Aspirin Resistance and Percutaneous Coronary Intervention (PCI): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Aspirin Resistance and Percutaneous Coronary Intervention (PCI) (NCT01103440), a randomized phase 2 study. The primary outcome is Number of Participants With Elevation of Cardiac Enzyme.

2. Clinical Question

The registry record describes a randomized, pilot, single-center study comparing conventional antiplatelet therapy with an aggressive strategy that added an intravenous glycoprotein IIb/IIIa inhibitor during the procedure. The study concerned aspirin-resistant patients undergoing percutaneous coronary intervention; stable angina is listed as the condition. Its stated objective was to evaluate whether aggressive antiplatelet therapy would reduce ischemic events after the procedure.

The primary endpoint is a count of participants meeting that biomarker definition. The registry also lists the number of participants with major adverse cardiac event as a secondary outcome, but a secondary-outcome result is not reported in the registry record. The question addressed by the posted primary results is therefore narrower than the study's broad stated objective about ischemic events.

3. Trial Design

This was a phase 2, randomized, parallel-group study with no masking. The registry record identifies Icahn School of Medicine at Mount Sinai as the sponsor and describes the study as investigator-initiated, pilot, and single-center. Enrollment was 36. The record lists the study as completed, with a start date of 2007-04 and primary completion in 2009-06.

Participants were assigned to a conventional strategy or an aggressive strategy. Each arm had 18 participants in the posted primary outcome results. Both strategies included oral ASA and a loading dose of Clopidogrel at the time of the procedure. The aggressive strategy also included an intravenous GP IIb/IIIa inhibitor bolus during the procedure. The registry's wording says “loading does” in the arm descriptions; the intervention details identify the loading dose as 600mg.

The primary outcome was the number of participants with elevation of cardiac enzyme during the 24 hours after completion of the procedure. It was defined as any elevation above baseline of CK-MB or Tn-I. The record lists MACE as a secondary outcome. It also lists two outcome measures, but does not report a MACE result in the information.

The registry record identifies the design as randomized and parallel, but the random sequence method, allocation concealment, and operational details of treatment assignment are not reported in the registry record. Masking is explicitly listed as none. The original statistical analysis plan, protocol details beyond the registry descriptions, and the rationale used to choose the enrollment target are not reported in the registry record. The posted results should therefore be read as results from a small pilot comparison, not as a complete account of every design or analysis decision.

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 Number of Participants With Elevation of Cardiac Enzyme, measured over 24 hours.

The primary endpoint counts participants with peri-procedural biomarker elevation. A participant met the stated definition if CK-MB or Tn-I rose above baseline within 24 hours after completion of the procedure. The endpoint is reported as a participant count for each arm, rather than as a continuous enzyme measurement or a time-to-event outcome.

As a general statistical concept, a binary endpoint reduces each participant's outcome to whether the event definition was met. This makes the group comparison directly about the proportion of participants with the event, while discarding information about the size or timing of an elevation beyond what the definition captures. The endpoint is also limited to the specified biomarkers and observation window. It does not, by itself, describe every possible ischemic event or the longer-term course of participants.

Biomarker outcomes are commonly used in clinical research to measure a biological change around a procedure. In this registry record, the stated measure is specifically the number of participants with any above-baseline elevation of either CK-MB or Tn-I during the defined period. The record does not report the magnitude of individual elevations, separate results for CK-MB and Tn-I, or a rationale for selecting this endpoint.

The posted count was 4 participants in the conventional strategy arm and 2 participants in the aggressive strategy arm. Those counts are the observed primary endpoint results; they should not be treated as a full measure of clinical benefit or harm. The secondary outcome of MACE is listed, but its result is not reported in the registry record.

7. Results Posted in the Registry

• Aggressive Strategy: 11.1% (2/18) versus 22.2% (4/18) on control; risk difference -11.1 percentage points (95% CI -35.2 to 13.0), risk ratio 0.50 (0.10–2.40); unadjusted two-proportion z-test p = 0.371.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary at the participant level: each person either met the registry definition of cardiac enzyme elevation or did not. The displayed counts are 4 of 18 participants for the conventional strategy and 2 of 18 for the aggressive strategy. A comparison of binary outcomes can be expressed in absolute terms, such as a risk difference, or in relative terms, such as a risk ratio or odds ratio. Each measure answers a different statistical question, so they are best read together rather than treated as interchangeable.

What does the risk difference describe?

The reported risk difference is -0.111 for aggressive versus conventional strategy. In this comparison, a negative value indicates that the observed event proportion was lower in the aggressive arm. The reported 95% confidence interval is -0.352 to 0.130. Because the interval spans zero, the data are compatible with no absolute difference as well as with differences in either direction. The estimate is unadjusted, based on the posted arm counts.

How do relative measures differ?

The risk ratio compares the event proportions as a ratio. Its reported estimate is 0.5, with a 95% confidence interval from 0.104 to 2.395. The odds ratio compares the odds of the event rather than the proportions themselves. Its estimate is 0.438, with a 95% confidence interval from 0.069 to 2.762. These relative measures have different interpretations and may diverge, especially when events are not rare. Here, both confidence intervals are broad and include the value corresponding to no relative association.

As a general statistical concept, the odds ratio is not the same as a risk ratio. An odds ratio compares event odds, whereas the risk ratio compares event probabilities. A numerical value from one measure should not be described as though it were the other. For this trial, the registry reports both measures, allowing readers to distinguish the effect scales.

What does the p-value tell the reader?

The reported unadjusted p-value is 0.371. In general, a p-value measures how unusual data at least as discrepant as those observed would be under a specified null model and the assumptions of the test. It is not the probability that the null hypothesis is true, nor is it a measure of the size or importance of an effect. The registry record does not report the test procedure or a complete statistical analysis plan, so the p-value is best presented as the posted unadjusted result without inferring unreported analysis details.

A non-small p-value does not demonstrate equivalence. To support a claim that strategies are sufficiently similar, a study would generally need a prespecified equivalence or noninferiority design and an appropriate margin. Such a margin and design are not reported in the registry record. The confidence interval is useful because it shows the range of effect estimates compatible with the data under the method used, rather than reducing the interpretation to a threshold decision.

Why does event scarcity matter?

As a general concept, precision in binary-outcome comparisons depends in part on the number of observed events, not just the total number of participants. When events are sparse, changing the outcome status of a small number of participants can materially change the estimated group contrast. This trial had 4 primary events in the conventional arm and 2 in the aggressive arm. The broad intervals around the absolute and relative estimates reflect the limited information available for estimating the contrast.

Over-dispersion is a concern in some data structures when observed variability exceeds what a chosen model assumes. The posted primary result is a simple binary comparison, and the registry record does not report a model-based analysis or an over-dispersion assessment. Such a method should not be inferred from the registry information. More generally, model complexity cannot create information that is absent from a small number of observed events.

The assignment was randomized according to the registry record, which supports interpreting the arms as a planned comparison. Randomization does not remove sampling uncertainty, guarantee balance in every characteristic in a small trial, or resolve questions about how allocation was implemented. The sequence-generation method and allocation concealment are not reported in the registry record. Masking is listed as none, so the study was open-label. The primary outcome is based on laboratory biomarkers, but the record does not describe laboratory assessment procedures or whether assessors were masked.

No adjusted analysis is reported, and the registry lists zero analyses. The displayed estimates should therefore be understood as unadjusted summaries of the posted counts. The registry record does not report covariates, analysis populations, missing-data methods, interim analyses, multiplicity procedures, or a prespecified statistical plan. These omissions limit assessment of whether the displayed comparison was the only planned analysis and how all randomized participants were handled.

10. Confidence Intervals and Precision

The principal precision message is that the estimated absolute difference is uncertain. The reported risk difference is -0.111, with a 95% confidence interval from -0.352 to 0.130. In general, a confidence interval is a range produced by a statistical procedure that reflects uncertainty in an estimate. It is not a guarantee that the true effect lies in that particular interval, and it does not assign probabilities to individual values within the interval.

The interval crosses zero, the value corresponding to no risk difference. It extends toward both a lower event proportion with the aggressive strategy and a higher event proportion with that strategy. The posted data therefore do not pin down the direction of the underlying difference. The interval is wide relative to the point estimate, consistent with limited precision from the small enrollment and sparse primary events.

The relative-effect intervals are also broad: the risk ratio is 0.5, with a 95% confidence interval from 0.104 to 2.395, and the odds ratio is 0.438, with a 95% confidence interval from 0.069 to 2.762. Each interval includes the relative value that corresponds to no association. The estimates should not be read as precise measures of the size of a treatment effect.

Confidence intervals describe statistical uncertainty under the method used; they do not account automatically for every limitation, such as unreported analysis choices, outcome measurement issues, or generalizability beyond the study setting. The registry record does not report methods for adjusted estimation or missing data. Precision is therefore only one part of interpreting the posted result.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm, not total events. They are illustrations based on the observed effect and are not the trial's original design calculation. The assumptions listed for this illustration are a two-sided significance level 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is the stated fraction of the observed effect.

The 80% power column gives the planned number of participants per arm under those assumptions for a design with 80% power to detect the specified effect. The 90% power column gives the corresponding participants per arm for a design with 90% power. Power is a property of a hypothetical study design under its assumptions; it is not a statement about the probability that the observed finding is true.

For 100% of the observed effect, the illustration gives 176 participants per arm for 80% power and 235 participants per arm for 90% power. Planning for 75% of the observed effect gives 334 participants per arm for 80% power and 446 participants per arm for 90% power. Planning for 50% of the observed effect gives 796 participants per arm for 80% power and 1,065 participants per arm for 90% power. Smaller effects require more participants because they are harder to distinguish from random variation under the same general design assumptions.

These values are not observed power and should not be used to assess the trial's success after the fact. The original sample-size justification and its assumptions are not reported in the registry record. The displayed values are planning illustrations based on the observed effect, which is itself uncertain in this small pilot study.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.222; treatment proportion p₁ = 0.111; average p̄ = 0.167.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.5270 = 1.0330.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.5212 = 0.4386.
4. n = (1.0330 + 0.4386)² / (-0.1111)² = 175.4, rounded up to 176 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.222222222222222                          # control proportion
p1 <- 0.111111111111111                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(1103440)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 176 (80% power), 235 (90% power)
 75% of observed effect: n per arm = 334 (80% power), 446 (90% power)
 50% of observed effect: n per arm = 796 (80% power), 1,065 (90% power)
power.prop.test: 175.4 
Simulated power at n = 176 per arm: 0.810 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome and one secondary outcome, the number of participants with MACE. The primary result is posted for cardiac enzyme elevation. A MACE result is not reported in the registry record. The record also lists two outcome measures, but does not supply a complete description of all planned comparisons or outcomes.

Multiplicity arises when several outcomes, time points, subgroups, or statistical tests are examined. As a general statistical concept, repeated testing can increase the chance of at least one apparently unusual result even when no underlying effects are present. Researchers may address this through a prespecified hierarchy or adjustment, or they may define some analyses as exploratory. The registry record does not report a multiplicity plan, so it is not possible to determine whether any adjustment or outcome hierarchy was intended.

The registry lists zero analyses. No adjusted analysis, subgroup analysis, or interim analysis is reported. The record does not report the trial's statistical analysis plan, the model or test used for the posted p-value, or whether the primary outcome was analyzed according to randomized assignment. The posted result is therefore interpreted as the unadjusted comparison reported for the arm counts, without attributing unreported procedures to the investigators.

Missing-data handling and analysis populations are also not reported in the registry record. Although 18 participants per arm appear in the primary outcome results, the record does not describe whether these represent all randomized participants, an intention-to-treat population, or another analysis population. It does not report withdrawals, missing endpoint observations, exclusions after randomization, or methods for handling missing outcomes. No missingness pattern should be inferred from the reported arm totals alone.

These reporting gaps do not change the posted counts, but they constrain interpretation of the analysis process. A reader cannot establish from the registry record whether all planned analyses are represented, whether multiplicity was considered, or how incomplete data were addressed.

14. 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 non-serious adverse event terms

The serious adverse event summary reports 0 serious events among 18 participants at risk in the conventional strategy group and 0 among 18 participants at risk in the aggressive strategy group. The summary reports 0 deaths in each group. These are the posted figures for the categories identified as serious events and deaths; they do not establish that no other adverse experiences occurred.

The record also lists 15 other adverse events in the conventional strategy group and 4 in the aggressive strategy group, with 18 participants at risk in each group. The registry information does not define those other events or provide their terms, severity, timing, or relationship to the assigned strategy. No serious adverse event terms are listed.

Zero observed serious events should be read as an absence of recorded events in these groups during the reported safety accounting, not as proof that the risk is zero. A small study may provide limited information about uncommon harms. The registry record does not report a detailed safety analysis plan, follow-up duration for adverse events, or how events were collected. These figures therefore describe the posted counts and should not be used to make broader claims about safety.

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

The result shows that cardiac enzyme elevation, as defined in the registry record, was observed in 4 participants in the conventional strategy arm and 2 participants in the aggressive strategy arm. The estimated risk difference for aggressive versus conventional strategy is -0.111. Its 95% confidence interval ranges from -0.352 to 0.130, and the unadjusted p-value is 0.371. The estimate points toward fewer observed events in the aggressive arm, while the uncertainty remains substantial.

These data do not establish that the strategies differ, but they also do not establish that they are equivalent. The trial enrolled 36 participants and had 18 per arm in the primary results, with few observed events. That leaves the effect estimate imprecise. The reported risk ratio and odds ratio also have broad confidence intervals that include no relative association.

The primary endpoint concerns a biomarker elevation during the 24 hours after completion of the procedure. It is not a complete account of all clinical outcomes, and the result does not answer the broader question of longer-term events. MACE is listed as a secondary outcome, but its result is not reported in the registry record. The absence of that result prevents drawing conclusions from this record about the secondary endpoint.

The posted comparison is not a basis for medical advice. It is a statistical description of a small randomized pilot study and its reported endpoint. The registry record does not report the original sample-size justification, the complete analysis plan, missing-data handling, or multiplicity procedures. Those limitations, along with the wide confidence intervals, should remain part of any interpretation.

16. Why This Trial Matters Statistically

This study illustrates how a randomized design and an imprecise result can coexist. Randomization provides a framework for comparing assigned strategies, but a small pilot study may still yield limited information about the size and direction of an effect. The registry reports 18 participants per arm and only a small number of primary endpoint events. In that setting, the point estimate is especially uncertain.

The example also shows why the outcome definition matters. The primary endpoint is not a general measure of every ischemic event: it counts participants with any above-baseline CK-MB or Tn-I elevation within 24 hours after the procedure. MACE is listed separately as a secondary outcome, and its result is not reported in the registry record. Keeping the endpoint definition distinct from the broader study objective prevents overinterpretation.

Effect estimates and confidence intervals add context beyond a p-value. The risk difference, risk ratio, and odds ratio express the comparison on different scales, while their intervals show substantial uncertainty. The unadjusted p-value alone cannot establish equivalence or rule out effects in either direction.

Finally, the planning illustrations demonstrate a general feature of study design: detecting a smaller effect generally requires a larger sample under otherwise similar assumptions. Those values are not the study's original design rationale. Distinguishing planning illustrations from observed trial evidence is important when reading pilot-study results and considering what the registry record does and does not establish.

17. 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.

This was a pilot, single-center study with enrollment of 36 participants. The small arm sizes and limited number of primary events result in imprecise estimates, as reflected in the broad confidence intervals. The findings are specific to the enrolled study population and setting; the registry record does not provide enough detail to characterize how closely that population represents other clinical settings.

The registry identifies the study as randomized and unmasked, but does not report the randomization sequence method or allocation concealment. The record does not describe laboratory assessment procedures or whether outcome assessors were masked. Because the primary outcome is biomarker-based, details of measurement and assessment could help readers understand how the endpoint was determined, but those details are not reported in the registry record.

The posted primary outcome covers a 24-hour period after procedure completion. It does not, on its own, address longer-term outcomes. MACE is listed as a secondary outcome, but its result is not reported in the registry record. The record also does not report a complete statistical analysis plan, original sample-size rationale, missing-data methods, analysis populations, interim analyses, or multiplicity procedures.

The safety summary reports zero serious events and deaths in both arms, but also lists other adverse event counts without descriptions of the events. It does not supply detailed event definitions or follow-up information. These limitations mean that both efficacy-related interpretation and safety interpretation should remain confined to the posted endpoint definitions and counts.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Aspirin Resistance and Percutaneous Coronary Intervention (PCI) — NCT01103440.
• Registry record last updated 2018-02-14; status last verified 2018-01.
• Results first posted 2018-02-14.
• 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.

21. Record Summary

NCT01103440 is a completed phase 2 randomized, parallel, unmasked pilot study sponsored by Icahn School of Medicine at Mount Sinai. The record describes a single-center comparison of conventional antiplatelet therapy with an aggressive strategy adding an intravenous GP IIb/IIIa inhibitor during percutaneous coronary intervention. Enrollment was 36, and the primary outcome was peri-procedural cardiac enzyme elevation within 24 hours.

The primary results report 4 events among 18 participants in the conventional arm and 2 among 18 in the aggressive arm. The reported risk difference is -0.111, with a 95% confidence interval from -0.352 to 0.130; the unadjusted p-value is 0.371. The MACE secondary result is not reported in the registry record.