randomized treatment comparison with an imaging-based continuous endpoint. The primary measure is not a direct clinical event; it is a change in mu-opioid receptor binding potential, described as a product involving available receptor density and affinity. That definition makes the distinction between a measured biomarker and a patient-centered outcome important. A precise biomarker estimate would still need cautious interpretation in relation to symptoms or clinical response.

The record's parallel design and masking designation are relevant to evaluating how a treatment comparison might be made. Randomization can support comparability between assigned groups, while masking may limit some forms of measurement or expectation bias. However, the registry does not provide implementation details or an analysis estimate. Design labels are therefore informative but cannot replace transparent reporting of the analysis population, methods and uncertainty.

The listed secondary outcomes connect imaging change to craving and withdrawal scales. Statistically, such relationships raise questions about how outcomes were prespecified, how multiple comparisons were handled, and whether the analysis distinguishes association from treatment effect. The registry does not report those methods or results. These omissions illustrate why a clearly defined endpoint is only one part of evaluating a clinical study.

The record also demonstrates the difference between a trial's completed status and an interpretable result. Without reported estimates, readers cannot judge effect size or precision, regardless of the study's rationale or design. The safety counts likewise require attention to the group sizes represented and the completeness of follow-up. For biostatisticians and clinical researchers, the central lesson is that conclusions depend on transparent outcome data and analysis reporting, not merely on the planned question.

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.

The main trial-specific limitation for interpretation is that the registry reports no analyses and no primary outcome estimate. The primary endpoint definition is detailed enough to explain the intended measurement, but it does not provide group-level results, a treatment contrast or uncertainty. The record also says the primary outcome has several categories or time points and was not reduced to one comparison. A single primary result therefore cannot be reconstructed from the registry entries.

The record does not specify how the healthy non-smoker comparison group was used in relation to the randomized patch and placebo groups. It does not provide participant flow, outcome-specific analysis counts, eligibility criteria beyond the stated condition and comparison-group description, or baseline characteristics. The recorded enrollment does not indicate how many participants contributed to scans or questionnaire outcomes.

Important methodological details are not reported in the registry record, including randomization sequence generation, allocation concealment, the identities of masked parties, imaging quality control, the primary analysis model, covariate adjustment, missing-data handling, analysis populations and multiplicity procedures. The record also does not report the trial's sample-size justification or interim analyses. These omissions limit assessment of bias, precision and the relationship between planned and reported analyses.

Safety interpretation is constrained because the listed at-risk counts are 6 per group, rather than the recorded enrollment, and the registry does not explain the scope or duration of safety observation. Finally, the study rationale includes gender-specific questions, but subgroup results are not reported. The available record therefore cannot support conclusions about those questions or about clinical outcomes beyond its stated measurement and recorded safety counts.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Nicotine Dependence, Withdrawal and Replacement Therapy Assessed by PET Imaging — NCT01664741.
• Registry record last updated 2019-05-09; status last verified 2019-04.
• Results first posted 2019-05-09.
• 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.

18. Record Summary

NCT01664741 is a completed, randomized, triple-masked, parallel phase 4 study sponsored by Johns Hopkins University. The registry records enrollment of 127 and identifies nicotine dependence as the condition. The interventions are a 21 mg transdermal nicotine patch and matching placebo patch; a healthy non-smoker comparison group is also described.

The primary outcome is mean change in mu-opioid receptor binding potential between baseline and post-patch scans, with standard error as the dispersion measure and 90 minutes as the listed timeframe. The record describes reference tissue graphical analysis using the occipital lobe as a reference region. Named secondary outcomes concern relationships between binding potential change and craving and withdrawal scale scores.

The registry reports 0 analyses and no primary treatment-effect estimate. Its safety record lists 0 serious adverse events, 0 other adverse events and 0 deaths in each treatment group, with 6 at risk per group for each adverse-event category. The design and outcome definitions are documented, but efficacy estimates and key analysis details are not reported in the registry record.