Aortoiliac Stenosis in Kidney Transplantation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Aortoiliac Stenosis in Kidney Transplantation (NCT06020534), a registered phase not stated study. The primary outcome is Patient Survival.

2. Clinical Question

The secondary outcomes listed are death-censored graft survival and graft function. Those outcomes could address graft outcomes separately from survival of the transplant recipient, but their definitions and comparative results are not reported in the registry record. The posted group counts include deaths, but counts alone do not establish how survival differed between groups over time. In particular, they do not account for when deaths occurred or how long each participant was followed. The central statistical question is therefore identifiable from the registered objective, while the evidence needed to quantify the group comparison is not reported in the registry record.

3. Trial Design

The registry identifies the study as “Aortoiliac Stenosis in Kidney Transplantation,” with the official title “Safety and Efficacy of Kidney Transplantation in Patients With Aortoiliac Stenosis.” Erasmus Medical Center is listed as the sponsor. The status is completed. The recorded study start is 2022-01-01, and the primary completion date is 2023-01-31. Enrollment is 655.

Participants are described in three categories: no pre-existing aortoiliac stenosis before kidney transplantation, TASC A or B stenosis, and TASC C or D stenosis. The registry presents these as groups rather than as treatment assignments. It does not state an allocation method, and the record explicitly notes that this is not a randomized comparison. Consequently, these categories are not a randomized treatment-versus-control design. Differences among them may reflect differences in participant characteristics or clinical circumstances as well as stenosis category; which factors were measured or addressed is not reported in the registry record.

The primary outcome is patient survival. Death-censored graft survival and graft function are listed as secondary outcomes. The registered survival timeframe extends from transplantation to death or data cut-off, whichever came first, and is assessed up to 10 years. The outcome description specifies all-cause death through the end of follow-up, identified as January, 2023. The registry record does not explain any difference between the timeframe wording and that end-of-follow-up date.

The statistical plan, sample-size justification, interim analyses, analysis populations, and methods for adjusting group comparisons are not reported in the registry record. The record indicates no analyses, and it does not provide formal comparative estimates for the registered outcomes. The enrollment figure and the group event counts therefore describe the study record but do not, on their own, establish the precision or interpretation of an effect estimate.

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: We initially identified 2127 participants. Thirty-six patients were excluded according to the exclusion criteria. In the remaining participants, propensity score matching was performed in a nearest neighbor-matching approach with a maximum caliper of 0.1 in a 1 : 4 ratio to match the baseline characteristics of participants with and without aortoiliac stenosis. The matching parameters included age at transplant, dialysis mode, retransplant, donor type, comorbidities, and smoking status.

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.

Population: Propensity score matching was performed in a nearest neighbor-matching approach with a maximum caliper of 0.1 in a 1 : 4 ratio to match patients in the stenosis group with individuals from the no-stenosis group who shared similar characteristics. The matching parameters included age, dialysis mode, retransplant, donor type, comorbidities, and smoking status.

6. Primary Endpoint

The registry lists the primary outcome as Patient Survival, measured over From the date of kidney transplantation till death or data cut-off, whichever came first, assessed up to 10 years..

Patient survival is the primary endpoint. It measures whether a participant is alive after kidney transplantation, with death from any cause counted as the event. The registry defines the observation period as beginning on the transplantation date and ending at death or data cut-off, whichever came first, assessed up to 10 years. Its endpoint description says all-cause death was followed through the end of follow-up, identified as January, 2023.

General statistical context: survival endpoints are useful when both whether an event occurs and when it occurs matter. A simple event count does not retain the timing information. Survival methods can use the follow-up time while accounting for participants whose observation ends before the event is recorded; this ending of observation is commonly called censoring. A survival estimate or comparison would therefore communicate more than the number of deaths alone.

The registry record does not report a survival curve, survival probability at a stated time, hazard ratio, confidence interval, or test result for this primary endpoint. Nor does it report how censoring was handled in an analysis. The deaths listed with the adverse-event figures are counts by group, not a reported time-to-event analysis. They cannot by themselves show the survival experience over the registered follow-up period. Thus, the endpoint is clearly named and described, but its comparative result and precision are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General statistical context: the method should follow the type of outcome and the way observations are collected. Patient survival is a time-to-event outcome: the event is death, and the time origin is the date of kidney transplantation. The registry states that observation ends at death or data cut-off, whichever came first. Participants who have not had a recorded event by the end of observation contribute follow-up up to that point; this is the basic setting in which censoring needs to be considered.

The registry record does not name a time-to-event method. It does not report Kaplan–Meier estimates, a log-rank test, a Cox model, or another survival analysis. These are examples of general approaches, not methods confirmed for this study. A Kaplan–Meier estimate, in general, describes survival over time while accounting for censored observations. A log-rank test, in general, compares survival experience between groups. A Cox model, in general, can estimate a relative event rate and may adjust for measured covariates, subject to model assumptions. No result from any of these methods is reported in the registry record.

For a time-to-event comparison, readers would ordinarily need an estimate, its uncertainty, a clear definition of the event and time origin, and a description of how censoring and group membership were handled. They would also need to know whether the analysis adjusted for relevant baseline differences. The endpoint description supplies the event and time origin, but the analysis method, censoring details, adjustment strategy, and resulting estimates are not reported in the registry record. Without those elements, the death counts cannot be expanded into a survival comparison.

What does the event-count format mean?

The primary outcome is described as a participant count, and the registry labels the outcome type as participants with an event. A count states how many participants had an event in the reported group. Counts are easy to interpret as totals, but they do not automatically account for different group sizes or durations of observation. A rate or proportion would require a specified denominator and calculation; a time-to-event estimate additionally uses follow-up timing. No such derived comparative results are reported in the registry record.

General statistical context: uncertainty around a count-based comparison depends on the amount of information and on the statistical model. Sparse event information in a group can make an estimate less precise, and a zero in a reported event column does not establish that the underlying event risk is exactly zero. This is especially important when the information is an event listing rather than a prespecified and fully described outcome analysis. The registry record does not provide confidence intervals for the group counts or an inferential method for them.

Why does the group structure affect interpretation?

The groups are defined by pre-existing stenosis status and category. The record states that allocation is not stated and that this is not a randomized comparison. General statistical context: random assignment can help balance known and unknown participant characteristics across assigned groups. When groups instead arise from participant characteristics, comparisons may be affected by differences in health status, clinical selection, or other factors. This does not show that any particular factor affected these results; the registry record does not report enough information to assess that question.

Adjustment can sometimes address measured differences, but it cannot be assumed. The registry does not report a covariate list, an adjusted model, or an analysis population. It also does not report whether participants were analyzed according to any specific grouping rule beyond the group descriptions. Thus, there is no basis for describing the posted death counts as adjusted, causal, or representative of an effect of stenosis category.

What is known about planning and analyses?

The registry lists no analyses. It does not report a sample-size justification, target power, interim analysis, stopping rule, or detailed statistical plan. General statistical context: a sample-size calculation is a planning exercise based on assumptions about an outcome, an effect of interest, variability or event frequency, and a chosen error rate. It is not a finding about the data collected. The record does not provide the trial's own planning rationale or enough analysis results to evaluate whether the study could estimate a particular survival contrast with useful precision.

A planning illustration based on an observed effect, if presented separately, is not observed power and should not be confused with a prespecified design justification. No illustration values are reported in the registry record. More broadly, enrollment alone cannot establish adequate precision: interpretation requires the outcome data, follow-up information, analysis method, and uncertainty around the estimates. Those comparative results are not reported for patient survival.

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("No-stenosis Group", "TASC A/B Stenosis", "TASC C/D Stenosis")
n      <- c(524, 96, 35)
events <- c(322, 48, 6)
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  No-stenosis Group  524  322  61.5  57.1  65.6  57.2  65.5  57.2  65.5
ARM  TASC A/B Stenosis  96  48  50.0  39.6  60.4  40.2  59.8  40.2  59.8
ARM  TASC C/D Stenosis  35  6  17.1  6.6  33.6  8.1  32.7  8.2  32.8

11. Multiplicity, Missing Data and Analysis Populations

The registry lists patient survival as the primary outcome and death-censored graft survival and graft function as secondary outcomes. It also reports 3 outcome measures, but no formal analyses are listed. Statistical methods for addressing multiple outcomes or multiple group comparisons are not reported in the registry record. It is therefore not possible to determine whether any multiplicity adjustment was planned or applied, or how the primary and secondary outcomes were prioritized in the analysis.

General statistical context: when researchers test several outcomes or make several comparisons, the chance of a false-positive finding across the set can increase if each test is interpreted independently. A prespecified hierarchy, adjustment procedure, or clear emphasis on estimation can help readers understand how to interpret multiple results. No such approach is described in the registry record. Since comparative results are not reported, there are no reported p-values or confidence intervals whose multiplicity handling can be evaluated.

Missing-data methods are also not reported. For a survival endpoint, the end of observation for a participant without a recorded death is usually represented through censoring, but the registry does not give analysis details about censoring, loss to follow-up, or completeness of follow-up. It does not report missing outcome data or a method for handling missing observations. The registry's stated data cut-off and follow-up description identify the intended observation window, but do not establish that every participant had complete follow-up.

Analysis populations are not described. The record does not state whether an analysis included all enrolled participants, only participants with particular records, or another defined group. It also does not report exclusions from analysis or handling of participants whose group classification or outcome information might be unavailable. These omissions limit assessment of how closely any result would represent the enrolled groups. Because no formal outcome analyses are reported, the impact of missing data, multiplicity, and analysis-set choices cannot be evaluated from the registry record.

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 information lists, for the no-stenosis group, 524 participants at risk, 0 participants with a serious event, 0 participants with another event, and 202 deaths. For the TASC A/B stenosis group, it lists 96 participants at risk, 0 with a serious event, 0 with another event, and 48 deaths. For the TASC C/D stenosis group, it lists 35 participants at risk, 0 with a serious event, 0 with another event, and 29 deaths. The registry lists no top serious-event terms.

These entries should be read as the counts recorded in the adverse-event listing, not as a complete estimate of safety. The zeros mean that the listed affected-participant counts are 0; they do not establish that no event occurred outside the way events were collected, classified, or reported. The registry record does not describe the adverse-event collection procedures, observation period for these entries, severity grading, or completeness of reporting.

Deaths are shown separately from the serious-event and other-event affected-participant counts in these entries. Their presence in this listing does not substitute for the primary patient-survival analysis. No comparative safety estimate, confidence interval, or adjustment is reported. The figures therefore describe what the registry records by group, but do not establish a causal safety difference between groups.

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

The registry record documents a study of kidney transplantation among patients grouped by pre-existing aortoiliac stenosis status. It names patient survival as the primary outcome and specifies all-cause death from transplantation through the end of follow-up. It also records group sizes and deaths in the adverse-event information. These details describe the study question and some posted counts.

What the record does not provide is a formal comparison of patient survival across groups. There are no reported survival probabilities, time-to-event estimates, confidence intervals, or statistical test results. The group death counts cannot reveal when deaths occurred, how long participants without a recorded death were followed, or how censoring was handled. They therefore cannot establish the magnitude or precision of a survival difference.

The absence of a reported comparison should not be interpreted as evidence that the groups are the same, nor as evidence that they differ. It is a limit of the posted statistical information. General statistical context: a conclusion about similarity requires an appropriate estimate and enough precision to rule out differences considered important; a lack of a reported test result does not demonstrate equivalence.

The group structure also prevents a straightforward causal interpretation. Stenosis category is a pre-existing characteristic, and the record states that this is not a randomized comparison. Other group differences may influence observed outcomes, but which factors were considered is not reported in the registry record. No adjusted result is available to separate such differences from the association with stenosis category.

The adverse-event entries report 0 serious-event and 0 other-event participants in each group, alongside death counts. Those figures are not enough to establish that the study captured every relevant safety event, and the record does not describe event ascertainment in detail. Overall, the posted information supports a descriptive account of the study groups and recorded counts, but not a definitive statistical or causal conclusion about survival, graft outcomes, or comparative safety.

14. Why This Trial Matters Statistically

This study addresses a clinically relevant statistical challenge: outcomes after kidney transplantation are being considered across groups defined by aortoiliac stenosis status and category. The registry includes a no-stenosis group and two stenosis categories, with patient survival as the primary endpoint. Such a question requires analysis that respects both the time until an event and the possibility that observation ends before an event is recorded.

It also illustrates why group counts should not be treated as a complete outcome comparison. Counts are useful for describing recorded events, but the primary endpoint is time-to-event. Follow-up duration and censoring affect how survival information is interpreted. Without survival estimates and uncertainty intervals, readers cannot tell how precisely the group experiences have been compared.

The nonrandomized grouping is another important feature. The registry explicitly says this is not a randomized comparison and does not state an allocation method. Statistical interpretation must therefore distinguish an observed association from a causal effect. Adjustment may be relevant in observational comparisons, but the registry record does not report whether adjustment was used or which participant characteristics were considered.

Finally, the record shows the value of complete statistical reporting. The study is marked completed and lists primary and secondary outcomes, yet formal analyses and comparative outcome estimates are not reported. Without these, readers cannot assess precision, multiplicity, missing-data handling, or the robustness of conclusions. The study question remains clear, while the posted quantitative evidence is insufficient to resolve it statistically.

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 registry record constrain interpretation. The primary endpoint is described, but comparative patient-survival estimates are not reported. The posted death counts do not include timing of events, follow-up distributions, censoring details, or uncertainty estimates. The registry record therefore does not permit assessment of the size or precision of a survival contrast.

The group definitions are based on pre-existing stenosis status, and the record states that this is not a randomized comparison. Allocation is not stated. The record does not report adjustment methods, covariates, or other steps that might address differences between groups. It is not possible to determine whether any observed group pattern would be attributable to stenosis category rather than other differences.

Follow-up is described as extending to death or data cut-off, assessed up to 10 years, while the endpoint description identifies the end of follow-up as January, 2023. The record does not explain this wording or provide participant-level follow-up summaries. The registry also does not report missing-data methods, analysis populations, exclusions, or outcome ascertainment details.

The adverse-event entries list 0 affected participants for serious events and 0 for other events in each group, but the record does not describe how events were solicited, classified, or monitored. Those counts cannot establish complete safety ascertainment. The secondary outcomes, death-censored graft survival and graft function, are named but their definitions and comparative results are not reported in the registry record.

Finally, the record does not provide a statistical analysis plan, sample-size justification, interim-analysis information, or multiplicity approach. With no analyses listed, it is not possible to assess whether the completed study's statistical methods matched a prespecified plan.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Aortoiliac Stenosis in Kidney Transplantation — NCT06020534.
• Registry record last updated 2025-01-07; status last verified 2024-12.
• Results first posted 2024-12-12.
• 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

NCT06020534 is a completed study sponsored by Erasmus Medical Center, with enrollment of 655. The record lists a study start of 2022-01-01 and primary completion on 2023-01-31. Participants are grouped as having no pre-existing aortoiliac stenosis, TASC A/B stenosis, or TASC C/D stenosis before kidney transplantation.

Patient survival is the primary outcome, defined by all-cause death from transplantation through the end of follow-up, assessed up to 10 years. Death-censored graft survival and graft function are listed as secondary outcomes. The adverse-event listing reports group-specific counts, including deaths, but the registry record lists no formal analyses and provides no comparative survival estimates or uncertainty intervals.

The record identifies this as a nonrandomized comparison and does not report allocation, adjustment methods, analysis populations, missing-data methods, or a statistical plan. Accordingly, the posted counts are descriptive and do not establish a causal or statistically quantified difference among the groups.