Middle School Cluster Randomized Controlled Trial (RCT) to Evaluate E-Cigarette Prevention Program: CATCH My Breath: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Middle School Cluster Randomized Controlled Trial (RCT) to Evaluate E-Cigarette Prevention Program: CATCH My Breath (NCT04843501), a randomized na study. The primary outcome is Number of Students Who Currently Use E-cigarettes.

2. Clinical Question

3. Trial Design

This was a randomized, parallel-group cluster trial with no masking reported. Schools, rather than individual students, were to be assigned to the CATCH My Breath program or the Texas Education Agency required tobacco prevention program. The registry summary describes 10 schools assigned to each arm and 70 students per school, with 700 students per arm and 1400 total planned. The record separately reports enrollment of 2059; it does not explain the difference between the planned totals and the recorded enrollment.

The two programs were described as being administered over 3 years. The CATCH My Breath intervention used four lessons of approximately 20-30 minutes each, with a range of educational strategies. The comparator was a state-supported tobacco prevention program that included online lessons and support materials. Both are behavioral interventions, so the comparison concerns alternative prevention approaches rather than a program versus no prevention.

The registry record gives a start date of 2020-12-13, a primary completion date of 2024-12-20, and a completed status. It identifies e-cigarette use as the condition. The record does not report further details about the sequence or concealment of school assignment, adherence, implementation fidelity, or the timing of outcome measurement after baseline. Those details should not be inferred from the randomized, cluster, or parallel labels.

Cluster assignment matters because students within a school may share experiences and conditions. Their outcomes therefore may be more alike than outcomes from students in different schools. The registry notes that a simple individual-level re-analysis would be misleading and that only the sponsor's own analysis is shown. No numerical comparative analysis is reported in the record summarized for this result.

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: Of the 2059 participants enrolled in the study, 5 participants withdrew before starting the study. Eligible individuals could enroll at the start of any semester. Participation was not required to be continuous, and participant numbers varied by semester.

Fall 2021

Spring 2022

Fall 2022

Spring 2023

Analysis population for the primary outcome, as defined in the registry: Participants who reported ever using e-cigarettes at baseline were included in the analysis for this outcome measure.

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 Number of Students Who Currently Use E-cigarettes, measured over baseline.

The primary outcome is the number of students who currently use e-cigarettes, measured at baseline. Current use is defined in the registry record as e-cigarette use in the last 30 days. The outcome is a count of participants with the event, and the stated analysis population consists of participants who reported ever using e-cigarettes at baseline.

A count of current users can describe the observed burden of recent use in a defined group. Restricting the described population to participants who had ever used e-cigarettes means the measure concerns current use among those with prior use, rather than current use among every enrolled student. This distinction matters when interpreting what the endpoint represents.

The trial's stated aim is to evaluate delaying the onset of e-cigarette use, but the listed primary outcome is at baseline. A baseline measure describes status before the intervention period can establish a later between-program difference. To assess a delay in onset, results at a later time and a comparison that reflects the randomized groups would be needed. Such a treatment-effect result is not reported in the registry record. The listed endpoint therefore should not be read as a reported estimate of the curriculum's effect on subsequent initiation.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Why does the cluster design matter?

In an individually randomized trial, each participant is assigned independently. In this study, schools were assigned to programs, so students within a school share the same assigned condition. They may also share school-level experiences, policies, and implementation conditions. As a general statistical matter, this dependence means that the information contributed by a group of students is not equivalent to the same number of fully independent observations. An analysis that ignores clustering can misstate uncertainty and make confidence intervals or significance tests unreliable.

The registry explicitly cautions that a simple individual-level re-analysis would be misleading and says that only the sponsor's own analysis is shown. A suitable analysis would need to respect school-level assignment and the resulting grouping of students. The record does not report which model or variance method the sponsor used, how school-level variation was handled, or whether the analysis adjusted for baseline characteristics. Those methodological details are not reported in the registry record.

What does the outcome type tell the reader?

The outcome is a count of participants with an event: students who meet the definition of current e-cigarette use. The event definition is use in the last 30 days, and the described analysis population includes participants who reported ever using e-cigarettes at baseline. As a general statistical distinction, a count of people with an event can be analyzed as a binary outcome at the participant level or summarized as a count for a group. The choice of method depends on the analysis plan and design; the registry record does not identify a model for this outcome.

The record reports no dispersion value for the outcome. In general, over-dispersion means that observed variability is greater than a model assumes. If a count model assumes too little variability, its uncertainty estimates can be too narrow. Whether over-dispersion was assessed or relevant in the sponsor's analysis is not reported in the registry record. No model assumptions should be attributed to the trial without that information.

What would an effect estimate and confidence interval convey?

In general, an effect estimate describes the observed contrast between assigned groups on a defined outcome. A confidence interval communicates the range of values reasonably compatible with the data and the analysis assumptions. Its width reflects precision: a wider interval indicates greater uncertainty about the size of the contrast. A confidence interval does not correct a poorly specified analysis, account for clustering by itself, or establish that a result is clinically important.

No treatment-effect estimate or confidence interval for the primary outcome is reported in the registry record details summarized for this interpretation. Thus, there is no numerical contrast to describe and no precision interval to assess. The count of enrolled participants cannot substitute for either quantity. Nor can a p-value, if one were available, describe the magnitude or precision of an effect on its own.

What is the role of the planning illustration?

The stated planning assumptions describe an illustration based on an observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. The effect to detect is defined as a fraction of the observed effect. For non-time-to-event outcomes, the intended planning quantity is participants per arm for a chosen power level; time-to-event planning uses total events. These are planning conventions, not observed trial outcomes and not evidence that the study had a particular probability of detecting an effect.

The record does not include numerical planning outputs or the underlying observed effect in the registry record. It also states that the illustration is not the trial's own design justification. Therefore, such planning assumptions should not be treated as the original sample-size rationale, proof of adequate enrollment, or observed power. The registry record does not report the protocol's sample-size justification.

Why should an unadjusted recalculation be treated cautiously?

A recalculation from posted summary statistics, when available, is generally an unadjusted reconstruction rather than the sponsor's full analysis. It may not reproduce a cluster-aware model, covariate adjustment, or other prespecified features. In a cluster-randomized trial, a calculation that treats students as independent can be especially misleading. The record's caution is to rely on the sponsor's own analysis rather than a simple individual-level re-analysis. No recalculated treatment effect is available in the registry record for this interpretation, so no comparison between a recalculation and sponsor analysis can be made.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("CATCH My Breath (CMB) Program for E-cigarette Prev", "Texas Education Agency Required Tobacco Prevention")
n      <- c(37, 17)
events <- c(9, 4)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  CATCH My Breath (CMB) Program for E-cigarette Prev  37  9  24.3  11.8  41.2  13.4  40.1  13.4  40.2
ARM  Texas Education Agency Required Tobacco Prevention  17  4  23.5  6.8  49.9  9.6  47.3  9.7  47.6

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists six outcome measures and zero analyses. It does not report which outcomes were designated as primary beyond the listed primary outcome, how tests across outcomes were managed, or whether any adjustment for multiple comparisons was planned or used. When several outcomes or repeated tests are considered, the chance of at least one apparently notable result can increase. As a general statistical matter, a prespecified testing strategy helps readers distinguish confirmatory questions from exploratory ones. The registry record does not provide enough detail to assess such a strategy.

Missing-data handling is not reported in the registry record. The record does not state how missing responses, loss to follow-up, or incomplete school participation were addressed in an analysis. It also does not provide the number of participants with outcome data for the primary measure. Without those details, the extent and potential influence of missingness cannot be evaluated.

The primary outcome description identifies participants who reported ever using e-cigarettes at baseline as the analysis population. The record does not describe other analysis populations or say whether the analysis followed assignment regardless of participation or adherence. It would therefore be inappropriate to label the reported population as intention-to-treat or per-protocol. Since the measure is specified at baseline, the record also does not establish which participants contributed to a later treatment comparison.

12. 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 and other adverse events separately for the two program groups. For CATCH My Breath, the record gives 1332 participants at risk for each category, with 0 serious adverse events, 0 other adverse events, and 0 deaths. For the Texas Education Agency required tobacco prevention program, it gives 727 participants at risk for each category, with 0 serious adverse events, 0 other adverse events, and 0 deaths.

These are the event counts recorded in the registry. A count of 0 means no events were reported in the listed category; it does not establish that no unreported event occurred or that the programs have no possible risks. The record does not describe the event-collection procedures, observation period, or criteria used to classify events. The at-risk counts also should not be assumed to be the denominator for every outcome unless the record specifies that relationship. These figures describe recorded safety reporting and do not establish a treatment effect.

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

The registry record describes a randomized school-level comparison of a CATCH My Breath e-cigarette prevention curriculum with the Texas Education Agency required tobacco prevention program. It gives the trial's aim, the planned school and student allocation, enrollment, intervention descriptions, and a baseline definition of current e-cigarette use. It also records adverse-event counts for the two program groups.

What the record does not provide is a numerical comparison of later e-cigarette use between the assigned programs. The stated primary outcome is measured at baseline and is restricted to participants who had ever used e-cigarettes at baseline. The record does not report a treatment-effect estimate, uncertainty interval, or statistical test for a later outcome. Therefore, these registry entries do not establish whether the program groups differed in subsequent onset or use.

That absence should not be misread as a finding of no difference. It is a limit on what can be concluded from the information reported. A result might be imprecise, favorable, unfavorable, or compatible with little difference; without the analysis estimate and its uncertainty, those possibilities cannot be distinguished. The enrollment count and the planned sample sizes do not reveal the direction or precision of an effect.

The cluster design is also central to interpretation. Schools were randomized, so valid statistical inference needs to reflect the grouping of students by school. The record cautions against a simple individual-level re-analysis. Any interpretation of a treatment contrast should therefore use the sponsor's cluster-aware analysis, whose numerical result and technical details are not reported in the registry record. The baseline count and safety reports remain descriptions, not substitutes for that comparison.

14. Why This Trial Matters Statistically

This trial is statistically notable because randomization occurred at the school level while the primary outcome is described for students. That structure requires the analysis to respect the difference between the unit assigned to a program and the individuals whose outcomes are measured. If clustering is ignored, uncertainty can be misrepresented. The registry itself highlights this issue by warning that a simple individual-level re-analysis would be misleading.

The comparison also uses an active prevention program as the comparator. The statistical question is therefore about the contrast between two prevention approaches as assigned in the trial, rather than a contrast with no prevention. That framing matters when interpreting any future reported effect: it would describe the relative outcome under these program conditions, not the effect of prevention versus its absence.

There is also an important alignment issue between the stated aim and the listed primary outcome. The aim concerns delaying onset, whereas the primary outcome is a baseline count of current users among participants who had ever used e-cigarettes at baseline. Baseline characterization and subsequent onset are distinct questions. Clear reporting of follow-up outcomes and the analysis population would be needed to judge the stated prevention question statistically.

Finally, enrollment alone does not communicate precision. Statistical interpretation depends on the observed contrast, its uncertainty, and methods appropriate to the cluster assignment. Those comparative results are not reported in the registry entries. The trial record is useful for understanding its design and measurement, while its lack of a reported analysis prevents a quantitative assessment of the primary treatment question.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The primary outcome is specified at baseline, while the trial's stated purpose is to evaluate delaying onset. The record does not report a later primary-outcome comparison, so the listed outcome does not itself answer the stated question about delay. The baseline analysis population is also restricted to participants who reported ever using e-cigarettes at baseline; the record does not explain how this population relates to any later outcome analysis.

The planned totals in the registry summary differ from the reported enrollment of 2059, and the record does not explain the relationship. It does not report the number of schools or participants actually analyzed, the number with outcome data, or the flow of participants through follow-up. The planned allocation figures should not be treated as observed analysis denominators.

Methods needed to assess the treatment comparison are not reported in the registry record. These include the sponsor's statistical model, its handling of school clustering, missing-data procedures, multiplicity strategy, and analysis populations beyond the baseline outcome description. The registry reports zero analyses. It also gives no numerical treatment-effect estimate, confidence interval, or test result. The record does not report implementation fidelity, adherence, or detailed outcome ascertainment beyond the baseline definition of current use.

Safety information is limited to the listed event counts and at-risk figures. The record does not describe the observation period or event-collection methods. These omissions limit interpretation of both the treatment question and the safety reports; they should not be filled by assumptions about the protocol.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Middle School Cluster Randomized Controlled Trial (RCT) to Evaluate E-Cigarette Prevention Program: CATCH My Breath — NCT04843501.
• Registry record last updated 2026-02-06; status last verified 2026-01.
• Results first posted 2026-02-06.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The completed, randomized, parallel-group trial compared the CATCH My Breath program with the Texas Education Agency required tobacco prevention program. Schools were the units of assignment, and the registry reports enrollment of 2059. The summary describes a plan for 10 schools per arm and 70 students per school, with programs administered over 3 years.

The listed primary outcome is the number of participants currently using e-cigarettes at baseline, defined as use in the last 30 days, among participants who had ever used e-cigarettes at baseline. The registry record reports zero analyses and provides no comparative treatment-effect estimate in the registry record. It cautions that a simple individual-level re-analysis would be misleading because of the cluster design. Recorded adverse-event and death counts are 0 in both groups. Missing-data methods, multiplicity handling, and further analysis details are not reported in the registry record.