Aspirin Responsiveness in Women With Coronary Artery Disease: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Aspirin Responsiveness in Women With Coronary Artery Disease (NCT01406990), a registered phase not stated study. The primary outcome is Women With Known CAD Who Are Hyporesponsive to Low Dose (81 mg) Aspirin.

2. Clinical Question

The study’s stated purpose was to measure the percentage of women with known CAD who were hyporesponsive to low-dose aspirin. Its primary outcome is described as a number of participants, while the purpose statement frames the question as a percentage. These are related ways of describing an outcome, but the registry record does not report the observed count or percentage. It therefore does not establish what proportion of the enrolled group met the definition.

The question is descriptive rather than a comparison of treatment groups. The record identifies women taking aspirin 81 mg but does not identify a valid control group or a randomized allocation. Without such a comparison, the result would not estimate a contrast between aspirin and another treatment, dose, or no treatment. Nor would a measured frequency by itself establish why a participant met the laboratory definition. The clinical question is limited to how often the specified response category was observed in this enrolled group at the stated measurement time.

3. Trial Design

The registry identifies this study as completed and lists enrollment of 15. The study is titled “Aspirin Responsiveness in Women With Coronary Artery Disease.” Its stated purpose is to measure the percentage of women with known CAD who are hyporesponsive to low-dose aspirin. The listed arm is “Aspirin 81 mg,” described as women with CAD taking 81 mg aspirin.

The recorded study start is 2011-06, and primary completion is recorded as 2012-04. The sponsor is Creighton University. The record lists 1 primary outcome measure, expressed as a number of participants and assessed at the time of enrollment. It describes the endpoint as a participant count rather than a comparison between treatment groups.

The registry record states that allocation was not stated and that the arms are not a like-for-like control comparison. This means the listed group should not be interpreted as one side of a randomized treatment contrast. Details about a comparator, recruitment procedures, eligibility criteria beyond the stated CAD population, or the measurement procedures are not reported in the registry record. Those missing details limit assessment of how participants entered the study and how widely the observations might apply.

The record lists no statistical analyses. It also does not report the primary outcome count or percentage. Consequently, the design description identifies what was intended to be measured, but does not permit a numerical account of the measured frequency or a comparison with another group. The planning illustration described in the registry assumptions is based on an observed effect and equal allocation between two arms; those assumptions do not turn this non-comparative record into a randomized comparison. Planning calculations are not evidence about outcomes observed in participants.

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

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 Women With Known CAD Who Are Hyporesponsive to Low Dose (81 mg) Aspirin, measured over Time of enrollment.

The primary endpoint concerns the number of women with known CAD who met the study’s definition of hyporesponsiveness to low-dose aspirin. The definition is an Aspirin Response Unit (ARU) value > 550, described in the record as equating to less than 50% platelet inhibition. The measurement timeframe is the time of enrollment.

This endpoint is used to classify participants according to a stated laboratory threshold. A count can describe how many people in the enrolled group met that definition. If the group size and outcome count are both available, a percentage can also express the frequency in a way that is easier to compare across groups of different sizes. The registry purpose refers to a percentage, but its listed outcome parameter is a number of participants.

The threshold makes the endpoint operational: a participant is classified by whether the recorded ARU crosses the stated cut point. As a general statistical point, a thresholded measure simplifies interpretation but can conceal variation among measurements on either side of the cut point. It does not, on its own, describe the full distribution of ARU values or show how close individual values were to the threshold.

The observed endpoint value is not reported in the registry record. Thus, the stated definition and timing can be described, but the number classified as hyporesponsive and the corresponding percentage cannot be interpreted from this record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a binary endpoint in terms of participants with an event, with the event being classification as hyporesponsive. The stated threshold is ARU > 550. The listed outcome parameter is a number of participants, and the assessment timeframe is the time of enrollment. No statistical analyses are listed in the registry record, and the observed endpoint value is not reported there.

What does a thresholded endpoint represent?

As a general statistical explanation, a threshold converts a measurement into a category. Here, the record defines the category using an ARU cut point and relates it to less than 50% platelet inhibition. The result of such classification is a count of participants meeting the definition. This can make a clinical or laboratory question easier to summarize, but it discards information about the exact measurement values. Participants just above the threshold and participants with much higher values would be placed in the same category, while measurements on opposite sides of the threshold would be placed in different categories.

A threshold also depends on the definition being used. It is important to report the measurement method and the cut point so that readers know what the event means. The record supplies the cut point and its stated interpretation, but details of the measurement procedure and any quality-control process are not reported in the registry record. The endpoint should therefore be understood according to the registry’s definition, without assuming additional laboratory procedures.

How should a count and a percentage be distinguished?

A count is the number of participants classified as having the outcome. A percentage relates that count to a denominator, such as the number evaluated for the outcome. As a general statistical principle, both the numerator and the relevant denominator are needed to interpret a percentage. The study purpose refers to measuring a percentage, whereas the listed endpoint is a participant count. The registry lists 15 enrolled participants, but the number assessed for the endpoint and the observed outcome count are not reported in the registry record. Enrollment should not be substituted for an outcome denominator unless the record establishes that every enrolled participant was assessed.

A proportion estimated from a group is also subject to sampling uncertainty. If repeated samples were drawn from a similar population, the observed proportion could vary. A confidence interval can express that uncertainty under a chosen statistical method. It does not account automatically for selection bias, measurement error, or differences between the enrolled group and a broader population. No estimate or confidence interval for this endpoint is reported in the registry record.

What can the listed design support?

The record identifies women with CAD taking aspirin 81 mg and notes that allocation was not stated. It explicitly warns that the arms are not a like-for-like control comparison. As a general principle, a descriptive study can estimate a frequency in the group observed, subject to how the group was selected and measured. A causal comparison requires a credible comparator and design that supports that interpretation. The record does not identify such a comparison, so it cannot support an estimate of the effect of aspirin relative to another treatment or condition.

The record’s planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. These are planning assumptions, not a report of the study’s own design or analysis. The registry record does not report a protocol-based sample-size justification, and it lists no analysis results. A planning calculation under assumed conditions is not observed power and does not show that a study did or did not detect an effect. In particular, planning assumptions about two arms do not establish that this record contains a valid two-arm comparison.

Why do analysis details matter?

Statistical interpretation depends on more than an endpoint definition. The analysis population, handling of missing endpoint measurements, and method used to calculate uncertainty all affect what an estimate means. Those details are not reported in the registry record. For a binary endpoint, an analysis might report a count and a proportion, with an uncertainty interval; however, no specific method can be attributed to this study because no statistical analysis is listed.

General methods also need to match the data structure. If the goal is a single-group frequency, analysis would focus on the estimated proportion and its uncertainty. If the goal is a treatment contrast, analysis would need to define the groups and estimate a between-group difference or another appropriate contrast. These are distinct questions. The record’s stated purpose is descriptive, and its note about non-comparable arms cautions against treating the study as a treatment contrast.

Finally, a statistical result cannot repair limitations in measurement or study selection. Even a precise estimate would describe the population and procedures that generated the data. Details about representativeness, endpoint completion, and the analysis population are not reported in the registry record. Here, the absence of the observed endpoint value is the most immediate constraint: without it, neither a frequency nor its precision can be evaluated.

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("Aspirin 81 mg")
n      <- c(15)
events <- c(0)
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  Aspirin 81 mg  15  0  0.0  0.0  21.8  0.0  20.4  0.2  20.6

11. Multiplicity, Missing Data and Analysis Populations

Multiplicity concerns arise when a study conducts multiple statistical tests or examines multiple outcomes, because repeated testing can increase the chance of finding an apparently noteworthy result by chance. The registry lists 1 primary outcome measure and 0 analyses. It does not report a multiplicity adjustment or a broader testing plan. With no analysis results listed, it is not possible to assess how any testing strategy was applied. Details of a prespecified statistical analysis plan are not reported in the registry record.

Missing data matter because the enrolled group and the group with measured outcomes may differ. If some participants lack an endpoint assessment, a count among those assessed can represent a different denominator from the count among all enrolled participants. The registry lists 15 enrolled participants but does not report endpoint completion, missing outcome status, or an analysis population. These details are not reported in the registry record, so the completeness of primary outcome ascertainment cannot be evaluated.

Analysis populations specify which participants contribute to a result. For a descriptive count, readers need to know which participants were assessed and whether all eligible observations were included. The record does not identify an analysis population or provide an analysis of the primary endpoint. It is therefore not possible to determine whether the intended analysis used all enrolled participants or a subset.

These gaps do not demonstrate that data were missing or that multiplicity affected the findings. They mean the relevant information is not reported in the registry record. The absence of reported analyses also prevents evaluation of whether analysis choices were prespecified or how they may have influenced a result.

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 5% reporting threshold.

The registry lists the aspirin 81 mg group with 15 participants at risk for serious adverse events and 0 affected. It also lists 15 at risk for other adverse events and 0 affected. These are reported event counts for the categories recorded in the registry. They should not be confused with the primary endpoint, which concerns hyporesponsiveness by the ARU definition.

A zero recorded count means no affected participants are listed for that category in the registry entry. As a general statistical principle, a zero observed count does not establish that the underlying risk is zero. Rare events may not occur in a limited observation group, and precision depends on the amount and duration of follow-up and the completeness of event capture. The follow-up window and adverse-event collection procedures are not reported in the registry record.

The deaths field is not populated with a count, so a death total is not reported in the registry record. The registry also does not list serious adverse-event terms. The available entries should therefore be read narrowly: they report zero affected for the stated serious and other adverse-event categories, but do not provide enough detail to characterize event ascertainment or establish broader safety.

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

The record identifies a focused descriptive question: whether women with known CAD taking aspirin 81 mg met a stated laboratory definition of hyporesponsiveness at enrollment. It provides the definition, the assessment time, and the enrolled group size. These details clarify what the study intended to measure and how the primary outcome was defined.

The central result itself is not reported in the registry record. Without the observed count, the record cannot show how many participants met the threshold or what percentage of the enrolled group did so. It also cannot show the uncertainty around that estimate. The record lists 0 analyses, so no inferential result is available to interpret alongside the endpoint definition.

Even if the descriptive outcome count were available, it would concern the group studied. It would not, by itself, establish that aspirin caused a particular response or that the observed frequency applies to all women with CAD. Generalizing beyond an enrolled group requires information about participant selection, measurement, and the similarity between the study group and the population of interest. Those details are not reported in the registry record.

The record also does not establish a comparative treatment effect. Allocation was not stated, and the registry cautions that the arms are not a like-for-like control comparison. Thus, no contrast with a control group should be inferred. The stated planning assumptions do not change that interpretation and do not constitute evidence that a treatment effect was observed.

The safety entries are similarly limited. The record lists 0 serious adverse events and 0 other adverse events among 15 at risk, but does not report the death count or event-collection timeframe. These entries do not resolve the primary endpoint question and should not be treated as a complete account of safety.

The most defensible interpretation is therefore about what the registry documents, rather than an unreported finding: a completed study intended to quantify a threshold-defined response in women with CAD taking aspirin 81 mg, with enrollment of 15 and no reported primary result or statistical analysis. The record does not support a conclusion about the frequency of hyporesponsiveness, the precision of that frequency, or a causal treatment effect.

14. Why This Trial Matters Statistically

This study matters statistically because it illustrates the distinction between defining an outcome and reporting an outcome. The registry gives a clear threshold for classifying hyporesponsiveness, ARU > 550, and identifies the assessment time as enrollment. But a definition does not tell readers how many participants met it. The registry does not report the observed count or percentage, leaving the central descriptive question unanswered.

It also highlights the importance of matching interpretation to design. The record describes women with CAD taking aspirin 81 mg and explicitly notes that allocation was not stated and the arms are not a like-for-like control comparison. A descriptive measurement and a comparative treatment estimate answer different questions. Recognizing that distinction prevents a single-group result, even if available, from being presented as evidence of a treatment contrast.

Reporting the analysis population and endpoint completion is equally important. Enrollment is recorded as 15, but the record does not state how many participants had an endpoint assessment or how missing measurements were handled. Without this information, readers cannot know the denominator for a frequency or judge whether the measured group differs from the enrolled group.

Finally, the safety entries demonstrate why event counts need context. The registry lists 0 affected for serious and other adverse events, but does not provide the follow-up window or a death count. Counts are useful, but interpretation depends on how events were defined, collected, and observed. These reporting gaps limit what can be learned statistically, even when the intended endpoint and group are identifiable.

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 interpretation is that the observed primary outcome count and percentage are not reported in the registry record. The record defines hyporesponsiveness and specifies when it was to be assessed, but supplies no result with which to answer the study’s stated question. No confidence interval, p-value, or other statistical analysis is listed.

The enrolled group is described as women with known CAD taking aspirin 81 mg, and enrollment is listed as 15. Further details about participant selection, eligibility criteria, baseline characteristics, or representativeness are not reported in the registry record. These omissions limit assessment of how closely the enrolled group reflects other women with CAD.

The record states that allocation was not stated and that the arms are not a like-for-like control comparison. It therefore does not support a randomized or otherwise interpretable treatment contrast. The registry does not describe a comparator that could anchor a causal estimate.

Endpoint ascertainment and analysis details are also limited. The measurement procedure, number assessed, missing endpoint data, analysis population, and handling of incomplete observations are not reported in the registry record. The record lists 0 analyses, so there is no reported method for estimating the frequency or its precision.

For safety, the record reports 0 serious and 0 other adverse events among 15 at risk, but the observation period and event-collection approach are not reported in the registry record. A death count is also not reported. These gaps prevent a fuller assessment of safety reporting. The planning assumptions do not supply these missing study details or replace an outcome analysis.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Aspirin Responsiveness in Women With Coronary Artery Disease — NCT01406990.
• Registry record last updated 2012-09-28; status last verified 2012-08.
• Results first posted 2012-09-28.
• 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 study sponsored by Creighton University, titled “Aspirin Responsiveness in Women With Coronary Artery Disease.” It lists a study start of 2011-06, primary completion of 2012-04, and enrollment of 15. The group is women with CAD taking aspirin 81 mg.

The primary outcome is a participant count for hyporesponsiveness at enrollment, defined as ARU > 550 and described as equating to less than 50% platelet inhibition. The study purpose refers to measuring a percentage, but the observed count and percentage are not reported in the registry record. The record lists 0 analyses.

Allocation was not stated, and the registry cautions that the arms are not a like-for-like control comparison. Safety entries list 0 serious and 0 other adverse events among 15 at risk; the death count is not reported in the registry record. The available information describes the intended measurement and enrollment but does not provide the primary result or its precision.