Reduced Exposure Study Using THS 2.2 Menthol With 5 Days in a Confinement Setting and 85 Days in an Ambulatory Setting: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Reduced Exposure Study Using THS 2.2 Menthol With 5 Days in a Confinement Setting and 85 Days in an Ambulatory Setting (NCT01970995), a randomized na study. The primary outcome is Concentration of Monohydroxybutenyl Mercapturic Acid (MHBMA).

2. Clinical Question

3. Trial Design

This was a randomized, controlled, multicenter, parallel-group study. The registry record describes no masking. The study title and arm descriptions specify a confinement period lasting 5 days, followed by 85 days in an ambulatory setting. Participants were assigned to ad libitum use of THS 2.2 Menthol, ad libitum use of their own preferred menthol conventional cigarette brand, or smoking abstinence.

The stated overall objective was to evaluate changes in biomarkers of exposure to selected harmful and potentially harmful smoke constituents. The abstinence group was included as a benchmark to provide context for exposure reduction. The primary endpoint reported in the registry record is a single biomarker measured at Day 5, so the reported primary comparison concerns the confinement period rather than the full 90-day study duration.

The registry record lists an enrollment of 160 and a status of completed. It records the study start as 2013-08 and primary completion as 2014-07. The phase is listed as NA. The sponsor is Philip Morris Products S.A.

Random assignment is intended to make treatment groups comparable, on average, with respect to factors that could affect the outcome. A parallel-group design assigns participants to distinct groups rather than having each participant receive every study condition. The lack of masking means participants and study personnel were not masked to assignment, according to the registry entry. The record does not describe further procedures for allocation concealment, the randomization sequence, or masking of outcome assessment.

The enrollment figure is not the same as the number included in each primary endpoint analysis. The primary population is defined as the Per Protocol set, and the reported group counts differ across groups. The registry record does not explain all reasons for the difference between enrollment and endpoint analysis counts.

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: Enrolled and randomized population = 160 subjects * 78 subjects in mTHS 2.2 * 42 subjects in mCC * 40 subjects in SA Number of subjects enrolled but NOT randomized (who tried the mTHS 2.2 at Day -2) = 0

Confinement Period (Population at Day 5)

Reasons for not completing this period:

End of Study (Population at Day 90)

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The analysis was performed on the Per Protocol set (PP) which included all randomized subjects who had no major protocol deviation impacting the evaluability during the confinement 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: Study population = all randomized subjects who had at least one post randomization product use experience and at least one valid biomarker of exposure measurement. 160 randomized subjects: 78 in mTHS 2.2, 42 in mCC and 40 in SA arms 155 completed, subjects who withdrew: 2 in mTHS 2.2, 1 in mCC and 2 in SA arms

6. Primary Endpoint

The registry lists the primary outcome as Concentration of Monohydroxybutenyl Mercapturic Acid (MHBMA), measured over 5 days.

The primary endpoint is the concentration of monohydroxybutenyl mercapturic acid (MHBMA) in urine, measured at Day 5 and adjusted for creatinine. The unit is pg/mg creat. The registry record describes the endpoint estimates as geometric least-squares means, presented as descriptive statistics, with 95% confidence intervals.

MHBMA is one of the selected biomarkers of exposure to harmful and potentially harmful smoke constituents named in the study objective. A biomarker of exposure measures an internal indicator associated with contact with a substance; it is not itself a direct measure of clinical disease or a health outcome. Urinary concentration can vary with urine dilution. Creatinine adjustment is used to account for differences in urine concentration, making the reported concentration a creatinine-adjusted measure.

Geometric means are often used for continuous measurements whose distributions are skewed or whose values vary multiplicatively. A least-squares mean is a model-based estimate, which can account for variables included in the analysis model. The registry record identifies the estimates as geometric least-squares means but does not specify the model covariates or provide further detail on their calculation.

The endpoint captures exposure at a particular time point: Day 5, during confinement. It does not, by itself, describe the trajectory across the 85 ambulatory days or establish the level of exposure at the end of the study. The choice of this biomarker makes the primary analysis relevant to a selected exposure measure, but it cannot stand in for every smoke constituent or for clinical health outcomes.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: it is a measured concentration rather than a count or a category. The registry record reports geometric least-squares means and confidence intervals for the three groups, and an ANCOVA comparison between THS 2.2 Menthol and menthol conventional cigarettes. The record does not state the full statistical analysis plan, model covariates, diagnostic checks or rules for handling values outside the measurement range.

What does ANCOVA do?

Analysis of covariance (ANCOVA) compares group outcomes using a statistical model that can adjust for other variables. Adjustment can improve precision or account for measured differences, depending on the model and study design. A model-adjusted estimate is not necessarily identical to a comparison of unadjusted group summaries. The registry record names ANCOVA but does not identify the adjustment variables, the model form or whether any transformations were used beyond describing the results as geometric least-squares means.

Randomization supports a group comparison by distributing measured and unmeasured characteristics across assigned groups on average. ANCOVA may then adjust for specified covariates, but the registry record does not say which covariates were included. Readers cannot assess from the registry entry alone whether the adjustment was prespecified, how model assumptions were evaluated, or whether alternative analyses were performed.

What does a geometric least-squares mean represent?

A least-squares mean is an estimate from a fitted model, evaluated for a group while accounting for the terms included in that model. A geometric mean is based on the multiplicative scale and is commonly used when continuous measurements are positively skewed. It can be more representative than an arithmetic mean when a few large values pull the distribution upward. The registry description states that geometric least-squares means are provided as descriptive statistics, but does not provide the underlying distribution or details sufficient to reconstruct those estimates.

A ratio of geometric least-squares means expresses a relative comparison on a multiplicative scale. Its interpretation depends on which group is in the numerator and which is in the denominator. Although the analysis lists the two groups, the registry record does not clearly state that ratio orientation in prose. The reported ratio is therefore best read together with its confidence interval and p-value, without inferring an explicit direction from the listed group order alone.

How should the confidence intervals be read?

A confidence interval gives a range of values compatible with the observed data under the model and its assumptions, at the stated confidence level. It communicates precision, not the probability that a fixed true value is inside the particular interval. For group estimates, the interval quantifies uncertainty about each model-based mean. For the ratio, it quantifies uncertainty about the model-based relative comparison. Comparing whether separate group intervals overlap is not a replacement for a formal test of the difference between groups.

The primary analysis population is the Per Protocol set. It includes randomized participants without a major protocol deviation affecting evaluability during confinement. This differs from an analysis of every randomized participant, and exclusion after randomization can affect how well the original randomized comparison is preserved. The record does not report an intention-to-treat primary analysis or explain the individual exclusions from the Per Protocol set.

Why can over-dispersion matter?

Over-dispersion is a concern mainly for models of counts or other outcomes where variability exceeds the model’s expected level. It can make standard errors too small if the model does not accommodate the extra variability. It is not a central description of this continuous concentration endpoint, and the registry record does not report an over-dispersion assessment. More generally, every model relies on assumptions about the data and error structure; the available record does not describe diagnostics for this analysis.

Sample-size calculations, when presented as planning illustrations, are not observed trial results and are not evidence of achieved power. The registry record does not report the trial’s own sample-size justification or assumptions for planning. It also does not report interim analyses or enough detail to determine whether any planned statistical procedures were changed. The reported significance test should be understood as the result registered for the stated comparison, not as a complete account of all analyses that may have been considered.

10. Analyses Reported by the Sponsor

The registry record reports a sponsor analysis using ANCOVA for the THS 2.2 Menthol and menthol conventional cigarette groups. The outcome is expressed as a geometric least-squares mean ratio of 13.49, with a 95% confidence interval from 10.96 to 16.60 and p <.001. The endpoint group estimates are also reported as geometric least-squares means, with their own confidence intervals.

The ratio is a model-based relative comparison, whereas the group estimates describe modeled concentrations. The registry record does not clearly explain the ratio’s numerator and denominator in prose, so its direction should not be inferred from the reported group ordering. The posted record does not flag a discrepancy between the sponsor analysis and a recalculation. No separate recalculated comparison result is reported for this endpoint.

The sponsor’s ANCOVA result is the available inferential comparison in the registry record. Its interpretation depends on model details that are not reported, including the adjustment variables and diagnostics. The ratio and confidence interval communicate the estimated relative comparison and its precision under that analysis; they do not establish a clinical effect or answer comparisons that were not reported, including a formal primary-outcome comparison against smoking abstinence.

11. Multiplicity, Missing Data and Analysis Populations

The primary endpoint is identified as MHBMA concentration at Day 5. The registry record lists five outcome measures and five analyses, but it does not explain whether the analyses were treated as a family for multiplicity control, whether any outcomes were designated secondary or exploratory, or whether an adjustment procedure was used. The record does not provide a complete prespecified statistical analysis plan. Therefore, the reported p-value should be interpreted as the result for its stated comparison; the record does not establish how it relates to any broader set of tests.

The record describes the primary analysis population as the Per Protocol set. This set includes randomized participants without a major protocol deviation affecting evaluability during confinement. The endpoint group counts are 76 for THS 2.2 Menthol, 42 for menthol conventional cigarettes and 39 for smoking abstinence. The registry record does not report a corresponding all-randomized analysis for this endpoint or a detailed accounting of participants excluded from the Per Protocol set.

Missing-data handling is not reported in the registry record. It does not state whether missing endpoint values occurred, how such values were treated, or whether sensitivity analyses assessed their potential effect. The reasons for any difference between enrollment and endpoint analysis counts are also not fully described. Without this information, it is not possible to determine how missing measurements or exclusions may have influenced the primary estimates.

The record does not report interim analyses, stopping rules or changes to the analysis plan. It also does not provide sample-size justification. Those omissions do not negate the posted estimates, but they limit assessment of whether analysis choices were prespecified and how robust the inference is to missingness or multiple testing. The available statistical interpretation should remain restricted to the named Per Protocol analysis and the reported comparison.

12. 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 non-serious adverse event terms

The registry record lists serious adverse events for three groups. There were 0 serious adverse events among 78 participants at risk in the THS 2.2 Menthol group, 0 among 42 participants at risk in the menthol conventional cigarette group, and 0 among 40 participants at risk in the smoking abstinence group. No serious adverse event terms are listed.

Other adverse events are reported separately: 16 among 78 participants at risk for THS 2.2 Menthol, 4 among 42 at risk for menthol conventional cigarettes, and 4 among 40 at risk for smoking abstinence. These figures are counts of participants affected as recorded, not a measure of event severity or duration. The registry record does not provide descriptions of the individual events in this summary.

Safety denominators differ from the primary endpoint analysis counts. The adverse-event figures should not be mixed with the Per Protocol endpoint population or treated as if they use the same analysis set. The registry record does not state how adverse events were collected, how long participants were followed for safety reporting, or whether events were judged related to a study product.

Zero reported serious adverse events in these groups describes the entries in the registry record; it does not prove that no serious event could occur or establish comparative safety. The other adverse-event counts likewise do not, by themselves, establish a cause or a treatment effect. No death counts are reported in the registry record.

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

The primary result is a comparison of a selected urinary exposure biomarker at Day 5. It describes creatinine-adjusted MHBMA concentrations among participants included in the Per Protocol analysis. The registry record reports group geometric least-squares means and an ANCOVA ratio for THS 2.2 Menthol and menthol conventional cigarettes. Those estimates can inform interpretation of this measured biomarker under the study conditions.

The result does not establish effects on symptoms, disease, long-term health or overall risk. MHBMA is one selected biomarker, and a change in a biomarker is not itself a clinical outcome. The result also does not cover every harmful or potentially harmful smoke constituent. The registry record does not report the primary outcome at the end of the 85-day ambulatory period, so the Day 5 estimates cannot be treated as a summary of the full study period.

The smoking abstinence group provides a benchmark in the study objective, but the registry record does not report a formal inferential comparison between that group and THS 2.2 Menthol for the primary endpoint. Similar-looking group estimates do not establish equivalence, and no equivalence margin is reported. The reported ANCOVA result addresses the two groups listed for that analysis, not every possible pairwise comparison.

The primary result applies to the Per Protocol set, not necessarily to every randomized participant. The record does not provide enough information about missing outcomes, exclusions or sensitivity analyses to assess their influence. It also does not describe all model details. These limitations matter when judging how far the numerical result can be generalized beyond the analysis population and its specified endpoint.

In general, a statistically small p-value is evidence against a model-based null hypothesis for the comparison tested, under the assumptions of the analysis. It is not a measure of the size, importance or clinical meaning of an effect. The confidence interval helps describe precision, but does not remove uncertainty about model assumptions, missing data or the broader relevance of a single biomarker.

14. Why This Trial Matters Statistically

This study is statistically informative because it places an exposure biomarker in a randomized, parallel-group comparison involving product use, continued conventional cigarette smoking and abstinence. The separate abstinence group provides context for interpreting the selected biomarker, while the conventional cigarette group supplies the active comparison reported in the primary ANCOVA analysis.

The outcome is measured during a controlled confinement period, and the study also includes a longer ambulatory period. That structure distinguishes a tightly observed early measurement from later use in a less controlled setting. The posted primary result, however, is specific to Day 5. Recognizing that time boundary is important: a precise estimate at one point does not answer what happened across the full follow-up.

The record also illustrates why statistical summaries need to be read alongside population definitions. The primary analysis used a Per Protocol set, while the adverse-event denominators and endpoint counts differ. Knowing which participants contribute to each result is essential when interpreting estimated group differences and their uncertainty.

Finally, a model-based ratio and descriptive group estimates answer related but distinct questions. The ratio is the reported inferential comparison; the group estimates show the modeled concentrations. Because the ratio orientation and full ANCOVA specification are not clearly described, careful reporting should preserve the published figures without adding unsupported direction or causal interpretation. This is a useful example of the limits of drawing broad conclusions from a selected biomarker and an incompletely documented statistical model.

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 give the full statistical analysis plan, the ANCOVA covariates, model diagnostics or details of any transformation. It does not clearly state which group forms the numerator of the reported geometric least-squares mean ratio. This limits independent interpretation of the relative estimate, even though the ratio, interval and p-value are reported.

The primary endpoint is measured at Day 5, while the study includes an additional 85 days in an ambulatory setting. The registry record does not provide a primary endpoint result for the end of that period in the registry record considered for this analysis. The Day 5 result therefore cannot describe the full study course.

The primary analysis uses the Per Protocol population, which excludes randomized participants with major protocol deviations affecting evaluability during confinement. The record does not provide a detailed flow of participants into the analysis or explain all differences between enrollment and analysis counts. Missing-data methods and sensitivity analyses are not reported in the registry record.

The primary result concerns one biomarker of exposure, not a clinical health outcome or all smoke constituents. The registry record reports the abstinence group as a benchmark but does not provide a formal primary endpoint test of that group against THS 2.2 Menthol. Multiplicity procedures are not described despite the listing of multiple outcome measures and analyses.

Other design details, including allocation concealment and masking of outcome assessment, are not reported in the registry record. The record also does not report the trial’s own sample-size justification or interim analyses. These gaps limit assessment of prespecification, robustness and generalizability without changing what the posted primary result states.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Reduced Exposure Study Using THS 2.2 Menthol With 5 Days in a Confinement Setting and 85 Days in an Ambulatory Setting — NCT01970995.
• Registry record last updated 2020-03-23; status last verified 2020-03.
• Results first posted 2017-02-07.
• 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

NCT01970995 is a completed randomized, controlled, multicenter, parallel-group study with no masking recorded. It enrolled 160 participants and compared THS 2.2 Menthol, menthol conventional cigarettes and smoking abstinence. Participants followed the assigned condition for 5 days in confinement and 85 days in an ambulatory setting.

The primary outcome was creatinine-adjusted urinary MHBMA concentration at Day 5, analyzed in a Per Protocol population. The registry record reports geometric least-squares means with 95% confidence intervals and an ANCOVA ratio for THS 2.2 Menthol and menthol conventional cigarettes. It also lists adverse-event counts for the three groups.

The main limits to interpretation are the single primary measurement time, the Per Protocol analysis, and statistical details that are not reported, including missing-data handling and the ratio’s direction. The result is a biomarker comparison, not a reported clinical health outcome.