Effects of a New Dispatcher-Assisted Basic Life Support Training Program: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effects of a New Dispatcher-Assisted Basic Life Support Training Program (NCT02142387), a non-randomized na study. The primary outcome is Number of Participants Surviving to Hospital Discharge.

2. Clinical Question

3. Trial Design

The study is registered as a nonrandomized, parallel, before-and-after intervention study. Its official title identifies a metropolitan-city setting. The registry lists enrollment of 18822 and a completed study, with a start date of 2014-01 and primary completion in 2017-12. The registry does not specify how participants or sites were assigned to training periods, nor does it report whether the groups were formed by calendar time, location, or another process.

The intervention group received the newer dispatcher-assisted basic life support training program, while the comparator group received the current basic life support training program. Neither allocation nor masking was randomized: the registry records nonrandomized allocation and no masking. This matters because people exposed to the two programs may differ for reasons other than the training itself. In a before-and-after design, changes over time can also coincide with the intervention, making it difficult to separate an intervention association from other temporal changes.

The registry lists survival to hospital discharge as the primary outcome, with return of spontaneous circulation and good neurological recovery as secondary outcomes. It does not describe the statistical method used to compare groups, how potential confounding was addressed, or which participants were included in each outcome analysis. The enrollment figure should not be read as the number analyzed for the primary endpoint; endpoint-specific analysis counts are not reported in the registry record.

Although the record gives a total enrollment figure, it does not explain how that figure relates to the outcome counts reported for the training groups. Those figures refer to different recorded quantities and should not be combined or treated as interchangeable. The study's completed status indicates its registration status, not that all results or analysis details are available.

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

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 Number of Participants Surviving to Hospital Discharge, measured over from date of discharge, assessed up to 3 months.

The primary endpoint is the number of participants surviving to hospital discharge. The registry describes survival as the proportion of patients discharged from hospital with spontaneous circulation recovered, with information collected through medical record review. The stated timeframe is from date of discharge, assessed up to 3 months.

This endpoint is used to describe an outcome that matters beyond the immediate resuscitation episode: whether a patient reaches hospital discharge alive. As a binary outcome, each eligible patient would be classified as either meeting or not meeting the survival definition, provided the record contains enough information to assign that status. Comparing the proportions between groups can describe the observed association between training group and survival.

General statistical context: a proportion is easier to interpret when its denominator is clear. That denominator should be the number of eligible people with an ascertainable endpoint in the relevant group, not automatically the overall enrollment. The registry does not report the primary endpoint counts, the analysis denominators, or the resulting proportions. It therefore does not allow readers to assess the observed survival contrast or its precision.

The record also does not describe rules for patients whose discharge status could not be established, or whether any additional endpoint adjudication was used. These details are relevant because outcome definitions and completeness of follow-up affect what a measured proportion represents.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a nonrandomized comparison estimate?

General statistical explanation: a group comparison describes how outcomes differ between the groups as observed. In a randomized study, assignment by chance is intended to make groups comparable on average before treatment, although randomization does not guarantee identical groups. In a nonrandomized study, assignment can be related to characteristics that also predict outcomes. A difference in outcomes can therefore reflect both the intervention and pre-existing or concurrent group differences.

This registry identifies nonrandomized allocation and a before-and-after intervention study. It does not report the precise assignment process, baseline characteristics, or a method for adjustment. The registry record therefore does not establish which factors were considered in the comparison, or whether the analysis sought to estimate an adjusted association rather than a raw group contrast.

Why does the before-and-after structure matter?

General statistical explanation: when an intervention is introduced over time, the intervention and calendar period may be entangled. Changes in clinical practice, staffing, patient mix, service organization, or outcome recording could coincide with the training change. If outcomes differ between periods, a before-and-after contrast alone cannot separate the intervention's association from all such changes. This is a design concern, not evidence that a particular time-related change occurred in this study. The registry does not report analyses of secular trends or other time-varying factors.

What does a binary endpoint mean?

General statistical explanation: a binary endpoint records whether each participant meets a defined outcome. A group proportion is the number meeting the outcome divided by the relevant analysis denominator. A contrast between proportions can be reported in more than one form, and each form answers a slightly different interpretive question. The registry defines survival to hospital discharge as a proportion but does not report the group counts, proportions, or effect estimate. No such quantity can therefore be interpreted from the registry record.

The endpoint is based on medical record review. For an analysis to be transparent, it is useful to know how records were obtained, how uncertain or absent discharge information was handled, and whether outcome classification was consistent across groups. Those procedures are not reported in the registry record.

How should uncertainty be assessed?

General statistical explanation: a confidence interval describes the precision of an estimate under a specified statistical model and its assumptions. A narrow interval indicates greater precision than a wide interval, but an interval does not remove bias caused by nonrandom assignment, incomplete outcome data, or an unsuitable model. A significance test addresses a different question: how compatible the observed data are with a specified null hypothesis under the test assumptions. Neither an interval nor a p-value can substitute for a clear estimate and a credible design.

The registry does not report a survival estimate, confidence interval, or p-value. It also does not identify the model, link function, covariates, or variance estimation method. Readers cannot determine how uncertainty was calculated or whether it accounted for any grouping or clustering in the study setting.

What is over-dispersion, and is it relevant?

General statistical explanation: over-dispersion occurs when observed variability is greater than a statistical model expects. If a model assumes less variability than is present, standard errors may be too small and confidence intervals may be too narrow. Methods that allow extra variability or account for clustering can be appropriate in some settings. The registry does not report whether over-dispersion was assessed or whether observations were clustered, so no claim about its presence or handling can be made for this study.

What do the planning assumptions mean?

The planning illustration is described as based on the observed effect, with a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation. It varies the effect to detect as a stated fraction of the observed effect. General statistical explanation: such calculations describe the sample size that a hypothetical design would require under its assumptions; they are not a measure of the power achieved by a completed study. The registry does not report the study's original sample-size justification, and the planning illustration should not be taken as evidence of observed power. The effect estimate and numerical planning outputs are not reported in the registry record.

The registry lists three outcome measures and three analyses, but does not describe the analyses or connect particular methods to particular outcomes. It does not report whether tests were one-sided or two-sided for the outcome analyses, whether estimates were adjusted, or how missing data and multiple comparisons were handled. Those features cannot be reconstructed from the design label or from the planning assumptions.

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("Districts Which Implement Newer DA-BLS Training Pr", "Districts Which Keep Traditional BLS Training Prog")
n      <- c(1486, 8641)
events <- c(85, 551)
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  Districts Which Implement Newer DA-BLS Training Pr  1486  85  5.7  4.6  7.0  4.6  7.0  4.7  7.0
ARM  Districts Which Keep Traditional BLS Training Prog  8641  551  6.4  5.9  6.9  5.9  6.9  5.9  6.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists survival to hospital discharge as the primary outcome and return of spontaneous circulation and good neurological recovery as secondary outcomes. It does not report the statistical analysis plan, the outcome-specific analysis methods, or how the three listed analyses correspond to those outcomes. A multiplicity adjustment, testing hierarchy, or strategy for interpreting several outcomes is not reported in the registry record.

General statistical context: evaluating several outcomes or conducting several tests can increase the chance that at least one result appears notable by chance. Prespecified priorities and an explicit multiplicity approach help readers distinguish confirmatory analyses from exploratory ones. No such approach is described, so the intended status of secondary comparisons and any adjustment to their interpretation are unclear.

The registry does not report missing-data counts, outcome ascertainment completeness, imputation, or sensitivity analyses. It also does not state the analysis population for survival, or whether all enrolled participants were included in each outcome analysis. General statistical context: missing outcomes can bias a comparison if the probability of missingness differs between groups or depends on the outcome. The degree and direction of any such concern cannot be assessed without information about missingness and the methods used.

Enrollment is listed as 18822, but the registry does not say that all enrolled participants contributed to every outcome analysis. Nor does it report a population definition such as intention-to-treat or per-protocol. The endpoint denominators should therefore not be inferred from enrollment or from the adverse-event counts.

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.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: death (94.3%).

The registry reports serious adverse event figures for the newer dispatcher-assisted training group and the current basic life support training group. It lists 1401 affected participants among 1486 at risk in the newer-program group and 8090 affected participants among 8641 at risk in the current-program group. Death is listed as the leading serious adverse event term, at 94.3%.

These are registry safety-reporting figures, not a substitute for the primary endpoint results. The registry does not explain how these serious adverse event counts relate to the survival endpoint, why the at-risk counts differ from the total enrollment, or whether adverse events were assessed over the same period as the primary outcome. The counts should not be combined with enrollment or treated as outcome-analysis denominators.

General statistical context: an adverse event recorded during a study is not automatically an event caused by the intervention. Assessing causality requires information about timing, definitions, ascertainment, comparison conditions, and the investigators' attribution process. Those details are not reported in the registry record. The figures therefore describe what the record lists, without establishing that training caused the events or that one program was safer.

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

The registry establishes that this was a completed, nonrandomized before-and-after study of a newer dispatcher-assisted basic life support training program compared with a current basic life support training program. It defines survival to hospital discharge as the primary endpoint and names return of spontaneous circulation and good neurological recovery as secondary outcomes. These details describe the research question and design; they do not provide the study's effect estimates.

The registry record does not report group-specific survival results, an estimated difference, or uncertainty around any survival comparison. It therefore does not show whether survival was higher, lower, or similar between the groups, nor how precisely an association was estimated. The secondary outcome results are also not reported. The listed adverse event figures do not fill this gap because they are not presented as the primary endpoint comparison.

Even if outcome estimates were available, the design would require cautious interpretation. General statistical context: nonrandomized assignment and a before-and-after structure can leave observed comparisons vulnerable to differences between groups and changes over time. Statistical adjustment can address measured factors under suitable assumptions, but it cannot automatically remove bias from unmeasured or poorly measured factors. The registry does not report whether such adjustment was performed.

The record also does not provide enough information to evaluate outcome completeness, analysis populations, multiplicity, or model assumptions. These omissions limit assessment of both the numerical results and their reliability. The sound conclusion from the registry is that the intended endpoint and comparison are identifiable, while the survival effect and its precision are not reported. No clinical recommendation or causal conclusion follows from the information in the registry record.

14. Why This Trial Matters Statistically

This study raises a statistical question that is important for interpreting evaluations of training programs: how should outcomes be compared when an intervention is introduced without random assignment? The record describes a before-and-after design, which can be informative about outcomes observed around a change in practice, but it does not by itself isolate the intervention from other differences between periods or groups.

The primary outcome is survival to hospital discharge, a clearly stated endpoint with a definition tied to discharge and recovered spontaneous circulation. Yet the registry does not report the outcome counts or estimated comparison. This contrast between a defined question and absent outcome estimates illustrates why registration details alone cannot establish the size or precision of an intervention association.

The record also illustrates the value of reporting analysis methods alongside results. Without the group-specific denominators, treatment of missing outcomes, model specification, adjustment strategy, and uncertainty estimates, readers cannot evaluate how the comparison was constructed. A completed status and an enrollment figure do not resolve those analytical questions.

Finally, the adverse event counts show why endpoint labels and denominators matter. Safety reporting and the primary survival endpoint may concern related events, but they are not automatically interchangeable measures. Clear definitions and explicit connections between analyses are needed before counts can be interpreted as evidence about an intervention's effects.

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.

Important study-specific details are absent from the registry record. The participant eligibility criteria, baseline characteristics, recruitment process, and exact assignment mechanism are not reported. The official title identifies a metropolitan-city study, but the city is not named in the registry record. The record does not describe whether the groups differed in measured characteristics or how such differences were handled.

The training descriptions are incomplete. The newer program is described as a one-hour course including a 30-minute video-based self-instruction session, a short role-play, and debriefing, but the description of the practice session ends without a complete account. The current program is also described as a one-hour course, but its description is incomplete. The registry therefore does not support a full comparison of course content or delivery.

The primary outcome results, secondary outcome results, endpoint denominators, confidence intervals, and statistical tests are not reported. Analysis populations, missing-data procedures, covariate adjustment, and handling of multiple outcomes are also not described. The relationship between enrollment and the group-specific adverse-event counts is not explained. These gaps prevent evaluation of the observed survival association, its precision, and the completeness of outcome reporting.

The registry identifies a nonrandomized before-and-after design and no masking. It does not report methods intended to address temporal changes, confounding, or possible clustering. These design and reporting limitations mean that even a reported crude group contrast would need cautious interpretation; however, the survival contrast itself is not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Effects of a New Dispatcher-Assisted Basic Life Support Training Program — NCT02142387.
• Registry record last updated 2020-05-01; status last verified 2020-04.
• Results first posted 2020-05-01.
• 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 registry describes a completed, nonrandomized, parallel before-and-after intervention study of dispatcher-assisted basic life support training compared with a current basic life support training program. Enrollment is listed as 18822. The study start is recorded as 2014-01 and primary completion as 2017-12.

Survival to hospital discharge is the primary outcome, defined by discharge with spontaneous circulation recovered and assessed up to 3 months. Return of spontaneous circulation and good neurological recovery are listed as secondary outcomes. The registry does not report outcome results or the statistical methods used to analyze them.

Serious adverse event figures are listed for both training groups, with death named as the leading serious adverse event term. The record does not explain their relationship to the primary endpoint or provide a causal assessment. Overall, the registry specifies the intended comparison and outcomes but does not report the survival effect or its precision.