AXIOS Stent & Delivery System Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for AXIOS Stent & Delivery System Study (NCT01419769), a na na study. The primary outcome is Safety - Freedom From Major Complications: Access Site-related Bleeding.

2. Clinical Question

In statistical terms, the primary endpoint is binary: a participant either meets the stated freedom-from-bleeding criterion or does not. The registry describes the endpoint unit as the percentage of patients. That description identifies the intended form of the outcome, but without a posted result it does not establish what percentage met the criterion.

The record also lists effectiveness outcomes concerning stent lumen patency, stent removability, technical success and clinical success. These are distinct from the primary safety question. Their specific results are not reported in the registry record. Follow-up was described at approximately 30 days and/or 60 days depending on confirmation of pseudocyst resolution, with a 1-week post-stent removal visit and possible later follow-up. The primary endpoint timeframe is specified separately as through the duration of the 1-week post-stent removal study period.

3. Trial Design

The registry describes a prospective, multi-center, non-blinded, single-arm, nonrandomized study of the AXIOS Stent and Delivery System. Its status is completed, and its phase and allocation are recorded as NA. With no randomized allocation and no comparator arm, the design focuses on observations in participants receiving the device rather than a between-group treatment contrast.

The enrollment field records 30. The brief summary describes a plan to enroll a total of 24 patients at up to 10 sites in the United States, European Community and/or Japan, with a majority in the United States. These figures refer to different descriptions in the registry record; the reason for the difference is not reported in the registry record. The study start is recorded as 2011-08 and primary completion as 2012-06.

The brief summary describes follow-up at approximately 30 days and/or 60 days, depending on confirmation of pseudocyst resolution. It also describes a visit at 1-week post-stent removal and possible follow-up at 3 and 6 month post-stent removal. The primary safety endpoint has its own stated timeframe: through the duration of the 1-week post-stent removal study period.

The intervention is listed as a device, and the study is described as non-blinded. The registry record does not report a statistical analysis plan, details of site-level enrollment, or an explanation of how missing observations were handled. Although the record lists secondary effectiveness outcomes, the presence of outcome definitions is not the same as a posted analysis or result. The registry reports 10 outcome measures and 0 analyses.

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:

Analysis population for the primary outcome, as defined in the registry: Intent-to-Treat population

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: Patients between 18 and 75 years of age, suitable for transluminal drainage of symptomatic pancreatic pseudocysts that are greater than or equal to 6 cm in diameter and adherent to the bowel wall are candidates for study treatment.

6. Primary Endpoint

The registry lists the primary outcome as Safety - Freedom From Major Complications: Access Site-related Bleeding, measured over Through the duration of the 1-week post-stent removal study period.

The primary endpoint is safety: freedom from access site-related bleeding requiring transfusion. The registry defines the measure as the percentage of patients and identifies the Intent-to-Treat population. Its timeframe extends through the duration of the 1-week post-stent removal study period.

This is a binary outcome at the participant level: the stated criterion is either met or not met. Reporting such an endpoint as a percentage can communicate how often the specified safety outcome occurred in the analyzed population. It is important, however, to know the numerator, denominator, and analysis population to interpret that percentage. The registry record does not report the primary endpoint result or a confidence interval, so the observed percentage and its precision cannot be assessed from the record.

The endpoint focuses on access site-related bleeding severe enough to require transfusion. That definition sets a specific threshold and scope; it does not describe every possible bleeding event or every safety outcome. The registry lists serious adverse events separately, but those entries do not substitute for the primary endpoint result. The record does not report whether any serious adverse event met the primary endpoint definition.

A safety endpoint can help characterize events during the specified follow-up, but a single-arm study does not provide a concurrent control rate for contextual comparison. Without the posted endpoint result and a comparator, the record cannot establish a comparative safety effect.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a single-arm design estimate?

General statistical explanation: a single-arm study records outcomes in a group receiving the intervention. It can describe the observed outcomes in that study population, but it does not directly estimate a contrast against a concurrent control group. Without random allocation and a comparator, differences from an external benchmark can reflect differences in participants, follow-up, event definitions, or other features as well as any intervention effect. The registry record describes this study as single-arm and nonrandomized, so its design does not support a randomized between-group comparison.

How should a binary endpoint be understood?

General statistical explanation: a binary endpoint classifies each participant according to whether a specified event or criterion occurred. A percentage expresses the share of the analyzed population in a category, but interpretation depends on the event definition, the analysis population, and the denominator. The primary endpoint is defined as freedom from access site-related bleeding requiring transfusion. The registry identifies the unit as percentage of patients and the population as Intent-to-Treat, but its primary result is not reported in the registry record. Thus, no primary endpoint percentage can be interpreted from the record.

What does a confidence interval add?

General statistical explanation: a confidence interval describes uncertainty around an estimated quantity under the assumptions of the statistical method. A narrower interval indicates greater precision, while a wider interval indicates less precision. An interval does not remove design limitations, and it cannot supply a missing comparison group. The registry record does not report a confidence interval for the primary endpoint. Without an estimate and its uncertainty, the precision of the primary endpoint result cannot be evaluated.

What can adverse-event counts tell readers?

General statistical explanation: counts and percentages describe the recorded events in the population and period to which they apply. They need a clear denominator, event definition, and follow-up context. If participants can experience more than one event or appear under more than one term, categories may overlap; the record must explain this before categories can be combined or interpreted as distinct participant totals. The adverse-event entries list serious events and other events with their own at-risk and affected counts. The record does not explain the relation of those counts to the enrollment field or clarify possible overlap among terms.

The listed serious adverse-event term percentages are descriptive entries, not a comparative analysis. They do not by themselves show whether an event was caused by the device. The registry record does not report causal attribution details for these terms. It also does not report a result for the specifically defined primary bleeding endpoint, so the adverse-event listing cannot answer that endpoint question.

How should the planning illustrations be read?

The sample-size assumptions describe planning illustrations computed from the observed effect, not the trial's own design. The stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is the stated fraction of the observed effect. For time-to-event tables, the assumption describes the total number of events, while other tables describe participants per arm. These are hypothetical planning assumptions and do not change the registry's single-arm design. Sample-size illustrations are not observed power and do not provide evidence that the trial had a particular probability of detecting an effect. No illustration values or observed-effect estimate are reported in the registry record.

The record reports 0 analyses. It does not report the statistical procedures used to analyze the primary endpoint, any confidence interval method, or any adjustment strategy. Those details should not be inferred from the endpoint format or from general methods used in other studies.

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("AXIOS Stent and Delivery System")
n      <- c(33)
events <- c(33)
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  AXIOS Stent and Delivery System  33  33  100.0  89.4  100.0  89.6  100.0  89.7  99.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 10 outcome measures, including the primary safety endpoint and secondary outcomes for stent lumen patency at 30 days and/or 60 days, stent removability at 30 days and/or 60 days, technical success, and clinical success. It reports 0 analyses. Results for the primary endpoint and the listed secondary outcomes are not reported in the registry record.

When a study evaluates multiple outcomes, multiplicity can arise if several statistical tests are used to support conclusions. General statistical explanation: testing multiple hypotheses can increase the chance of at least one apparently notable result by chance, and a prespecified analysis plan can state whether and how that issue is addressed. The registry record does not report a multiplicity strategy or a statistical analysis plan. It is therefore not possible to determine whether any adjustment was planned or used.

The primary population is described as Intent-to-Treat. The registry record does not report how that population was operationalized, how many participants contributed to the primary analysis, or how missing endpoint observations were handled. The brief summary describes scheduled follow-up around pseudocyst resolution and after stent removal, but does not provide completion or missingness data. No imputation method, sensitivity analysis, or missing-data assumption is reported in the registry record.

These omissions matter because outcome estimates depend on which participants and observations are included. The enrollment field and adverse-event at-risk counts are not the same figure, and the reason for that difference is not reported in the registry record. Without the analysis denominator and missing-data handling, the listed safety counts cannot be reconciled with the primary endpoint population.

12. 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: abdominal pain (18.2%), infection (9.1%), nausea and vomiting only after eating (6.1%), pancreatitis (6.1%), abdominal pain and nausea after eating (3.0%).

The registry's adverse-event entries for the AXIOS Stent and Delivery System list 33 at risk and 16 affected for serious events, and 33 at risk and 15 affected for other events. These are category-specific figures; the record does not explain whether the same participant could contribute to both categories or to multiple event terms. The adverse-event at-risk count is not the same as the enrollment field, which records 30. The reason for the difference is not reported in the registry record.

The serious-event terms and percentages are Abdominal Pain, 18.2%; Infection, 9.1%; Nausea and vomiting only after eating, 6.1%; Pancreatitis, 6.1%; Abdominal pain and nausea after eating, 3.0%; and Abdominal pain and vomiting after eating, 3.0%. The registry does not state the denominator for these percentages or whether terms overlap, so they should not be added or interpreted as separate participant totals.

These listings are not the primary endpoint result. The primary endpoint concerns freedom from access site-related bleeding requiring transfusion, and that result is not reported in the registry record. Deaths are not reported in the registry record. The entries describe recorded safety information, but the record does not provide details that establish causation or permit a comparison with another group.

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

The record establishes that a prospective, multi-center, non-blinded, single-arm study of the AXIOS Stent and Delivery System was completed. It defines a primary safety endpoint and lists adverse-event information. The primary endpoint result is not reported in the registry record, so the record does not show what percentage met the freedom-from-bleeding criterion or how precisely that percentage was estimated.

The serious adverse-event listings provide recorded counts and term percentages, but do not provide the context needed to make them a comparative estimate. The record does not report a control group, causal attribution, or the reason the adverse-event at-risk counts differ from the enrollment field. The event terms and percentages therefore describe registry entries rather than an estimate of excess risk or a device-related effect.

The record also lists effectiveness outcomes, but their results are not reported. Accordingly, the information in the registry record does not establish an effectiveness result. Nor does the absence of a posted primary result establish that the endpoint was met or not met; the outcome is simply not reported in the registry record.

General statistical interpretation: a study's design determines what its estimates can address. A single-arm study can describe events in its enrolled population, while a comparative claim generally requires a relevant comparison and an analysis that accounts for uncertainty and design. This record does not report a randomized comparison, a primary endpoint estimate, or a statistical analysis plan. Its design and posted adverse-event entries should be interpreted within those limits, without turning descriptive information into a conclusion about treatment effect.

14. Why This Trial Matters Statistically

This study illustrates why endpoint definitions, analysis populations, and reported results need to be read together. The primary endpoint is not a broad measure of all safety events: it is freedom from access site-related bleeding requiring transfusion, with a stated follow-up period and an Intent-to-Treat population. That specificity helps define the question, but the absence of a posted endpoint result means the question cannot be answered from the registry record.

The study also illustrates the distinction between a safety listing and a primary endpoint analysis. Serious adverse-event counts and term percentages provide descriptive information, but they are not interchangeable with a result for the defined bleeding endpoint. Clear denominators and event relationships are essential for interpreting those entries; relevant details are not reported in the registry record.

Statistically, the single-arm, nonrandomized design is important. It permits description of outcomes in the study group but does not create a concurrent randomized comparison. This distinction helps prevent overinterpretation of observed events as comparative effects. The record's planning assumptions likewise should not be confused with the study design or with evidence from observed outcomes: they describe hypothetical sample-size illustrations, not observed power.

Finally, the enrollment field and the brief summary's planned enrollment differ, while the reason is not reported in the registry record. Together with the absence of posted analyses, primary results, and missing-data details, this makes transparent reporting especially important for readers seeking to assess precision and interpretability.

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 does not report the primary endpoint result, its confidence interval, or the number of participants contributing to that endpoint analysis. It also does not report results for the listed secondary effectiveness outcomes. The record therefore cannot support an assessment of the observed primary safety percentage or the precision of an efficacy estimate.

The design is single-arm, nonrandomized and non-blinded, with no comparator group. This limits interpretation to description of the recorded study experience and prevents a randomized comparison. The record does not report a statistical analysis plan, multiplicity handling, methods for missing data, or sensitivity analyses.

The enrollment field records 30, whereas the brief summary describes a total of 24 patients planned. The reason for the difference is not reported in the registry record. The adverse-event entries list 33 at risk for serious and other events, and the relation of those counts to enrollment and the primary Intent-to-Treat population is not explained. The record also does not clarify overlap between adverse-event terms, provide percentage denominators, or report deaths.

Follow-up is described as depending partly on pseudocyst resolution and stent removal, with possible later visits. The record does not report follow-up completion, participant-level timing, or how incomplete observations were addressed. These limits restrict interpretation of both the endpoint and the safety listings.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: AXIOS Stent & Delivery System Study — NCT01419769.
• Registry record last updated 2015-09-21; status last verified 2015-09.
• Results first posted 2014-11-19.
• 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 a completed, prospective, multi-center, non-blinded, single-arm, nonrandomized study of the AXIOS Stent and Delivery System for pancreatic pseudocysts. Enrollment is recorded as 30; the brief summary describes a planned total of 24 patients. The primary endpoint is freedom from access site-related bleeding requiring transfusion through the duration of the 1-week post-stent removal study period, in the Intent-to-Treat population.

The record lists 10 outcome measures and 0 analyses. It includes serious and other adverse-event counts and serious-event term percentages, but the primary endpoint and secondary effectiveness results are not reported in the registry record. The design has no comparator group, and the record does not report a statistical analysis plan or missing-data methods.