Prehabilitation of Veterans With Exercise and Nutrition: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Prehabilitation of Veterans With Exercise and Nutrition (NCT04485611), a na na study. The primary outcome is Feasibility, Measured as Acceptance Rate.

2. Clinical Question

In statistical terms, the central question is whether eligible patients enter the pilot, not whether the intervention changes outcomes relative to a control group. The registry record lists physical function, anxiety, depression, and health-related quality of life among secondary outcome areas. It does not report the results of those outcome measures. The clinical question is therefore limited by the information recorded: feasibility is the primary focus, and comparative effectiveness cannot be assessed from this single-group design.

3. Trial Design

The registry record describes PREVENT as a completed, single-group pilot study of prehabilitation for veterans with frailty. The intervention combines supervised aerobic and resistance training with nutritional support. The cohort description states that participants would undergo the intervention and be followed for up to 6 months; no comparator group is included. The registry lists enrollment of 20 participants, with study start on 2021-05-27 and primary completion on 2024-03-29. The recorded status is COMPLETED.

Allocation is listed as NA, and masking is listed as NONE. These entries are consistent with the stated single-group design: the study does not assign participants between a prehabilitation group and a concurrent control group. The phase is listed as NA. Further details about recruitment procedures, eligibility criteria, intervention scheduling, adherence definitions, or protocol changes are not reported in the registry record. The record does not describe randomization or a planned controlled comparison.

The primary endpoint is feasibility measured as acceptance rate, defined using the number enrolled and the number of eligible patients. Its timeframe runs from initial screening to enrollment (~7 days). Because the registry record gives the enrollment count but not the eligible-patient denominator, it does not give a numerical acceptance rate. Secondary outcomes include physical function—described in terms of aerobic endurance, lower-extremity strength and balance—along with HADS anxiety, HADS depression, and SF-36. The record lists eight outcome measures, but does not report numeric results for these secondary measures.

The study’s design can describe what happened within the participating cohort, if outcome data and appropriate analyses are available. It cannot by itself distinguish intervention effects from changes over time, other care, or participant characteristics. The posted record does not include outcome-analysis entries. The design should therefore be read as a pilot feasibility study, not as a randomized or controlled estimate of comparative treatment effects.

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: 20 patients were enrolled in the study. One patient underwent the baseline evaluation but withdrew before starting the intervention. One patient enrolled but his clinical condition changed and was therefore withdrawn from the study before the initial baseline evaluation was completed. A total of 18 participants started the prehabilitation intervention.

Prehabilitation

Reasons for not completing this period:

Rehabilitation

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.

Population: A total of 63 patients were screened and offered to participate, and 29 agreed to enroll and undergo a physical function evaluation. Of these, 20 patients (69%) were frail or pre-frail and qualified for the intervention. One patient withdrew before the initial evaluation was completed. One patient completed the baseline evaluation but was later withdrawn from the study due to a change in his medical condition.

6. Primary Endpoint

The registry lists the primary outcome as Feasibility, Measured as Acceptance Rate, measured over From initial screening to enrollment (~7 days).

The primary endpoint is feasibility, operationalized as acceptance rate. The registry defines the measure as the number of enrolled patients divided by the number of eligible patients. The timeframe is from initial screening to enrollment (~7 days). This kind of endpoint is used to describe whether an intervention can attract participation among people who meet eligibility criteria. It addresses recruitment and uptake, rather than a physiological or patient-reported clinical outcome.

The record lists enrollment of 20 participants, but does not report the number of eligible patients who were screened or otherwise considered for enrollment. Without that denominator, a numerical acceptance rate cannot be read from the registry record. Enrollment alone is not the acceptance rate: it is the numerator in the stated definition, while the denominator is also needed. The number who declined, were not approached, or were excluded at screening is not reported in the registry record.

Feasibility endpoints can inform whether a larger study may be workable, but they do not establish whether an intervention improves physical function, reduces complications, or changes quality of life. The registry describes those as broader research interests and lists several secondary outcome domains, but does not report their results. Accordingly, the primary endpoint supports a narrow interpretation about recruitment only if its numerator and denominator are available. As recorded, the denominator and calculated rate are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods should be interpreted in relation to the question a study is designed to answer. PREVENT is recorded as a single-group pilot with no comparator. Its primary endpoint is a count-based feasibility measure: the number enrolled among the number eligible. That definition is conceptually different from comparing an outcome between randomized groups. The record identifies the endpoint and its timeframe, but it does not report a calculated acceptance rate or an analysis of that endpoint.

What does a count-based endpoint represent?

For a count such as participants enrolled, the raw count gives the number of observed people meeting the endpoint definition. A rate or proportion requires a clearly specified denominator. Here, the stated denominator is eligible patients, and the numerator is enrolled patients. This denominator matters because the same enrollment count can have different interpretations depending on how many eligible people were considered. Neither an eligible-patient count nor a feasibility threshold is reported in the registry record, so the acceptance endpoint cannot be compared with a target or interpreted as a proportion.

Count data also need a clear observation window and eligibility definition. The record specifies the timeframe from initial screening to enrollment (~7 days), but does not describe detailed screening procedures, how eligibility was adjudicated, or how people who could not be contacted were handled. Those details affect which people enter the denominator. Their absence limits reproducibility and interpretation, but does not justify assuming a particular screening or recruitment process.

What can a single-group design estimate?

In a single-group study, summaries can describe the participants who enrolled and their measured outcomes at recorded times. If observations are made repeatedly, a within-person change can be estimated when the needed values and analysis are available. However, a before-and-after difference does not by itself identify the causal effect of the intervention. The participants have no concurrent control group to represent what would have happened over the same period without the intervention. Time, surgery, usual care, recovery, and other factors may coincide with the intervention.

Random allocation and masking are recorded as NA and NONE, respectively, and the design is explicitly single group. There is therefore no randomized contrast to interpret. The absence of a comparator is not a statistical defect that can be corrected simply by applying a more complex model: it constrains which causal questions the design can answer. Registry analyses for the outcomes are not reported, so no specific model, adjustment strategy, or estimation method can be described.

How should precision be understood?

In general, an estimate is more informative when its uncertainty is also reported. A confidence interval is a range calculated by a statistical procedure to express uncertainty about an estimate under its assumptions. A narrow interval indicates greater precision than a wide interval, while neither interval width nor statistical significance alone establishes clinical importance. No confidence intervals for the primary or secondary outcomes are reported in the registry record. No effect estimate for the primary endpoint is available because the eligible denominator is not reported.

For a single-group count or proportion, uncertainty depends on the number observed and the definition of the denominator, among other assumptions. Without the eligible count and an analysis, there is no basis for describing the precision of an acceptance-rate estimate. For the functional and patient-reported measures, the outcome summaries and their variability are not reported, so their precision cannot be assessed either.

What do the planning assumptions mean?

The registry’s planning description refers to a hypothetical two-arm calculation using a two-sided significance level of 0.05, equal allocation between arms, a normal approximation, and an effect defined as a stated fraction of an observed effect. Such assumptions describe a planning illustration, not the actual single-group design. A hypothetical equal-allocation comparison is not evidence that participants were randomized or that a control arm existed. The record does not report a numerical planning estimate in the registry record for interpretation, a protocol sample-size justification, or a prespecified effect to detect.

General power calculations ask how often a specified statistical procedure would detect an assumed effect under specified conditions. They do not tell whether a completed study actually had that probability of detecting an effect; that would be an interpretation of observed data and design, not an observed outcome. Planning illustrations are prospective scenarios, not observed power. If an assumed effect is based on an observed effect, the illustration can be sensitive to that estimate and should not be treated as proof that the effect is real or reproducible. The registry record does not report the inputs needed to assess a numerical calculation.

Why do distributional assumptions matter?

General statistical methods often rely on assumptions about how observations vary. For example, a normal approximation can be useful for some calculations when its conditions are reasonable. Count outcomes may instead have variability that differs from a simple model’s assumptions. Over-dispersion means that observed variation exceeds what a chosen count model expects; ignoring it can make uncertainty appear smaller than it should be. These are general considerations, not evidence that over-dispersion occurred in this study. The registry record does not describe a count model, a diagnostic assessment, or any adjustment for over-dispersion.

Repeated measurements also require attention to dependence: observations from the same participant are related rather than independent. General analysis methods can account for that structure, but the registry record does not state whether repeated measurements were analyzed, how within-person correlation was handled, or whether outcome time points were combined. Since no analyses are reported, no method-specific assumptions can be checked.

The appropriate methodological conclusion is limited. The endpoint definition and single-group structure are recorded, as are some planning assumptions, but a statistical analysis plan, estimation method, uncertainty measures, and outcome results are not reported in the registry record. General concepts can clarify what information would be needed; they cannot substitute for missing study-specific analyses.

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("Prehabilitation")
n      <- c(29)
events <- c(20)
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  Prehabilitation  29  20  69.0  49.2  84.7  50.8  82.7  50.6  82.7

11. Multiplicity, Missing Data and Analysis Populations

The registry lists eight outcome measures and names secondary domains that include aerobic endurance, lower-extremity strength and balance, HADS anxiety, HADS depression, and SF-36. The record does not report analyses for these outcomes. It also does not report a prespecified hierarchy among secondary outcomes, a family of hypotheses, or a method for controlling multiplicity. Multiplicity arises when several outcomes or comparisons are examined: the more statistical claims considered, the greater the chance that at least one appears notable by chance if no adjustment or interpretive plan is used. That is a general statistical concern, not a claim that a particular false-positive result occurred in this study.

The primary endpoint is clearly identified as feasibility measured by acceptance rate, but its eligible denominator and calculated value are not reported. The registry record does not provide an analysis population definition, such as how participants with incomplete screening or follow-up information would be handled. It also does not describe missing-data methods, imputation, sensitivity analyses, or reasons for missing observations. These methods should not be inferred from the number at risk recorded for adverse-event groups.

For outcome analyses, it would matter whether results were based on all enrolled participants, participants with observed measurements, or another defined group. Such distinctions are especially relevant in a pilot with follow-up and perioperative time points. The registry record does not state which populations were used for the listed outcomes or whether analyses followed an intention-to-treat principle. No missing-data assumption or procedure is reported in the registry record.

Without analysis details, outcome estimates, or a missingness account, neither multiplicity handling nor the effect of missing data can be evaluated. These are reporting limitations, not proof that the investigators did or did not use a particular approach.

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 event counts, other adverse event counts, and deaths for four labeled groups: Baseline, Post-prehabilitation, Post-surgery, and Post-rehabilitation. Each group lists zero serious events, zero other events, and zero deaths. The number at risk is 18 for the baseline and post-prehabilitation entries, and 14 for the post-surgery and post-rehabilitation entries.

These are descriptive counts at the specified group labels. They do not provide a comparison with an untreated or usual-care group, because the study has no comparator. The changing numbers at risk also mean that the recorded denominators are not identical across the entries. The registry record does not explain the change, identify why some participants are absent from later entries, or provide event definitions and ascertainment details beyond the listed categories.

Zero events in the posted record means that no events are listed for those categories and groups; it does not establish that the true risk is zero or that an intervention has no safety concerns. The record gives no uncertainty estimates for these counts. The counts should be read as a limited descriptive account of recorded events, not as a comparative safety analysis or a guarantee about outcomes in other participants or settings.

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

The registry record documents a completed pilot that enrolled 20 participants into a single-group prehabilitation cohort. The intervention is described as supervised aerobic and resistance training with nutritional support, with follow-up planned for up to 6 months. The primary feasibility question is whether eligible patients enrolled, but the eligible denominator and calculated acceptance rate are not reported in the registry record. The enrollment count alone cannot answer that question fully.

The record’s research context emphasizes functional recovery and prehabilitation before high-risk surgery. It also lists physical function and patient-reported measures among secondary outcome areas. Those aims identify what the study is intended to investigate; they are not findings. Numeric results and analyses for these outcomes are not reported in the registry record, so no direction or size of change can be described from the available information.

The absence of a comparator places a firm boundary on interpretation. The study cannot provide a direct estimate of how outcomes under the intervention differ from outcomes under a separate control condition. Even if change within the cohort were available, changes could reflect multiple influences, including surgery, usual care, recovery, or other factors. The registry record does not report analyses that would support attribution to the intervention.

The adverse-event entries report zero serious events, zero other events, and zero deaths in the listed groups, with differing numbers at risk across time points. These are descriptive registry counts. They do not establish absence of risk, explain the changing denominators, or support a comparison with another care strategy.

In practical statistical terms, the record contributes information about the study’s design, endpoint definition, enrollment, and recorded adverse-event counts. It does not report a primary acceptance-rate result, a treatment-effect estimate, confidence intervals, or secondary-outcome analyses. Consequently, the evidence described in the registry record is limited to study conduct and descriptive entries, rather than conclusions about clinical benefit or comparative safety.

14. Why This Trial Matters Statistically

Pilot studies can address whether a proposed research approach is workable, and that question is distinct from whether an intervention changes health outcomes. PREVENT’s primary endpoint reflects this distinction: acceptance rate is a feasibility measure based on enrollment among eligible patients. The endpoint’s focus is useful because recruitment is part of conducting a larger study, but its interpretation depends on a denominator and a defined eligibility process. The registry record reports enrollment of 20 while leaving the eligible-patient count and calculated rate unreported.

The study also illustrates why design and statistical question must be considered together. A single-group cohort can describe enrolled participants, intervention delivery, and recorded outcomes when those data and analyses are reported. Without a comparator, it cannot isolate intervention effects from time, surgery, usual care, or other influences. A completed status and an enrollment count do not resolve that design limitation.

The named secondary measures cover physical function and patient-reported domains that align with the study’s stated interest in recovery and quality of life. However, the registry record does not report their results or analyses. Listing outcomes signals what was planned or registered, but does not show what happened to participants on those measures.

These distinctions matter when interpreting pilot evidence. Feasibility information, clinical outcome estimates, and comparative effects answer different questions and require different data. The record supports a clear account of the pilot’s structure and its primary endpoint definition, while also showing important gaps in the reported numerical outcome information. Keeping those claims separate prevents an enrollment count or an event count from being mistaken for evidence of an intervention effect.

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 main limitation is the single-group design. With no comparator group, the study cannot directly estimate how outcomes would differ under another condition. This limits causal interpretation even if within-cohort outcomes were reported. Allocation is listed as NA and masking as NONE, and no randomized comparison is described.

The primary endpoint is defined as enrolled divided by eligible, but the registry record reports only the enrollment count of 20. It does not report the number of eligible patients, a calculated acceptance rate, or a feasibility target. Screening details and reasons eligible patients did not enroll are also not reported in the registry record. These gaps prevent a complete interpretation of the primary feasibility measure.

Although secondary outcome areas are listed, their numeric results and statistical analyses are not reported in the registry record. The record does not describe outcome-specific analysis methods, estimates of uncertainty, or handling of repeated measurements. It also does not report a statistical analysis plan, missing-data methods, analysis populations, or multiplicity procedures. These omissions mean that the robustness and precision of any outcome findings cannot be assessed.

The adverse-event counts are descriptive and the numbers at risk differ across the recorded time points. Reasons for the difference and the completeness of event ascertainment are not reported. The registry record also does not provide sufficient detail to assess intervention adherence or variation in delivery. These limitations constrain interpretation to what is explicitly recorded; they do not establish that unreported procedures or analyses were absent.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Prehabilitation of Veterans With Exercise and Nutrition — NCT04485611.
• Registry record last updated 2025-08-22; status last verified 2025-08.
• Results first posted 2025-08-22.
• 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

PREVENT (NCT04485611) is recorded as a completed, single-group pilot concerning prehabilitation for veterans with frailty. The intervention is supervised aerobic and resistance training with nutritional support. The record lists enrollment of 20, a study start date of 2021-05-27, and primary completion on 2024-03-29. There is no comparator group; allocation is listed as NA and masking as NONE.

The primary endpoint is feasibility measured as acceptance rate, defined as enrolled divided by eligible during initial screening to enrollment (~7 days). The eligible denominator and calculated acceptance rate are not reported in the registry record. Secondary outcome areas include physical function, HADS anxiety, HADS depression, and SF-36, but their results and analyses are not reported. Adverse-event entries list zero serious events, zero other events, and zero deaths in each recorded group, with 18 at risk at baseline and post-prehabilitation and 14 at risk post-surgery and post-rehabilitation. These descriptive data do not support a controlled estimate of intervention effects.