Smoking Cessation in Hispanic Construction Workers: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Smoking Cessation in Hispanic Construction Workers (NCT02873377), a randomized phase 4 study. The primary outcome is Prolonged Abstinence Rates.

2. Clinical Question

The trial’s stated aim was to develop and evaluate a cessation program for an underserved population of Hispanic male construction workers. The registry describes the work as a pilot cluster-randomized clinical trial intended to test feasibility and potential efficacy. The primary endpoint concerns prolonged abstinence, defined as no smoking, not even a puff, after a two-week grace period following the quit date. It is assessed by follow-up questionnaire and confirmed with a saliva cotinine level of <15 ng/ml.

The central comparison is between the enhanced package, which adds behavioral counseling to nicotine replacement therapy and quitline referral, and the standard-care package of nicotine replacement therapy and quitline referral. The registry descriptions do not establish which individual components account for any difference between groups. Numerical results for the primary comparison are not reported in the registry record, so the size and precision of any observed difference cannot be described.

3. Trial Design

The registry identifies NCT02873377 as a completed, randomized, parallel-group, Phase 4 study sponsored by the University of Miami. It lists enrollment of 134. The study began on 2017-04-13, and its primary completion date is 2018-10-11. Its title is “Smoking Cessation in Hispanic Construction Workers,” and the official title describes a novel worksite intervention for Hispanic construction workers.

The registry describes the study as a pilot cluster-randomized clinical trial. In a cluster-randomized design, groups such as worksites or other naturally organized units, rather than necessarily each participant individually, are assigned to study arms. Participants within the same cluster can have more similar outcomes than participants in different clusters. This dependence matters for statistical analysis because the amount of independent information may be less than an individual-level analysis would suggest. The number and definition of clusters, the allocation procedure, and the handling of clustering in the sponsor’s analysis are not reported in the registry record.

The parallel arms were Enhanced Care and Standard Care. Enhanced Care combined nicotine replacement therapy, behavioral counseling, and a quitline referral. The arm description specifies a single face-to-face counseling session at the construction-site lunch truck. Standard Care included nicotine replacement therapy and a quitline referral; its description specifies a fax referral to the Florida quitline and up to 8 weeks of free nicotine replacement therapy, with up to 6 weeks from the study and 2 weeks from the quitline. The available Enhanced Care description is incomplete, so further details about its delivery are not reported in the registry record.

Masking is listed as none. This means the registry does not describe the study as masked; it does not establish whether outcome assessment or laboratory testing had any separate safeguards. The registry marks the study completed, but completion status alone does not convey whether the planned enrollment, follow-up, or analysis proceeded as intended. Protocol deviations and the analysis population 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.

Period 1: Enrollment

Period Title 2: 3 Months Follow up

Reasons for not completing this period:

Period Title 3: 6 Months Follow up

Reasons for not completing this period:

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 Prolonged Abstinence Rates, measured over 6-month.

The primary endpoint is prolonged abstinence at 6-month follow-up, expressed as a percentage of participants. The registry defines prolonged abstinence as no smoking, not even a puff, after a two-week grace period following the quit date. It says the outcome is assessed by follow-up questionnaire and confirmed using a saliva cotinine level of <15 ng/ml.

This endpoint combines a behavioral definition with biochemical confirmation. The questionnaire captures reported smoking behavior over the stated period, while the cotinine measure is an objective check used to support the abstinence classification. In general, combining self-report with a biological measure can make an endpoint more specific than relying on self-report alone; it does not eliminate every source of measurement error. The registry does not report the timing or procedures for collecting saliva, the handling of missing or discordant questionnaire and cotinine results, or the exact rule used to classify such cases.

A percentage endpoint summarizes how common the defined outcome is in each arm. A comparison between those percentages can describe the observed separation between arms, while an interval estimate can communicate uncertainty around that comparison. However, no arm-specific abstinence percentages, effect estimate, confidence interval, or statistical test are reported in the registry record. The endpoint definition is therefore available, but the posted record does not permit a numerical assessment of the primary outcome.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The study is described as a pilot cluster-randomized trial with parallel arms. The primary endpoint is binary at the participant level: a participant either meets the stated prolonged-abstinence definition or does not. The registry reports the outcome as a percentage of participants. The key analytical challenge is that assignment occurred by cluster, so a participant’s outcome may be related to the outcomes of others in the same cluster.

Why does cluster assignment affect analysis?

General statistical principle: When outcomes within a cluster are correlated, those observations do not contribute as much independent information as the same number of unrelated observations. An analysis that ignores this dependence can produce confidence intervals that are too narrow and tests that are too optimistic. Cluster-aware methods account for the assignment unit and the within-cluster similarity. The registry itself cautions that a simple individual-level re-analysis would be misleading. It does not report the number of clusters, their sizes, an intracluster correlation estimate, or the method used in the sponsor’s analysis. Those details are needed to evaluate the analysis in depth.

Randomization is intended to support a fair comparison by allocating study units to the intervention strategies according to a chance-based process. Here, the registry says the study was randomized and cluster randomized, but it does not describe sequence generation, allocation concealment, stratification, or implementation. Masking is listed as none. Lack of masking can matter for outcomes that rely on participant reports or behavior, although the primary outcome also includes biochemical confirmation. The registry does not give enough detail to determine how outcome assessment was conducted or whether laboratory personnel were masked.

What does a percentage estimate communicate?

General statistical principle: A percentage expresses the frequency of an outcome relative to the participants evaluated. A between-arm comparison can be expressed in different ways, such as an absolute difference or a relative measure. Each has a different interpretation, and the choice should match the analysis plan and clinical question. The registry reports the primary outcome’s unit as a percentage but does not report an effect estimate or specify which contrast was used. No comparison should be reconstructed from the record.

A confidence interval is a range of estimates compatible with the observed data under the model and its assumptions. It communicates precision as well as direction and magnitude; a wide interval indicates substantial uncertainty, while a narrow interval indicates greater precision. A p-value, when reported, describes how compatible the data are with a specified null model under the test assumptions. Neither quantity is available for the primary endpoint in the registry record. In general, statistical significance alone does not establish practical importance, and a non-significant result would not establish equivalence.

How should the planning illustration be read?

The record describes planning calculations based on the observed effect, using a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. It states that the effect to detect is a stated fraction of the observed effect. These are planning assumptions, not a report of the trial’s observed power. Planning sample sizes are illustrations of the number of participants per arm that might be needed under the specified assumptions; they are not evidence that the trial had that power or that the assumed effect was established. The registry does not report a sample-size justification for the original trial, and the planning values are not reported in the registry record.

For a cluster-randomized study, planning and analysis may also depend on how many clusters are available and how similar participants within clusters are. General statistical principle: greater within-cluster similarity reduces the effective information available compared with an analysis that assumes every participant is independent. The registry’s planning description does not state how clustering was handled in those illustrations, so no cluster-adjusted planning interpretation can be made from the record.

What can be concluded from the posted analysis information?

The registry lists 0 analyses. It therefore does not provide outcome estimates or an analysis method to assess. The record’s warning against individual-level re-analysis is important: an unadjusted calculation from aggregate counts would not resolve the cluster dependence and could be misleading. The sponsor’s own cluster-aware analysis is the relevant analysis according to the registry note, but its numerical results and methods are not reported in the registry record. The responsible reading is to distinguish a registered design and endpoint from an available result: the former are described, while the latter cannot be evaluated statistically from this record.

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("Enhanced Care", "Standard Care")
n      <- c(50, 46)
events <- c(18, 14)
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  Enhanced Care  50  18  36.0  22.9  50.8  24.1  49.9  24.1  49.9
ARM  Standard Care  46  14  30.4  17.7  45.8  19.1  44.8  19.1  44.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 8 outcome measures. The named secondary outcomes cover 7 areas: 7-day point-prevalence prolonged abstinence, enrollment rate, quitline response rate, follow-up rate, questionnaire response rate, compliance with the intervention, and change in the number of cigarettes smoked. The primary endpoint is prolonged abstinence at 6-month follow-up. Numerical findings for these outcomes are not reported in the registry record.

Multiplicity arises when several outcomes or comparisons are assessed. General statistical principle: the more statistical tests considered, the greater the chance that at least one result may appear noteworthy by chance if each test is interpreted independently. Researchers may prespecify a primary outcome, use a testing hierarchy, or adjust for multiple comparisons. The registry record does not report a multiplicity strategy, a hierarchy among secondary outcomes, or whether any adjustment was used. Without results and an analysis plan, it is not possible to assess how multiplicity affects interpretation.

Missing-data methods are also not reported in the registry record. This matters because the primary endpoint relies on follow-up questionnaire assessment and cotinine confirmation, and the registry separately lists follow-up and questionnaire response rates as secondary outcomes. General statistical principle: if outcome availability is related to participants’ smoking status or differs between arms, a complete-case comparison can be biased. Appropriate handling depends on the reasons for missingness and the prespecified analysis approach. The record does not report missing outcome counts, imputation, sensitivity analyses, or rules for discordant or unavailable cotinine results.

The analysis population is not reported in the registry record. It is therefore unclear from the record whether the planned comparison included all assigned participants, only those with observed outcomes, or another defined group. No conclusions about attrition, protocol adherence, or the treatment of participants who changed or did not receive an intervention can be drawn from the posted analysis information.

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’s adverse-event figures list 0 serious events among 65 participants at risk in Enhanced Care and 0 among 69 participants at risk in Standard Care. It also lists 0 other events in each arm and 0 deaths in each arm. These are the recorded figures in the registry; they should not be read as proof that no adverse experience occurred or that the interventions carry no risk.

Event counts are most informative when read alongside clear definitions, the period of collection, the number assessed, and the completeness of reporting. The registry record does not provide serious-event terms, event descriptions, severity criteria, relatedness assessments, or details of the observation period. It also does not explain how the at-risk groups were defined. The absence of listed serious-event terms is consistent with the zero counts shown, but does not provide additional clinical detail.

Zero recorded events in an arm means that the registry lists no event in that category for that arm; it does not establish a zero underlying event rate. General statistical principle: when an event is uncommon, observing no events can still be compatible with a range of possible underlying risks, and the precision of that assessment depends on the amount and completeness of follow-up. No confidence intervals or additional safety analyses are reported in the registry record. These figures should therefore be treated as a limited safety summary, not as a definitive comparison of safety between the care strategies.

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

This trial record describes a focused worksite smoking-cessation question in Hispanic male construction workers. The enhanced-care strategy adds behavioral counseling to nicotine replacement therapy and quitline referral, while the standard-care description includes nicotine replacement therapy and quitline referral. The registered primary outcome is prolonged abstinence at 6-month follow-up, defined by the absence of smoking after a two-week grace period and confirmed with saliva cotinine below the stated threshold.

The record does not report the numerical primary outcome or the sponsor’s analysis. It therefore does not show whether abstinence percentages differed between the arms, how large any difference was, or how precisely it was estimated. The completed status and the stated aim to assess feasibility and potential efficacy do not supply those missing results. The registry’s list of secondary outcomes likewise does not establish whether recruitment, follow-up, quitline response, questionnaire response, intervention compliance, or cigarette consumption changed as intended.

Even with results, interpretation would need to account for the cluster-randomized design. General statistical principle: cluster assignment can create correlated outcomes, so the analysis should reflect the assignment structure. The registry specifically warns against a simple individual-level re-analysis and points to the sponsor’s own analysis as the appropriate basis. Because the sponsor’s numerical analysis is not reported in the registry record, its conclusions and precision cannot be evaluated.

The record also cannot isolate the contribution of individual program components. Enhanced Care combines counseling with nicotine replacement therapy and quitline referral; the comparison is between packages, not between each component separately. Nor does the record establish how broadly results would apply beyond the population and setting described. No subgroup results or details about other populations are reported in the registry record.

Accordingly, the statistical meaning is limited but clear: the registry documents a completed pilot study, its care strategies, and a clinically interpretable abstinence endpoint, while leaving the effect estimate unavailable. It supports no conclusion that one strategy produced more abstinence, no conclusion that the strategies were equivalent, and no conclusion about the magnitude or certainty of any difference.

14. Why This Trial Matters Statistically

This trial is statistically notable because it studies a worksite intervention in a population the registry describes as hard to reach and underserved. The study’s stated purpose was to develop, administer, and evaluate a smoking-cessation program for Hispanic male construction workers, with a pilot cluster-randomized design intended to assess feasibility and potential efficacy. That makes both implementation outcomes and the abstinence endpoint relevant to understanding the research question.

The cluster-randomized design is central to interpreting any comparison. In general, assigning clusters can make delivery practical when an intervention is organized around a worksite or shared setting, but it changes the assumptions needed for analysis. Participants in a cluster may resemble one another, and methods that treat all observations as independent can misstate uncertainty. The registry explicitly warns that simple individual-level re-analysis would be misleading, making the appropriate sponsor analysis particularly important.

The contrast also tests a package of services rather than a single isolated component. Enhanced Care adds behavioral counseling to nicotine replacement therapy and quitline referral, while Standard Care includes nicotine replacement therapy and quitline referral. If numerical results were available, they would describe the comparison between these packages in the enrolled study population; they would not by themselves establish the separate effect of counseling, medication, or referral.

Finally, the registry distinguishes an ambitious research question from the evidence available to answer it. The endpoint and follow-up timing are described, but the numerical analyses are not. This limits what can be learned from the public record about both statistical uncertainty and practical relevance. Transparent reporting of cluster-aware estimates, missing-data handling, and feasibility outcomes would be necessary to judge how informative the pilot was and how it could guide further research.

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 principal limitation of the registry record for statistical interpretation is the absence of numerical outcome analyses. It lists 0 analyses, so there are no posted primary or secondary outcome estimates, confidence intervals, or p-values to assess. The registry’s completed status does not resolve this reporting gap. Without the sponsor’s numerical analysis, the direction and size of any observed effect remain unknown.

Information about the cluster structure is limited. The record identifies a cluster-randomized design and warns against individual-level re-analysis, but cluster definitions, cluster counts, cluster sizes, and the analysis method are not reported in the registry record. No estimate of within-cluster correlation is reported. These details are important for assessing precision and the suitability of the analysis.

The intervention descriptions are also incomplete. The Enhanced Care description ends before all follow-up details are available, while the Standard Care description specifies the referral and planned nicotine replacement therapy. Actual receipt, adherence, fidelity, and contamination between arms are not reported in the registry record. Because the arms are intervention packages, the record would not permit component-specific attribution even if the overall comparison were reported.

Outcome ascertainment is described through questionnaire and cotinine confirmation, but procedures for missing questionnaires, unavailable samples, or discordant results are not reported in the registry record. The missing-data strategy, analysis population, multiplicity approach, and protocol deviations are also not reported. These omissions restrict assessment of bias and robustness.

The record includes adverse-event counts but not event definitions, descriptions, collection duration, or detailed safety analyses. Its planning illustration is not the original trial’s design justification and does not establish observed power. Generalizability is also uncertain from this record: it concerns Hispanic male construction workers, and information about other populations, settings, and subgroup effects is not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Smoking Cessation in Hispanic Construction Workers — NCT02873377.
• Registry record last updated 2019-11-07; status last verified 2019-10.
• Results first posted 2019-10-24.
• 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

NCT02873377 is a completed, randomized, parallel-group Phase 4 study sponsored by the University of Miami. The registry lists enrollment of 134, a start date of 2017-04-13, and a primary completion date of 2018-10-11. It describes a pilot cluster-randomized trial among Hispanic male construction workers.

Enhanced Care included nicotine replacement therapy, behavioral counseling, and a quitline referral. Standard Care included nicotine replacement therapy and a quitline referral. The primary endpoint was prolonged abstinence at 6-month follow-up, defined as no smoking after a two-week grace period and confirmed with saliva cotinine of <15 ng/ml.

The registry lists 8 outcome measures and 0 analyses. Numerical efficacy results, the sponsor’s analysis methods, missing-data procedures, and the multiplicity strategy are not reported in the registry record. The adverse-event record lists 0 serious events, 0 other events, and 0 deaths in each arm. Those counts are a limited registry summary and do not establish absence of risk.