ABSORB EXTEND Clinical Investigation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for ABSORB EXTEND Clinical Investigation (NCT01023789), a na na study. The primary outcome is Number of Participants With Major Adverse Cardiac Events (MACE; Cardiac Death, Protocol MI, ID-TLR).

2. Clinical Question

The ABSORB EXTEND Clinical Investigation was intended to continue the assessment of the safety and performance of the ABSORB Bioresorbable Vascular Scaffold System. Its clinical setting was treatment of de novo native coronary artery lesions, with the intervention described as ABSORB BVS implantation for coronary artery disease. The registry record lists 812 participants enrolled and identifies a primary endpoint focused on major adverse cardiac events during the hospital period after the index procedure.

The primary question is descriptive: how many participants in the study’s intention-to-treat population experienced the specified composite event within the stated timeframe? The composite includes cardiac death, myocardial infarction, and ischemia-driven target lesion revascularization. It is not a comparison of outcomes between randomized treatment groups: the record identifies a single-group model and gives allocation as NA. There is no like-for-like control group in the registry entry, so the study design does not support a randomized contrast between ABSORB BVS and another treatment.

The registry also lists secondary outcomes related to procedural success, cardiac events, myocardial infarction, and revascularization. It does not report a result for the primary endpoint in the record. The question that can be answered from the record is therefore about what the study set out to measure, how its design frames interpretation, and what the recorded safety entries contain—not whether the device is superior to another approach or what would happen for an individual patient.

3. Trial Design

The registry describes ABSORB EXTEND as a completed, single-group clinical investigation sponsored by Abbott Medical Devices. Enrollment is recorded as 812. The study start is listed as 2010-01 and primary completion as 2016-10. Phase is listed as NA. The intervention is the ABSORB BVS device, described as an implantation procedure for coronary artery disease.

The study model is single group, masking is NONE, and allocation is NA. These entries matter because they define what kinds of comparisons the design can support. The record does not describe random allocation to alternative interventions, nor does it list a concurrent control arm. Outcomes therefore describe participants in the study group; they do not estimate a randomized between-group treatment effect. The absence of masking also means the registry does not identify a masked study design, although the record does not describe how individual outcomes were assessed.

The primary outcome is a count of participants with major adverse cardiac events, with a timeframe of up to 7 days after the index procedure while in hospital. Its listed population is the ITT population, per-subject analysis. The registry lists 64 outcome measures overall and identifies secondary outcomes including clinical device success, clinical procedure success, cardiac death, myocardial infarction, and ischemia-driven revascularization outcomes. The record also lists adverse-event information.

Several design details needed to assess the protocol more fully are not reported in the registry record. These include the eligibility criteria, recruitment procedures, detailed follow-up schedule, the sample-size justification, and any interim analyses. A complete statistical analysis plan is also not reported in the registry record. The dates and completion status describe the registration entry, but do not by themselves establish how complete the outcome data were or how closely the conduct followed a protocol.

As a single-group investigation, the study can describe event counts and safety entries among enrolled participants. It cannot separate outcomes associated with the intervention from the background risk of the population or from other influences without an appropriate comparison. This is a design limitation for causal interpretation, not a statement about the observed performance of the device.

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: Out of the 812 subjects registered, a total of 43 subjects discontinued the study due to death (n=29) , withdrawal of consent (n=1) and lost-to-follow-up or missed the final 3 year follow-up visit (n=13).

30-day Follow-up Visit

180-day Clinical Follow-up

1 - Year Visit

2 - Year Visit

Analysis population for the primary outcome, as defined in the registry: ITT population (per subject analysis).

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 Major Adverse Cardiac Events (MACE; Cardiac Death, Protocol MI, ID-TLR), measured over ≤ 7 days post index procedure (In hospital).

The primary endpoint counts participants who experienced a composite of major adverse cardiac events: cardiac death, myocardial infarction classified as Q-wave or non-Q-wave, or ischemia-driven target lesion revascularization by coronary artery bypass grafting or percutaneous coronary intervention. The registry calls this outcome MACE and specifies the timeframe as up to 7 days after the index procedure, in hospital. It identifies the analysis population as ITT, with each subject contributing to the participant-level analysis.

A composite endpoint combines several clinically relevant event types into one outcome. In general, composites can capture a broader range of events than any single component and can provide a concise summary of event experience over a defined period. But the components need not occur equally often or have equivalent clinical importance. A composite count alone therefore does not reveal which component contributed most. Component-specific results and clear rules for classifying events are needed for that interpretation; the primary endpoint entry defines the components but does not report their separate results.

The endpoint is a count of participants with an event, not a measure of event severity, time to event, or repeated event burden. The registry record does not report the primary endpoint count, component counts, or an uncertainty interval. Consequently, the endpoint’s definition can be described, but the observed frequency and precision of that frequency cannot be assessed from this entry.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

A participant count is a summary of how many people meet an outcome definition. For this trial, the primary outcome is a count of participants with at least one event within the specified period, rather than a count of every event or an event rate per unit of follow-up. In general, participant counts are straightforward to interpret only when the outcome definition, analysis population, observation period, and handling of incomplete follow-up are clear. The registry states the first three for the primary endpoint, but does not report the endpoint count or how missing endpoint information was handled.

What does a composite endpoint summarize?

In general, a composite combines several distinct event types into one outcome. It may make a broad summary possible when events are individually uncommon, but its meaning depends on the components and their relative frequency. A result for the composite cannot identify which component drove the overall count. For ABSORB EXTEND, the defined components are cardiac death, myocardial infarction, and ischemia-driven target lesion revascularization. The record specifies that myocardial infarction includes Q-wave and non-Q-wave MI, and that target lesion revascularization may be by CABG or PCI. Separate component results are not reported in the registry record.

What does a single-group design allow?

In general, an uncontrolled single-group study describes outcomes in the group that received the intervention. A comparison with a separate group can be affected by differences in patient characteristics, care, or outcome measurement; random assignment is one way trials seek to balance such factors. This registry record identifies no randomized allocation and no concurrent control group. As a result, even a reported event frequency would be descriptive rather than a randomized estimate of the effect of ABSORB BVS relative to another option. The record does not report a protocol-based external comparator or an adjusted comparison.

How should uncertainty be considered?

In general, a confidence interval expresses the range of values reasonably compatible with the data under a specified statistical model. It communicates precision as well as the point estimate: a wider interval indicates greater uncertainty, while a narrower interval indicates greater precision. A p-value, when used, addresses how compatible the observed data are with a specified null model; it is not a measure of clinical importance or the probability that a treatment works. The primary endpoint entry reports neither an estimate nor a confidence interval or p-value. Such statistics are not reported in the registry record for this outcome.

Why do analysis populations matter?

An intention-to-treat population generally aims to retain participants according to their study assignment or enrolled group, according to the trial’s stated rules. In a single-group investigation, the label still identifies the population used for the analysis, but it does not create a randomized comparison. The record describes the primary endpoint population as ITT, per-subject analysis. It does not give details of exclusions, deviations, withdrawals, or the rules used to include participants with incomplete records. Those details are not reported in the registry record.

How should planning calculations be read?

In general, sample-size calculations are planning tools based on assumptions about the outcome, the effect to detect, the significance level, allocation, and statistical method. They are not evidence that a study had a particular probability of finding a result after the data were observed. The registry’s planning description says its illustrations use the observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; it describes the effect as a stated fraction of the observed effect. It also distinguishes total event counts for time-to-event calculations from participants per arm for other calculations. These are planning illustrations, not the original trial’s design justification and not observed power. The registry record does not report the trial’s own sample-size justification. Because the study itself is single-group, hypothetical two-arm planning assumptions should not be mistaken for its actual allocation or for a trial comparison.

Finally, statistical analysis requires more than a named outcome and a count. It also depends on prespecified definitions, methods for incomplete observations, and decisions about multiple outcomes or repeated analyses. The registry lists 64 outcome measures and no analysis entries. The detailed statistical plan, multiplicity approach, and missing-data methods are not reported in the registry record. Without those details and the primary endpoint result, neither the magnitude nor precision of the primary outcome can be evaluated from the entry.

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("ABSORB BVS")
n      <- c(812)
events <- c(14)
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  ABSORB BVS  812  14  1.7  0.9  2.9  1.0  2.9  1.0  2.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 64 outcome measures, including the primary MACE count and secondary outcomes related to procedural success, cardiac events, myocardial infarction, and revascularization. When a study examines multiple outcomes, the chance of at least one apparently unusual result can increase if each is tested separately. In general, a prespecified hierarchy or multiplicity adjustment can help define how such results should be interpreted. The registry record does not report whether outcomes were tested, what hierarchy governed interpretation, or whether any multiplicity adjustment was planned. It lists no analysis entries.

The primary endpoint population is described as ITT, per-subject analysis. The registry does not report how missing outcome information, withdrawals, protocol deviations, or incomplete follow-up were handled. It also does not report the number of participants with evaluable primary endpoint data. These omissions limit assessment of whether the reported analysis population would include all enrolled participants and how missing observations might affect an estimate. The enrollment figure alone does not establish endpoint completeness.

The record defines a short in-hospital primary endpoint period but does not supply a detailed analysis plan, endpoint adjudication procedures, or interim-analysis information. Those details are not reported in the registry record. Without them, it is not possible to assess whether analyses were prespecified or how event classification and incomplete data were managed. These are uncertainties about documentation and analysis, not evidence that a particular method was or was not used.

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: angina pectoris (9.9%), acute myocardial infarction (2.6%), non-cardiac chest pain (2.5%), angina unstable (1.5%), post procedural myocardial infarction (1.2%).

The adverse-event entry lists the ABSORB BVS group with 812 participants at risk for serious adverse events and 295 affected. For other adverse events, it lists 812 at risk and 808 affected. It also records 7 deaths. These are registry safety figures; the primary endpoint is a separate composite with its own definition and timeframe. The adverse-event entry does not identify the causes of the deaths or, in this summary, the follow-up duration used for the safety counts.

The serious-event terms and their listed percentages are angina pectoris, 9.9%; acute myocardial infarction, 2.6%; non-cardiac chest pain, 2.5%; angina unstable, 1.5%; post procedural myocardial infarction, 1.2%; and coronary artery dissection, 1.1%. The registry does not state in this entry whether people could contribute to more than one term, or specify a denominator for each percentage. The terms therefore should not be added together or treated as a mutually exclusive distribution.

These numbers describe reported events in a single-group study. Without a comparator and fuller information about event definitions, timing, ascertainment, and completeness, they do not establish comparative safety or causation.

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

The registry record establishes that ABSORB EXTEND was a completed, single-group investigation of ABSORB BVS, with 812 participants enrolled and a primary endpoint defined as a count of participants with a composite cardiac event during the in-hospital period up to 7 days after the index procedure. It also records adverse-event counts and selected serious-event terms. These registry entries describe the study’s stated design and reporting.

The record does not report the primary endpoint count, the component counts, or an estimate with an uncertainty interval. It therefore does not establish the observed frequency or precision of MACE for the study population. The safety entries are available as descriptive registry data, but they do not provide a randomized comparison. The record also does not provide the information needed to attribute an event to the device or procedure, or to compare the safety figures with another treatment group.

A single-group study can contribute descriptive evidence about what was recorded among participants under its methods. It cannot, by itself, distinguish intervention-related outcomes from underlying disease risk, other care, or other influences. That limitation applies even if a count is reported; it is especially important when the primary count itself is absent from the registry entry.

The findings should not be translated into advice for an individual or interpreted as proof that the device is effective or ineffective. The registry record does not report enough primary outcome results or comparative evidence to support either conclusion. Its documented purpose was continued assessment of safety and performance, but purpose is not a result. A complete assessment would require the endpoint results, component-level reporting, methods for missing data and event adjudication, and fuller analysis documentation. Those details are not reported in the registry record summarized in the study entry.

14. Why This Trial Matters Statistically

This investigation is statistically informative because it illustrates how study design controls the claims that an outcome can support. A clearly defined composite and timeframe make the intended primary measurement identifiable: participant-level MACE during the in-hospital period up to 7 days after the index procedure. The registry also identifies an ITT per-subject population. Those definitions help readers understand what a primary result would represent, even though the result itself is not reported in the registry record.

At the same time, the single-group design sets a firm limit on comparative interpretation. Without a control group or randomized allocation, an observed count would describe the study group rather than isolate the effect of the device. Statistical sophistication cannot replace the missing comparison: adjustment or a confidence interval could characterize an estimate, but would not turn a single-group description into a randomized treatment contrast.

The record also demonstrates why reporting completeness matters. A large set of listed outcomes—64 in total—does not substitute for the primary endpoint result or a documented analysis plan. Interpretation depends on knowing the outcome counts, their precision, how multiple outcomes were handled, and how incomplete observations were treated. Those details are not reported in the registry record.

Finally, safety counts and event-term percentages require their own context. Denominators, follow-up, definitions, and potential overlap affect their meaning. Treating these entries as a comparison or adding event categories without that context would overstate what the data establish. The statistical lesson is to match each conclusion to the design and reporting actually available.

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 main trial-specific limitation is the absence of a control group: the registry identifies a single-group model and allocation as NA. This prevents a randomized comparison and limits the study’s ability to distinguish outcomes associated with the intervention from background event risk or other influences. Masking is listed as NONE, but the registry does not describe outcome-assessment procedures, so the implications for ascertainment cannot be evaluated from this entry.

The primary endpoint is defined, but its participant count and component results are not reported in the registry record. Neither an estimate of precision nor a primary endpoint p-value is reported. The record also does not provide baseline characteristics, detailed eligibility criteria, endpoint adjudication methods, follow-up completeness, or rules for handling missing data and protocol deviations. These omissions prevent assessment of representativeness, event classification, and the potential effect of incomplete observations.

The registry lists 64 outcomes but no analysis entries. It does not report the statistical analysis plan, multiplicity procedures, or interim analyses. The study’s sample-size justification is not reported in the registry record. Safety information is listed, but the adverse-event entry does not, in this summary, explain the follow-up duration, the causes of deaths, or whether the displayed serious-event terms overlap. These limitations concern what can be assessed from the registry record; they do not establish that an unreported procedure was not performed.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: ABSORB EXTEND Clinical Investigation — NCT01023789.
• Registry record last updated 2018-02-14; status last verified 2017-12.
• Results first posted 2017-12-18.
• 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

ABSORB EXTEND is listed as a completed, single-group clinical investigation sponsored by Abbott Medical Devices, with 812 participants enrolled. The intervention was ABSORB BVS implantation for coronary artery disease; masking is listed as NONE and allocation as NA. The primary endpoint is the participant count for a composite of cardiac death, myocardial infarction, and ischemia-driven target lesion revascularization during the in-hospital period up to 7 days after the index procedure. The analysis population is described as ITT, per-subject analysis.

The primary endpoint result is not reported in the registry record. The adverse-event entry lists 295 participants affected by serious adverse events, 808 affected by other adverse events, and 7 deaths, with selected serious-event terms and percentages. No randomized comparator is listed, and detailed statistical, missing-data, and multiplicity methods are not reported in the registry record. The entry supports a description of the study design and recorded safety data, but not a comparative treatment-effect conclusion.