Quit or Switch: E-cigarette Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Quit or Switch: E-cigarette Study (NCT05525078), a randomized na study. The primary outcome is Percentage of Participants Who Have Biochemically-confirmed Abstinence From Cigarette Smoking at Week 4.

2. Clinical Question

The clinical question is framed around a specific group: smokers who had already tried and failed to quit with pharmacotherapy within the past year. The trial compared two different next-step approaches rather than comparing an intervention with no treatment. One group was assigned to switch to e-cigarettes, while the other was assigned to try quitting again with combination nicotine replacement therapy.

The primary outcome combines a self-reported account of abstinence with an expired-carbon-monoxide criterion. It therefore addresses reported cigarette abstinence at a particular follow-up point, with a biochemical measure included in the endpoint definition. It is not a measure of long-term abstinence, all tobacco use, or health outcomes such as cancer. The registry record gives Week 4 as the primary outcome timeframe.

The trial was randomized and parallel-group, with 20 participants in the Switch Group and 10 in the Meds Group. The outcome counts were 7 and 1, respectively. These counts describe the posted result in this small enrolled sample; they do not by themselves establish how the approaches compare in a wider population. The registry record does not report a formal primary analysis beyond the posted comparison statistics.

3. Trial Design

NCT05525078, titled “Quit or Switch: E-cigarette Study,” is a completed, randomized, parallel-group trial. The registry lists the Medical University of South Carolina as sponsor and Tobacco Use as the condition. The listed phase is NA. Masking is listed as none. Enrollment was 30. The record gives a start date of 2022-08-01 and a primary completion date of 2023-07-17.

Participants were current smokers who had failed to quit with FDA-approved pharmacotherapy within the past year. They were randomly assigned to one of two groups: the Switch Group, with 20 participants, or the Meds Group, with 10 participants. Participants selected a Target Switch / Quit Date on which they would stop smoking. The Switch Group received a 5-week supply of e-cigarettes. The Meds Group received a 5-week supply of combination nicotine replacement therapy consisting of a transdermal nicotine patch and a short-acting nicotine lozenge.

The registry describes the comparison as randomized and parallel, with no masking. The two groups therefore represent distinct assigned approaches, but the record does not report details such as the randomization sequence method, allocation concealment, adherence assessment, or any procedures to reduce bias in outcome assessment. Those details are not reported in the registry record.

The primary outcome was the count of participants with biochemically confirmed cigarette abstinence at Week 4. The posted counts were 7 in the Switch Group and 1 in the Meds Group. The registry record lists two outcome measures but no posted secondary outcome results. Its analysis count is zero, so the record does not supply a named analytic plan or detailed analysis population. The original design assumptions, including any sample-size justification, are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants Who Have Biochemically-confirmed Abstinence From Cigarette Smoking at Week 4, measured over Week 4.

The primary endpoint is titled “Percentage of Participants Who Have Biochemically-confirmed Abstinence From Cigarette Smoking at Week 4.” The registry specifies the measure as a count of participants, with a Week 4 timeframe. Its description defines the outcome as self-reported point-prevalence abstinence from cigarettes together with expired carbon monoxide < 6 ppm. The posted results are counts: 7 participants in the Switch Group and 1 participant in the Meds Group.

The endpoint is a snapshot of cigarette abstinence at the specified follow-up point. Self-report captures participants’ reports about smoking, while the carbon-monoxide criterion adds a biochemical check to the endpoint definition. This combination makes the measure more specific than self-report alone, but it remains limited to cigarette abstinence at Week 4. The record does not describe how the measurement was conducted, how missing measurements were handled, or whether another abstinence definition was used in analyses.

General statistical context: A binary endpoint classifies each participant as having or not having the specified event. Reporting counts makes the number of participants meeting the endpoint visible in each group, but counts alone do not indicate how precisely the underlying group outcomes have been estimated. Interpretation also depends on the comparison estimate and its uncertainty, as well as on the population and timeframe to which the result applies.

7. Results Posted in the Registry

• Meds Group: 10.0% (1/10) versus 35.0% (7/20) on control; risk difference -25.0 percentage points (95% CI -53.0 to 3.0), risk ratio 0.29 (0.04–2.01); unadjusted two-proportion z-test p = 0.144.

8. Statistical Interpretation

9. Statistical Methods Explained

General statistical context: The primary outcome is binary: each participant either meets the defined abstinence endpoint at Week 4 or does not. In a two-group randomized comparison, the observed event counts describe how many participants in each group met the endpoint. A comparative estimate then expresses the contrast between groups on a chosen scale. Here, the registry posts a risk difference and an unadjusted p-value, along with an interval for the risk difference.

What does the risk difference describe?

A risk difference expresses the difference between the proportions meeting an outcome in two groups. It is an absolute contrast on the probability scale, rather than a ratio. The registry lists the Meds Group comparison with a risk difference of -0.25 and identifies the Switch Group as the control group. The negative sign indicates that the event outcome is lower in the Meds Group relative to the reference group in the posted contrast. The estimate is based on the observed counts of 7 in the Switch Group and 1 in the Meds Group.

The point estimate is only one description of the evidence. With a small sample, the estimated contrast can be imprecise, and the interval gives a range of values compatible with the data under the method used to construct it. The reported interval runs from -0.530 to 0.030. Since it includes zero, it does not rule out no risk difference at the interval’s stated level. The registry record does not identify the interval-construction method or its confidence level, so those details should not be inferred.

What does the p-value say?

The registry reports an unadjusted p-value of 0.144. General statistical context: a p-value measures how unusual data at least as incompatible with a specified null model would be, assuming that model and the analysis assumptions. It does not give the probability that the null model is true, nor does it measure the probability that the observed result occurred by chance in an everyday sense. It also does not quantify the size or practical importance of an effect.

“Unadjusted” means the posted p-value is not described as adjusted for multiple comparisons. The registry lists two outcome measures, but no secondary outcomes are posted and no analyses are listed. The statistical plan, including any prespecified testing hierarchy or multiplicity procedure, is not reported in the registry record. Accordingly, the p-value should be interpreted as the posted comparison statistic rather than as a fully documented confirmatory testing result.

Why does randomization matter?

General statistical context: random assignment is intended to make assigned groups comparable, on average, with respect to factors that could affect the outcome. This supports causal interpretation when the trial’s conduct and analysis preserve the benefits of randomization. It does not ensure that the realized groups are identical, particularly in a small trial. Nor does the registry entry alone establish that all randomized participants were included in the analysis or that outcome data were complete. The record does not report the analysis population, handling of missing values, or adherence to assigned approaches.

The design is parallel-group and unmasked. No masking is listed. The registry record does not describe allocation concealment, the sequence-generation method, or additional safeguards in outcome assessment. These omissions limit what can be concluded about potential sources of bias from the registry entry alone.

What can be concluded from these methods?

The reported counts and comparison provide a compact description of a randomized contrast at Week 4. The effect estimate indicates the direction and magnitude of the observed risk difference, while the interval and p-value describe statistical uncertainty in different ways. They should be read together and in the context of the small enrolled groups. They do not establish long-term outcomes, results in people outside the stated eligibility group, or the effect of switching on other health outcomes.

The registry record does not report a detailed statistical analysis plan, original sample-size assumptions, interim analyses, or a named model for the primary outcome. The planning calculations associated with the observed result are illustrations and are not the original trial design justification. They are also not a measure of the probability that this completed study detected an effect. These absences matter because design and analysis choices affect how strongly the posted comparison can support a confirmatory interpretation.

10. Confidence Intervals and Precision

The risk-difference estimate is -0.25. The reported interval extends from -0.530 to 0.030. Because the interval includes zero, the posted results are compatible with no risk difference as well as with a range of contrasts in either direction. The interval is broad in relation to the point estimate, reflecting substantial uncertainty around the comparison. The registry record does not state the interval’s confidence level or construction method, so it is best described as the reported interval rather than assigned a confidence label not present in the record.

The sample contributing to this comparison is limited: 20 participants were assigned to the Switch Group and 10 to the Meds Group. The primary outcome counts were 7 and 1, respectively. With few participants, a change in the outcome classification of a small number of people could materially alter the observed group counts and estimated contrast. This is one reason the point estimate should not be treated as a precise prediction for other samples.

The unadjusted p-value is 0.144. The p-value and interval are related ways to express uncertainty but do not answer exactly the same question as the estimated effect’s practical importance. The p-value should not be used as a binary verdict, and an interval that includes zero does not prove that the groups are equivalent. The record does not report an equivalence or non-inferiority objective.

General statistical context: A confidence interval, when its method and confidence level are specified, reflects the uncertainty that would arise from repeated sampling under the model and procedure. It is not a range containing a fixed proportion of individual participant outcomes, nor does it guarantee that the true effect lies inside a particular interval. In this record, the level and method are not reported, so interpretation should remain anchored to the posted bounds and the fact that they include zero.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size figures are planning illustrations based on the observed effect, not the original design assumptions for this trial. They report participants per arm, not total events. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is the stated fraction of the observed effect. The original sample-size justification and original design assumptions are not reported in the registry record.

The 80% power column gives the illustrated number of participants per arm for a design with an 80% chance of detecting the specified effect under the stated assumptions, if that effect and the assumptions are correct. The 90% power column gives the corresponding planning number for a 90% chance under those assumptions. These are prospective planning quantities, not evidence about how likely the completed trial was to detect an effect. This is not observed power.

The rows describe planning for 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. For the listed scenarios, the participants-per-arm figures are 43 and 57 for the full observed effect, 84 and 112 when planning for 75% of the observed effect, and 205 and 274 when planning for 50% of the observed effect, for 80% and 90% power respectively. Smaller effects need more participants because a weaker contrast is harder to distinguish from sampling variation under the same assumptions.

The illustrations assume equal group allocation even though the enrolled groups in this trial were not equal in size. They use the observed effect as their starting point, which is uncertain in a small trial. They should therefore be read as conditional planning examples, not recommendations or a reconstruction of the study’s original design.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.350; treatment proportion p₁ = 0.100; average p̄ = 0.225.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.5906 = 1.1575.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.5635 = 0.4742.
4. n = (1.1575 + 0.4742)² / (-0.2500)² = 42.6, rounded up to 43 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.35                          # control proportion
p1 <- 0.1                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(5525078)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 43 (80% power), 57 (90% power)
 75% of observed effect: n per arm = 84 (80% power), 112 (90% power)
 50% of observed effect: n per arm = 205 (80% power), 274 (90% power)
power.prop.test: 42.6 
Simulated power at n = 43 per arm: 0.829 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures and no secondary outcome results. It lists zero analyses. The primary outcome is the Week 4 count of participants meeting the biochemically confirmed abstinence definition, and the registry posts an unadjusted comparison for that outcome. The record does not report a statistical analysis plan, a hierarchy of outcomes, or a method for controlling multiplicity. It is therefore not possible to determine from the registry entry whether the primary outcome was the sole confirmatory endpoint or how multiple comparisons, if any, were intended to be handled.

Multiplicity matters when several outcomes or comparisons are tested: considering more tests can increase the chance of at least one apparently unusual result under a null model. This is general statistical context, not a claim that a particular multiplicity problem occurred in this trial. Since no secondary results are posted and the analysis count is zero, the record does not establish what analyses were conducted beyond the posted comparison.

The registry record does not report how missing Week 4 outcome data were treated, whether all randomized participants were included in the reported counts, or what analysis population was used. It also does not report whether participants were analyzed according to their randomized assignment, whether any per-protocol population was defined, or how deviations from assigned treatment were handled. These are important distinctions: the number randomized and the number contributing to a particular analysis can differ if data are missing or exclusions are made.

The record does not describe imputation, sensitivity analyses for missing data, or the handling of withdrawals. It also does not report interim analyses or any adjustment related to repeated looks at accumulating data. These details are not reported in the registry record. Without them, the posted counts and comparison can be described, but the robustness of the analysis to missingness, population choices, or other analytic decisions cannot be assessed from this record alone.

14. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: suicidal thoughts (10.0%).

The registry reports serious adverse events for 0 participants among 20 in the Switch Group and 1 participant among 10 in the Meds Group. Deaths are reported as 0 in each group. The record lists “Suicidal Thoughts” among the top serious-event terms, with 10.0%. It does not provide further detail about timing, duration, severity beyond the serious-event classification, or the relationship of this term to treatment assignment.

Other adverse events are reported for 8 participants among 20 in the Switch Group and 10 participants among 10 in the Meds Group. The registry does not provide definitions or a detailed breakdown of these other events in the stated details. These counts should be kept distinct from the serious adverse-event counts; the categories are reported separately.

General statistical context: adverse-event counts describe events recorded in the enrolled groups during the study, not necessarily events caused by the assigned approach. With small groups, these figures offer limited precision for comparing safety outcomes. The registry record does not report attribution assessments, exposure-adjusted analyses, or additional safety analysis methods. The figures should therefore be read as descriptive reporting, not as a causal comparison.

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

The posted data show that 7 participants in the Switch Group and 1 participant in the Meds Group met the Week 4 primary abstinence endpoint. The registry comparison reports a risk difference of -0.25 for the Meds Group relative to the Switch Group, with an interval that includes zero and an unadjusted p-value of 0.144. Together, these results describe a difference in the observed counts but also substantial uncertainty about the underlying contrast.

The finding does not establish that switching to e-cigarettes causes higher abstinence than trying to quit with combination nicotine replacement therapy. Nor does it establish that the approaches are equivalent. The registry record does not report an equivalence or non-inferiority design. The small sample and broad reported interval leave considerable uncertainty, and details about missing data and the analysis population are not reported.

The endpoint is cigarette abstinence at Week 4, defined by self-report plus expired carbon monoxide < 6 ppm. It does not answer whether participants remained abstinent later, whether they stopped using all tobacco or nicotine products, or whether their health outcomes changed. The record describes the enrolled population as smokers who had failed to quit using FDA-approved pharmacotherapy within the past year. Generalizing beyond that population requires evidence not established by this trial record.

The results also do not resolve the broader question of whether e-cigarettes reduce harmful health outcomes. The endpoint is an abstinence measure, not a cancer outcome or a comprehensive measure of harm. The registry summary gives a rationale for studying switching, but the posted primary outcome cannot establish effects on long-term health. The appropriate conclusion is limited to the observed Week 4 counts and their uncertain statistical comparison in this randomized sample.

16. Why This Trial Matters Statistically

This trial is statistically informative as an example of a small randomized comparison with an active comparator. Rather than comparing the Switch Group with no intervention, it contrasts a 5-week supply of e-cigarettes with a 5-week supply of combination nicotine replacement therapy. The result therefore concerns the observed comparison between two assigned approaches in the population described by the registry, not an intervention-versus-no-treatment contrast.

The primary endpoint is a binary outcome measured at a specified follow-up point. The result can be presented as direct participant counts, alongside a risk-difference estimate and its interval. That combination illustrates why an estimate’s direction is not enough: the interval includes zero, so the point estimate should be read with the uncertainty around it. The unadjusted p-value of 0.144 also illustrates why a single threshold should not replace attention to the estimated contrast and its precision.

The enrollment of 30 and the unequal group sizes make the fragility of small-sample comparisons visible. Sparse outcome counts can yield substantial uncertainty, and the estimated effect observed in a small study may not be a stable basis for planning or generalization. The planning illustrations based on the observed effect show how required participants per arm increase when planning to detect smaller effects, but those illustrations do not reconstruct the trial’s original design.

The registry record also highlights reporting questions that affect statistical interpretation: the analysis population, missing-data handling, multiplicity plan, and detailed analysis methods are not reported. Describing these omissions is part of interpreting evidence responsibly. The result is useful as a record of what was observed in this trial, while its limitations constrain the strength and scope of conclusions that can be drawn.

17. 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 enrolled sample was 30, divided between 20 participants in the Switch Group and 10 in the Meds Group. The small groups limit the precision of the comparison, as reflected in the reported interval extending across zero. The unadjusted p-value is 0.144, and the registry record does not provide a detailed analysis plan with which to assess the intended inferential framework.

The trial is listed as unmasked. The record does not explain whether outcome assessment was masked or how the self-reported component of the primary endpoint was collected. It also does not report the method used to generate the randomization sequence or whether allocation was concealed. These details are not reported in the registry record.

The primary outcome covers Week 4 only and is specific to cigarette abstinence, with a self-report and expired-carbon-monoxide definition. Long-term abstinence, use of other tobacco or nicotine products, and health outcomes are not captured by this primary endpoint. The registry lists two outcome measures but posts no secondary results. It also lists zero analyses.

The record does not report the analysis population, the treatment of missing outcomes, withdrawals, adherence, or deviations from assigned approaches. It does not report a sample-size justification, original design assumptions, interim analyses, or a detailed statistical plan. These omissions prevent assessment of whether the posted comparison reflects all randomized participants and whether the analysis followed prespecified procedures. The safety information is also limited to the reported counts and term, without further detail on event timing or attribution.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Quit or Switch: E-cigarette Study — NCT05525078.
• Registry record last updated 2024-04-26; status last verified 2023-11.
• Results first posted 2024-04-26.
• 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.

21. Record Summary

NCT05525078 is a completed randomized, parallel-group trial sponsored by the Medical University of South Carolina. It enrolled 30 current smokers who had failed to quit with FDA-approved pharmacotherapy within the past year. Participants were assigned to the Switch Group, which received a 5-week supply of e-cigarettes, or the Meds Group, which received combination nicotine replacement therapy.

The primary endpoint was Week 4 self-reported point-prevalence cigarette abstinence with expired carbon monoxide < 6 ppm. The posted counts were 7 of 20 in the Switch Group and 1 of 10 in the Meds Group. The registry reports a risk difference of -0.25, an interval from -0.530 to 0.030, and an unadjusted p-value of 0.144.

The record lists two outcome measures, no secondary results, and zero analyses. The original sample-size justification, detailed analysis plan, and missing-data procedures are not reported in the registry record. The result describes the observed Week 4 comparison, with substantial uncertainty and limited scope.