This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Effects of E-Cigarette Power and Nicotine Content in Dual Users and Vapers (NCT03830892), a randomized na study. The primary outcome is Breakpoint of Drug Purchase Tasks (DPT).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03830892 |
| Phase | NA |
| Condition | Electronic Cigarettes |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Single |
| Enrollment | 48 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Virginia Commonwealth University |
| Results posted | Yes |
2. Clinical Question
Population
The study included exclusive e-cigarette users and dual users. The registry lists enrollment of 48. A protocol change after study completion means results are not reported for 4 Dual Users.
Intervention
Laboratory sessions varied device power and nicotine concentration: 15 watts or 30 watts, with 10 mg or 30 mg nicotine. The study also included an own-brand e-cigarette session for exclusive users and an own-brand e-cigarette/cigarette session for dual users.
Comparator
The conditions allow questions about how session-specific product settings relate to willingness to pay and price sensitivity. The registry record does not report a single comparison or specify which condition served as the reference for an analysis.
Primary question
The primary outcome was the breakpoint of Drug Purchase Tasks, measured in US Dollars. The study aimed to understand how device power and nicotine concentration relate to willingness to pay for session-specific tobacco products, as well as price sensitivity. The record does not report a primary-outcome result.
3. Trial Design
The registry describes a randomized, single-masked, crossover study of e-cigarette power and nicotine content in exclusive e-cigarette users and dual users. The listed enrollment is 48. The study status is terminated, with a start date of 2019-01-18 and primary completion date of 2020-03-06. The phase is recorded as NA.
The laboratory conditions varied power between 15 watts and 30 watts and nicotine concentration between 10 mg and 30 mg. The listed sessions also include own-brand product use: an e-cigarette session for exclusive users and an e-cigarette/cigarette session for dual users. The record describes these as study sessions, but the schedule, order, washout arrangements, and allocation sequence are not reported in the registry record.
In a crossover design, participants may experience multiple conditions, making within-participant comparisons possible in principle. That general design feature does not establish which comparisons were planned or how observations were analyzed in this study. The registry record does not report the statistical model, handling of period or order effects, or who was masked. It also does not report a sample-size justification.
The record states that the protocol changed after study completion for 4 Dual Users and that results are not being reported on those participants. This is an important qualification when considering who is represented by any reported results. No primary-outcome analysis result is 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.
Before assignment: Each participant will participate in 6 sessions. Sessions differ by the tobacco product used (see study arms). The sessions are ordered by latin-square; however, session order was NOT expected to change any outcomes and order effects are not relevant to the study. Therefore all outcome data was merged and analyzed only by arm and session without regard to order.
Overall Study
| Stage | E-cigarette User (Exclusive) | Dual User |
|---|---|---|
| STARTED | 25 | 23 |
| 15 Watts, 10 mg Nicotine | 19 | 17 |
| 15 Watts, 30 mg Nicotine | 19 | 17 |
| 30 Watts, 10 mg Nicotine | 19 | 17 |
| 30 Watts, 30 mg Nicotine | 19 | 17 |
| Own Brand | 19 | 17 |
| COMPLETED | 19 | 17 |
| NOT COMPLETED | 6 | 6 |
Reasons for not completing this period:
| Reason | E-cigarette User (Exclusive) | Dual User |
|---|---|---|
| Physician Decision | 2 | 3 |
| Study terminated due to COVID | 4 | 0 |
| Protocol Violation | 0 | 1 |
| Withdrawal by Subject | 0 | 2 |
Analysis population for the primary outcome, as defined in the registry: Protocol was changed after study completion by 4 Dual Users so results are not being reported on those participants.
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: Protocol was changed after study completion by 4 Dual Users so results are not being reported on those participants due to the protocol changes.
| Characteristic | Unit | E-cigarette User (Exclusive) | Dual User | Total |
|---|---|---|---|---|
| Participants analysed | 19 | 13 | 32 | |
| Age, Continuous | years | 27.53 (SD 7.53) | 29 (SD 6.84) | 28.13 (SD 7.18) |
| Sex: Female, Male: Female | Participants | 6 | 6 | 12 |
| Sex: Female, Male: Male | Participants | 13 | 7 | 20 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 1 | 1 | 2 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 18 | 12 | 30 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Race/Ethnicity, Customized: American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race/Ethnicity, Customized: Asian | Participants | 1 | 1 | 2 |
| Race/Ethnicity, Customized: Middle Eastern | Participants | 0 | 1 | 1 |
| Race/Ethnicity, Customized: Black or African American | Participants | 3 | 3 | 6 |
| Race/Ethnicity, Customized: White | Participants | 13 | 8 | 21 |
| Race/Ethnicity, Customized: More than one race | Participants | 2 | 0 | 2 |
| Region of Enrollment: United States | participants | 19 | 13 | 32 |
6. Primary Endpoint
The registry lists the primary outcome as Breakpoint of Drug Purchase Tasks (DPT), measured over Up to 180 minutes.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | US Dollars |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the breakpoint of the Drug Purchase Tasks, expressed in US Dollars. The task is described as producing measures of willingness to pay and price sensitivity for the tobacco products used in a particular session. Choices are not reinforced during the session, so the endpoint reflects choices made in the task rather than a purchase carried out as part of that task.
The task was completed once per study session. Its timing could be 90 minutes or approximately 180 minutes into a session, depending on task order and potentially on choices in earlier tasks. The overall timeframe is listed as up to 180 minutes. This variation in timing is relevant when interpreting measurements across conditions: the registry does not state whether timing was accounted for in an analysis.
As a general statistical matter, a breakpoint can provide a behavioral measure of the price at which a participant’s stated willingness to purchase changes. It is not itself a measure of a clinical health outcome. The registry record does not report endpoint values, a comparison between conditions, or an estimate of the precision of any difference.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a behavioral primary outcome but does not report its results. It lists the breakpoint of Drug Purchase Tasks as a mean in US Dollars, with standard deviation as the dispersion measure. However, no primary-outcome estimate, comparison, confidence interval, or analysis is reported. The record also notes that the primary outcome has several categories or time points and was not reduced to a single comparison. The posted information therefore does not support a conclusion about the direction or size of any difference between study conditions.
The study’s stated aim was to understand how device power and nicotine concentration relate to the likelihood that someone would use or abuse e-cigarettes. The listed primary endpoint instead concerns willingness to pay and price sensitivity for session-specific tobacco products. That endpoint can inform a behavioral question, but the record does not provide a result establishing how it varied by power, nicotine concentration, or participant group.
The design is randomized and crossover, but those labels alone do not reveal the specific allocation process, condition order, or analysis strategy. A crossover design can support comparisons within participants as a general matter, while also requiring attention to order, timing, and possible carryover. Whether these issues were assessed or adjusted for is not reported in the registry record.
The registry lists 10 outcome measures and 0 analyses. The absence of a listed analysis means the posted record offers no inferential result to interpret, such as an estimated effect or a measure of uncertainty. It should not be read as evidence that the conditions were equivalent, nor as evidence of a particular effect. No finding about use, abuse, or clinical benefit can be drawn from the information reported.
Planning illustrations based on an observed effect are a different kind of information from a trial result. Such illustrations describe sample sizes under assumptions; they are not observed power and do not establish that the study was designed or analyzed using those assumptions. The registry record does not report the trial’s own sample-size justification. Interpretation should therefore remain limited to the design, endpoint, participant qualification, and safety figures that are explicitly recorded.
9. Statistical Methods Explained
What does a mean represent?
The primary endpoint is specified as a mean of a continuous measure. In general, a mean summarizes the center of a set of measurements, while the standard deviation describes how spread out measurements are around that center. A mean can be useful for comparing conditions, but it does not show the full distribution of individual values. Skewed values or a small number of unusually high or low measurements can affect a mean. The registry record does not report the observed mean or standard deviation for the primary outcome, so neither the endpoint’s observed center nor its variability can be assessed from the posted results.
What would a confidence interval add?
In general, a confidence interval communicates uncertainty around an estimated quantity. It helps readers judge which effect sizes are reasonably compatible with the data and analysis, rather than focusing only on a point estimate. A narrow interval indicates greater precision than a wide interval, but precision is not the same as clinical importance. No confidence interval for the primary endpoint is reported in the registry record. Without an estimate and its uncertainty, the size and precision of any condition difference cannot be evaluated.
How does crossover design affect interpretation?
In general, crossover studies collect measurements under multiple conditions from the same participant. Comparing measurements within a participant can account for stable characteristics that differ between people. That advantage depends on the design and analysis being appropriate for the data. The condition order, allocation sequence, washout arrangements, and statistical treatment of period or carryover effects are not reported in the registry record. Randomized allocation is stated, but the details of what was randomized are not reported. The registry also describes masking as single without stating who was masked.
For a continuous endpoint in a crossover study, an analysis might account for the pairing of measurements and the structure of repeated observations. This is a general methodological consideration, not a description of the analysis used in this study. The record lists 0 analyses, so the method used to estimate any condition effect is not reported in the registry record.
Why does endpoint timing matter?
The Drug Purchase Task could occur 90 minutes or approximately 180 minutes into a session, with timing varying according to task order and potentially choices made in earlier tasks. In general, measurements taken at different points in a session may not be directly comparable if timing relates to the outcome. Statistical methods can sometimes account for such variation, but whether that was done is not reported in the registry record. The endpoint timeframe is listed as up to 180 minutes.
What do the planning assumptions mean?
General statistical explanation: a sample-size illustration estimates the number of participants that might be needed under specified assumptions to detect a chosen effect with a chosen level of statistical power. The registry’s planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is expressed as a stated fraction of the observed effect. These are planning illustrations, not the trial’s own design justification and not observed power. The registry record does not report the trial’s sample-size justification. A planning calculation cannot substitute for an observed treatment estimate or its uncertainty.
A significance threshold is a decision convention used in some statistical procedures; by itself it does not tell readers whether an effect is large, precise, or practically important. Similarly, power is a property of a design under assumptions, not a finding about whether a study result is true. No analysis result is reported for the primary endpoint, so the planning assumptions do not provide evidence about the observed outcome.
What can be inferred from a missing analysis?
The registry lists 10 outcome measures and 0 analyses. This means the posted record does not provide an analysis estimate to assess. It does not establish that no data were collected, nor does it establish that the conditions had the same outcomes. The primary outcome is described as having several categories or time points and not being reduced to one comparison. The registry record does not report how those categories or time points were handled, whether adjustments were made, or which analysis population was used.
Over-dispersion is a general concern in analyses of count data when observed variability exceeds what a model assumes. It does not directly describe this continuous mean endpoint. More broadly, statistical methods should match the type and structure of the outcome. The registry record does not identify a model for the primary endpoint or provide enough analysis detail to evaluate model assumptions. No specific statistical procedure should therefore be attributed to this study beyond the design and endpoint descriptions recorded.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 10 outcome measures, while the primary outcome is described as having several categories or time points and not being reduced to one comparison. When a study assesses multiple outcomes, categories, time points, or contrasts, there can be more than one opportunity to identify an apparently notable result. As a general statistical matter, multiplicity procedures can address that issue, but the choice depends on the questions and analysis plan.
The registry record does not report a multiplicity strategy, a hierarchy of outcomes, or which comparisons were intended to be confirmatory. It lists 0 analyses, so there are no posted primary-outcome estimates or associated uncertainty measures to interpret. This absence does not establish whether multiplicity was considered outside the registry record.
The record states that results are not reported on 4 Dual Users because the protocol changed after study completion. It does not describe the nature of the change, the reason for it, or how the affected observations were handled. The analysis population and missing-data methods are not reported in the registry record. It is therefore not possible to assess whether missing observations were related to outcomes, whether any imputation was used, or how the change affected the analysis.
As a general principle, exclusions and missing-data assumptions can influence both the estimate and its precision. The stated omission should be considered when interpreting any eventual results, but the posted record does not provide enough information to quantify its effect. It also does not report a prespecified statistical analysis plan or interim-analysis procedures.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| E-cigarette User (Exclusive) | 1 | 19 | 5.3% |
| Dual User | 0 | 13 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| E-cigarette User (Exclusive) | 0 of 19 |
| Dual User | 0 of 13 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| E-cigarette User (Exclusive) | 3 of 19 |
| Dual User | 7 of 13 |
Most frequent serious adverse event terms
| Event term | Organ system | E-cigarette User (Exclusive) | Dual User |
|---|---|---|---|
| Hospitalization | Surgical and medical procedures | 1 of 19 | 0 of 13 |
Most frequent non-serious adverse event terms
| Event term | Organ system | E-cigarette User (Exclusive) | Dual User |
|---|---|---|---|
| Worsening cough | Respiratory, thoracic and mediastinal disorders | 1 of 19 | 1 of 13 |
| Shortness of breath | Respiratory, thoracic and mediastinal disorders | 1 of 19 | 1 of 13 |
| Fatigue | General disorders | 1 of 19 | 1 of 13 |
| Injury | Injury, poisoning and procedural complications | 0 of 19 | 2 of 13 |
| Nausea | Gastrointestinal disorders | 0 of 19 | 1 of 13 |
| Abdominal pain | Gastrointestinal disorders | 0 of 19 | 1 of 13 |
Serious events with the highest arm-level rate: hospitalization (5.3%).
The registry lists serious and other adverse-event figures separately for the two participant groups. In the E-cigarette User (Exclusive) group, 19 were at risk for serious events and 1 serious event is listed; 19 were at risk for other events and 3 other events are listed. In the Dual User group, 13 were at risk for serious events and 0 serious events are listed; 13 were at risk for other events and 7 other events are listed. Deaths are recorded as 0 in both groups.
Hospitalization, with 5.3%, is listed among the top serious-event terms. The registry record does not provide enough detail to assign that term to a particular group or condition. These figures describe the adverse-event entries in the record; they do not by themselves establish that an event was caused by a study condition. The record does not report event timing, severity beyond the serious/other classification, relatedness assessments, or the method used to collect events.
Comparisons of these counts require caution. The groups differ in their listed at-risk counts, and the study has a crossover design with multiple sessions. The record does not clarify whether the event figures are organized by participant, session, or another unit. The figures should therefore be read as registry safety entries, not as a causal comparison of the study conditions.
12. What the Result Does, and Does Not, Mean
The record establishes that a randomized, single-masked crossover study examined e-cigarette power and nicotine concentration in exclusive e-cigarette users and dual users. Its primary endpoint was a Drug Purchase Task breakpoint, intended to measure willingness to pay and price sensitivity for session-specific tobacco products. Those details describe the question and design, not an answer to the question.
No primary-outcome analysis result is reported in the registry record. There is no posted estimate showing how breakpoint values differed across power or nicotine conditions, no uncertainty interval, and no reported statistical test. The record also notes that the outcome had several categories or time points and was not reduced to one comparison. Consequently, the posted information does not establish the direction, magnitude, or precision of any primary-outcome difference.
The task measures choices in a purchase task. It should not be treated as a direct measure of actual purchasing, e-cigarette use, abuse, or a clinical health outcome. The study aim refers to likelihood of use or abuse, while the primary endpoint described in the record concerns willingness to pay and price sensitivity. No reported analysis links the task result to those broader outcomes.
The safety entries provide descriptive counts, including 0 listed deaths in each group, but the record does not establish causal attribution or a comparison by study condition. The protocol-change note also qualifies the population represented: results are not reported for 4 Dual Users. These limits mean that the registry information is best read as a description of the study framework and recorded safety entries, rather than evidence for or against an effect.
13. Why This Trial Matters Statistically
This study is statistically notable for combining randomized allocation with a crossover design and a behavioral endpoint. In principle, crossover data can support within-participant comparisons, which may reduce the influence of stable differences between participants. That potential depends on the order of conditions, timing, repeated-measure structure, and analysis method. The registry record does not report those details or an analysis result, leaving the main statistical question unresolved in the posted information.
The endpoint also raises an important distinction between a measurable task outcome and the broader behavior named in the study aim. A willingness-to-pay breakpoint can describe price sensitivity in a structured task. It does not automatically establish actual use, abuse, or clinical consequences. Clear interpretation depends on matching conclusions to the outcome that was measured.
The timing variation matters methodologically because the task could occur 90 minutes or approximately 180 minutes into a session, depending on task order and potentially earlier choices. The registry does not report how this variation was treated. The protocol-change note for 4 Dual Users further highlights why analysis populations and exclusions need transparent reporting.
Finally, the registry lists 10 outcome measures and 0 analyses, and the primary outcome is not presented as a single comparison. Without reported estimates and uncertainty, readers cannot assess effect size, precision, or the relationship between the study aim and measured endpoint. The record therefore illustrates the importance of complete outcome reporting alongside a clearly described design.
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 principal limitation for statistical interpretation is that the registry record does not report an analysis of the primary outcome. There is no posted mean, standard deviation, condition contrast, confidence interval, or test result for the Drug Purchase Task breakpoint. The primary outcome is also described as having several categories or time points without being reduced to one comparison, which leaves the intended inferential question unclear.
Design and analysis details are limited. Although the study is recorded as randomized, single-masked, and crossover, the allocation sequence, condition order, washout arrangements, identity of the masked party, and treatment of period or carryover effects are not reported in the registry record. The analysis model and analysis population are also not reported.
Task timing varied between 90 minutes and approximately 180 minutes according to task order and potentially earlier choices. The record does not state whether timing was included in an analysis. It also does not describe missing-data procedures or the consequences of the protocol change after study completion for 4 Dual Users whose results are not reported.
Safety figures are presented without enough information to determine the unit of reporting, event timing, or attribution to a study condition. The record lists 10 outcome measures but 0 analyses, and does not report a sample-size justification. These gaps limit assessment of precision, multiplicity, representativeness, and the relationship between the stated study aim and the endpoint.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Effects of E-Cigarette Power and Nicotine Content in Dual Users and Vapers — NCT03830892.
- Registry record last updated 2021-06-04; status last verified 2021-05.
- Results first posted 2021-06-04.
- 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.
Continue through the Clinical Biostats statistical pathway
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18. Record Summary
NCT03830892 is recorded as a terminated, randomized, single-masked crossover study titled Effects of E-Cigarette Power and Nicotine Content in Dual Users and Vapers. The sponsor is Virginia Commonwealth University. The record lists enrollment of 48, a start date of 2019-01-18, and primary completion on 2020-03-06.
The study included exclusive e-cigarette users and dual users, with laboratory sessions varying power and nicotine concentration, as well as own-brand sessions. The primary endpoint was the Drug Purchase Task breakpoint in US Dollars, measuring willingness to pay and price sensitivity. The record lists 10 outcome measures and 0 analyses. Results are not reported for 4 Dual Users following a protocol change after study completion.
The registry lists adverse-event counts by group, including 0 deaths in each group. It does not report a primary-outcome estimate or analysis method. The posted record therefore describes the study design, endpoint, participant qualification, and safety entries but does not provide an inferential result for the primary question.