Effects of Nicotine Salt Aerosol on Cigarette Smokers: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effects of Nicotine Salt Aerosol on Cigarette Smokers (NCT03974152), a randomized na study. The primary outcome is Plasma Nicotine.

2. Clinical Question

In statistical terms, the intended question was whether plasma nicotine measurements differed across the three product conditions within a randomized crossover design. That design can make within-person contrasts possible because the same participant can experience each condition. It does not, by itself, establish that a valid contrast was estimated: the required measurements and an analysis must also be available. Neither an endpoint result nor an analysis is reported in this record.

3. Trial Design

This was a randomized, open-label crossover study. The registry lists three products: participants’ own brand cigarettes, an ENDS device with protonated nicotine, and an ENDS device with unprotonated nicotine. The listed sequences vary the order in which those conditions were to be experienced. Enrollment was 11, and the study status is terminated. The record gives a start date of 2019-06-10 and a primary completion date of 2020-03-05.

In a crossover design, participants receive more than one condition, with order assigned according to a randomized sequence. As a general statistical principle, comparisons within the same participant can account for stable characteristics shared across that person’s observations. This is useful only when measurements are collected in each condition and the analysis accounts appropriately for the repeated observations. The record does not report an outcome analysis to assess such a within-person contrast.

The described procedure included a prompted puff every 30 seconds for 5 minutes, followed by an approximately 1-hour ad lib use period. The primary-outcome timeframe specifies blood collection at baseline, 5 minutes after the start of a 10-puff product-use period, and before and after the ad lib period. Although these collection points were planned, the record states that plasma nicotine could not be collected because of staffing issues and difficulties with blood draws.

The record identifies randomization and no masking. It does not report how the random sequence was generated or concealed, whether there was a washout between sessions, how adherence was assessed, or whether period and order effects were incorporated into a planned analysis. A sample-size justification and a detailed statistical analysis plan are not reported in the registry record. The study’s termination status describes the recorded study status; it does not supply a reason beyond the stated collection difficulties for the unavailable primary outcome.

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: This is a within-subjects design study with 3 conditions on 3 separate follow-ups after an initial screening visit. Enrolled participants were sometimes excluded from the study, primarily due to loss to follow-up.

Overall Study

Analysis population for the primary outcome, as defined in the registry: We were unable to collect this outcome measure (plasma nicotine) due to staffing issues and difficulties with blood draws.

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 ended early due to COVID and funding delays.

Only the first 6 of 7 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Plasma Nicotine, measured over Blood will be taken 4 times in each session: baseline, 5 minutes after the start of a 10-puff product use, and then before and after an approximately 1-hour ad lib use period..

The primary endpoint was change in plasma nicotine level. Plasma nicotine is a measured concentration in blood and was intended to characterize nicotine exposure after use of the cigarette or ENDS product. In general, a biomarker endpoint can provide a direct measurement of a biological quantity at specified times; repeated measurements can describe how that quantity changes over the observation period. Such measurements do not automatically answer every question about product use or other outcomes named in the study summary.

The protocol timeframe specified blood collection at baseline, 5 minutes after starting a 10-puff product-use period, and before and after an approximately 1-hour ad lib use period. Those planned time points could have been used to describe changes over time and compare product conditions, if the measurements had been obtained and analyzed. The record states that the plasma nicotine outcome was unable to be collected because of staffing issues and difficulties with blood draws. It reports no plasma nicotine values, change estimates, uncertainty intervals, or statistical test results.

Accordingly, the endpoint remains a planned measure rather than an observed result in this record. The intended measurement schedule explains what the outcome was designed to capture, but it cannot substitute for the missing blood measurements. Other outcomes mentioned in the study summary, including craving, are not presented as posted results in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The design was randomized and crossover, with no masking. The registry lists randomized orders for participants to use their own brand cigarette, an ENDS product with protonated nicotine, and an ENDS product with unprotonated nicotine. Random assignment concerns the order of conditions; it is not itself a statistical analysis of outcome differences. Since the primary measure was not collected, the record cannot show whether the randomization resulted in comparable sequences or whether any condition contrast was estimated.

What does a crossover comparison require?

As a general explanation, crossover data contain repeated observations from the same participant under different conditions. Those observations are correlated: a participant’s measurements may tend to resemble one another more than measurements from different participants. An analysis should account for this within-person structure rather than treating every measurement as independent. When measurements are available, a crossover analysis may also need to consider the order in which conditions occurred and differences between sessions. The registry record does not report a planned model or whether such effects were considered.

The within-person structure can be valuable because each participant can serve as their own comparator for characteristics that remain stable across sessions. It does not remove all possible sources of bias or uncertainty. For example, general statistical concerns include changes over time, effects carried from one condition into a later condition, and differences related to session order. Whether those concerns were relevant and how they would be addressed depend on protocol details and analysis choices. A washout interval and a method for evaluating period or carryover effects are not reported in the registry record.

What does randomization contribute?

Randomizing order can reduce systematic assignment of particular participants to particular sequences. In general, randomization supports a fair comparison when the assigned sequence is followed and outcomes are measured and analyzed according to an appropriate plan. It does not guarantee balance in a small study, and it cannot correct for an outcome that was not collected. The record identifies randomization but does not describe the sequence-generation procedure, allocation concealment, or checks of adherence to assigned order.

What can be inferred from the planned measurement times?

The endpoint description plans measurements at baseline, 5 minutes after starting a 10-puff product-use period, and before and after an approximately 1-hour ad lib period. Repeated measurements could be analyzed in several ways, depending on the clinical question. A comparison might focus on a particular time point, change from baseline, or the pattern across time. Those estimands are not interchangeable: they define different quantities and may yield different interpretations. The registry record gives no numerical measurements or analysis specification that identifies an estimated quantity.

As a general statistical explanation, a model for repeated measurements can use the relationship among observations from the same participant and can estimate condition differences while representing uncertainty. Model choice depends on the outcome distribution, measurement schedule, and intended contrast. No distributional assumptions, model terms, variance structure, or inferential procedure are reported. Since the endpoint was not collected, no model can be assessed against observed plasma nicotine data from the record.

How should significance and precision be understood?

Statistical significance is not a substitute for the size or precision of an effect. A p-value, when reported, is interpreted in the context of a prespecified question and statistical model. A confidence interval, when reported, describes uncertainty in an estimate under the model’s assumptions. Neither is available for the primary endpoint. The record reports 0 analyses, so there is no posted test or interval to interpret.

In general, measurement variability and limited information can make estimates imprecise. The enrollment figure alone cannot establish the precision of an endpoint estimate, especially when the outcome observations were not collected. The record does not report a sample-size justification, a target precision, or a statistical power calculation for the planned outcome. It is therefore not possible to judge whether the planned study size was expected to answer a particular contrast with a specified degree of precision.

What about multiple comparisons?

The study involved multiple product conditions and planned blood collection at several time points. If several comparisons or time-specific tests are performed, the chance of at least one false-positive result can increase. As a general principle, investigators may define a primary contrast in advance or use an appropriate multiplicity strategy. The registry record does not report a multiplicity plan, a prespecified contrast, or any completed analysis. Because no endpoint data or analyses are posted, there are no multiple-test results to interpret.

These methodological principles explain what would ordinarily be considered in analyzing a randomized crossover study; they are not claims that a particular model, adjustment, or procedure was used in this study. The registry record does not report those details, and the missing primary measurement prevents a statistical reconstruction of the intended efficacy comparison.

10. Multiplicity, Missing Data and Analysis Populations

The registry identifies one primary outcome measure, change in plasma nicotine level, with blood collection planned at several time points and across the product conditions. A single named primary measure does not necessarily imply a single statistical test: investigators might ask about a selected time point, change from baseline, or a pattern across measurements. The registry record does not report which contrast was designated as primary, whether secondary comparisons were planned, or how multiplicity would be addressed.

As a general statistical principle, conducting multiple tests can increase the chance of observing a nominally unusual result even when no true difference exists. Prespecifying the main contrast or using a suitable adjustment can help make interpretation more disciplined. No such plan or test results are reported. The record lists 0 analyses, so there is no reported multiplicity-adjusted or unadjusted result to compare.

The main missingness issue is that the stated primary outcome could not be collected because of staffing issues and difficulties with blood draws. This is not described merely as a subset of missing values within an otherwise reported plasma nicotine dataset. No plasma nicotine results or analysis population are presented. The registry record does not state whether any blood samples were obtained, how many participants had usable measurements, or whether an alternative endpoint was analyzed.

As a general explanation, methods for handling missing values depend on why data are absent, how much information is missing, and the analysis question. Such methods cannot recover an observed result without assumptions, and the assumptions themselves need to be assessed. The record does not report a missing-data strategy, a sensitivity analysis, or a definition of the population included in an outcome analysis. There is therefore no basis for interpreting a complete-case or imputed estimate, or for assessing whether missingness could have affected an estimated comparison.

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 0% reporting threshold.

The registry lists safety counts separately for own brand cigarette use, ENDS with 18 mg nicotine salt described as protonated, and ENDS with 18 mg nicotine described as unprotonated. The at-risk counts are 5 for the cigarette group, 5 for the protonated ENDS group, and 6 for the unprotonated ENDS group. Each group entry reports 0 serious adverse events, 0 other adverse events, and 0 deaths.

These are the recorded counts, not estimates of risk differences or comparative safety effects. No percentages or uncertainty intervals are reported, and none can be inferred from the counts alone. In a crossover study, the same participant may experience multiple conditions; the entries should therefore not be added together or treated as a count of distinct participants. The registry record does not explain how the at-risk counts relate to exposure periods or provide additional details about adverse-event ascertainment.

As a general statistical point, zero recorded events in a group does not establish that the true event rate is zero. The observation may be compatible with a range of underlying risks, particularly when the number observed is limited. These safety entries do not compensate for the uncollected plasma nicotine outcome and do not establish a product effect. The definitions and severity criteria used for adverse events are not reported in the registry record.

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

The record documents a randomized crossover study designed to compare cigarette smoking with two nicotine aerosol conditions in cigarette smokers. It also documents that the planned primary endpoint, change in plasma nicotine, could not be collected because of staffing issues and difficulties with blood draws. This means the central planned statistical comparison is unavailable in the registry record.

There is no reported plasma nicotine estimate, no contrast between products, and no precision measure or statistical test. As a result, the record cannot establish the direction or size of any difference, or whether the conditions produced similar or different plasma nicotine changes. Lack of a reported result should not be read as evidence of no difference. It also should not be read as evidence favoring any one condition.

The randomized crossover design describes a potentially informative way to compare conditions within participants. In general, such a design can reduce the influence of stable between-person differences, but it relies on collected measurements and an analysis that accounts for repeated observations and relevant features of the sequence. The registry record does not provide an analysis plan or outcome data with which to assess those issues.

The safety entries report 0 serious adverse events, 0 other adverse events, and 0 deaths in each listed group, with the group-specific at-risk counts recorded as 5, 5, and 6. Those counts are limited to the registry entries and are not a test of comparative safety. They should not be generalized beyond the recorded groups or treated as proof that no event could occur.

The study is marked terminated, and enrollment is recorded as 11. These registry entries describe the study record but do not supply an efficacy result. The registry does not report other outcomes as analyzed results, a reason for termination beyond the noted outcome-collection difficulties, or a statistical conclusion. The appropriate reading is that the planned primary comparison remains unanswered by the posted results.

13. Why This Trial Matters Statistically

This study illustrates an important distinction between a trial’s design and the evidence available from its results. Randomization and a crossover structure can support a carefully planned comparison, but the design alone does not yield an estimate. For the intended primary question, blood measurements were necessary. The registry states that plasma nicotine was not collected, leaving no endpoint data or analysis to interpret.

That distinction matters because readers can otherwise mistake a detailed protocol for a completed statistical comparison. The record specifies products, randomized order, and planned measurement times, but those details describe what investigators intended to do. They do not show what happened to plasma nicotine under any condition. Statistical interpretation must be anchored in observations and the analysis that connects those observations to a defined question.

The case also highlights the practical role of measurement feasibility. A biomarker endpoint may be central to a question, yet collection can be disrupted by staffing or procedural difficulties. When the primary measurement is unavailable, a protocol’s scientific rationale cannot replace the missing evidence. Transparent reporting of the missing outcome and its reason is important because it allows readers to distinguish an unavailable result from a null or inconclusive estimate.

Finally, the safety counts and efficacy endpoint answer different questions. Zero recorded events in the listed safety categories does not provide information about the uncollected plasma nicotine measurements. Keeping these outcomes separate prevents a limited safety record from being misread as evidence about the trial’s primary pharmacological question. The record is therefore statistically informative mainly as an example of why outcome collection, prespecified analysis, and cautious interpretation are all necessary parts of clinical research.

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 most direct limitation is the absence of the primary outcome. The record says plasma nicotine could not be collected because of staffing issues and difficulties with blood draws. It reports no endpoint values, change estimates, uncertainty intervals, or tests. This prevents evaluation of the trial’s principal planned comparison, regardless of its randomized crossover structure.

Enrollment was 11, but the record does not explain how many participants completed each session or how many contributed to any outcome. It does not report an analysis population, adherence to assigned sequence, withdrawals, or missing-data procedures. The study is marked terminated. The registry record does not give further details about the circumstances of termination beyond the stated collection difficulties.

The design description does not include a reported washout interval, allocation-concealment method, or statistical approach for repeated measurements. It also does not state how period, sequence, or possible carryover effects would be handled. These omissions matter for evaluating what a crossover comparison would mean, but the missing endpoint means no such comparison is available to examine.

Several contextual details are not reported in the registry record, including a sample-size justification, the statistical analysis plan, a multiplicity strategy, and detailed eligibility criteria. The brief summary refers to nicotine delivery, craving, and other outcomes, but the record presented does not report analyses of these outcomes. The safety entries contain zero recorded events in the listed categories, but the record does not provide event definitions or enough information to estimate comparative risks. These limitations restrict interpretation to the reported design and recorded counts, without supporting conclusions about efficacy or comparative safety.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Effects of Nicotine Salt Aerosol on Cigarette Smokers — NCT03974152.
• Registry record last updated 2024-03-26; status last verified 2024-02.
• Results first posted 2024-02-02.
• 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

NCT03974152 is a randomized, unmasked crossover study titled “Effects of Nicotine Salt Aerosol on Cigarette Smokers,” sponsored by Eastern Virginia Medical School. It enrolled 11 and is marked terminated. The registry lists a start date of 2019-06-10 and a primary completion date of 2020-03-05.

The planned comparison involved participants’ own brand cigarettes, an ENDS product with 18 mg protonated nicotine, and an ENDS product with 18 mg unprotonated nicotine. The primary outcome was change in plasma nicotine, measured at planned time points during product-use sessions. The record states that this outcome could not be collected because of staffing issues and difficulties with blood draws; it reports 0 analyses.

For each listed safety group, the registry records 0 serious adverse events, 0 other adverse events, and 0 deaths. The record does not report an efficacy estimate, a statistical analysis plan, or a sample-size justification. The planned primary comparison therefore has no posted result in the registry record.