Novel Angioplasty Using Coronary Accessor: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Novel Angioplasty Using Coronary Accessor (NCT00815997), a randomized na study. The primary outcome is Number of Patients With Radial Artery Occlusion.

2. Clinical Question

The comparison concerns a procedure-related outcome after coronary intervention through the radial artery. The registry describes a randomized, parallel-group design, with participants assigned to one catheter-size group. It does not report the method used to generate or conceal the allocation sequence, so those aspects of randomization cannot be assessed from the registry record.

The primary outcome is a count of participants with radial artery occlusion, rather than a measure of how severe any occlusion was or how long it persisted. The endpoint description specifies an assessment the day after TRI and defines occlusion by absence of a radial pulse confirmed by a reverse Allen's test. The primary timeframe is recorded as within 2 days after TRI. The record does not explain the relationship between these two descriptions in further detail.

The clinical question is therefore focused: whether the recorded frequency of this defined outcome differed between the catheter groups during the stated follow-up window. It does not directly answer broader questions about long-term artery status, patient experience, or other consequences of the procedure. The registry lists additional outcomes, but their presence does not change the primary comparison.

3. Trial Design

The registry record describes a completed randomized, parallel-group trial with enrollment of 160 participants. The comparison assigned participants to TRI using either a 6-Fr or a 4-Fr guiding catheter; the primary results list 80 participants in each group. The recorded intervention is percutaneous coronary intervention, and the arm descriptions specify the catheter size used for TRI.

The trial is marked as having no masking. This means the registry does not indicate blinding; it does not establish which people involved in the procedure, outcome assessment, or analysis knew the assigned catheter size. Those details are not reported in the registry record. The allocation method, allocation concealment, trial sites, participant characteristics, and detailed eligibility criteria are also not reported in the registry record.

The record gives a start date of 2009-01-01 and a primary completion date of 2010-12-31, and it lists the study status as completed. The phase is recorded as NA. The sponsor is listed as NAUSICA Investigators. These administrative details identify the registry entry but do not describe how the trial was conducted beyond the design features recorded above.

The primary endpoint is the number of participants with radial artery occlusion within 2 days after TRI. The registry describes the endpoint as absence of a radial pulse confirmed by a reverse Allen's test, with the primary endpoint description specifying assessment the day after TRI. The posted group counts are 3 participants in the 6 Fr TRI group and 0 in the 4-Fr TRI group. The posted comparison is a risk difference for 4-Fr relative to 6 Fr, with an unadjusted p value of 0.08.

The record lists secondary outcomes for successful PCI, major adverse cardiac events, access-site complications, fluoroscopy time, contrast dye volume, procedure time, and hemostasis time. Numerical results are posted for only some of these outcomes. The registry record does not report the trial's statistical analysis plan, sample-size justification, interim analyses, or analysis populations.

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.

Population: The trial was powered to show the noninferiority of 4-Fr compared with 6-Fr in achieving the primary endpoint of radial artery patency, with a 2-sided alpha level of 0.05. Assuming a radial artery occlusion rate of 1% in the 4-Fr and 6% in the 6-Fr, with a noninferiority margin, δ, of 5%.

6. Primary Endpoint

The registry lists the primary outcome as Number of Patients With Radial Artery Occlusion, measured over within 2 days after TRI.

The primary endpoint counts participants with radial artery occlusion after TRI. The registry defines the event as absence of a radial pulse confirmed by a reverse Allen's test. Its primary endpoint description places the assessment the day after TRI, while the recorded timeframe is within 2 days after TRI. No further details about assessment procedures or adjudication are reported in the registry record.

This endpoint is used to quantify whether the artery remained detectably patent after access through the radial artery. In general, a binary endpoint such as this classifies each participant as having or not having the defined event during the specified assessment period. It provides a direct event count for comparing groups, but it does not capture degrees of impairment, duration, or later outcomes unless these are separately measured.

The endpoint is specific to the artery and the assessment method recorded for this trial. Its interpretation depends on how consistently the pulse assessment and reverse Allen's test were performed, and on whether outcome assessors knew the assigned catheter size. The registry identifies the trial as unmasked but does not report assessor blinding or further measurement procedures. Those missing details limit assessment of potential measurement differences between groups.

The registry's stated aim was to investigate whether the occlusion rate with 4-Fr TRI would be no more than that with 6-Fr TRI. The posted endpoint is a count of participants, and the comparison presents a risk difference. This allows the reader to consider the observed difference in event frequency and its uncertainty, but it does not by itself establish a prespecified non-inferiority margin or a formal non-inferiority conclusion. Such a margin and the corresponding analysis plan are not reported in the registry record.

7. Results Posted in the Registry

• 4-Fr TRI: 0.0% (0/80) versus 3.8% (3/80) on control; risk difference -3.8 percentage points (95% CI -7.9 to 0.4); unadjusted two-proportion z-test p = 0.080.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Number of Patients With Successful PCI

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • 4-Fr TRI: 98.8% (79/80) versus 98.8% (79/80) on control; risk difference 0.0 percentage points (95% CI -3.4 to 3.4), risk ratio 1.00 (0.97–1.04); unadjusted two-proportion z-test p = 1.000.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between 4-Fr TRI and the control. The interval gives the range of effects that remain compatible with the data.

Number of Patients With Access-site Complications

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • 4-Fr TRI: 0.0% (0/80) versus 6.2% (5/80) on control; risk difference -6.2 percentage points (95% CI -11.6 to -0.9); unadjusted two-proportion z-test p = 0.023.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically lower for 4-Fr TRI than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Fluoroscopy Time Used for the Procedure

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • 4-Fr TRI: mean 13.00 versus 12.00 on control; difference 1.00 (95% CI -2.11 to 4.11), standardized effect d = 0.10; z-test p = 0.529.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between 4-Fr TRI and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes cover procedural success, access-site complications, and procedure-related measures, alongside additional outcomes named in the registry. Their general pattern is not a single, consistent signal across all aspects of the intervention: the posted numerical outcomes include both binary and continuous measures, and the results are not available for every outcome listed. Results for major adverse cardiac events, contrast dye volume, procedure time, and hemostasis time are not reported in the registry record.

These outcomes relate to the primary result by providing other views of the procedure and its immediate outcomes. They do not directly confirm or refute the radial artery occlusion comparison, because they measure different events or quantities. In general, an outcome such as procedural success may help describe whether the intervention was completed, while procedural times describe resource or process measures; neither replaces follow-up for the defined primary endpoint.

The registry provides unadjusted comparisons for the secondary outcomes with posted numerical results. The analysis plan does not report whether a hierarchy or a correction for multiple comparisons was used. When several outcomes are examined, the chance of observing an apparently notable result by chance can increase. For that reason, unadjusted secondary findings generally carry less weight than a clearly prespecified primary analysis, especially when the secondary results are incomplete or exploratory.

The secondary results should therefore be read as descriptive evidence about the recorded outcomes, not as a comprehensive demonstration of overall benefit or harm. Their interpretation is further limited by the absence of reported analysis details, participant-level information, and results for several listed outcomes. The registry does not report a combined endpoint or an overall summary measure across the secondary outcomes.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Number of Patients With Successful PCI
• Number of Patients With Measure Adverse Cardiac Event (MACE)
• Number of Patients With Access-site Complications
• Fluoroscopy Time Used for the Procedure
• Contrast Dye Volume Used for the Procedure
• Time Used for the Procedure
• Time Used for Hemostasis

9. Statistical Interpretation

10. Statistical Methods Explained

The posted comparison expresses the primary outcome as a risk difference: the event frequency in the 4-Fr group minus the event frequency in the 6 Fr group. A negative estimate means the recorded event frequency was lower in the 4-Fr group. This is an unadjusted comparison of the group summaries, rather than an estimate adjusted for participant characteristics or other factors. The registry does not report adjusted analyses.

What does a risk difference describe?

In general, a risk difference expresses the contrast between two group event frequencies on the same absolute scale. It can be easier to relate to an outcome count than a relative measure because it describes the separation between the groups' observed event frequencies. Its value depends on the event definition, the timeframe, and the participants included in each group. Here, the comparison is tied to the registry's definition of radial artery occlusion within 2 days after TRI.

The posted primary comparison has a negative risk difference, consistent with the observed counts of 0 events in the 4-Fr group and 3 in the 6 Fr group. The registry reports an unadjusted p value of 0.08. Because the event count is small, the estimate is sensitive to a small number of outcome events. The apparent direction of the group difference should therefore be considered alongside the confidence interval, not as a stand-alone conclusion.

How should the p value be read?

In general, a p value measures how compatible the observed data are with a specified null model, under the assumptions of the statistical test. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of an effect. The registry labels the posted value as unadjusted. The test specification and any adjustment for covariates are not reported in the registry record. A p value above a conventional threshold does not show that the groups are equivalent.

The record describes the study aim in terms of whether the 4-Fr rate would be no more than the 6 Fr rate. In general, a formal non-inferiority assessment requires a prespecified margin defining how much worse an intervention could be while still meeting the criterion, along with an appropriate analysis plan. A margin and such a plan are not reported in the registry record. The observed direction and p value alone therefore cannot establish non-inferiority.

What does the confidence interval add?

In general, a confidence interval gives a range of effect values compatible with the data and the method used to calculate it. A narrower interval indicates greater precision; a wider interval indicates less precision. For a risk difference, an interval that includes zero is compatible with no group difference under the interval's statistical framework. The posted primary interval crosses zero, so it includes values on both sides of no difference. That is consistent with the reported p value not crossing the conventional 0.05 threshold.

An interval is not a guarantee that the true effect lies within its bounds, and it does not account for every source of uncertainty. It reflects statistical uncertainty under the calculation method. Possible limitations in measurement, missing outcomes, allocation procedures, and analysis choices are separate concerns. Details needed to judge those issues are not reported in the registry record.

Why do small event counts matter?

In general, sparse binary outcomes yield estimates that may be imprecise because relatively few observed events anchor the comparison. When one group has no recorded events, the observed count should not be mistaken for certainty that events cannot occur. The confidence interval helps show that uncertainty, while the raw group counts keep the scale of the evidence visible. No model details beyond the posted unadjusted comparison are reported in the registry record.

Secondary comparisons include both binary and continuous outcomes. In general, a binary outcome records whether an event occurred, while a continuous outcome such as fluoroscopy time is summarized by a mean and standard deviation. These measures answer different questions and should not be combined into a single overall effect without a prespecified method. The record does not report a joint or composite analysis across the secondary outcomes.

How should the sample-size illustrations be understood?

The registry's planning illustration is computed from an observed effect, not from the trial's own design. It states a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and effects set to stated fractions of the observed effect. In general, such calculations illustrate the sample sizes that a future study might require under those assumptions; they do not show the power achieved by the completed trial and do not explain how its enrollment was chosen.

The illustration gives participants per arm for 80% and 90% power at 100%, 75%, and 50% of the observed effect. Those figures are planning scenarios, not observed results. The trial's own sample-size justification is not reported in the registry record. Because the observed effect is uncertain, planning directly from it can be unstable; using smaller fractions of the observed effect illustrates how a more modest target effect would require larger planning numbers under the stated assumptions.

11. Confidence Intervals and Precision

The primary comparison is based on few recorded events: 3 in the 6 Fr TRI group and 0 in the 4-Fr TRI group. The posted risk-difference confidence interval crosses zero. It therefore includes values consistent with a lower event frequency in the 4-Fr group and values consistent with a small difference in the other direction. The interval does not support a precise estimate of the comparative effect.

In general, a confidence interval describes statistical uncertainty around an estimate under a particular method. Its width is useful for assessing precision, while its location shows the range of effects compatible with the data. An interval that crosses zero for a difference does not prove equivalence. Equivalence would require a prespecified range of differences considered acceptably small and an analysis showing that the interval lies within that range. Such a range is not reported in the registry record.

The event count affects how much information the primary outcome provides. An observed zero in one group is not enough to establish that the underlying risk is zero, and the small number of events means that each event has appreciable influence on the comparison. The posted p value of 0.08 is consistent with the interval's inclusion of no difference, but the p value does not communicate the full range of plausible effect sizes.

Precision is also distinct from measurement quality and generalizability. The registry identifies the outcome definition and timeframe, but further assessment procedures, assessor blinding, and outcome completeness are not reported in the registry record. These details matter because a statistically precise estimate would still depend on the validity and completeness of the measurements. The available results therefore show a direction in the observed counts, but they leave uncertainty about the size and clinical meaning of the underlying difference.

12. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when several outcomes or statistical comparisons are considered. In general, the more comparisons made, the greater the possibility that at least one result will appear unusual by chance, even when there is no underlying effect. Statistical approaches such as prespecified outcome hierarchies or adjusted significance thresholds can address this issue, but the appropriate approach depends on the trial's objectives and analysis plan.

The registry identifies one primary outcome and lists multiple secondary outcomes. It does not report a multiplicity strategy, an outcome hierarchy beyond identifying the primary endpoint, or whether any secondary analyses were intended to be confirmatory. The secondary comparisons are labeled unadjusted in the posted summaries. They should therefore be interpreted cautiously and should not be treated as independent confirmation of the primary result.

Missing-data methods and analysis populations are not reported in the registry record. The posted primary outcome groups each list 80 participants, but this alone does not establish whether every randomized participant contributed an observed outcome, how missing outcomes were handled, or whether the analysis followed an intention-to-treat principle. The registry does not describe exclusions, protocol deviations, or a per-protocol analysis.

The record also does not report an interim-analysis plan, stopping rules, or a statistical analysis plan. These details are relevant because they can affect how outcome definitions, analysis choices, and significance thresholds are interpreted. Their absence from the registry record should not be taken as evidence that no such procedures existed; it means their details cannot be assessed from this record.

There is no reported sample-size justification for the completed trial. The posted planning illustration is based on the observed effect and is explicitly separate from the trial's own design. It cannot fill the gap in information about the original planning assumptions, target effect, or intended precision. These reporting gaps limit the assessment of how closely the posted analyses reflect the trial's prespecified methods.

13. 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 5% reporting threshold.

The registry's adverse-event figures list 0 serious adverse events, 0 other adverse events, and 0 deaths in each group. These are the recorded counts for the groups and the adverse-event categories in the registry entry. No serious adverse-event terms are listed.

Zero recorded events should be read as an observation in this trial record, not as proof that an event is impossible or that the procedures have no safety risks. Safety estimates are uncertain when few or no events are recorded, and the record does not provide detailed event definitions, ascertainment procedures, severity categories beyond the listed fields, or longer-term follow-up.

The registry's adverse-event counts are distinct from the primary endpoint and the secondary access-site complication outcome. The adverse-event summary does not replace those outcome-specific results. The record also does not report how adverse events were collected or whether the people assessing them were masked to catheter assignment. These omissions limit the conclusions that can be drawn from the safety counts alone.

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

The posted primary results show 3 participants with radial artery occlusion in the 6 Fr TRI group and 0 in the 4-Fr TRI group during the recorded period. The estimated risk difference is negative for 4-Fr relative to 6 Fr, but its confidence interval crosses no difference and the unadjusted p value is 0.08. The results therefore describe an observed difference without precisely establishing the underlying comparative effect.

This is not evidence that the groups are equivalent. A failure to reach a conventional statistical threshold does not demonstrate that any difference is absent or acceptably small. The registry's stated expectation that the 4-Fr rate would be no more than the 6 Fr rate does not itself constitute a formal non-inferiority conclusion. A non-inferiority margin and supporting analysis are not reported in the registry record.

The data also do not establish that the underlying risk in the 4-Fr group is zero. No event was recorded there, but the small number of primary events leaves uncertainty about the event frequency that could occur beyond the observed participants. The confidence interval is important because it conveys uncertainty that the raw counts alone can obscure.

Interpretation should remain tied to the endpoint and timeframe: radial artery occlusion defined by pulse absence confirmed by a reverse Allen's test, with follow-up recorded as within 2 days after TRI. The record does not establish longer-term patency or outcomes beyond this assessment window. It also does not provide detailed information about participant characteristics, outcome assessment procedures, missing data, or analysis populations.

The secondary results provide additional, but incomplete, information about procedural outcomes. They do not establish a broad conclusion across all aspects of efficacy or safety, particularly because results for several listed outcomes are not reported and the multiplicity plan is not reported. In sum, the registry records fewer primary events in the 4-Fr group, while the uncertainty and reporting limitations prevent a definitive conclusion about the comparative effect.

15. Why This Trial Matters Statistically

This trial is statistically informative as an example of how a randomized comparison can produce a directionally clear count pattern but still leave substantial uncertainty. The primary outcome has only a few recorded events, including none in one group. With sparse events, the estimate can appear striking when expressed as a difference in counts, yet the confidence interval may remain compatible with a range of underlying effects.

The record also illustrates why a stated clinical expectation and a formal statistical claim are not interchangeable. The study aim describes an expectation that the 4-Fr occlusion rate would be no more than the 6 Fr rate. A defensible non-inferiority conclusion requires a defined margin and an analysis designed to evaluate it. Those elements are not reported in the registry record, so the posted comparison should be interpreted as an unadjusted estimate with uncertainty, rather than as proof of non-inferiority.

Another statistical lesson is that secondary outcomes can broaden the description of a trial without necessarily strengthening its main conclusion. The registry lists several procedural and safety outcomes, but numerical results are posted for only some. Without a reported multiplicity strategy, isolated secondary results warrant restraint. Different outcome types also answer different questions and should not be collapsed into one overall interpretation without a prespecified method.

Finally, the record distinguishes a planning illustration from the original study design. Illustrative sample sizes based on an observed effect can help show how assumptions about a target effect influence future planning, but they are not evidence of the completed trial's power or its original rationale. The original sample-size justification and statistical analysis plan are not reported. These distinctions are essential for reading both the result and the limits of the registry entry.

16. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record leaves important design and conduct details unspecified. It does not report participant characteristics, detailed eligibility criteria, the randomization sequence method, allocation concealment, trial sites, or the reasons for any exclusions. It identifies the study as unmasked but does not say whether outcome assessors or analysts were aware of group assignment.

The primary endpoint description specifies assessment the day after TRI, while the timeframe is recorded as within 2 days after TRI. The record does not explain whether assessments occurred at a single scheduled time or at any point within that window. Further details about pulse examination, reverse Allen's test procedures, assessor training, and adjudication are not reported in the registry record.

Although the primary results list 80 participants in each group, the registry does not report the analysis population, participant flow, or missing-outcome handling. It is therefore not possible from this record to determine whether the posted comparison includes all randomized participants or how any unavailable measurements were addressed. The statistical analysis plan, sample-size justification, interim analyses, and multiplicity approach are also not reported.

Only some of the listed secondary outcomes have numerical results posted. Results for major adverse cardiac events, contrast dye volume, procedure time, and hemostasis time are not reported in the registry record. The adverse-event summary lists zero events in its categories, but event-collection methods and longer-term safety follow-up are not described.

The primary outcome's small event count limits precision, and the short recorded timeframe limits conclusions to the immediate post-procedure period. These constraints do not invalidate the posted comparison, but they restrict what it can establish about longer-term outcomes, measurement consistency, and the broader clinical population.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: Novel Angioplasty Using Coronary Accessor — NCT00815997.
• Registry record last updated 2019-05-06; status last verified 2019-02.
• Results first posted 2019-05-06.
• 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.

20. Record Summary

The registry record describes a completed randomized, unmasked, parallel-group trial comparing 4-Fr with 6 Fr TRI. Enrollment was 160, with 80 participants listed in each primary-outcome group. The primary endpoint was radial artery occlusion within 2 days after TRI, defined by absence of a radial pulse confirmed by a reverse Allen's test.

The primary count was 0 in the 4-Fr group and 3 in the 6 Fr group. The posted risk difference favors fewer observed events with 4-Fr, but its confidence interval crosses no difference; the unadjusted p value is 0.08. These findings do not establish equivalence or formal non-inferiority.

The registry lists multiple secondary outcomes, with numerical results posted for some but not all. The statistical analysis plan, sample-size justification, multiplicity strategy, missing-data methods, and analysis populations are not reported in the registry record. The primary result is therefore best read as a limited, imprecise comparison for the recorded endpoint and follow-up window.