Robotic Single Port Donor Nephrectomy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Robotic Single Port Donor Nephrectomy (NCT01925677), a na na study. The primary outcome is Successful Completion of the Surgical Procedure.

2. Clinical Question

This is a feasibility question about performing a surgical procedure with a particular platform, rather than a randomized test of comparative effectiveness. The primary outcome is a participant count, not a measure of operative time, blood loss or surgeon ergonomics. Those topics appear among the listed secondary outcomes, but their results are not reported in the registry record. The record describes a study of donor nephrectomy for a left kidney; it does not establish that the findings apply to other operations, platforms or patient groups. Because there is no control arm for the primary outcome, the study cannot provide a controlled estimate of differences between robotic-assisted and standard laparoscopic approaches.

3. Trial Design

The registry record describes a completed, single-group study of the da Vinci Single-Site device for robotic-assisted single-incision laparoscopic nephrectomy. Its listed enrollment is 3. The study is marked as not having an applicable phase, with allocation listed as not applicable and masking listed as none. There is no randomized allocation or like-for-like control comparison described for the primary outcome.

The primary objective is feasibility of using the Single-Site platform to perform donor nephrectomy before vascular division and extraction. The record says that the portions of the operation using the robotic device were to be recorded. The primary outcome is successful completion of the surgical procedure, assessed during the operation. The record also lists operative times, blood loss and a comparison of surgeon ergonomic questionnaires in robotic-assisted versus standard laparoscopic single-port donor nephrectomies as secondary outcomes. It does not report results for those outcomes.

The sponsor is the University of Maryland, Baltimore. The recorded study start is 2015-01, primary completion is 2017-08, and status is completed. The record lists 4 outcome measures and 0 analyses. It does not report a detailed statistical analysis plan, the rationale for the enrollment target, or additional details about how participants were selected or followed. Completion status describes the study’s status in the registry; it does not itself establish that the intended procedure was completed successfully or that all planned outcomes were reported.

The study’s single-group design can describe what was recorded among participants undergoing the procedure, but does not support a controlled comparison of approaches. The ergonomic outcome’s reference to standard laparoscopic procedures does not, by itself, establish that a comparator group was enrolled in this study.

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

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 Successful Completion of the Surgical Procedure, measured over during operation.

The primary endpoint is successful completion of the surgical procedure, recorded as a count of participants and assessed during the operation. The endpoint is intended to address the study’s feasibility objective: whether the Single-Site platform can be used to perform donor nephrectomy before vascular division and extraction. The registry also says that the portions of the operation using the robotic device were to be recorded, giving procedural context for the feasibility assessment.

A completion count is a direct, operational measure for a feasibility study. It focuses on whether the specified procedure reached its intended endpoint, rather than on a comparative estimate of benefit or on a continuous measure such as operative time. In general, a binary completion outcome distinguishes participants whose procedures meet the defined completion criterion from those whose procedures do not. That kind of endpoint can be useful when evaluating whether an approach can be carried through in practice, but its interpretation depends on a clear definition of success and consistent recording.

The registry record does not report the number of participants whose operations were successful, nor does it provide a more detailed operational definition of completion beyond its description of the objective. Consequently, the primary endpoint result cannot be interpreted from the registry record. The record’s enrollment figure alone does not establish how many operations met the endpoint, and no outcome value should be inferred from the study’s completed status.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General: A binary outcome classifies each participant according to whether an event or defined condition occurred. For this study, the primary outcome is expressed as a count of participants with successful completion. To interpret such a count, a reader needs both the number meeting the definition and the number assessed. The registry lists enrollment of 3, but the primary outcome count is not reported in the registry record. The event count and resulting estimate therefore cannot be recovered from the posted information.

General: A proportion is often used to describe a binary outcome in a cohort. Its meaning depends on a stable outcome definition, complete ascertainment and a clear denominator. A confidence interval can express sampling uncertainty around an estimated proportion. In a small cohort, uncertainty can remain substantial even when the observed count appears clear; the interval describes statistical precision under its assumptions, not whether the study population represents others. No proportion or confidence interval for the primary endpoint is reported in the registry record.

General: A single-group feasibility study is suited to describing whether and how a procedure was performed in the enrolled participants. It does not, on its own, separate the effect of the surgical platform from other influences or estimate a difference from an alternative approach. A randomized or otherwise suitable comparator design would be needed for a comparative question, with methods appropriate to the chosen design. No such control group is described for the primary outcome in this registry record.

The listed primary endpoint is a count of participants, with the timeframe stated as during the operation. The objective further refers to recording which portions of the operation used the robotic device. This makes the endpoint procedural and immediate, rather than a follow-up measure of later health status. The registry record does not describe an adjudication process, a more detailed success criterion, or the handling of a procedure that was started robotically but completed by another method. Those details are not reported in the registry record.

General: Statistical inference requires more than a point estimate. A prespecified analysis plan can identify the estimand, outcome definition, analysis population, missing-data approach and uncertainty measure. It can also specify whether estimates are adjusted and how any comparisons are made. The registry lists 0 analyses and does not report a detailed statistical analysis plan, adjustment methods or confidence intervals. No inferential result should be attributed to the study without those details.

The record lists 4 outcome measures. It names operative times, blood loss and surgeon ergonomic questionnaires as secondary outcomes, in addition to the primary completion endpoint. These outcomes have different measurement types and interpretation needs. For example, a time or blood-loss measure is generally summarized differently from a participant count, while questionnaire comparisons require information about the instrument and scoring. The record does not give the results, detailed definitions, summaries or analysis methods for those secondary measures.

General: Over-dispersion is relevant when count data vary more than a chosen statistical model expects. Ignoring it can make estimated uncertainty too small and tests too optimistic. It is not a feature that can be assessed from a simple binary completion count alone without an appropriate model and enough relevant information. The registry record does not describe an over-dispersion analysis, and there is no basis to claim that such a model was used.

The registry’s sample-size assumptions describe planning illustrations, not the trial’s own design justification. Those illustrations are stated to use a two-sided significance level of 0.05, equal allocation between two arms and a normal approximation, with the effect to detect set as a stated fraction of the observed effect. For time-to-event illustrations, the stated quantity is total events; other illustrations are expressed as participants per arm. These are general planning conventions and do not change the actual single-group design described for the study. The registry record does not report a sample-size justification for this study. Nor does a planning illustration represent observed power or show that the study had a particular probability of detecting an effect.

Because the primary result and analysis are not reported, there is no estimate to recalculate from posted summary statistics. A recalculation, where available, would be an unadjusted calculation based on the reported summaries, not a replacement for the study’s own analysis. The record does not report a discrepancy between an analysis and a recalculation. In general, when a discrepancy is identified, the sponsor’s own analysis takes precedence for describing the sponsor-reported result, while the recalculation can help explain how the summary statistics relate to one another.

Overall, the registry supports description of the intended endpoint and high-level study design, but not reconstruction of an endpoint estimate or evaluation of its statistical precision. The analysis methods needed to make such an assessment are not reported in the registry 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("da Vinci® Single-Site™")
n      <- c(3)
events <- c(3)
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  da Vinci® Single-Site™  3  3  100.0  29.2  100.0  43.9  100.0  39.8  99.4

11. Multiplicity, Missing Data and Analysis Populations

The record lists 4 outcome measures: successful completion of the surgical procedure as the primary outcome, and operative times, blood loss and surgeon ergonomic questionnaires among the secondary outcomes. Considering multiple outcomes can raise a multiplicity issue when several statistical tests are conducted and interpreted as confirmatory. In general, a prespecified testing strategy can identify which outcome is primary, how secondary outcomes are interpreted and whether any adjustment for multiple testing is planned. The registry record lists 0 analyses and does not report a multiplicity strategy, so it is not possible to determine whether any adjustment was planned or used.

Missing-data handling is also not described. The record does not report missing outcome counts, whether all enrolled participants contributed data to each measure, or how unavailable observations were treated. For a procedural endpoint, it would be useful to know whether the endpoint was assessed for every participant and how incomplete or non-evaluable procedures were classified. These details are not reported in the registry record. No missingness pattern or analysis population can be inferred from the listed enrollment figure.

The record does not specify an intention-to-treat, per-protocol or other analysis population. In general, such definitions explain which participants contribute to each estimate and how deviations from the planned procedure are handled. With a single-group design, the distinction still matters for describing the denominator and the population to which the result applies. Because neither the primary outcome result nor the analysis population is reported, the endpoint denominator and its treatment in analysis cannot be verified.

Accordingly, the posted record does not permit assessment of multiplicity control, missing-data assumptions or the consistency between enrolled participants and analyzed participants. These are reporting gaps, not evidence that a particular method was or was not used.

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 adverse-event figures list the da Vinci Single-Site group as having 3 participants at risk for serious adverse events and 0 serious adverse events. The same group lists 3 participants at risk for other adverse events and 0 other adverse events, with 0 deaths. These are the counts recorded in the registry.

In general, an observed count of zero means that no event in that category is recorded among the participants at risk in the posted data. It does not establish that the underlying risk is zero, nor does it show what would occur in a larger or different population. A small, single-group study cannot provide a controlled comparison of safety with another surgical approach. The registry also does not provide serious adverse-event terms, since no top serious terms are listed.

The figures should be read as descriptive safety counts, not as a demonstration that the device or procedure is risk-free. They do not resolve whether all adverse events were captured using the same definitions or over the same observation period, because those details are not reported in the registry record.

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

The study addresses whether robotic-assisted single-incision donor nephrectomy using the da Vinci Single-Site platform can be carried out, with attention to successful completion and the portions of the operation using the device. The record identifies this as a feasibility objective and lists enrollment of 3 participants. It also records 0 serious adverse events, 0 other adverse events and 0 deaths among 3 participants at risk in the device group.

Those details do not reveal the primary endpoint outcome. The count of participants whose procedures were successfully completed is not reported in the registry record. Nor are results reported for operative times, blood loss or surgeon ergonomic questionnaires. As a result, the record does not establish the observed feasibility result, describe the secondary outcomes, or show how precise any estimate might be.

The study’s single-group design is important to interpretation. It can be used to describe what happened in participants receiving the intervention, but it does not provide a controlled estimate of how outcomes differ from standard laparoscopic surgery. Although the registry names a questionnaire comparison as a secondary outcome, it does not describe its results or establish the structure of that comparison. No comparative conclusion follows from that listing alone.

More generally, feasibility findings from a small cohort are not automatically generalizable to other settings, surgeons, devices or donor populations. The registry does not report participant characteristics or detailed eligibility criteria, which further limits assessment of the population represented. The observed safety counts are likewise descriptive and do not show that adverse events cannot occur.

The appropriate conclusion is narrow: the registry records a completed feasibility study and its intended outcomes, but omits the primary and secondary outcome results. It therefore cannot support a claim about the observed success rate, comparative performance or the broader safety profile. Those questions would require reported outcome data and analysis details that are not reported in the registry record.

14. Why This Trial Matters Statistically

This study is statistically interesting because its central question is one of feasibility, not a conventional comparison of treatment effects. Feasibility work can clarify whether a procedure can be performed as intended and identify what aspects of the procedure are recorded. Here, the stated objective is to assess use of a robotic single-site platform before vascular division and extraction, with successful completion as the primary outcome.

That objective highlights the need to distinguish a planned endpoint from a reported result. A registry can describe what investigators intended to measure, but design information alone does not establish what the observations showed. In this case, enrollment is listed as 3 and the primary outcome is named, yet the completion count and outcome analyses are not reported in the registry record. Statistical interpretation must stop short of estimating feasibility from those design details.

The single-group structure also clarifies what the study can and cannot answer. It can describe the use of the device in the enrolled participants if results are reported, but it does not provide a concurrent control comparison for the primary question. The mention of standard laparoscopic procedures in a secondary ergonomic outcome is not enough to infer a comparative design or result.

The safety counts illustrate another general statistical principle: zero observed events in a small cohort is a descriptive finding, not proof of no risk. The uncertainty around rare events cannot be resolved by the observed count alone. Reporting denominators and follow-up definitions matters, and comparative safety questions require appropriate comparison data.

Finally, the record’s listed planning assumptions should be kept separate from the actual study design. Planning illustrations can help explain how target effects and design assumptions relate to sample-size requirements, but they are not observed power, do not justify the enrollment chosen for this trial and cannot replace missing outcome results. The distinction between design, analysis and reporting is central to a careful reading of feasibility 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.

Several limitations specific to this study restrict interpretation. The registry record lists enrollment of 3, but does not report the primary endpoint result. As a result, the principal feasibility outcome cannot be evaluated from the posted information. The record also lists 4 outcome measures and 0 analyses; it does not report results for the secondary outcomes of operative times, blood loss or surgeon ergonomic questionnaires.

The design is single-group, with allocation listed as not applicable and masking as none. There is no like-for-like control arm described for the primary outcome. Consequently, even if a completion result were available, this design would not by itself provide a controlled estimate of differences between robotic-assisted and standard laparoscopic approaches. The reference to standard laparoscopic procedures in a secondary questionnaire outcome does not establish that a comparator group was enrolled.

The registry does not provide participant characteristics, detailed eligibility criteria, a full definition of successful completion, or additional detail on how device use across portions of an operation was classified. It does not report missing-data handling, analysis populations, outcome denominators, confidence intervals or a detailed statistical analysis plan. Those omissions prevent assessment of endpoint ascertainment, precision and the relationship between enrollment and analyzed participants.

The listed safety counts are limited to the recorded group and do not constitute a comparative safety analysis. With 3 participants at risk, the counts cannot characterize uncommon events or establish safety beyond the observations recorded. The registry does not report additional details about adverse-event definitions or observation periods. These limitations concern the information available in the registry record; they should not be read as claims about what investigators may have collected outside that record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Robotic Single Port Donor Nephrectomy — NCT01925677.
• Registry record last updated 2019-11-20; status last verified 2019-11.
• Results first posted 2019-11-20.
• 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 record describes NCT01925677, a completed, single-group feasibility study of robotic-assisted single-incision donor nephrectomy using the da Vinci Single-Site platform. The sponsor is the University of Maryland, Baltimore. The recorded study start is 2015-01, primary completion is 2017-08, and enrollment is 3.

The primary outcome is successful completion of the surgical procedure during the operation. Secondary outcomes include operative times, blood loss and surgeon ergonomic questionnaires. The record lists 4 outcome measures and 0 analyses. It does not report the primary or secondary outcome results. The safety figures list 0 serious adverse events, 0 other adverse events and 0 deaths among 3 participants at risk in the device group.

The single-group design does not provide a like-for-like control comparison for the primary outcome. The posted record therefore describes the study’s objective and structure but does not establish the observed feasibility result or comparative performance.