Pharmacogenetics, Emotional Reactivity and Smoking: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pharmacogenetics, Emotional Reactivity and Smoking (NCT00507728), a randomized phase 2, phase 3 study. The primary outcome is Emotional Reactivity By Pharmacotherapy.

2. Clinical Question

3. Trial Design

The registry describes a randomized, double-masked, parallel-group, placebo-controlled clinical trial listed as phase II and phase III. Its stated goals were to evaluate emotional reactivity during a smoking-cessation attempt under bupropion, varenicline, or placebo and to determine whether genotype moderated treatment differences. Enrollment was 646. The record lists M.D. Anderson Cancer Center as sponsor and gives the status as completed.

The recorded start date is 2005-12-08, and the primary completion date is 2019-12-18. These dates describe the trial record; they do not establish the duration of treatment or follow-up for every participant. The placebo regimen is described as oral treatment for 12 weeks. Drug schedules are given for bupropion and varenicline, while the registry does not report the duration of those regimens in the arm descriptions.

Smoking-cessation counseling is listed as a behavioral intervention, but its content, timing, and distribution among the groups are not reported in the registry record. The allocation ratio, sequence-generation method, details of concealment, and which parties were masked are also not reported. The label double-masked indicates the recorded masking category, but the identities of the masked parties should not be inferred from that label alone.

The registry lists smoking abstinence at 3 months and 6 months, including outcomes by DRD2 A1 allele, alongside measures of nicotine withdrawal, affect, depression, smoking satisfaction, and psychological reward. These are secondary outcomes; their numerical results are not reported in the registry record. The listed enrollment is not a substitute for outcome-specific denominators, which are not given for the primary endpoint.

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: 646 participants signed consent, 392 were screen failures

Randomization to Month 3

Reasons for not completing this period:

From 3 Months to 6 Months

Reasons for not completing this period:

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: The analysis dataset is comprised of all treated participants, i.e. Intention to Treat.

6. Primary Endpoint

The registry lists the primary outcome as Emotional Reactivity By Pharmacotherapy, measured over Baseline to 1 month.

The primary endpoint is emotional reactivity from baseline to 1 month, measured in microvolts. The registry defines it using peak eye-blink electromyography of the orbicularis oculi muscle in response to an acoustic startle probe presented while participants viewed pleasant, unpleasant, neutral, and smoking-related pictures. A single value was estimated by averaging within a specific time interval, but the interval itself is not reported in the registry record.

This measure captures a physiological response during exposure to emotionally meaningful stimuli. In general, a continuous measurement can retain information about the degree of response rather than reducing the outcome to a yes-or-no event. The registry’s stated focus is emotional reactivity during a cessation attempt, so the measure addresses a different question from whether participants achieved smoking abstinence. It is not itself a measure of abstinence, withdrawal symptoms, depression, or smoking satisfaction.

The primary outcome parameter is described as a least-squares mean with a 95% confidence interval. In general, a least-squares mean is a model-based estimate; what variables or model were used to obtain it is not reported in the registry record. The numerical means and confidence intervals for the primary endpoint are not reported in the registry record, preventing assessment of the size or precision of the observed responses.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The methods can be understood from the design labels and the endpoint description, while important details of the statistical analysis remain unreported in the registry record. The explanations below describe general statistical concepts and distinguish them from what can be established about this particular trial.

What does randomization contribute?

In general, randomization assigns participants to treatment groups using a chance-based process. It is intended to reduce systematic differences between groups at assignment, so that a comparison can be interpreted more fairly. It does not guarantee that groups will be identical, and it does not remove the need to account for missing outcomes, measurement choices, or chance variation. The registry records the allocation as randomized, but the sequence-generation procedure, allocation ratio, and concealment method are not reported in the registry record.

What does double masking mean?

The registry classifies the trial as double-masked. In general, masking can reduce the possibility that knowledge of treatment assignment influences participant behavior, treatment delivery, or outcome assessment. The label alone does not identify exactly who was masked or how masking was maintained. Those details are not reported in the registry record, so the possible influence of unmasking cannot be assessed from this information.

How should a least-squares mean be understood?

A least-squares mean is generally an estimate generated from a statistical model. It may represent a group mean adjusted for variables included in that model, but which variables were included depends on the analysis specification. The registry identifies the primary parameter as a least-squares mean; it does not report the model, covariates, handling of baseline values, or the contrast used to compare groups. It would therefore be inappropriate to assume that the estimate was adjusted for any particular participant characteristic or baseline measurement.

What does a 95% confidence interval communicate?

In general, a confidence interval represents uncertainty about an estimated quantity under the statistical model and its assumptions. A narrower interval indicates greater precision for that estimate than a wider interval, while the interval’s location indicates which values are compatible with the data and model at the stated confidence level. A confidence interval is not a probability statement about a fixed true value after the interval has been calculated. Here, the registry names a 95% confidence interval but does not report its endpoints for the primary outcome. Neither precision nor compatibility with a particular treatment difference can therefore be evaluated.

Why does the outcome structure matter?

The emotional-reactivity measure uses responses to several picture categories and is described as averaged within a specific interval. The registry flags the primary outcome as involving several categories or time points and does not reduce it to one comparison. This matters because an analysis might compare groups at a particular time, assess change from baseline, or test a pattern across stimulus categories. Those approaches answer different questions. The registry does not report which comparisons were analyzed, how the categories were represented in a model, or whether there was a prespecified hierarchy of comparisons.

When an outcome includes several measurements or comparisons, the chance of at least one nominally unusual result can increase if many tests are considered without an appropriate plan. General approaches to address multiplicity include prespecifying a primary contrast, adjusting inference across tests, or treating secondary comparisons as exploratory. The registry record does not report which, if any, approach was used. No multiplicity-adjusted result can be inferred from the outcome list.

What is over-dispersion, and is it relevant?

In general, over-dispersion occurs when the variability in data is greater than a statistical model assumes. It can lead to uncertainty estimates that are too small if the model does not account for the extra variation. The primary endpoint is a continuous physiological measure, but the registry does not report the analysis model or any assessment of its assumptions. There is no basis in the record for saying whether over-dispersion was assessed or was a concern. More broadly, continuous-outcome analyses may require attention to distribution, outliers, repeated measurements, and dependence among observations; the registry does not describe how those issues were handled.

What do the planning assumptions mean?

The record describes planning illustrations using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It states that the effect to detect is a stated fraction of the observed effect. These are planning assumptions, not evidence about the trial’s original design or an observed treatment benefit. The registry does not report its own sample-size justification or the numerical outputs of the illustrations. Such calculations are not observed power and cannot establish whether a completed trial was adequately powered for its primary question.

The stated assumptions also concern a two-arm illustration, whereas the trial lists bupropion, varenicline, and placebo. They should not be read as a description of the trial’s actual allocation plan or its full analysis. The record does not report a complete statistical analysis plan, the model used for the primary endpoint, or how the genotype moderation question was tested.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 12 outcome measures, including emotional reactivity, smoking abstinence at 3 months and 6 months, and measures of withdrawal, affect, depression, smoking satisfaction, and psychological reward. Some abstinence outcomes are also listed by DRD2 A1 allele. Considering several outcomes, time points, stimulus categories, or genotype subgroups can create multiple opportunities for statistical comparisons. In general, multiplicity matters because interpreting many tests at once without a prespecified strategy can increase the chance of apparently notable findings arising by chance.

The registry record does not report a multiplicity strategy, a complete statistical analysis plan, or which comparisons were designated primary beyond the stated primary outcome. The primary outcome is flagged as having several categories or time points and is not reduced to one comparison. The record lists 0 analyses, so it does not provide estimates or tests to assess how the outcome structure was handled.

Missing-data methods and analysis populations are also not reported in the registry record. The record does not state how participants with missing measurements were treated, whether outcomes were analyzed according to randomized assignment, or whether any per-protocol or other analysis population was defined. The enrollment figure does not establish how many participants contributed data to the primary endpoint at each time point. No imputation procedure, sensitivity analysis, or reasons for missing measurements are reported.

The safety figures have their own at-risk denominators and should not be treated as primary-outcome analysis denominators. Without endpoint-specific counts and analysis definitions, the completeness of the primary outcome data cannot be determined.

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 1% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: shortness of breath (2.7%), chest pain - cardiac (1.3%), increased coughing (1.3%), dizziness (1.1%), eczema (1.1%).

The registry reports serious adverse-event counts for the varenicline group with 75 at risk and 2 affected, the bupropion group with 89 at risk and 2 affected, and the placebo group with 90 at risk and 0 affected. It reports 0 deaths in each group. These are counts for the reported at-risk groups; they are not outcome estimates for emotional reactivity.

The registry also reports other adverse events: 63 affected among 75 at risk for varenicline, 69 among 89 at risk for bupropion, and 66 among 90 at risk for placebo. These counts should be read using their stated denominators and event categories. The record does not report enough detail to determine how events were defined, how overlapping events were counted, or whether the groups had comparable follow-up for safety reporting.

The listed serious-event terms and percentages are Shortness of Breath at 2.7%, Chest pain - cardiac at 1.3%, Increased Coughing at 1.3%, Dizziness at 1.1%, Eczema at 1.1%, and Urinary Incontinence at 1.1%. The registry record does not provide further context for these terms in the listed information. Counts and percentages describe reported events; by themselves they do not establish whether treatment caused an event or support a definitive comparison of safety between groups.

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

The trial’s stated purpose was to compare emotional reactivity during a cessation attempt among participants treated with bupropion, varenicline, or placebo and to examine whether genotype moderated those differences. The primary outcome has a defined physiological measure, unit, and timeframe: peak eye-blink EMG in microvolts from baseline to 1 month. These details identify the intended question, but they do not show what the trial found.

The registry does not report numerical primary-outcome results, confidence-interval endpoints, or tests. It is therefore not possible to say whether the observed means differed, which group had the larger response, how large a difference may have been, or whether the estimates were precise. Lack of reported results does not mean that the treatments produced identical outcomes, nor does it establish that any treatment changed emotional reactivity.

The measure should not be conflated with smoking cessation itself. The registry lists smoking abstinence at 3 months and 6 months as secondary outcomes, along with other measures of withdrawal, affect, depression, satisfaction, and reward. Their presence indicates a broader set of questions, but numerical results for those outcomes are not reported in the registry record. A physiological response to affective and smoking-related pictures cannot stand in for an abstinence outcome without evidence connecting the measures.

Likewise, the stated genotype question concerns moderation, not simply whether genotype is associated with an outcome. In general, moderation asks whether a treatment contrast varies across levels of a characteristic. The record does not report the estimates or tests needed to judge that question. Mention of DRD2 A1 allele in secondary outcomes is not enough to establish a genotype-specific primary result.

The safety counts provide limited descriptive information about reported events in the stated at-risk groups. They do not establish causation or provide a complete comparative safety assessment. The registry’s completion status describes the study record, not the completeness of its posted outcome analyses. The defensible interpretation is therefore about trial design and measurement, rather than treatment effects or clinical benefit.

13. Why This Trial Matters Statistically

This trial is statistically notable for pairing a randomized, double-masked treatment comparison with a continuous physiological endpoint and a proposed genotype-moderation question. Those features create distinct analytical tasks. A group comparison concerns average emotional-reactivity measurements, while moderation asks whether that comparison varies by genotype. The latter generally requires an explicit interaction analysis and adequate information within genotype groups; the registry does not report those analyses or the relevant estimates.

The endpoint is also measured across emotional and smoking-related picture categories and summarized within a specified interval. When a study has several categories or time points, the way measurements are combined and the comparisons chosen affect what a result means. The registry flags this complexity and does not reduce the primary outcome to one comparison. This makes the missing analysis details particularly important: without the model and planned contrast, even a reported mean would need context to interpret as a treatment difference.

The trial also lists multiple secondary outcomes spanning abstinence and psychological measures. In general, a collection of outcomes can illuminate different aspects of a research question, but it raises questions about outcome hierarchy, multiplicity, and interpretation across analyses. The record does not report a statistical plan or results with which to assess those issues.

For biostatistical interpretation, the central lesson is the distinction between a clearly described study aim and an evaluable result. Randomization and masking describe design features; they do not supply effect estimates, uncertainty intervals, or evidence about missingness. Here, the posted information permits a careful account of the question and measurement, while leaving the primary statistical conclusion unavailable.

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 is that the registry record does not report numerical results for the primary endpoint. It identifies a least-squares mean and 95% confidence interval but gives neither the estimates nor the interval limits. The primary outcome is flagged as involving several categories or time points and is not reduced to one comparison, so a single primary contrast cannot be evaluated from the record.

Important analysis details are also absent. The statistical model, covariates, handling of baseline values, treatment contrasts, and approach to genotype moderation are not reported in the registry record. The record does not describe how missing endpoint data were handled, which analysis populations were used, or whether sensitivity analyses were conducted. These omissions limit assessment of bias, precision, and robustness.

The record lists smoking-cessation counseling but does not describe its delivery or distribution across the treatment groups. It also does not report the allocation ratio or the procedures used to generate and conceal the randomization sequence. The masking category is given, but the parties masked and procedures for maintaining masking are not described. Eligibility criteria and participant baseline characteristics are not reported in the information available.

The primary measure is averaged within a specific time interval, but the interval is not defined in the registry record. The record also does not explain how responses to different picture categories contributed to the reported endpoint. As a result, the measurement definition is not sufficiently detailed to reproduce the analysis from the registry information alone.

Safety counts are reported for at-risk groups, but the record does not provide further detail about event ascertainment or comparative follow-up. The outcome list and completed status cannot remedy these gaps. These limitations concern what can be evaluated from the registry record; they do not establish that the trial itself lacked procedures or analyses that were not reported.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Pharmacogenetics, Emotional Reactivity and Smoking — NCT00507728.
• Registry record last updated 2021-05-06; status last verified 2021-04.
• Results first posted 2021-05-06.
• 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.

18. Record Summary

NCT00507728, titled Pharmacogenetics, Emotional Reactivity and Smoking, is recorded as a completed randomized, double-masked, parallel-group trial listed as phase II and phase III. M.D. Anderson Cancer Center is the sponsor. The registry gives enrollment of 646, a start date of 2005-12-08, and a primary completion date of 2019-12-18.

The stated primary question concerns emotional reactivity during a smoking-cessation attempt under bupropion, varenicline, or placebo, and whether genotype moderates treatment differences. The primary measure is peak eye-blink EMG in microvolts from baseline to 1 month, reported as a least-squares mean with a 95% confidence interval. Smoking-cessation counseling is also listed as an intervention.

The registry lists 12 outcome measures and 0 analyses. Numerical primary and secondary outcome results, analysis methods, missing-data procedures, and a multiplicity strategy are not reported in the registry record. Safety counts and the listed serious adverse-event terms are available, but they do not provide the missing primary treatment-effect estimates.