Standard Open Surgery Versus Endovascular Repair of Abdominal Aortic Aneurysm (AAA): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Standard Open Surgery Versus Endovascular Repair of Abdominal Aortic Aneurysm (AAA) (NCT00094575), a randomized phase 4 study. The primary outcome is All-cause Mortality.

2. Clinical Question

The trial compared two procedural strategies for repairing abdominal aortic aneurysms. Its primary endpoint was all-cause mortality, with vital status assessed from randomization until the end of study follow-up or death, whichever occurred first. The registry describes follow-up as lasting up to 9 years.

The registry also lists secondary outcomes concerning additional therapeutic procedures and health-related quality of life, including SF-36, EQ-5D, and IIEF-5 measures. These outcomes broaden the comparison beyond mortality, but their measures and analysis approaches differ from the primary endpoint. Their findings therefore need to be read on their own terms rather than treated as interchangeable evidence about mortality.

The central statistical question is whether the observed mortality data distinguish the groups with useful precision. The registry’s sponsor-reported analysis uses a log-rank method and reports a hazard ratio with a confidence interval and p-value. An unadjusted re-calculation expresses the group contrast as a risk difference from the posted counts. Those summaries address the same broad endpoint but use different statistical expressions; neither should be interpreted as proof that the procedures are equivalent or that a difference is absent.

3. Trial Design

The registry describes the OVER trial as a randomized, multicenter, parallel-group study comparing endovascular repair with standard open repair for abdominal aortic aneurysms. It is listed as phase 4, with no masking. The sponsor is the VA Office of Research and Development. The trial is marked completed.

The registry reports enrollment of 881. The posted primary outcome counts are 146 participants with all-cause mortality among 444 in the endovascular-repair group and 146 among 437 in the open-repair group. These are the group counts for the posted endpoint and should be distinguished from the registry’s overall enrollment figure.

The study start is recorded as 2002-10, and primary completion as 2011-10. The primary endpoint description says participants were followed for the duration of the study, up to 9 years. Vital status was assessed from randomization until end of study follow-up, dated 10/15/2011 in the description, or death, whichever occurred first.

The trial’s stated purpose included comparison of long- and short-term results, cost, and quality of life associated with the two repair strategies. The posted secondary outcome list includes secondary therapeutic procedures, SF-36 mental and physical component scores, a physical component score including deaths, EQ-5D index and visual analog scale scores, and IIEF-5. The registry indicates 8 outcome measures and 8 analyses overall, while 7 secondary outcomes are posted in the available record.

The original sample-size justification, detailed allocation procedures, and full statistical analysis plan are not reported in the registry record. Randomization is reported, but further details about sequence generation or concealment are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

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 All-cause Mortality, measured over Participants were followed for the duration of the study, up to 9 years.

The primary endpoint is all-cause mortality, recorded as the number of participants who died. The registry says vital status was assessed from randomization to the end of study follow-up or death, whichever occurred first, with follow-up lasting up to 9 years. This endpoint counts deaths from any cause rather than restricting the outcome to a particular cause.

All-cause mortality is a clinically important endpoint in a comparison of repair strategies because it captures survival regardless of the attributed cause of death. Its definition is comparatively direct: a participant either died during the stated follow-up or did not, according to the vital-status assessment. The endpoint does not, by itself, describe the timing or cause of each death, nor does a count alone show how risk changed over follow-up.

The posted counts are 146 deaths among 444 participants in the endovascular-repair group and 146 among 437 in the open-repair group. These counts provide the basis for the unadjusted risk comparison. The registry also reports a time-to-event analysis using the log-rank method and a hazard ratio. That analysis uses information about event timing, whereas a simple comparison of the proportions with an event treats the outcome as a binary count over the observed follow-up period.

How missing or incomplete vital-status information was handled is not reported in the registry record. The endpoint description establishes the intended follow-up window, but does not provide further details about censoring or the completeness of outcome ascertainment.

7. Results Posted in the Registry

• Open Repair: 33.4% (146/437) versus 32.9% (146/444) on control; risk difference 0.5 percentage points (95% CI -5.7 to 6.7), risk ratio 1.02 (0.84–1.23); unadjusted two-proportion z-test p = 0.868.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Secondary Therapeutic Procedures

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Open Repair: 17.8% (78/437) versus 22.1% (98/444) on control; risk difference -4.2 percentage points (95% CI -9.5 to 1.0), risk ratio 0.81 (0.62–1.06); unadjusted two-proportion z-test p = 0.117.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Open Repair and the control. The interval gives the range of effects that remain compatible with the data.

The registry lists secondary outcomes spanning additional therapeutic procedures and several quality-of-life measures. The posted results include analyses for secondary therapeutic procedures, while the record indicates that 7 secondary outcomes are posted overall. These outcomes cover different constructs and measurement scales, so a common interpretation cannot be applied across all of them.

As a broad pattern, the secondary outcomes add information about procedures and patient-reported health dimensions that mortality alone does not capture. They complement the primary endpoint rather than provide a second version of it. A difference on a procedure or quality-of-life measure would not, by itself, establish a mortality difference; conversely, a mortality comparison does not summarize all of the secondary domains.

The secondary comparisons should be interpreted cautiously because the record does not report a multiplicity strategy. When several outcomes are tested, the chance of at least one apparently notable result arising by chance can increase. Unless the testing plan accounts for that, unadjusted secondary p-values provide weaker confirmatory evidence than a prespecified primary analysis. The registry reports a chi-squared p-value of 0.12 for secondary therapeutic procedures; that result should be read as an unadjusted secondary comparison, not as independent confirmation of the primary mortality finding.

The record does not report enough detail to establish the hierarchy, prespecification, or complete analysis approach for every secondary endpoint. It also does not report how missing measurements were handled for the quality-of-life outcomes. Accordingly, the overall secondary pattern is best treated as supportive and exploratory context, with each outcome interpreted according to its measure and uncertainty rather than combined into a single conclusion.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Secondary Therapeutic Procedures
• SF-36 Mental Component Score (MCS)
• SF-36 Physical Component Score (PCS)
• SF-36 Physical Component Deaths Included Score (PCTD)
• European Quality of Life-5 Dimension (EQ-5D) Index Score
• European Quality of Life-5 Dimension (EQ-5D) Visual Analog Scale
• International Index of Erectile Function (IIEF-5)

9. Statistical Interpretation

10. Statistical Methods Explained

The registry reports two kinds of primary-outcome comparison: a sponsor-reported time-to-event analysis and unadjusted re-calculations based on the posted event counts. They summarize the same broad mortality question but do not use identical statistical methods. The distinction is useful because a point estimate alone does not convey how uncertain the comparison is, and because the timing of events can be relevant when follow-up varies.

What does the risk difference describe?

A risk difference compares the proportions of participants with an event in two groups. In the posted re-calculation, open repair is compared with endovascular repair. The estimate is 0.005, with a 95% confidence interval from -0.057 to 0.067. A value of zero represents equal observed risks; positive and negative values indicate differences in opposite directions according to the stated group order. Because the interval spans zero, the data are compatible with either direction as well as a small difference.

This is an unadjusted comparison. It uses the posted event counts and group sizes without adjustment for other variables. It is not a replacement for the sponsor’s analysis, and it does not incorporate event timing. In general, unadjusted summaries are transparent and easy to interpret, but they may not reflect the exact estimand or model used in a trial’s primary analysis.

What do the risk ratio and odds ratio add?

The risk ratio expresses one group’s event risk relative to the other group’s risk. The posted estimate is 1.016, with a confidence interval from 0.842 to 1.226. The odds ratio compares the odds of an event between groups; its estimate is 1.024, with a confidence interval from 0.773 to 1.356. For both measures, the no-difference value is 1, and both intervals include that value.

These measures express the contrast on different scales. A ratio near 1 indicates that the estimated group risks or odds are similar on the ratio scale, but the confidence interval still matters: it shows which values remain compatible with the data under the method’s assumptions. Odds ratios and risk ratios are not interchangeable quantities, even when they point in a similar direction.

How does the log-rank analysis differ?

The sponsor reports a log-rank analysis with a hazard ratio of 0.97, a 95% confidence interval from 0.77 to 1.22, and p = 0.81. A time-to-event approach considers when events occur, and can account for participants having different lengths of observed follow-up through censoring. A hazard ratio summarizes the relative instantaneous event rates over the observed period, subject to the model and assumptions. It is not simply the ratio of the final event counts.

The log-rank test assesses whether the observed event-time patterns differ between groups under its null hypothesis. Its p-value does not measure the probability that the null hypothesis is true, nor does it describe the size of a possible effect. The hazard-ratio confidence interval is more informative about precision and includes values on either side of 1.

What does a p-value tell the reader?

A p-value measures how unusual results at least as incompatible with a specified null hypothesis would be under the test’s assumptions, if that null hypothesis held. It is not a measure of clinical importance, nor does a large p-value establish equivalence. Here, the unadjusted risk-difference p-value is 0.868, while the sponsor-reported log-rank p-value is 0.81. The two values belong to different analyses and should not be treated as competing estimates of effect.

General statistical interpretation: confidence intervals combine an estimate with a range of values that remain reasonably compatible with the data under the analysis. They depend on assumptions and are not guarantees that the true value lies within the observed interval. For trial interpretation, effect size and interval width should be considered alongside the test result.

What information is not reported?

The registry record does not report the detailed statistical analysis plan, assumptions of the sponsor’s time-to-event model, or the handling of missing outcome data and censoring. It also does not report whether any covariate adjustment was planned or used in the sponsor analysis. Accordingly, the posted results support a description of the stated estimates and their precision, but not a complete reconstruction of every analytic decision.

For binary outcomes, over-dispersion is generally a concern when observed variability exceeds what a chosen probability model expects; the record does not report an over-dispersion method for these outcomes. More generally, matching an analysis to the endpoint, follow-up, and trial design is important. The registry’s reported log-rank result and the simple unadjusted re-calculation answer related but not identical statistical questions.

11. Confidence Intervals and Precision

The primary risk-difference estimate is 0.005, with a 95% confidence interval from -0.057 to 0.067. This interval is wide enough to include values on both sides of zero, so the posted binary counts do not pin down the direction of a possible difference. The point estimate alone can look close to zero, but it should not be read without the uncertainty interval.

The sponsor-reported hazard ratio is 0.97, with a 95% confidence interval from 0.77 to 1.22. This interval crosses 1, the reference value for equal hazards. It permits a range of relative event-rate patterns rather than identifying one precise effect. The time-to-event estimate and binary risk-difference estimate use different methods, so their intervals should be interpreted separately.

The posted unadjusted risk-ratio interval, from 0.842 to 1.226, and odds-ratio interval, from 0.773 to 1.356, also include their respective no-difference values. Across these measures, the central estimates are close to no difference, but the intervals allow departures from it. Thus, the result is not a precise estimate of equivalence.

In general, a confidence interval represents uncertainty under the statistical method and its assumptions. It is not a range containing a fixed proportion of individual outcomes, and it does not account automatically for unreported sources of bias or incomplete outcome ascertainment. The registry record does not report a clinically important difference threshold, so it is not possible to judge the intervals against a stated equivalence or non-inferiority margin.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size display is a planning illustration based on the observed effect, not the original trial design. For this time-to-event primary outcome, the figures are TOTAL numbers of events, using the Schoenfeld approach; they are not participants per arm. The planning assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Each row considers detecting a stated fraction of the observed effect.

The 80% power column gives the required total number of events under those planning assumptions for an 80% chance of detecting the specified effect, if that effect were real and the assumptions held. The 90% power column describes the corresponding event requirement for a 90% chance. The values are planning targets, not event counts observed in the trial.

The rows illustrate how the required information changes when the target effect is smaller than the observed effect: planning for 75% of the observed effect requires more events than planning for 100%, and planning for 50% requires more again. Smaller effects are harder to distinguish from random variation, so they require more information to detect at a given power level.

This is not observed power. It is a forward-looking illustration calculated from the observed effect, not a measure of the probability that the completed trial detected a true effect. The original sample-size justification and design assumptions are not reported in the registry record, so these planning figures should not be presented as the trial’s own recruitment target or as evidence that the original design was adequate or inadequate.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.329; treatment proportion p₁ = 0.334; average p̄ = 0.331.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6657 = 1.3048.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6657 = 0.5603.
4. n = (1.3048 + 0.5603)² / (0.0053)² = 125,377.8, rounded up to 125,378 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.328828828828829                          # control proportion
p1 <- 0.334096109839817                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(94575)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 125,378 (80% power), 167,845 (90% power)
 75% of observed effect: n per arm = 222,672 (80% power), 298,094 (90% power)
 50% of observed effect: n per arm = 500,507 (80% power), 670,036 (90% power)
power.prop.test: 125377.8 
Simulated power at n = 125,378 per arm: 0.802 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

The sponsor’s reported primary analysis is a log-rank comparison with a hazard ratio of 0.97, a 95% confidence interval from 0.77 to 1.22, and p = 0.81. This is a time-to-event analysis that uses event timing over follow-up. The unadjusted re-calculation instead compares the posted event proportions, reporting a risk difference of 0.005, a 95% confidence interval from -0.057 to 0.067, and p = 0.868.

The two estimates are not expected to be numerically identical: a hazard ratio and a risk difference use different scales and methods. Both results place the estimate near their no-difference value, and both intervals include that value. The re-calculation is a simple check based on posted summary counts; it does not reproduce the sponsor’s time-to-event analysis.

The registry record does not report the full model specification or detailed analysis plan needed to reconstruct the sponsor’s result. The discrepancy indicator is false, so there is no flagged discrepancy requiring the sponsor analysis to take precedence over a conflicting recalculation. The sponsor’s analysis remains the reported trial analysis, while the recalculation is supplementary and should not be described as a replacement.

15. Multiplicity, Missing Data and Analysis Populations

The registry record lists multiple secondary outcomes in addition to all-cause mortality. It does not report a multiplicity adjustment, a hierarchy for testing outcomes, or a detailed plan for interpreting multiple comparisons. This matters because repeated testing across several endpoints can make chance findings more likely. Without a stated strategy, secondary p-values should not be treated as if each were the sole confirmatory test.

The primary endpoint is identifiable in the record, but the full prespecified statistical analysis plan is not reported in the registry record. It is therefore unclear from the posted information whether there were planned subgroup analyses, interim analyses, adjusted models, or other procedures affecting interpretation. Their existence or absence should not be guessed.

The outcome counts identify the groups and recorded events, but the record does not report the full analysis population definition. It does not specify whether the primary analysis followed an intention-to-treat principle, whether participants were analyzed according to randomized assignment, or whether any participants were excluded from particular analyses. The registry’s randomization description alone does not answer those questions.

For mortality, vital status was assessed from randomization to the end of follow-up or death. However, details on loss to follow-up, incomplete vital-status ascertainment, censoring rules, and missing-data handling are not reported in the registry record. For secondary quality-of-life measures, the registry does not report the amount or pattern of missing measurements or the method used to address them.

These gaps do not invalidate the posted statistics, but they restrict how completely they can be assessed. Missingness can affect the target population represented by an analysis, while multiplicity affects how much weight to give a set of test results. A full assessment would require the analysis plan and outcome-ascertainment details, neither of which is reported in the registry record.

16. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

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

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pneumonia (10.8%), chronic obstructive pulmonary disease (8.7%), fall (7.1%), cardiac failure congestive (6.4%), death (5.4%).

The adverse-event record reports serious adverse events affecting 336 of 444 participants in the endovascular-repair group and 329 of 437 in the open-repair group. It also reports other adverse events affecting 127 of 444 and 177 of 437, respectively. These are separate registry categories; the record does not define their relationship in greater detail, so they should not be combined or interpreted as mutually exclusive categories.

The registry lists pneumonia (10.8%), chronic obstructive pulmonary disease (8.7%), fall (7.1%), cardiac failure congestive (6.4%), death (5.4%), and myocardial infarction (5.3%) among the top serious-event terms. The record does not provide the corresponding group-specific breakdown for these terms in the listed summary. The death term in this adverse-event listing is not a substitute for the primary all-cause mortality analysis.

These summaries describe recorded adverse events; they do not by themselves establish whether a procedure caused an event. Definitions, severity coding details, timing, and statistical comparisons for the event terms are not reported in the registry record. The group-level figures should therefore be read descriptively and not as a complete comparative safety analysis.

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

The posted results show similar observed numbers of deaths in the two randomized groups: 146 in each. The unadjusted risk difference is 0.005, with a 95% confidence interval from -0.057 to 0.067. The sponsor’s log-rank analysis reports a hazard ratio of 0.97, with a 95% confidence interval from 0.77 to 1.22. Both analyses have estimates near their no-difference values, and their intervals include those values.

These findings mean that the posted analyses did not identify a clear difference in all-cause mortality between the groups. They do not prove that the procedures are equivalent, that no meaningful difference exists, or that the true effect is exactly zero. The intervals leave room for effects in either direction, and the registry record does not state a margin for equivalence or clinical importance.

The primary endpoint concerns mortality over follow-up of up to 9 years. It does not fully describe other outcomes that may matter to patients or clinicians, such as additional procedures or quality of life. Those outcomes are listed separately, and their results require their own interpretation. Nor does the primary mortality comparison establish the cause of any individual death.

Randomization supports a comparative design, but statistical conclusions still depend on the outcome data, analysis methods, and completeness of follow-up. The registry record does not report several details needed for a full audit, including the full statistical plan, missing-data handling, and analysis-population definition. These limits should temper claims extending beyond the stated endpoint and posted analyses.

The most defensible reading is therefore narrow: in the recorded follow-up, the mortality estimates were close between groups, while the uncertainty intervals do not rule out differences in either direction. The results are informative about the observed comparison but do not answer every question about the relative consequences of the repair strategies.

18. Why This Trial Matters Statistically

This trial is statistically notable because it compares two procedural strategies using randomized allocation and follows a direct endpoint, all-cause mortality, over a period described as up to 9 years. The registry also reports a time-to-event analysis alongside group event counts, making it possible to distinguish a comparison of observed proportions from an analysis that uses event timing.

The results illustrate why a near-zero point estimate and a non-small p-value are not enough to conclude that groups are equivalent. The risk-difference interval spans negative and positive values, while the hazard-ratio interval spans values below and above 1. The estimates are close to no difference, but their precision still permits effects in either direction. This distinction is central to sound interpretation of randomized trials.

The posted summaries also show how different statistical measures express the same broad comparison on different scales. Risk difference communicates an absolute contrast, while risk ratio and odds ratio express relative contrasts; the sponsor’s hazard ratio concerns event rates over time. These measures should not be conflated, even when their general direction is similar.

Finally, the trial demonstrates the importance of separating the primary endpoint from secondary outcomes and from safety-event listings. Mortality, additional procedures, quality-of-life measures, and adverse-event terms address different questions. Careful interpretation requires attention to each outcome’s definition, analysis, uncertainty, and multiplicity context rather than a single broad claim based on one test result.

19. 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 registry record gives a useful description of the randomized comparison and primary endpoint, but several trial-specific details are not reported. The detailed randomization procedures, allocation concealment, and complete statistical analysis plan are not reported in the registry record. The record identifies no masking, but further operational details are not reported.

For the primary mortality outcome, the record states that vital status was followed from randomization until death or the end of study follow-up. It does not report the number of participants with incomplete vital-status information, loss-to-follow-up details, censoring rules, or the approach to missing outcomes. The sponsor’s hazard-ratio model specification and assumptions are also not reported in the registry record.

The original sample-size justification and the design assumptions used when planning recruitment are not reported. The posted planning illustration is based on the observed effect and cannot establish what the trial was designed to detect. No prespecified equivalence or non-inferiority margin is reported, which limits claims that the groups were equivalent.

The registry lists several secondary measures, but does not report a multiplicity strategy or enough detail to determine the complete testing hierarchy. It also does not provide full missing-measurement information for the quality-of-life outcomes. The adverse-event summary supplies group totals and selected serious-event terms, but does not provide full event definitions, timing, or group-specific counts for the listed terms.

These limitations concern the detail available in the registry record; they do not imply that the underlying trial lacked such procedures or information. They mean that conclusions should stay close to the posted endpoint definitions and estimates, without assuming undocumented analytic decisions or outcome handling.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Standard Open Surgery Versus Endovascular Repair of Abdominal Aortic Aneurysm (AAA) — NCT00094575.
• Registry record last updated 2016-03-07; status last verified 2016-02.
• Results first posted 2013-12-31.
• 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.

23. Record Summary

The registry describes the completed, phase 4, multicenter randomized OVER trial, which compared endovascular repair with standard open repair for abdominal aortic aneurysms. It lists no masking and a parallel-group design. Enrollment is 881, and the sponsor is the VA Office of Research and Development.

The primary endpoint was all-cause mortality during follow-up of up to 9 years. The posted counts are 146 deaths among 444 participants assigned to endovascular repair and 146 among 437 assigned to open repair. The sponsor-reported log-rank analysis gives a hazard ratio of 0.97, a 95% confidence interval from 0.77 to 1.22, and p = 0.81. The unadjusted risk-difference re-calculation is 0.005, with a 95% confidence interval from -0.057 to 0.067.

The registry lists secondary procedural and quality-of-life outcomes. The mortality estimates are close to their no-difference values, but the confidence intervals allow effects in either direction and do not establish equivalence. Important details about the complete analysis plan, missing data, and analysis populations are not reported in the registry record.