Caverject User Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Caverject User Study (NCT01008605), a non-randomized phase 3 study. The primary outcome is Percentage of Participants Who Successfully Operated the Caverject Impulse Delivery System.

2. Clinical Question

3. Trial Design

This completed study is registered as a Phase 3, single-group usability study of the Caverject Impulse Delivery System. The registry reports enrollment of 48 participants and identifies the condition as erectile dysfunction. Its stated purpose was to demonstrate the usability of the system. The intervention is listed as a delivery system, and the arm is described as representative users. The registry lists Pfizer as the sponsor.

The design was non-randomized and had no masking. As a result, the record does not describe a randomized allocation process, blinded outcome assessment, or a like-for-like control comparison. There is one listed group, so the study is best read as an assessment of participants’ ability to use the system under the stated instructions, not as a comparative estimate of performance between devices or instruction formats.

The primary outcome was assessed on Day 1. The registry’s primary population is the Full Analysis Set, defined as eligible participants who read the instructions and attempted to deliver Alprostadil using the device. Each participant tested one device/dose combination. Details about how eligibility was assessed, how users were recruited, or how the tested combinations were selected are not reported in the registry record.

The registry lists a number of additional outcomes, including categorical responses to four participant assessment questions, time required for each step, and whether participants commented on any assessment question. It lists 7 outcome measures in total, but numerical results for these outcomes are not reported in the registry record. The study is marked completed, with a start and primary completion date of 2011-02. The registry does not report the conduct details needed to determine whether all planned assessments were completed as intended.

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

Analysis population for the primary outcome, as defined in the registry: Full Analysis Set (FAS): All eligible participants who read the instructions and attempted to deliver Alprostadil using the Caverject Impulse Delivery System. Each participant tested one device/dose combination.

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 Percentage of Participants Who Successfully Operated the Caverject Impulse Delivery System, measured over Day 1.

The primary endpoint is the percentage of participants who successfully operated the Caverject Impulse Delivery System on Day 1. Success was defined as being able to expel the selected dose while relying on the modified Instructions for Use. The assessment therefore focuses on a specific operating task, rather than a clinical outcome or a comparison of treatment effects.

A percentage is suitable for describing how commonly participants completed a defined task in the study group. The registry also specifies a confidence-interval criterion: the lower bound of the 95% confidence interval had to be more than 80% overall for the process to be considered successful. In general, a confidence interval expresses uncertainty around an estimated quantity; its lower bound represents the lower end of the stated interval. The criterion focuses on whether that lower bound exceeds the stated benchmark, not simply whether the observed percentage does.

The numerical percentage and its confidence interval are not reported in the registry record. Consequently, readers cannot establish from this record how many participants succeeded, how uncertain the estimated percentage was, or whether the stated criterion was met. The endpoint’s wording also does not establish how ease of use, errors, or user understanding were assessed beyond the defined dose-expulsion task. Other usability-related measures are listed separately in the registry, but their numerical findings are not reported there.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is a percentage: the proportion of participants who successfully expelled the selected dose using the delivery system and modified instructions. In general, a binary outcome records whether each person did or did not meet a defined condition. Here, the condition is successful dose expulsion. Summarizing these individual outcomes as a percentage gives a group-level description of task completion. The numerical result is not reported in the registry record.

What does the confidence interval convey?

The registry defines success of the process using the lower bound of a 95% confidence interval, which had to be more than 80% overall. In general, a confidence interval gives a range of values compatible with the data under the method used to calculate it. Its width communicates precision: a wider interval indicates more uncertainty about the estimated percentage, while a narrower interval indicates greater precision. The lower bound is especially relevant because the stated decision rule uses that bound rather than the point estimate alone.

The record does not report the point estimate, lower bound, or interval width. It also does not provide enough information to independently reproduce the interval. Accordingly, the threshold can be explained, but its application to the observed data cannot be checked from the registry record. The wording “more than” also means that simply being near the benchmark would not establish that the lower bound crossed it; the actual bound is needed.

Why does the analysis population matter?

The registry defines the Full Analysis Set as all eligible participants who read the instructions and attempted delivery. This definition identifies who was intended to contribute to the primary endpoint. In general, specifying an analysis population helps readers understand which participants are represented by a result and how exclusions may affect its interpretation. The registry reports enrollment of 48, but the number included in the Full Analysis Set and the number with evaluable outcome data are not reported in the registry record.

The distinction matters because enrollment is not necessarily the same as the number analyzed. The registry’s definition also conditions inclusion on reading the instructions and attempting delivery. The record does not say whether any eligible participants failed to attempt the task, whether any data were missing, or how such cases were handled. These details are not reported in the registry record and should not be inferred from the stated enrollment.

What does the single-group design allow?

In general, a single-group study can describe outcomes observed under the tested conditions, but it does not provide a randomized control comparison. This study is listed as non-randomized, with no masking and a single group. It therefore cannot, on the information in the registry, separate the observed task performance from possible influences of the testing context, participant selection, or instructions. Those are general interpretive considerations, not claims that a particular influence occurred in this study.

Each participant tested one device/dose combination. The record does not report the number of combinations, how they were assigned, or whether performance was summarized by combination. Thus the overall endpoint’s definition can be described, but the degree to which results might vary across combinations cannot be assessed from the registry record.

How should other outcomes be understood?

The registry lists categorical responses to four participant assessment questions, time required for each step, and the number of participants providing comments to any question. These measures could describe different aspects of the task: stated responses, duration, and comments. They are not substitutes for the primary dose-expulsion endpoint, and their numerical findings are not reported in the registry record. The record lists 7 outcome measures overall and 1 analysis, but does not provide further statistical-analysis details.

Multiplicity refers, in general, to the interpretive issue created when multiple outcomes or comparisons are assessed. The record does not report a multiplicity adjustment, an outcome hierarchy beyond identifying the primary endpoint, or an analysis plan explaining how the listed outcomes were to be interpreted together. It would be inappropriate to assume a correction or infer a prespecified strategy that is not described.

What can be checked from the posted information?

The record specifies the endpoint, the Day 1 timeframe, the Full Analysis Set definition, and the confidence-interval criterion. It does not report the numerical endpoint result, confidence interval, missing-data handling, or enough computational detail to verify the analysis. In general, reproducibility requires both a defined method and the information needed to apply or check it. Here, the definition is available, but the reported results needed for evaluation are not.

The registry’s listed sample-size assumptions describe planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. These are not the design of this single-group study: the record does not describe two arms or equal allocation. The trial’s own sample-size justification and statistical plan are not reported in the registry record. Any sample-size illustrations elsewhere on the page should therefore be read as planning examples, not as the study’s actual design or as observed power.

10. Multiplicity, Missing Data and Analysis Populations

The registry identifies one primary endpoint and lists 7 outcome measures overall. The additional measures include participant responses to four assessment questions, time required to perform each step, and comments on any question. The numerical findings for these measures are not reported in the registry record. The record also does not report a statistical analysis plan describing a hierarchy among outcomes, a multiplicity adjustment, or how findings across outcomes were to be interpreted.

In general, multiplicity matters when several outcomes or comparisons are examined, because the chance of finding an apparently notable result can depend on how many analyses are considered and how they are handled. That general concern does not establish that the study used, or should have used, a particular adjustment. The registry record does not describe one, so none should be assumed.

The primary analysis population is defined as eligible participants who read the instructions and attempted to deliver Alprostadil. The registry reports enrollment of 48, but does not report how many participants were included in that population or how many contributed an evaluable primary outcome. It also does not describe missing-data handling, exclusions after enrollment, or whether any outcome values were unavailable. These details are not reported in the registry record.

As a result, the population definition is visible, but its implementation and the handling of incomplete observations cannot be assessed. The missing primary estimate and confidence interval further prevent evaluation of the endpoint itself. The record’s stated threshold remains interpretable as a decision criterion, but its application is not verifiable from the information posted.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry lists 0 serious adverse events among 48 participants at risk and 0 other adverse events among 48 participants at risk. These figures describe the event counts recorded for the group during the study. They should be read as reported counts, not as evidence from a comparative safety analysis: the study was single-group, non-randomized, and had no control group listed.

Zero recorded events does not mean that the study could establish the absence of all possible harms. In general, event counts need to be interpreted in relation to the population observed, the period of observation, the definitions used, and how completely events were collected. The registry lists the study’s primary timeframe as Day 1, but does not provide further detail about safety surveillance or reporting procedures. Those details are not reported in the registry record.

The number of deaths is not reported in the registry record. The posted adverse-event figures do not describe the primary usability outcome and cannot be used to infer whether participants successfully operated the delivery system. Nor do they allow a comparison with another device or group, since no comparator is described.

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

This registry record explains what the study set out to assess: whether representative users could expel a selected dose using the Caverject Impulse Delivery System and modified Instructions for Use. It specifies a Day 1 percentage endpoint and a criterion based on the lower bound of a 95% confidence interval being more than 80% overall. That definition tells readers what the planned assessment meant.

The record does not report the observed primary percentage or its confidence interval. It therefore does not show how many participants succeeded, how precisely success was estimated, or whether the stated criterion was met. The study’s purpose and the presence of a prespecified threshold should not be confused with a reported finding. On the registry information available, the endpoint’s outcome remains unknown.

The design was a non-randomized, single-group study without masking. It can be described as an assessment under the stated conditions, but it is not a randomized comparison against another delivery system, another instruction set, or usual practice. The registry does not establish comparative performance or explain what would have happened under different conditions.

The listed secondary outcomes may have been intended to describe user responses, task duration, and comments. Their results are not reported in the registry record, so they cannot clarify where users may have encountered difficulty or how they viewed the assessment. Similarly, the recorded adverse-event counts are descriptive and do not provide the missing usability result.

The appropriate conclusion is limited: the registry defines a usability endpoint and describes the broad study design, but the numerical primary result required to judge the endpoint is not reported. The posted information does not support a conclusion about whether the threshold was attained, whether the system was easy to use, or how its performance compares with alternatives.

13. Why This Trial Matters Statistically

This study is statistically distinctive because its central question is framed as a threshold assessment of task completion in a single group, rather than as a comparison between randomized groups. The endpoint is a percentage, and the registry’s stated rule uses the lower bound of a 95% confidence interval. This makes the distinction between an observed estimate and its precision important: the stated criterion depends on both the estimated level of success and uncertainty around it.

The record gives a specific definition of the user task, a target threshold, a timeframe, and an analysis-population definition. Those elements help readers identify what was intended to count as success and which participants were intended to inform the primary measure. At the same time, the absence of the numerical outcome and interval means that the central statistical question cannot be answered from the record.

The design also illustrates why the type of question matters. A single-group usability assessment can describe performance under the tested conditions, but it does not estimate a randomized contrast with an alternative. Calling attention to the non-randomized design prevents the endpoint from being read as evidence of relative advantage or disadvantage.

Finally, the registry lists multiple outcomes beyond the primary measure, including responses, task times, and comments. Such measures can be relevant to understanding usability, but they need their own reported findings and a clear account of how they relate to the primary endpoint. Here, those results and the detailed statistical plan are not reported in the registry record. The case therefore shows how a clearly described statistical criterion can coexist with insufficient posted results to evaluate whether that criterion was met.

14. 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 limitation for interpretation is that the numerical primary outcome and its 95% confidence interval are not reported in the registry record. Without them, the percentage of successful users, its precision, and whether the stated lower-bound criterion was met cannot be assessed. The listed secondary outcome descriptions likewise do not include numerical findings.

The study’s single-group, non-randomized design and lack of masking mean that the registry does not provide a controlled comparison. The record describes no comparator, so it cannot establish relative performance between this system and another device or instruction format. These design features do not negate the stated usability question, but they define what conclusions the design could support.

Enrollment was 48, while the number included in the Full Analysis Set and the number with complete primary outcome data are not reported in the registry record. The record also does not describe missing-data handling, exclusions, recruitment methods, participant characteristics, or how device/dose combinations were selected. Each participant tested one combination, but results by combination are not reported.

Further detail about the statistical analysis plan, the method used to calculate the confidence interval, and any approach to the listed outcomes is not reported in the registry record. The record also does not provide enough information to assess the duration or completeness of safety monitoring; deaths are not reported. These gaps limit reproducibility and contextual interpretation, and should not be filled by assumptions about the protocol or conduct.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Caverject User Study — NCT01008605.
• Registry record last updated 2012-04-06; status last verified 2012-04.
• Results first posted 2012-03-28.
• 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.

18. Record Summary

The record describes a completed Phase 3, single-group, non-randomized study of the Caverject Impulse Delivery System, with no masking and enrollment of 48. Its purpose was to assess usability among representative users. The primary endpoint was the percentage who could expel the selected dose using modified Instructions for Use on Day 1. The stated success criterion required the lower bound of the 95% confidence interval to be more than 80% overall.

The primary numerical result and confidence interval are not reported in the registry record, so whether the criterion was met cannot be determined. The record lists 7 outcome measures, including assessment responses, task times, and participant comments, but their numerical results are also not reported. It records 0 serious adverse events and 0 other adverse events among 48 participants at risk; deaths are not reported. The single-group design does not provide a randomized comparison.