Trial on Endovascular Aneurysm Management: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Trial on Endovascular Aneurysm Management (NCT00537134), a randomized na study. The primary outcome is Number of Participants With Disease or Treatment-related Morbidity and Mortality..

2. Clinical Question

The clinical question reflects a tension described in the registry record: an unruptured aneurysm may later bleed, while intervention also has immediate risks and does not eliminate every subsequent risk. The trial therefore compared an active endovascular approach with deferral of treatment rather than assuming that either strategy was risk-free.

The primary outcome classified modified Rankin Scale scores of 0, 1, or 2 as “good” and scores of 3, 4, 5, or 6 as “bad.” The scale ranges from 0, indicating no symptoms, to 6, indicating mortality. The question was whether morbidity or mortality meeting the stated definition occurred by the specified follow-up, not whether every aneurysm was occluded or whether all measures of cognition and quality of life differed.

Secondary outcomes addressed additional aspects of the comparison, including hemorrhage, modified Rankin Scale scores, health status measured with the SF-36, aneurysm occlusion, and cognitive function assessed with MoCA. These outcomes broaden the clinical picture, but their results are not reported in the posted record. Eligibility criteria, baseline characteristics, and the clinical characteristics of participants are not reported in the registry record.

3. Trial Design

The trial is registered as randomized, single-masked, and parallel-group. Its arms were conservative management, described as watchful observation, and endovascular treatment, identified as embolization by coiling. The phase is recorded as NA. The condition is brain aneurysm, and the stated clinical focus is unruptured intracranial aneurysms.

The registry title describes a randomized comparison with indefinite deferral of treatment in 2002 patients followed for 10 years. The enrollment recorded in the trial details is 80, and the trial status is terminated. These entries do not establish that the title’s intended population or follow-up duration was achieved. The registry record does not explain the termination, report the actual duration of follow-up for participants, or reconcile the title’s description with the recorded enrollment.

The recorded start is 2006-04 and the primary completion date is 2009-06-28. The primary outcome timeframe is 1 year after treatment or observation. The record does not report the timing of recruitment by arm, how long participants were followed in practice, or whether all participants reached the stated primary-outcome assessment.

Posted primary-outcome arm records list n=12 for conservative management and n=11 for endovascular treatment. Those counts are not interchangeable with the recorded enrollment, and the registry record does not explain the relationship between these outcome records and enrollment. The adverse-event records separately list 38 at risk in the conservative group and 42 at risk in the endovascular group. The record does not describe why the populations or denominators differ across these entries.

Random allocation is useful because, when implemented and preserved, it can reduce systematic differences between groups at the outset. The registry record does not report the randomization procedure, allocation concealment, or masking details beyond the single-masked designation. It does not identify who was masked. It also does not report a sample-size justification, a protocol, or the reasons for ending the trial.

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: there are no pre-assignment procedures before assignment to groups

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 Number of Participants With Disease or Treatment-related Morbidity and Mortality., measured over 1 year after treatment or observation.

The primary endpoint is the count of participants with disease- or treatment-related morbidity or mortality, assessed 1 year after treatment or observation. The registry record says the assessment used the modified Rankin Scale, with scores assigned through a structured interview process. Scores of 0, 1, or 2 were categorized as a “good” primary outcome; scores of 3, 4, 5, or 6 were categorized as “bad.” The scale’s stated range runs from 0 for no symptoms to 6 for mortality.

This endpoint is intended to capture clinically consequential disability or death, rather than an imaging finding alone. It makes outcomes after the two different management strategies comparable under a shared functional definition. In general, a scale-based outcome can translate a complex clinical state into a prespecified category that can be counted and compared between groups. That simplification is also a limitation: participants within a category may have different experiences, and the binary good/bad grouping does not preserve all distinctions across the scale’s scores.

The primary outcome title refers to disease- or treatment-related morbidity and mortality, while the description specifies classification by modified Rankin Scale. The registry record does not report further rules for attributing events to disease or treatment, handling assessments that were unavailable, or resolving scores near category boundaries. The posted primary results give participant counts, not a full distribution of modified Rankin Scale scores.

7. Results Posted in the Registry

• Endovascular: 0.0% (0/11) versus 0.0% (0/12) on control; risk difference 0.0 percentage points (95% CI 0.0 to 0.0); unadjusted two-proportion z-test p = n/a.

8. Statistical Interpretation

9. Statistical Methods Explained

What does a risk difference describe?

In general, a risk difference compares the proportions of participants experiencing an outcome in two groups by subtracting one group’s proportion from the other’s. A value of 0 indicates no observed difference in the proportions under the calculation used. Unlike a relative measure, a risk difference expresses the contrast on the outcome’s absolute scale. Its interpretation depends on a clearly defined outcome, consistent follow-up, and the populations represented in each group.

The registry reports a risk difference of 0.0 for endovascular treatment relative to conservative management. Both posted primary outcome arm records list 0.0 participants with the bad outcome. The record also gives an interval from 0.0 to 0.0. No p-value is reported. Because the arm records are small and the registry’s different population entries are unexplained, the point estimate alone cannot establish that the underlying risks are equal.

What does the modified Rankin Scale contribute?

In general, a functional scale can turn varied clinical states into an outcome that is consistently assessed. This registry describes the modified Rankin Scale as ranging from 0 for no symptoms to 6 for mortality, with scores attributed using a structured interview. The primary definition groups scores 0, 1, or 2 as good and scores 3, 4, 5, or 6 as bad. Converting a scale into two categories makes the primary outcome easier to count, but loses detail about how participants are distributed across the original scores.

The endpoint is described as disease- or treatment-related morbidity and mortality, but the record does not explain how attribution was judged or whether assessors were masked. The study is labeled single-masked, yet the registry does not state who was masked. These omissions matter when an outcome involves an interview-based assessment, because knowledge of treatment assignment could potentially influence assessment in general. That is a methodological consideration, not evidence that bias occurred in this trial.

How should the interval be understood?

In general, a confidence interval is a range of values generated by a statistical procedure to convey uncertainty around an estimate. Its width depends on features such as the amount of information in the data and the method used. A narrow interval can appear precise, but it is meaningful only if the underlying calculation and analysis population are appropriate and the interval has been calculated and reported transparently.

The registry reports an interval whose two endpoints are both 0.0. With no events recorded in either primary arm, this displayed interval does not communicate the uncertainty a reader would ordinarily need to judge the range of plausible effects. The registry does not describe the interval method. No recalculation is reported, and there is no basis in the record to substitute a different estimate. The presented interval should therefore be read as the registry’s posted result, not as evidence that clinically relevant differences have been excluded.

What do randomization and masking mean in general?

Randomization assigns participants to groups by chance. In general, successful random allocation helps balance measured and unmeasured baseline factors across groups, so that a between-group comparison can more plausibly be attributed to the assigned strategies. That benefit depends on implementation and follow-up. The registry identifies this trial as randomized but does not report the sequence-generation method, concealment of allocation, or procedures for departures from assignment.

Masking means that some people involved in a trial do not know which treatment a participant received. In general, masking can reduce the influence of treatment expectations on care, reporting, or outcome assessment. The registry marks the trial as single-masked but does not identify the masked party. It also does not state whether outcome assessors were masked. These details are not reported in the registry record, so the practical protections against assessment bias cannot be evaluated from the entry.

Why do denominators and analysis populations matter?

A group’s outcome count is interpretable only alongside the participants included in that analysis and the follow-up available for them. The primary arm records list n=12 and n=11; the adverse-event records list 38 and 42 at risk; and overall enrollment is recorded as 80. These are distinct registry entries. Without an explanation of their relationship, it is not possible to determine whether the entries reflect different follow-up sets, outcome availability, or other reporting choices. The record does not provide participant flow, missing-outcome counts, or analysis-population definitions.

In general, analyzing participants according to their randomized assignment preserves the comparison created by randomization. Other analysis populations can answer different questions but may weaken that protection if inclusion depends on events after randomization. The registry record does not state which analysis population was used for the primary result or whether participants were analyzed as randomized.

What can be inferred from the registry’s analysis entries?

The record lists 0 analyses. This describes the analyses posted in the registry entry, not necessarily every analysis performed by the investigators. It does not report a statistical analysis plan, model specification, prespecified contrasts, or handling of missing data. A p-value is not reported for the primary comparison. Accordingly, the available results support a descriptive account of the posted counts and estimate, but offer limited material for evaluating the full inferential analysis.

In general, multiple outcomes and repeated testing can increase the chance of at least one apparently notable finding if results are selected or interpreted without a plan. This trial lists a primary outcome and secondary outcomes addressing hemorrhage, functional scores, health status, occlusion, and cognitive function. The registry does not report a multiplicity adjustment or a hierarchy for interpreting secondary outcomes. The posted secondary outcome results are not available in the record described, so they should not be inferred from the primary result.

The sample-size section uses planning assumptions based on an observed effect, equal allocation, a two-sided significance level of 0.05, and a normal approximation. Such figures, when presented, are planning illustrations rather than observed power. They do not establish that the original study had adequate power, and they are not the trial’s own design justification. The registry does not report the original sample-size justification or the assumptions used when planning the trial.

10. Confidence Intervals and Precision

The posted primary risk difference is 0.0, and its reported interval extends from 0.0 to 0.0. That is the interval recorded for the comparison; the registry does not describe how it was calculated. A p-value is not reported in the registry record. The arm records show 0.0 bad outcomes in the conservative group, with n=12, and 0.0 in the endovascular group, with n=11.

In general, an interval is intended to show how uncertain an estimate is, rather than merely repeat the estimate. A reported interval with identical endpoints may appear to convey complete precision. In this setting, however, zero events in the posted records and limited information about the method and analysis population make that appearance difficult to interpret. The registry does not report enough detail to assess whether the displayed interval captures the uncertainty relevant to the treatment comparison.

Absence of an observed event is not the same as absence of risk. When event counts are zero, the observed contrast can be zero even while the true group risks remain uncertain. This is a general statistical point, not a recalculation of the trial result. The posted risk difference should be understood as a summary of the recorded data, not as proof that a meaningful difference is impossible.

Precision is further difficult to judge because the primary outcome arm counts do not match the enrollment or adverse-event populations described elsewhere in the record. The relationship between n=12 and n=11, enrollment of 80, and adverse-event counts at risk of 38 and 42 is not reported. The actual completeness of follow-up at 1 year is also not reported. Without those details, the reader cannot determine how representative the primary records are of the randomized participants or how missing information affected the estimate.

The title’s reference to 10 years of follow-up does not supply precision for the primary endpoint, whose stated timeframe is 1 year after treatment or observation. Actual long-term outcome data are not reported in the registry record. Thus, the record does not support a precise conclusion about long-term hemorrhage risk or the comparative effects of the strategies over the title’s stated period.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome and secondary outcomes covering hemorrhage, modified Rankin Scale results, SF-36 health measures, aneurysm occlusion, and MoCA cognitive function. It records 9 outcome measures and 8 secondary outcomes posted. The record does not report a plan for controlling the risk of chance findings across multiple outcomes, a testing hierarchy, or which secondary outcomes were prespecified for formal inference. It is therefore not possible to assess multiplicity handling from the registry entry.

The registry lists 0 analyses. A primary risk difference is nevertheless posted, but a full statistical analysis plan is not reported. The p-value for the primary comparison is not reported. The record also does not specify model choices, the treatment of repeated measures, or whether any adjustments were made. These details should not be inferred from the descriptive result.

Missing-data information is limited. The registry does not report how many participants lacked the primary endpoint, whether incomplete follow-up occurred, how missing values were handled, or whether sensitivity analyses were conducted. The primary-outcome arm records list n=12 and n=11, whereas enrollment is 80 and adverse-event groups list 38 and 42 at risk. The registry does not explain how these populations relate. Without participant flow and analysis-population definitions, the effect of missing data or exclusions cannot be assessed.

The record also does not state whether the primary comparison followed randomized assignment, whether participants were analyzed as treated, or whether another analysis population was used. In general, the choice can affect how well a randomized comparison retains the protection of random allocation. The trial is identified as randomized, but the analysis details needed to judge this feature are not reported in the registry record.

These reporting gaps do not establish that multiplicity or missing data were mishandled. They mean that the available registry information is insufficient to evaluate those aspects of the analysis. The posted counts and estimate should be interpreted descriptively, with the stated limitations in mind.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: hemorrhage (2.4%).

The adverse-event entry lists the conservative group with 38 at risk, 0 serious adverse events, 2 other adverse events, and 0 deaths. The endovascular group is listed with 42 at risk, 1 serious adverse event, 3 other adverse events, and 0 deaths. These counts are reported as recorded; the registry does not explain how the at-risk populations relate to the primary-outcome arm records or to overall enrollment.

Hemorrhage is listed as a top serious adverse-event term at 2.4%. The record does not provide a further breakdown of that term in the information available, so it should not be assigned to a particular arm or interpreted as a comparative rate. Serious and other adverse events are separate categories in the registry entry; the record does not define their classification criteria in detail.

In general, safety counts are most informative when their follow-up period, event definitions, and population at risk are clear and comparable. Those details are not fully. The adverse-event counts therefore describe what the registry lists, but do not establish that the treatment strategies have equal safety, or that an event not recorded in these entries could not occur.

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

The primary result has a narrow descriptive meaning: the posted primary outcome records list no participants with the defined bad modified Rankin Scale outcome in either arm. The comparison is reported as a risk difference of 0.0, with an interval from 0.0 to 0.0. A p-value is not reported. These data do not establish that the underlying risks are identical or that either strategy is free of risk.

The result does not answer every clinical question raised by the trial. The primary outcome is assessed 1 year after treatment or observation and concerns a thresholded measure of morbidity or mortality. It is not itself a complete assessment of aneurysm hemorrhage, aneurysm occlusion, quality of life, or cognitive function. Although the registry lists secondary outcomes in those areas, their results are not reported in the information available.

The result also does not show that the planned long-term comparison was completed. The title refers to 2002 patients followed for 10 years, but enrollment is recorded as 80 and the trial status is terminated. The record does not explain the discrepancy, report actual long-term follow-up, or give the reason for termination. No conclusion about long-term prevention of aneurysmal hemorrhage can be drawn from the primary outcome entry alone.

The differing population counts further limit interpretation. The primary outcome entries list n=12 and n=11, while adverse-event entries list 38 and 42 at risk. These should not be treated as a single population or reconciled by assumption. Participant flow, missing-data handling, and analysis-population definitions are not reported in the registry record.

In general, a randomized comparison can help estimate the effect of assigned strategies when allocation, follow-up, outcome ascertainment, and analysis are adequately documented. Here, the registry confirms randomized allocation but provides limited detail about its implementation and the analysis. The posted data support a cautious description of the reported counts; they do not establish equivalence, provide a precise estimate of long-term effects, or justify a treatment recommendation.

14. Why This Trial Matters Statistically

This trial addresses a statistical challenge common to comparisons of prevention and intervention: the outcome of interest may be uncommon, while each strategy may carry distinct risks. The registry describes unruptured aneurysms as a setting in which hemorrhage incidence is debated and endovascular treatment has immediate risks. A randomized comparison is a potentially useful design for separating treatment effects from differences in who receives each strategy, provided the trial is implemented and reported with enough detail.

The record also illustrates why a point estimate cannot be interpreted on its own. A reported risk difference of 0.0 may look decisive, but the primary arm entries contain no bad outcomes and list n=12 and n=11. In general, sparse or absent events can leave substantial uncertainty even when the observed contrast is zero. The posted interval, also 0.0 to 0.0, does not offer a transparent account of that uncertainty because the calculation method is not reported.

Another statistical lesson is the importance of keeping outcome populations distinct. Enrollment is recorded as 80, primary-outcome arm counts are n=12 and n=11, and adverse-event records list 38 and 42 at risk. Without participant flow or analysis-population definitions, a reader cannot tell how these entries fit together. Clear reporting of denominators is essential to interpreting both benefits and harms.

Finally, the difference between a title’s planned scope and the results recorded matters. The title refers to 2002 patients and 10 years of follow-up, while the trial is marked terminated and the enrollment entry is 80. The registry does not explain this gap or report long-term outcomes. That context limits what the primary result can establish and highlights the value of complete reporting about recruitment, follow-up, outcomes, and analysis.

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 registry record leaves substantial uncertainty about the conduct and reach of the trial. It labels the study randomized, single-masked, and parallel-group, but does not describe the randomization procedure, allocation concealment, or who was masked. The structured interview used to assign modified Rankin Scale scores is described, but assessor masking is not reported. These omissions limit evaluation of potential bias without demonstrating that bias occurred.

There is no participant flow account explaining how the recorded enrollment of 80 relates to the primary outcome arm counts of n=12 and n=11 or to the adverse-event groups with 38 and 42 at risk. Reasons for missing outcomes, exclusions, or differences in analysis populations are not reported. The record does not state whether all randomized participants were included in the primary analysis.

The trial is marked terminated. The reason for termination, whether recruitment ended as planned, and whether the stated follow-up was completed are not reported in the registry record. The title refers to 2002 patients and 10 years of follow-up, but the recorded enrollment is 80; no reconciliation is given. The primary outcome timeframe is 1 year after treatment or observation, and actual follow-up completeness is not described.

The primary result includes a risk difference and an interval, but the statistical method used to calculate the interval is not reported. A p-value is not reported, and the record lists 0 analyses. The analysis plan, sample-size justification, missing-data approach, and multiplicity strategy are also not reported. Secondary outcomes are listed, but their results are not available in the registry information described.

These limitations concern what can be evaluated from the record. They do not establish that the trial’s methods were inadequate or that unreported analyses were not performed. They do mean that the posted result cannot, on its own, support a detailed assessment of bias, precision, long-term effects, or the comparative interpretation of outcomes beyond the primary count.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Trial on Endovascular Aneurysm Management — NCT00537134.
• Registry record last updated 2022-12-30; status last verified 2022-12.
• Results first posted 2022-12-30.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry describes a randomized, single-masked, parallel-group trial comparing conservative watchful observation with endovascular treatment by coiling for unruptured intracranial aneurysms. The primary outcome is the number of participants with disease- or treatment-related morbidity or mortality, assessed by modified Rankin Scale 1 year after treatment or observation. Scores 0, 1, or 2 are categorized as good; scores 3, 4, 5, or 6 are categorized as bad.

The primary outcome arm records list 0.0 bad outcomes in the conservative group, with n=12, and 0.0 in the endovascular group, with n=11. The reported risk difference is 0.0, with an interval from 0.0 to 0.0; a p-value is not reported. The registry records enrollment of 80, status as terminated, and 0 analyses. The relationship between the primary outcome counts, adverse-event populations, and enrollment is not explained. Long-term follow-up, the reason for termination, and detailed analysis methods are not reported in the registry record.