E-Cigarettes and Financial Incentives to Promote Tobacco Harm Reduction Among Adults Accessing Shelter Services: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for E-Cigarettes and Financial Incentives to Promote Tobacco Harm Reduction Among Adults Accessing Shelter Services (NCT03743532), a randomized na study. The primary outcome is Combustible Cigarette Cessation.

2. Clinical Question

The trial record describes this as a randomized controlled evaluation of feasibility and potential efficacy. Its primary comparison therefore concerns whether adding financial incentives to an e-cigarette switching approach was associated with a different short-term cessation count than switching alone. It does not directly isolate the effect of e-cigarettes against usual care or against no intervention, because both groups were offered e-cigarettes and advised to switch.

3. Trial Design

The registry describes a randomized, parallel-group trial with no masking. Enrollment was 60, and the record marks the study as completed. The recorded start date is 2022-09-14, and primary completion is recorded as 2023-03-01. The sponsor was the University of Oklahoma. The phase is listed as NA.

The two groups were e-cigarette switching (EC) and e-cigarette switching plus financial incentives (EC+FI). Participants in both groups received an e-cigarette device and nicotine pods and were advised to switch completely from combustible cigarettes to e-cigarettes. The EC+FI group also earned escalating financial incentives tied to self-reported and carbon-monoxide-verified combustible cigarette abstinence. Participants in the EC group did not earn abstinence incentives. The EC description says participants were yoked with a participant in the EC+FI group; the registry description does not fully explain the implications of this arrangement.

The primary outcome was assessed 4 weeks post-switch date. It counted participants meeting a previous-7-day abstinence definition based on self-report and carbon monoxide verification at or below 6 ppm. Missing cigarette-smoking status was classified as smoking. The posted primary results give a group size of 30 for each arm, with 1 cessation event in EC and 4 in EC+FI.

Secondary outcomes cover complete-case cessation, change in expired carbon monoxide, days of combustible cigarette smoking, and days of e-cigarette use. The posted secondary results include complete-case cessation and results for carbon monoxide change and days of combustible cigarette smoking. The registry record does not report the trial’s original sample-size justification, detailed randomization procedures, or a masking procedure; masking is listed as none.

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

Analysis population for the primary outcome, as defined in the registry: Participants with missing cigarette smoking status were considered smoking.

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 Combustible Cigarette Cessation, measured over 4 weeks post-switch date.

The primary endpoint is combustible cigarette cessation, measured as the count of participants who met the trial’s abstinence definition at 4 weeks post-switch date. To qualify, a participant had to report no combustible cigarette smoking during the previous 7 days and have carbon monoxide verification at or below 6 ppm. The registry specifies that missing cigarette-smoking status counted as smoking.

This endpoint combines a participant’s report with an objective verification measure. The self-report describes recent smoking behavior, while the carbon monoxide criterion is intended to help verify abstinence from combustible cigarettes. The endpoint is binary at the participant level: each participant either meets the stated definition or does not. The posted outcome is therefore a count, rather than a mean level of smoking or a time-to-cessation measure.

Using a fixed assessment point gives the groups a common time frame for comparison, but the result speaks specifically to status at that assessment. It does not, by itself, describe abstinence at later times, continuous abstinence throughout the study, or outcomes beyond the registry’s stated timeframe. The posted primary counts were 1 participant in the EC group and 4 participants in the EC+FI group. Because the outcome is short-term and uses a defined verification threshold, interpretation should remain tied to that definition and assessment point.

7. Results Posted in the Registry

• E-cigarette Switching (EC) + Financial Incentives: 13.3% (4/30) versus 3.3% (1/30) on control; risk difference 10.0 percentage points (95% CI -3.8 to 23.8), risk ratio 4.00 (0.47–33.73); unadjusted two-proportion z-test p = 0.161.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Combustible Cigarette Cessation (Complete Case Analysis)

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • E-cigarette Switching (EC) + Financial Incentives: 26.7% (4/15) versus 6.2% (1/16) on control; risk difference 20.4 percentage points (95% CI -4.9 to 45.7), risk ratio 4.27 (0.54–33.98); unadjusted two-proportion z-test p = 0.122.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between E-cigarette Switching (EC) + Financial Incentives and the control. The interval gives the range of effects that remain compatible with the data.

Expired Carbon Monoxide (CO), Parts Per Million (Ppm), Change From Baseline

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • E-cigarette Switching (EC) + Financial Incentives: mean -8.73 versus 0.31 on control; difference -9.04 (95% CI -16.15 to -1.93), standardized effect d = -0.88; z-test p = 0.013.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for E-cigarette Switching (EC) + Financial Incentives than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Days of Combustible Cigarette Smoking, Past 7 Days

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • E-cigarette Switching (EC) + Financial Incentives: mean 2.20 versus 4.25 on control; difference -2.05 (95% CI -3.94 to -0.16), standardized effect d = -0.76; z-test p = 0.034.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for E-cigarette Switching (EC) + Financial Incentives than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The secondary outcomes broaden the picture beyond the primary binary cessation definition. They include a complete-case version of cessation, change in expired carbon monoxide, days of combustible cigarette smoking, and days of e-cigarette use. The posted results cover complete-case cessation and provide group summaries for carbon monoxide change and days of combustible cigarette smoking. These measures capture different aspects of recent behavior and carbon monoxide exposure; they should not be treated as interchangeable with the primary endpoint.

Across the posted secondary comparisons, the estimates for carbon monoxide change and days of combustible cigarette smoking favor EC+FI in the direction recorded, while the complete-case cessation estimate also favors EC+FI. The complete-case comparison has a confidence interval that includes no difference. The continuous-outcome comparisons have intervals that do not include zero, but they remain secondary, unadjusted analyses. The registry lists days of e-cigarette use as an outcome, but no result for that measure is included among the posted secondary results described in this record.

The secondary outcomes may help contextualize the primary result because they measure related behaviors and exposure at the same 4-week post-switch timeframe. However, a reduction in a mean measure or a difference in reported days does not establish that an individual met the primary abstinence definition. Conversely, the primary binary outcome does not capture all variation in smoking frequency or carbon monoxide change.

Unadjusted secondary results carry less weight because the record includes multiple outcomes and does not report a multiplicity strategy or detailed analysis plan. When many comparisons are examined, some may look notable by chance. The registry also lists no reported analyses for the secondary outcomes. These findings are best regarded as exploratory context for the primary comparison rather than independent confirmation of it.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Combustible Cigarette Cessation (Complete Case Analysis)
• Combustible Cigarette Cessation (Complete Case Analysis)
• Expired Carbon Monoxide (CO), Parts Per Million (Ppm), Change From Baseline
• Expired Carbon Monoxide (CO), Parts Per Million (Ppm), Change From Baseline
• Days of Combustible Cigarette Smoking, Past 7 Days
• Days of Combustible Cigarette Smoking, Past 7 Days
• Days of E-cigarette Use, Past 7 Days
• Days of E-cigarette Use, Past 7 Days

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is binary: participants either met the abstinence definition at the assessment or did not. For a binary outcome, a group’s event proportion is the count meeting the definition relative to the group size. The reported values are 1 of 30 in EC and 4 of 30 in EC+FI. The comparison is framed as EC+FI versus EC, so a positive risk difference indicates a higher observed event proportion in the incentive group.

What does the risk difference express?

The risk difference is the subtraction of the two group event proportions, expressed on an absolute scale. The posted estimate is 0.1. This conveys the estimated separation between the groups’ event proportions, rather than a relative change. Absolute differences are often useful when considering the scale of an outcome, but they remain estimates subject to sampling variation. The interval from -0.038 to 0.238 indicates that the estimate is not precise enough to rule out no difference or a difference in the opposite direction.

How should relative measures be read?

The risk ratio compares the event proportions as a ratio, while the odds ratio compares their odds. The record reports a risk ratio of 4.0 and an odds ratio of 4.462. Each is accompanied by a broad interval that includes values on either side of no relative difference. When outcome events are sparse, relative estimates can be particularly unstable: a small change in the event count can materially change the ratio. For that reason, relative estimates should be read alongside the underlying counts and the absolute risk difference, rather than as standalone evidence.

What does the p-value tell the reader?

The unadjusted p-value for the primary comparison is 0.161. In general, a p-value measures how unusual results at least as incompatible with a specified null model would be if that model and the test assumptions held. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of an effect. A p-value above a conventional threshold does not demonstrate equivalence or absence of an effect. The registry record does not report a multiplicity adjustment for this comparison, so the posted value is described as unadjusted.

Why does uncertainty matter with sparse events?

Confidence intervals express uncertainty around an estimated effect under the statistical model used to calculate them. With a small number of events, the observed group proportions can be sensitive to the outcomes of a few participants. This can produce broad intervals even when the point estimate appears substantial. The primary interval crosses zero on the risk-difference scale, which means the posted data do not sharply distinguish the observed estimate from no difference.

What do the secondary analyses add?

The complete-case cessation analysis excludes participants whose relevant outcome information was not included in that analysis. It reports 1 event among 16 participants in EC and 4 among 15 in EC+FI, with a risk difference of 0.204 and an interval from -0.049 to 0.457. This is not the same analysis population as the primary outcome, which treats missing smoking status as smoking. The complete-case result is therefore a sensitivity-oriented view of cessation among participants included in that analysis, not a replacement for the primary result.

The secondary continuous outcomes compare group means. For expired carbon monoxide change from baseline, the reported mean difference is -9.04 ppm, with a confidence interval from -16.15 to -1.926. For days of combustible cigarette smoking during the past 7 days, the reported mean difference is -2.05 days, with an interval from -3.94 to -0.160. In general, a mean difference is the contrast between group averages; a negative estimate means the EC+FI group’s posted mean change or number of days was lower than the EC group’s, using the recorded direction of comparison. These outcomes and their measures are distinct from the primary binary cessation definition.

The registry lists no reported analyses for these secondary results. The posted p-values are unadjusted, and multiple outcomes can create more opportunities for apparently notable results by chance. Without a reported analysis plan or multiplicity strategy, secondary findings merit more caution than a single prespecified primary comparison. The registry record does not report the methods used for any adjusted analyses or interim analyses.

For continuous outcomes, standard deviations describe variability among observations within each group. In general, a standard deviation is not the same as the standard error of the mean: the former describes spread among participants, while the latter describes uncertainty in an estimated mean. The posted continuous-outcome comparisons include group means, standard deviations, and confidence intervals for mean differences. These summaries do not show the distribution of individual participant values, and they do not establish whether model assumptions were checked.

11. Confidence Intervals and Precision

The primary risk-difference estimate is 0.1, with a confidence interval from -0.038 to 0.238. A confidence interval gives a range of effect estimates reasonably compatible with the data and the method’s assumptions. It does not mean that there is a 95% probability that the true effect lies within this particular interval. The interval crosses zero, the value corresponding to no risk difference, and stretches from a possible difference favoring EC to a possible difference favoring EC+FI.

The event counts were 1 in EC and 4 in EC+FI. With few observed events, the estimate is vulnerable to substantial sampling uncertainty. This is reflected in the interval’s width. The point estimate alone would give an incomplete impression: it favors EC+FI, but the interval leaves considerable uncertainty about the size and direction of the underlying difference.

The relative estimates are also imprecise. The risk ratio of 4.0 has an interval from 0.474 to 33.73, and the odds ratio of 4.462 has an interval from 0.468 to 42.51. Both intervals include the value corresponding to no relative difference and span a wide range. The intervals reinforce that these data do not pin down a stable relative effect.

Precision is different from whether a result crosses a significance threshold. A wide interval can be compatible with several materially different explanations, whether or not a p-value falls on one side of a chosen cutoff. The registry’s primary comparison should therefore be read as an uncertain estimate, not as proof of benefit, no effect, or equivalence.

12. 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 planning illustrations give participants per arm for the binary outcomes and continuous outcomes. They are not totals across both groups. For the primary cessation comparison, planning for 100% of the observed effect gives 119 participants per arm for 80% power and 159 participants per arm for 90% power. Planning for 75% of the observed effect gives 183 participants per arm for 80% power and 244 participants per arm for 90% power. Planning for 50% of the observed effect gives 344 participants per arm for 80% power and 460 participants per arm for 90% power.

The illustrations use 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. In plain language, 80% power describes a design that would have an 80% chance of detecting an effect of the specified size under the planning assumptions if that effect were present. The 90% column describes the corresponding chance at the higher power target. Higher power generally requires more participants for the same planned effect.

Smaller effects require more participants because they are harder to distinguish from random variation. That pattern is reflected in the increasing per-arm planning figures as the assumed effect moves from 100% to 75% to 50% of the observed effect. These are planning illustrations based on the observed effect, not the trial’s original design assumptions. The original sample-size justification is not reported in the registry record. This is not observed power.

13. 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 = 0.033; treatment proportion p₁ = 0.133; average p̄ = 0.083.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.3909 = 0.7661.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.3844 = 0.3235.
4. n = (0.7661 + 0.3235)² / (0.1000)² = 118.7, rounded up to 119 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 <- 0.0333333333333333                          # control proportion
p1 <- 0.133333333333333                          # 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(3743532)
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 = 119 (80% power), 159 (90% power)
 75% of observed effect: n per arm = 183 (80% power), 244 (90% power)
 50% of observed effect: n per arm = 344 (80% power), 460 (90% power)
power.prop.test: 118.7 
Simulated power at n = 119 per arm: 0.838 (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.

14. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary endpoint and multiple secondary outcomes, but it does not report a statistical analysis plan describing how the primary comparison was selected or how multiple comparisons were handled. The reported p-values are unadjusted. No multiplicity correction is reported, so the secondary p-values should not be read as if they accounted for the number of outcomes examined. The record also does not report interim analyses or stopping rules.

The primary outcome definition handles missing cigarette-smoking status by classifying it as smoking. This rule is explicit and affects the interpretation: the primary result is not limited to participants with a recorded smoking status. A separate complete-case cessation outcome is also posted. That analysis includes 16 participants in EC and 15 in EC+FI and uses a different analysis population from the primary endpoint. The record does not report why outcome information was unavailable or describe additional missing-data methods, such as imputation or sensitivity analyses under alternative assumptions.

For the continuous secondary outcomes, the posted group summaries use 16 participants in EC and 15 in EC+FI. The registry record does not explain missingness for those measures or report whether the analyses were adjusted for baseline values or other variables. The carbon monoxide outcome is described as change from baseline, but no further model details are reported.

The randomized allocation and parallel-group structure support a comparison between assigned approaches, but the record does not report allocation concealment procedures or a detailed account of how randomization was implemented. Masking is listed as none. The record also does not report a full prespecified statistical plan, the rationale for the enrolled sample size, or details of any interim monitoring. These omissions limit assessment of how the analysis decisions were made and how robust the results are to alternative analytic choices.

15. 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 reports serious adverse events in 0 of 30 participants at risk in the EC group and 0 of 30 participants at risk in the EC+FI group. It also reports other adverse events in 0 of 30 participants at risk in each group, and deaths in 0 participants in each group. No serious adverse-event terms are listed.

These figures mean that no events in those reported categories were recorded during the trial for the groups shown. They do not establish that adverse events cannot occur, or that the approaches have no safety risks. The event counts are observed within this trial’s recorded participants and follow-up; the registry record does not provide further detail about adverse-event definitions, collection procedures, or the duration of safety surveillance. The absence of reported events should therefore be read as a description of the registry’s safety results, not as proof of safety in other populations or over longer periods.

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

The results describe a short-term randomized comparison of two approaches that both included e-cigarettes and advice to switch from combustible cigarettes. The primary outcome was defined using self-reported abstinence and carbon monoxide verification at 4 weeks post-switch date, with missing smoking status counted as smoking. The observed cessation counts were 1 in EC and 4 in EC+FI, and the estimated risk difference was 0.1.

The confidence interval from -0.038 to 0.238 shows that the estimate is uncertain. It includes no difference and a range of possible effects in either direction. The data therefore do not precisely establish how much the added financial-incentive approach changed cessation compared with e-cigarette switching alone. The p-value of 0.161 likewise does not prove that the approaches are the same or that there is no effect.

The comparison cannot establish the effect of e-cigarettes versus no e-cigarette support, since both groups received e-cigarettes and switching instructions. It also does not establish whether any observed difference persists beyond the stated assessment, whether participants maintained abstinence over a longer period, or what the outcomes would be in a different setting. The registry describes the study as a feasibility and potential-efficacy evaluation, which is consistent with treating the findings as preliminary.

Secondary outcomes provide related behavioral and exposure measures but do not replace the primary endpoint. Their unadjusted status and the absence of a reported multiplicity plan mean that they should be interpreted cautiously. Overall, the posted data offer a small-sample estimate of a short-term comparison, with substantial uncertainty and limits on generalization. They do not support a definitive claim about treatment effects or clinical benefit.

17. Why This Trial Matters Statistically

This trial is statistically useful because its primary endpoint is a clear participant-level binary outcome, and the comparison is randomized between two approaches that share an e-cigarette switching component. The design focuses on the incremental contrast associated with adding financial incentives, rather than asking whether e-cigarettes themselves outperform no intervention. Keeping that contrast clear is essential when interpreting the estimated difference.

The event counts show why effect estimates need to be read with their uncertainty. A point estimate can look large on a relative scale when there are few events, while its confidence interval remains broad. Here, the risk-difference interval crosses zero, and the relative-measure intervals are wide. Reporting the counts, absolute difference, relative measures, and intervals together gives a more complete account than a p-value alone.

The registry also distinguishes a primary missing-data rule from a complete-case secondary analysis. Counting missing smoking status as smoking makes the primary endpoint’s handling explicit, while the complete-case result describes a different analysis population. Recognizing that distinction prevents the two estimates from being mistaken for identical analyses.

Finally, the record illustrates why planning calculations should not be confused with the design of the completed study. The planning figures are illustrations based on observed effects and stated assumptions; the trial’s original sample-size justification is not reported. Such information matters when readers assess whether an early-stage trial was designed to estimate feasibility, detect a particular effect, or answer another question. The registry describes feasibility and potential efficacy, and the estimates should be interpreted in that context.

18. 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 primary comparison has few observed cessation events, making the estimated effect imprecise. The confidence interval includes no difference and a range of possible effects, while the relative estimates also have wide intervals. This limits the strength of conclusions that can be drawn from the point estimate.

The assessment was at 4 weeks post-switch date. The registry record does not provide a longer-term primary outcome in the results described, so the findings do not establish whether any observed smoking behavior persisted. The primary endpoint measures recent abstinence under a specific self-report and carbon monoxide definition; it does not describe every dimension of tobacco use or longer-term outcomes.

Both groups received e-cigarettes and advice to switch, so the trial does not compare e-cigarettes with no intervention. The EC+FI group additionally received escalating incentives, but the EC description notes a yoking arrangement that is not fully explained in the record. The registry descriptions are also incomplete in detail about the intervention procedures.

Secondary analyses are unadjusted, and the record does not report a multiplicity strategy or a full statistical analysis plan. Missing-data information beyond the primary rule and the complete-case analysis is not reported in the registry record. The record also does not report the original sample-size justification, detailed randomization procedures, allocation concealment, or interim analyses. These gaps limit assessment of analytic choices and the extent to which findings may generalize beyond the studied setting.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: E-Cigarettes and Financial Incentives to Promote Tobacco Harm Reduction Among Adults Accessing Shelter Services — NCT03743532.
• Registry record last updated 2025-02-21; status last verified 2025-02.
• Results first posted 2024-06-07.
• 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.

22. Record Summary

NCT03743532 is a completed, randomized, parallel-group trial with no masking, sponsored by the University of Oklahoma. It enrolled 60 adults accessing shelter services and compared e-cigarette switching alone with e-cigarette switching plus financial incentives. Both groups received e-cigarettes and nicotine pods and were advised to switch from combustible cigarettes.

The primary endpoint was combustible cigarette cessation at 4 weeks post-switch date, defined by self-report and carbon monoxide verification at or below 6 ppm; missing smoking status was counted as smoking. The posted counts were 1 in EC and 4 in EC+FI. The estimated risk difference was 0.1, with a confidence interval from -0.038 to 0.238 and an unadjusted p-value of 0.161.

The registry describes the study as a feasibility and potential-efficacy evaluation. The short-term estimate is imprecise, and the record does not report the trial’s original sample-size justification or a full statistical analysis plan.