TAXUS Libertē Post Approval Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for TAXUS Libertē Post Approval Study (NCT00997503), a registered phase not stated study. The primary outcome is Cardiac Death or Myocardial Infarction.

2. Clinical Question

This is a post-approval outcomes study rather than a stated randomized trial comparing the stent with an alternative stent or treatment. Its stated purpose was to collect real-world safety and clinical outcomes among people receiving the TAXUS Liberté stent and prasugrel as part of a dual antiplatelet therapy regimen. The registry record identifies a broad enrolled population and multiple clinical outcomes, but does not give enough information to define a randomized treatment contrast or estimate a comparative treatment effect.

The central statistical question is therefore descriptive: how often did the specified event occur in the eligible population during the stated follow-up period? The record does not report the primary endpoint percentage, its uncertainty, or an analysis comparing groups. Without those results, the incidence of cardiac death or myocardial infarction cannot be determined from the registry record. The study's contribution to research on dual antiplatelet therapy duration is described as data contribution; findings from that separate research question are not reported in the registry record.

3. Trial Design

The TAXUS Libertē Post Approval Study is described as a prospective, multi-center, U.S. post-approval study. It was FDA-mandated and intended to collect real-world safety and clinical outcomes among patients receiving one or more TAXUS Liberté paclitaxel-eluting stents and prasugrel as part of a dual antiplatelet therapy regimen. The registry lists 4199 participants as enrolled. The study status is completed, with a start date of 2009-12 and primary completion in 2013-03.

The registry record does not state an allocation method. Its comparison information cautions that this is not a randomized comparison and that any arms should not be treated as a like-for-like control comparison. A placebo is listed among the interventions, but the record does not explain how placebo use relates to the study population or describe a randomized contrast. Therefore, the listed interventions alone do not establish which treatment groups can be compared causally.

The primary outcome is cardiac death or myocardial infarction, measured as a percentage of participants at 12 months. The outcome description refers to the TAXUS Liberté Post-Approval Study enrolled population. The record says that 140 patients were not eligible for the 12-month analyses because they did not meet either a minimum follow-up duration of 335 days or the criterion of having an endpoint event up to 365 days after the stent implant procedure.

The registry lists 37 outcome measures, including outcomes concerning stent thrombosis, target vessel failure in a medically treated diabetic population, and major adverse cardiac and cerebrovascular events. Several MACCE and MACE descriptions appear more than once in the listed outcomes. The listed secondary outcomes provide context for the breadth of follow-up, but the record does not report their numerical results in the information available for this analysis.

The study description says that its patient data would also contribute to an FDA-requested and industry-sponsored research study of the optimal duration of dual antiplatelet therapy. The protocol details, allocation procedures, follow-up schedule beyond the stated endpoint information, and statistical analysis plan are not reported in the registry record. The record also does not state a sample-size justification or interim-analysis plan.

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: There were 140 patients that were not eligible for the 12-month analyses, as they did not meet the following criteria: either a minimum number of days of follow-up of 335 days or an endpoint event up to 365 days post-stent implant procedure.

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 Cardiac Death or Myocardial Infarction, measured over 12 months.

The primary endpoint is cardiac death or myocardial infarction, expressed as a percentage of participants and assessed at 12 months. It combines two serious cardiac outcomes into a single measure. A participant meeting either component falls within the endpoint definition, although the registry does not provide the separate component counts or the combined endpoint result.

A composite endpoint can summarize whether any event from a defined set occurred, which may capture more aspects of clinical outcome than either component considered alone. Its interpretation depends on the exact component definitions and on the contribution of each component to the combined result. Those details, including any adjudication procedures, are not reported in the registry record. The endpoint description gives the broad event definition and the follow-up period, but not further operational definitions.

The percentage is intended to describe the occurrence of the event in the study population at the specified follow-up. It is not, by itself, a comparison with an untreated or alternative-treatment group. Because allocation is not stated and a comparable control group is not identified, the primary endpoint as described supports a population outcome summary rather than an established treatment-effect contrast.

The primary endpoint value and its uncertainty are not reported in the registry record. The record also notes that 140 patients were not eligible for the 12-month analyses under the stated follow-up or endpoint-event criteria. Without the result and fuller details of the analysis population, the endpoint's observed frequency and precision cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What kind of study is described?

The registry describes a prospective, multi-center, FDA-mandated post-approval study. Prospective data collection means outcomes are planned for observation after enrollment rather than being assembled solely from past records. A multi-center design collects information across participating centers, which can include a range of clinical settings. These general features describe how evidence may be gathered; they do not by themselves establish random allocation, a control group, or causal comparability between groups.

The record does not state the allocation method. It explicitly cautions that the study is not a randomized comparison and that arms are not like-for-like controls. Randomization, when used, can help balance measured and unmeasured characteristics between comparison groups. Without a stated randomized allocation, group differences may reflect differences in who received each intervention, clinical decisions, or other factors, as well as any treatment effects. The registry record does not provide enough detail to assess those possibilities.

What does a percentage of participants represent?

For a binary outcome, each participant is classified according to whether the defined event occurred during the stated assessment period. The percentage describes the share of the analysis population meeting that event definition. The primary outcome is cardiac death or myocardial infarction at 12 months, and the registry identifies the measure as a percentage of participants. The observed percentage is not reported in the registry record, so its magnitude cannot be interpreted.

A percentage should be read with its denominator and analysis population in mind. Here, the record notes that 140 patients were not eligible for the 12-month analyses under the stated follow-up or event criteria. It does not fully describe the handling of every other incomplete observation or provide the final denominator used for the primary outcome. These omissions limit assessment of who contributed to the estimate and how representative that group was of everyone enrolled.

How should uncertainty be understood?

General statistical explanation: an estimate from a study population is subject to sampling variability. A confidence interval, when reported, gives a range of values compatible with the data and the interval's statistical procedure. A narrower interval generally indicates greater precision, while a wider interval indicates more uncertainty. A confidence interval does not correct bias from a non-comparable design, incomplete follow-up, or outcome misclassification.

The registry information considered for this analysis does not report a confidence interval for the primary endpoint. It also does not report a standard error or a statistical test for a primary treatment comparison. Therefore, neither the estimate's precision nor a test-based conclusion can be recovered from the endpoint definition or enrollment information alone. No numerical uncertainty measure should be inferred from the reported enrollment count.

Why does the study design constrain comparisons?

General statistical explanation: a treatment-effect comparison requires a clearly defined contrast between groups and an analysis that addresses differences in their baseline characteristics and follow-up. In a randomized trial, allocation is designed to make groups comparable on average. In a nonrandomized setting, adjustment methods may be used, but they depend on measured information and assumptions. The registry record does not describe an adjustment strategy, a randomized allocation, or an analysis comparing intervention groups.

The interventions listed include the stent, prasugrel, placebo, and aspirin. Their presence in the registry does not establish that each corresponds to a distinct arm, nor does it establish a control contrast. The registry record does not describe the allocation or how the listed interventions were combined. The appropriate reading is therefore descriptive unless an explicitly reported analysis establishes otherwise.

What do the sample-size illustrations mean?

General statistical explanation: a sample-size calculation asks how much information a future study might need to detect a specified effect under stated assumptions. Such a calculation depends on the target effect, significance level, desired power, allocation, outcome type, and analysis method. Changing those assumptions changes the planning result. A planning calculation is not a measure of what a completed study actually detected.

The record describes planning illustrations based on the observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. The target effect is expressed as a stated fraction of the observed effect. For time-to-event outcomes, the illustration gives a total number of events using the Schoenfeld approach; for other outcomes, it gives participants per arm. These are planning conventions, not a report of the study's original design. The registry record does not report its sample-size justification or original power assumptions. Such calculations should not be called observed power, and they cannot establish the reliability of an unreported endpoint result.

Why can over-dispersion matter?

General statistical explanation: over-dispersion occurs when observed variability exceeds what a statistical model assumes. If a model does not account for that extra variability, standard errors can be too small and intervals can appear more precise than warranted. The relevance of over-dispersion depends on the outcome and model. The registry record does not report a model or an over-dispersion assessment for the primary endpoint, so no claim about its presence or handling can be made for this study.

What is known about the analysis plan?

The registry record lists the primary endpoint and a range of secondary outcomes, but it does not report the statistical analysis plan, interim analyses, or the methods used to handle missing data beyond the eligibility note for the 12-month analysis. It also does not report whether outcomes were adjusted for multiple testing. A planned list of outcomes is not a substitute for information about the statistical procedures used to estimate or compare them.

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("TAXUS Libertē Post-Approval Study Enrolled Populat")
n      <- c(4059)
events <- c(85)
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  TAXUS Libertē Post-Approval Study Enrolled Populat  4059  85  2.1  1.7  2.6  1.7  2.6  1.7  2.6

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 37 outcome measures, including the primary endpoint and secondary outcomes concerning stent thrombosis, target vessel failure, MACCE, and MACE. Some MACCE and MACE descriptions recur in the list, including stent-related descriptions. The record does not explain whether repeated entries represent different time points, populations, definitions, or registry listing conventions. The analysis information lists zero analyses, and inferential results for the outcome list are not reported in the registry record.

When many outcomes or comparisons are examined, the chance of at least one apparently unusual finding can increase. General statistical explanation: multiplicity procedures can address this by adjusting inference or by defining a limited set of confirmatory outcomes in advance. The registry record does not report a multiplicity plan, a hierarchy of outcomes, or whether any adjustment was applied. It is therefore not possible to determine how multiple outcome assessments were handled.

For the primary 12-month analysis, 140 patients were not eligible because they did not meet either a minimum follow-up duration of 335 days or the endpoint-event criterion up to 365 days after the stent implant procedure. This is the registry's stated eligibility rule; it does not fully describe all missing-data circumstances. The numbers of participants with other forms of missing outcome information, the reasons for any loss to follow-up, and any imputation or sensitivity analyses are not reported in the registry record.

The record does not fully specify the analysis population beyond the eligibility note, nor does it state whether all analyses used the same population. Without details on outcome completeness, denominators, and analysis populations, readers cannot assess the potential influence of missingness or compare results across outcomes. These omissions limit interpretation independently of whether the planned outcome definitions were clinically relevant.

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: angina pectoris (6.0%), non-cardiac chest pain (3.8%), angina unstable (2.4%), coronary artery disease (1.8%), gastrointestinal haemorrhage (1.2%).

The registry's serious adverse event listing is for the TAXUS Liberté overall enrolled population. It reports 4199 at risk and 1232 affected for serious events, and 4199 at risk and 293 affected for the other listed event category. The record does not provide a death count. These figures are safety summaries and are distinct from the primary endpoint result, which is not reported in the registry record.

The listed serious adverse event terms and percentages are angina pectoris, 6.0%; non-cardiac chest pain, 3.8%; angina unstable, 2.4%; coronary artery disease, 1.8%; gastrointestinal haemorrhage, 1.2%; and coronary artery stenosis, 1.2%. The registry does not provide further information in this record about the event definitions, whether a participant could contribute to more than one term, or the relationship between these terms and the primary outcome.

These are descriptive safety figures. They do not establish that the stent or a drug caused an event, and they do not provide a comparison with a like-for-like control group. The allocation method is not stated, and the registry cautions against treating arms as comparable controls. The record also does not report a statistical comparison or uncertainty interval for these safety summaries. The percentages should therefore be read as listed event frequencies, not as causal estimates or measures of comparative risk.

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

The results record establishes that this completed study was designed to collect post-approval safety and clinical outcome information among recipients of the TAXUS Liberté stent and prasugrel as part of dual antiplatelet therapy. It identifies cardiac death or myocardial infarction at 12 months as the primary outcome and describes criteria affecting eligibility for that analysis. It also lists selected serious adverse event summaries. These details clarify the study's scope, but they do not supply the primary outcome result.

The record does not establish the percentage of participants with cardiac death or myocardial infarction, the precision of that percentage, or whether any observed outcome differed from an alternative treatment. It does not report the primary endpoint's confidence interval or a comparative statistical test. Because the study is not described as a randomized comparison and the record warns that arms are not like-for-like controls, a causal interpretation of any group difference would require information and methods not reported in the registry record.

The serious adverse event listings describe event frequencies within the overall enrolled population. They cannot show whether an event was caused by a device or drug, and they are not a comparison against a control population. The absence of a death count in the listing also should not be interpreted as a count of zero; the registry record does not report that figure.

Likewise, sample-size illustrations based on the observed effect are planning exercises under stated assumptions. They are not observed power, do not establish the original design rationale, and do not replace a reported result. The registry record does not state the original sample-size justification or full statistical plan.

In short, the record supports a description of the study design, enrolled population, endpoint definition, eligibility note, and listed safety events. It does not support a numerical conclusion about the primary outcome or a claim that one treatment caused better or worse outcomes than another. The contribution to separate research on dual antiplatelet therapy duration is described, but results from that research question are not reported in the registry record.

14. Why This Trial Matters Statistically

Post-approval studies can add information about clinical outcomes after a device enters use beyond the evidence generated before approval. This study was prospectively designed across multiple centers to collect safety and clinical outcome data among patients receiving the TAXUS Liberté stent and prasugrel as part of dual antiplatelet therapy. The registry also describes a contribution of patient data to a separate study evaluating the optimal duration of dual antiplatelet therapy.

Statistically, the record illustrates why an endpoint definition, a design description, and a numerical result are all needed for interpretation. The primary outcome is clearly named and has a stated assessment time, but its percentage and uncertainty are not reported in the registry record. Knowing the enrolled population and the endpoint does not reveal the event frequency. Nor can a descriptive safety listing substitute for the missing primary result.

The study also illustrates the importance of distinguishing post-approval observation from a randomized treatment comparison. The record cautions that arms are not like-for-like controls and does not state allocation. This shapes what can be concluded: outcome frequencies can describe the studied population, while treatment-effect claims require a defined and credible comparison. The existence of a placebo listing does not by itself define such a comparison.

Finally, outcome multiplicity and analysis eligibility are essential context. The registry lists 37 outcome measures and notes that 140 patients were not eligible for the 12-month analysis under specified follow-up or event criteria, while the full multiplicity and missing-data plans are not reported. These issues affect how findings would be evaluated even if numerical results were available. The statistical value of the record is thus both in what it documents and in making clear which questions remain unanswered.

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 primary limitation for interpreting the study's main question is that the cardiac death or myocardial infarction result at 12 months is not reported in the registry record. Neither its estimate nor an uncertainty measure is available, so the event frequency and precision cannot be assessed.

The registry does not state the allocation method and explicitly cautions that this is not a randomized comparison and that arms are not like-for-like controls. It lists a placebo among the interventions but does not explain its role or identify a valid comparison group. The record therefore does not support causal interpretation of between-group differences.

The registry notes that 140 patients were not eligible for the primary 12-month analyses because they did not meet either the minimum follow-up criterion of 335 days or the endpoint-event criterion up to 365 days after the implant procedure. Further details on missing outcomes, follow-up completeness, the final analysis population, and sensitivity analyses are not reported in the registry record. Those omissions limit assessment of the effect of eligibility and missing data on a potential result.

The record lists 37 outcome measures, but it does not describe a multiplicity strategy, outcome hierarchy, or statistical analysis plan. It also does not report interim analyses or the original sample-size justification. The repeated MACCE and MACE descriptions are not explained, making it unclear from the listing alone how those entries relate to distinct analyses.

The serious adverse event figures are presented without further details about definitions, overlap among terms, or causal attribution. A death count is not reported. These limits mean the safety listing should be treated as descriptive rather than as a comparative estimate. Overall, important design and reporting details needed to assess precision, bias, and robustness are not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: TAXUS Libertē Post Approval Study — NCT00997503.
• Registry record last updated 2015-08-07; status last verified 2015-03.
• Results first posted 2015-04-13.
• 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 TAXUS Libertē Post Approval Study (NCT00997503) is a completed, FDA-mandated, prospective, multi-center U.S. post-approval study sponsored by Boston Scientific Corporation. The registry lists 4199 enrolled participants, a start date of 2009-12, and primary completion in 2013-03. It concerns coronary artery disease and outcomes among patients receiving one or more TAXUS Liberté paclitaxel-eluting stents and prasugrel as part of dual antiplatelet therapy.

The primary endpoint is cardiac death or myocardial infarction, measured as a percentage of participants at 12 months. The registry says 140 patients were not eligible for the 12-month analyses under the stated follow-up or endpoint-event criteria. The primary result and its uncertainty are not reported in the registry record. The study is not described as a randomized comparison, and the registry cautions that arms are not like-for-like controls. Serious adverse event terms and frequencies are listed, but they do not establish causation or comparative treatment effects.