Acetylcholine, Tobacco Smoking, Genes and Nicotinic Receptors: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Acetylcholine, Tobacco Smoking, Genes and Nicotinic Receptors (NCT02008292), a na na study. The primary outcome is Change in Acetylcholine (ACh) Levels After Physostigmine Administration as Confirmed by PET Images..

2. Clinical Question

The study’s stated aim is to measure whether PET binding of Norchloro-fluoro-homoepibatidine (NCFHEB) responds to changes in endogenous acetylcholine levels. The primary outcome is described as percentage change in acetylcholine levels after physostigmine administration, confirmed by PET images. The registry says that this change is determined through change in NCFHEB binding potential. The planned scan sequence is a first 150 minute scan at baseline followed by a second 150 minute scan starting 10 minutes after physostigmine administration.

The hypotheses describe potentially different responses in smoking and nonsmoking subjects, both among healthy participants and among participants with schizophrenia. The summary also describes a separate aim involving PHNO binding and dopamine levels in healthy smoking and nonsmoking subjects before and after an amphetamine challenge. These are research questions and hypotheses, not reported findings. Numerical outcome estimates, confidence intervals, and test results are not reported in the registry record, so the size and precision of any observed change cannot be assessed from this record.

3. Trial Design

This is a completed, single-group study sponsored by Yale University. The registry lists enrollment of 80, allocation as NA, and masking as none. Its arm description says there is only one arm and that all subjects will receive physostigmine and amphetamine. The registered intervention list names physostigmine. There is no separate untreated or active-control arm described, so the study is not a like-for-like randomized comparison between groups.

The central acetylcholine measurement uses a within-participant scan sequence: a baseline PET scan and a second scan beginning 10 minutes after physostigmine administration. The registry describes both scans as 150 minute scans. The summary frames the study population as healthy smoking and nonsmoking subjects and smoking and nonsmoking subjects with schizophrenia. The primary outcome description is narrower in its wording, referring to healthy controls and smoker subjects. The record does not fully resolve which participants were included in each primary-outcome subgroup.

The registry lists the study start as 2013-09, primary completion as 2021-12, and status as completed. Phase is listed as NA. The record describes both the acetylcholine-related NCFHEB assessment and an additional assessment of PHNO binding in relation to dopamine levels before and after an amphetamine challenge. The two registered outcome measures are not accompanied by posted numerical results or analysis details in the information available for this interpretation.

Because there is no separate comparator arm, the design can describe changes in measured binding over time in participants who received the study drugs, but it cannot by itself isolate a between-group treatment contrast. The hypotheses about smoking and schizophrenia status would require subgroup results and a description of how those comparisons were analyzed. Those details 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.

Overall Study

Analysis population for the primary outcome, as defined in the registry: 66 of 80 participants were analyzed in primary study as 14 had signed consent but did not fully complete aim (i.e. Medical DQ by MD prior to drug administration or Relapse in smoking cessation by participant or medical aline failure, participant unable reschedule. For primary measure we only included participants that voluntarily completed both primary measures successfully.

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 Change in Acetylcholine (ACh) Levels After Physostigmine Administration as Confirmed by PET Images., measured over first 150 minute scan at baseline, second 150 minute scan start 10 minutes post physostigmine administration.

The primary endpoint is titled as change in acetylcholine levels after physostigmine administration, confirmed by PET images. It is expressed as a percentage of change, with the outcome parameter described as a mean and dispersion described as a standard deviation. The record says that the change in acetylcholine levels is determined through change in binding potential of Norchloro-fluoro-homoepibatidine (NCFHEB). The measurement compares a baseline scan with a second scan that starts 10 minutes after physostigmine administration; each scan is described as 150 minutes long.

In general, an imaging-based binding measure can serve as an indirect indicator of the biological process of interest when the study defines a relationship between the measured signal and that process. Here, the registry specifically presents NCFHEB binding potential as the basis for determining acetylcholine-level change. It hypothesizes that higher endogenous acetylcholine after physostigmine will reduce nicotinic-receptor availability for radioligand binding. That is the proposed interpretation, not a reported result.

The endpoint is useful for framing the study’s biological question because it links a pre-administration measurement to a post-administration measurement in the same study context. However, the record does not provide a numerical mean change, standard deviation, confidence interval, or analysis result. It therefore does not establish the observed direction, magnitude, or precision of the primary outcome.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary outcome as a mean of a continuous measure, expressed as percentage of change, with standard deviation as the dispersion measure. In general, a mean summarizes the average observed change across participants, while a standard deviation describes how spread out individual measurements are around that average. The mean alone does not show whether participants had similar responses or widely varying responses. Neither statistic, by itself, indicates the precision of the estimated average; a confidence interval or other uncertainty measure would be needed for that purpose. Numerical primary-outcome values and confidence intervals are not reported in the registry record.

What does a within-participant scan comparison estimate?

The primary assessment is described as a baseline scan followed by a second scan starting 10 minutes after physostigmine administration. In a general pre/post design, the contrast is the change in measured outcome between the two time points for participants with measurements at both times. Pairing measurements within participants can account for stable participant characteristics when estimating that change. The comparison remains an observed change over time, however. Without a separate comparison group or further design information, it does not automatically distinguish a drug-related change from other time-related influences, measurement variability, or changes in participant state.

The study’s stated biological interpretation is that changes in endogenous acetylcholine can affect NCFHEB binding potential. The registry says that change in acetylcholine levels is determined by change in that binding potential. In general, a biomarker or imaging signal used as a proxy requires a clear connection between the signal and the process of interest. The registry describes the intended connection and the hypothesis about reduced radioligand binding, but it does not report validation results, the numerical observed binding change, or a statistical model linking binding to acetylcholine levels.

How should uncertainty be assessed?

A confidence interval, in general, gives a range of values compatible with the data and the method used to calculate it. Its width helps readers judge precision: a wider interval indicates greater uncertainty about the estimated quantity than a narrower interval, under the same method. A test result or p-value addresses a different question and does not show the size or practical importance of an effect. The registry information does not report a confidence interval, p-value, test statistic, or model estimate for the primary outcome, so neither statistical significance nor precision can be assessed from the posted results.

The listed endpoint uses a mean and standard deviation, but the analysis method is not reported in the registry record. It does not specify whether the primary analysis used a paired test, a regression model, covariate adjustment, or another method. It also does not describe assumptions about the distribution of change scores or how departures from those assumptions would be handled. These omissions matter because different methods can yield different uncertainty estimates, particularly when data are incomplete or the distribution is highly skewed.

What is the role of the planning illustration?

The registry’s planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and detection of a stated fraction of an observed effect. Such calculations are planning illustrations, not observed power. They do not show the probability that this completed study detected an effect, and they do not replace an analysis of the observed data. The assumptions describe two arms, while this record describes a single-group study without a like-for-like control arm. Numerical planning requirements are not reported in the registry record, and the record does not report an observed effect value from which to assess such an illustration.

In general, over-dispersion means that outcome variability is greater than a chosen model assumes. When that occurs, uncertainty estimates based on the narrower assumed variability can be too small, making results appear more precise than warranted. The registry record does not report count-model outcomes for the primary endpoint, which is continuous, nor does it describe a distributional assessment or any correction for over-dispersion. This concept is relevant generally to statistical modeling but cannot be assessed as a specific feature of this trial from the available record.

How should subgroup questions be handled?

The hypotheses refer to smoking status and schizophrenia status, while the summary also distinguishes healthy participants from participants with schizophrenia. In general, subgroup comparisons need clear definitions of the groups, an analysis method, and uncertainty estimates for both subgroup effects and any difference between them. A difference in statistical significance across subgroups is not, by itself, proof that the subgroup effects differ; a direct interaction or contrast is generally needed. The registry record does not report subgroup estimates, interaction analyses, or methods for these comparisons. It also does not fully specify how the primary analyzed population maps to the groups in the hypotheses.

Overall, the record supplies design and endpoint descriptions but not the statistical analysis details or numerical results needed to evaluate the primary estimate. The analyses and modeling decisions are not reported in the registry record. The stated planning assumptions should therefore be read as planning context only, not as evidence about the observed outcome or the precision of the study findings.

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("ACH Levels in Healthy Controls After Physostigmine", "ACH Levels in Smokers After Physostigmine Administ")
n   <- c(34, 32)
m   <- c(5.9, 4.3)
sp  <- c(6.5, 8.4)
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  ACH Levels in Healthy Controls After Physostigmine  34  5.900  6.500  3.632  8.168
CARM  ACH Levels in Smokers After Physostigmine Administ  32  4.300  8.400  1.271  7.329

11. Multiplicity, Missing Data and Analysis Populations

The record lists two outcome measures and describes both an acetylcholine-related NCFHEB assessment and a PHNO binding assessment related to dopamine. It does not explain how the primary and additional outcomes were prioritized for statistical testing, nor does it report a method for controlling the chance of false-positive findings across multiple outcomes or subgroup questions. In general, multiplicity matters when several outcomes, time points, or subgroup contrasts are examined because repeated testing can increase the chance of obtaining a nominally unusual result. Whether any adjustment was planned or used is not reported in the registry record.

The primary-outcome description states that 66 of 80 participants were analyzed and that 14 participants signed consent but did not fully complete the aim. Reasons listed include a medical review before drug administration, relapse in smoking cessation, “medical aline failure,” and inability to reschedule. The record does not provide counts by reason, details of missing measurements, or a complete account of which participants contributed data at each scan or outcome.

Missing-data handling is not reported in the registry record. It is not stated whether the analysis included only participants with both scans, whether any imputation was used, or whether sensitivity analyses assessed the effect of missing outcomes. The record also does not report an intention-to-treat analysis or define another formal analysis population. The population description ends before fully specifying whom the primary measure includes, which limits interpretation of the analyzed count and its relationship to the stated study groups. These gaps prevent assessment of whether missingness or population selection could have influenced the reported estimate; no numerical estimate is available in any case.

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 0% reporting threshold.

The registry lists serious adverse event and other adverse event counts for two groups: Healthy Controls for 1210010989 and Healthy Smoker Controls for 1210010989. In the healthy-control group, 43 participants are listed as at risk, with 0 affected by serious adverse events, 0 affected by other adverse events, and 0 deaths. In the healthy-smoker-control group, 37 participants are listed as at risk, with 0 affected by serious adverse events, 0 affected by other adverse events, and 0 deaths.

These figures describe the recorded event counts for the listed groups and categories. A zero count means that no affected participants are recorded in that category for that group; it does not establish that no symptoms or safety concerns of any kind occurred. The record does not provide event terms beyond stating that there are no top serious event terms, nor does it describe the duration or completeness of safety monitoring in the information available. The listed groups are not a substitute for a full safety narrative, and these counts should not be generalized beyond the participants and categories recorded.

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

This record describes a completed study of PET binding changes after physostigmine administration, with a primary outcome tied to NCFHEB binding potential and an additional dopamine-related research aim. It also identifies the study as single-group and unmasked, with no separate comparator arm. Those details clarify what the study set out to measure and the structure of the comparison, but they do not establish what the measurements showed.

The registry describes a hypothesis that elevated acetylcholine would reduce radioligand binding and that responses could differ by smoking and schizophrenia status. Hypotheses are not results. Because the numerical primary outcome estimate, its variability, and uncertainty measures are not reported in the registry record, the observed magnitude, direction, and precision of the change cannot be determined from the available information. The same limitation applies to the PHNO and dopamine aim and to the proposed subgroup comparisons.

In general, a pre/post imaging comparison can characterize change over time among measured participants. Without a separate comparison arm, it cannot by itself establish that the intervention caused any observed change. A biological signal used as a proxy also needs to be interpreted according to the relationship specified for that signal; the registry gives the proposed link between NCFHEB binding and acetylcholine but does not report results that quantify it.

The analysis population is reported as 66 of 80 participants, with reasons for incomplete participation described but not fully quantified. The registry does not report how missing data were handled or provide a detailed analysis plan. The safety counts record no affected participants in the listed serious or other adverse-event categories for the two named groups, but these counts do not address every possible safety outcome or establish that no events occurred outside those categories.

Thus, the record supports a description of the question, design, outcome definition, analyzed count, and recorded safety figures. It does not support a conclusion about whether the hypothesized biological changes occurred, how large they were, or how precisely they were estimated. It also does not support a clinical conclusion about treatment benefit or harm.

14. Why This Trial Matters Statistically

This study is statistically notable for using a within-participant imaging sequence to investigate a biological response rather than a randomized comparison between treatment groups. The baseline and post-administration scans frame a change-over-time question. That structure can be informative about measured change in the participants who completed the scans, while leaving causal interpretation dependent on the design and analysis details. The registry describes no separate comparator arm, so readers should distinguish a pre/post observation from a controlled treatment contrast.

The endpoint also illustrates the difference between a biological quantity of interest and the measurement used to represent it. The primary outcome is framed as acetylcholine-level change, with NCFHEB binding potential used to determine that change. The registry states the hypothesized relationship between acetylcholine and radioligand binding. Assessing the strength and precision of that relationship would require numerical estimates and uncertainty measures, which are not reported in the registry record.

The study raises subgroup questions about smoking status and schizophrenia status. Those questions can be statistically demanding because subgroup estimates may be less precise than an overall estimate, and claims of differing responses require a direct comparison of subgroup effects. The registry does not report those estimates or the methods used to compare them. This makes the distinction between a stated hypothesis and an analyzed result especially important.

Finally, the record shows why enrollment and analysis populations should be read separately. Enrollment is 80, while the primary outcome description reports 66 analyzed and identifies incomplete participation among the remainder. A clear account of missing observations, analysis populations, and uncertainty is needed to judge how representative an estimate may be. Without numerical results or those methods, the study’s statistical contribution can be described through its question and design, but not quantified from the registry record.

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 registry record does not report numerical primary outcome results, including the mean percentage change, standard deviation, confidence interval, or test result. This prevents assessment of the observed direction, magnitude, and precision of the main outcome. The secondary PHNO and dopamine-related results are also not reported in the available information.

The single-group design has no separate comparator arm. Although the primary endpoint compares baseline and post-physostigmine scans, a pre/post difference alone cannot separate an intervention-associated change from other influences over time. The record gives no details of any design or analysis features intended to address that limitation. Masking is listed as none, and allocation is listed as NA.

The population description is not fully specified. The summary discusses healthy smoking and nonsmoking subjects and subjects with schizophrenia who smoke or do not smoke, while the primary outcome description refers to healthy controls and smoker subjects. The record states that 66 of 80 participants were analyzed and lists possible reasons for incomplete participation, but it does not provide counts by reason or clarify the relationship between the analyzed population and each subgroup.

The analysis plan, missing-data methods, subgroup methods, and approach to multiple outcomes are not reported in the registry record. The record also does not provide enough detail to assess endpoint measurement assumptions, model fit, or the handling of potential measurement variability. These limitations constrain both statistical interpretation and the extent to which results, if available elsewhere, could be evaluated using this registry information alone.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Acetylcholine, Tobacco Smoking, Genes and Nicotinic Receptors — NCT02008292.
• Registry record last updated 2023-10-25; status last verified 2023-10.
• Results first posted 2023-02-06.
• 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

The registry record describes a completed, single-group study sponsored by Yale University, with enrollment of 80, no masking, and allocation listed as NA. Its stated primary outcome is percentage change in acetylcholine levels after physostigmine administration, determined through change in NCFHEB binding potential using PET. The scan sequence consists of a 150 minute baseline scan and a second 150 minute scan starting 10 minutes after physostigmine administration.

The primary outcome description reports that 66 of 80 participants were analyzed and notes incomplete participation among 14. The registry lists two outcome measures and describes an additional PHNO binding assessment related to dopamine. It reports safety counts for two groups, with zero affected participants in the listed serious and other adverse-event categories and zero deaths. Numerical efficacy results, statistical analyses, missing-data methods, and multiplicity procedures are not reported in the registry record.