Adherence in Patients Receiving PegIntron Pen/Rebetol for Hepatitis C in Conjunction With a Patient Assistance Program (Study P04281)(COMPLETED): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Adherence in Patients Receiving PegIntron Pen/Rebetol for Hepatitis C in Conjunction With a Patient Assistance Program (Study P04281)(COMPLETED) (NCT00704522), a registered phase not stated study. The primary outcome is Number of Participants Who Complete Treatment With PegIntron Pen/Rebetol Therapy for Hepatitis C When Administered With a Patient Assistance Program.

2. Clinical Question

This is a question about treatment completion in the described care and support setting, not a randomized comparison of assistance programs. The record does not state how completion was defined beyond the endpoint title, or report the number who completed treatment. It therefore does not establish how completion compares with another support program or with care without a program. The study’s stated context is the collection of experience that could inform future comparative phase IV studies. No comparative result from those other clinics is included in the registry record.

3. Trial Design

The record marks the study as completed and reports enrollment of 601 participants. Its listed group is “Patients with hepatitis C,” described as patients receiving a patient assistance program during hepatitis C therapy at sites in Austria. The interventions are peginterferon alfa-2b, ribavirin, and the patient assistance program. The brief summary says participants would receive PegIntron Pen and Rebetol according to label and with the assistance program.

The record does not describe a concurrent control arm. It explicitly characterizes the study as not a randomized comparison, and allocation is not stated. Thus, the record describes participants receiving the treatment and support arrangement rather than allocation between alternative interventions. It says the study would be compared with similar studies from other clinics using various patient support programs, to help design future comparative phase IV studies. The results of those external comparisons are not reported in the registry record.

The primary endpoint timeframe is 24 or 48 weeks depending on genotype, with 24 weeks of follow-up. The record also lists two outcome measures, but only the treatment-completion measure is characterized as primary in the registry entries. The second outcome’s content is not reported in the registry record. The start is listed as 2005-03, and primary completion as 2009-04.

Specific methods of recruitment, eligibility criteria, site count, treatment adherence measurement, and follow-up procedures are not reported in the registry record. The study’s statistical analysis plan, allocation procedures beyond the statement that allocation is not stated, and sample-size justification are also not reported. The enrollment figure alone does not explain how the study size was selected or whether the planned enrollment was reached for every endpoint.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All participants

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 Who Complete Treatment With PegIntron Pen/Rebetol Therapy for Hepatitis C When Administered With a Patient Assistance Program, measured over 24 or 48 weeks (depending on genotype) and 24 weeks of follow up.

The primary endpoint is the number of participants who complete PegIntron Pen/Rebetol therapy for hepatitis C when administered with a patient assistance program. It is a count of participants, and the stated population is all participants. The timeframe is 24 or 48 weeks depending on genotype, followed by 24 weeks of follow-up.

A completion count can describe how many people in the study reached the specified treatment-completion outcome. In general, treatment completion is useful for describing the experience of delivering a treatment regimen in a particular setting. It can also help identify questions for later studies, including whether support arrangements are associated with different completion patterns. That general use does not make a count from a single group a comparative treatment effect.

The registry record does not provide the observed completion count, a denominator for the endpoint, a definition of what counted as completion, or a confidence interval. It is therefore not possible to assess the endpoint’s observed frequency or its precision from this record. The record also does not report whether completion was analyzed separately by genotype or treatment duration. No such subgroup result should be inferred from the timeframe description.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registered primary endpoint is a participant count: the number who complete PegIntron Pen/Rebetol therapy with a patient assistance program. The endpoint is not reported as a time-to-event measure or a continuous measurement. For a count endpoint, the basic descriptive result would state the number meeting the endpoint and the population used as its denominator. The registry record identifies all participants as the primary population but does not report the completion count or endpoint denominator. Without both, an observed completion proportion cannot be interpreted from this record.

What does a confidence interval convey?

In general, a confidence interval describes uncertainty around an estimate under the assumptions of the statistical method used. It is not a guarantee about an individual participant’s outcome. A narrow interval generally indicates greater statistical precision than a wide interval, while the interval’s coverage depends on the model and data. No confidence interval for treatment completion is reported in the registry record, so its precision cannot be assessed. The record also does not state which interval method, if any, was planned.

Why does the study structure matter?

The registry record describes a group receiving treatment with a patient assistance program and states that the study is not a randomized comparison. In general, a randomized concurrent comparison can support an estimate of the difference between assigned groups, subject to the quality of conduct and analysis. A single-group description instead reports outcomes in the group studied. It cannot separate the effects of treatment and support from other influences on the outcome. The record’s mention of comparison with similar studies from other clinics does not make those clinics randomized control groups. Methods for any cross-study comparison are not reported in the registry record.

Accordingly, the clinical question and the statistical estimand should not be confused. The registered question asks for a count of participants completing treatment in this setting. It does not specify a between-group contrast. The registry record does not report an analysis population beyond listing all participants for the primary endpoint, nor does it define how an incomplete or unknown completion status would be classified.

What do the planning assumptions mean?

The accompanying sample-size illustrations are described as planning calculations based on the observed effect, rather than as the study’s own design. Their stated assumptions include a two-sided significance level of 0.05, equal allocation between two hypothetical arms, and a normal approximation. The target effect is described as a stated fraction of the observed effect. Those assumptions do not describe the registered study’s allocation, which is not stated, and the study is not a randomized comparison. The calculations therefore should not be read as the actual trial’s sample-size plan or as evidence that its design had a particular power.

In general, a planning calculation asks how much information might be needed to detect a specified effect under specified assumptions. Its answer depends on the assumed effect, variability, significance threshold, allocation, and analysis method. If an assumed effect is based on an observed estimate, uncertainty in that estimate can make the planning illustration uncertain too. Such calculations are not “observed power,” and they do not establish that an unreported result is statistically persuasive. The registry record does not report a sample-size justification for this study, and no numerical planning outputs for the study’s own design are included in the registry record.

Why can over-dispersion matter?

In general, over-dispersion occurs when observed variation is greater than a statistical model expects. For count outcomes, that mismatch can make standard errors too small if the model assumes less variability than the data contain. Analysts may then consider a model that accommodates extra variation or use another justified method. This is a general statistical consideration; the primary outcome is a participant count, but the registry record does not report a count model, evidence of over-dispersion, or an analysis for the endpoint. It would be inappropriate to claim that over-dispersion was assessed or corrected.

For a binary participant outcome, a simple descriptive presentation might show the number meeting the endpoint and the number evaluated. A more elaborate analysis could account for design features or prespecified covariates, but those choices must be documented and justified. Here, the endpoint result and analysis methods are not reported in the registry record. The study’s single-group description also means there is no within-trial treatment contrast to estimate from the stated design. Neither a model nor a planning illustration can supply the missing observed endpoint result.

The record lists 601 enrolled participants and a safety group of 597 at risk. These counts describe different registry entries and should not be substituted for one another without knowing their definitions and analysis populations. The record does not explain how the safety population was formed or whether the primary endpoint used the same participants. No numerical reconciliation or assumption about exclusions is warranted.

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("PegIntron Pen/Rebetol Without Patient Assistance P", "PegIntron Pen/Rebetol With Patient Assistance Prog")
n      <- c(481, 120)
events <- c(298, 75)
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  PegIntron Pen/Rebetol Without Patient Assistance P  481  298  62.0  57.4  66.3  57.5  66.2  57.5  66.2
ARM  PegIntron Pen/Rebetol With Patient Assistance Prog  120  75  62.5  53.2  71.2  53.6  70.6  53.6  70.7

11. Multiplicity, Missing Data and Analysis Populations

The record lists two outcome measures and identifies treatment completion as the primary endpoint. The content of the other outcome measure is not reported in the registry record. It lists zero analyses, so there are no reported outcome-specific statistical analyses to assess. The record does not state whether any multiplicity strategy was planned, such as prioritizing outcomes, adjusting tests, or treating additional analyses as exploratory.

In general, multiplicity matters when several outcomes or comparisons are tested because repeated testing can increase the chance of a false-positive finding across the set. A prespecified hierarchy or adjustment can clarify how evidence is evaluated. No such approach is reported, and no inference about the second outcome or any multiplicity adjustment is possible.

Missing-data handling is also not reported in the registry record. The primary population is described as all participants, but this does not specify how missing completion status, withdrawal, or incomplete follow-up was handled. The record does not state whether participants were analyzed according to an intention-to-treat principle, whether imputation was used, or whether sensitivity analyses were conducted. These are distinct methodological choices, not details that can be inferred from the population label.

The record also does not report a statistical analysis plan, endpoint-specific denominator, or reasons for any unavailable data. These omissions limit assessment of whether the endpoint was analyzed consistently with a prespecified plan and how robust any result might be to missing information. Since the primary endpoint result itself is not reported, the consequences of missing data cannot be evaluated.

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.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: hepatic neoplasm malignant (0.3%), hospitalisation (0.3%), pancytopenia (0.2%), diarrhoea (0.2%), vomiting (0.2%).

For the PegIntron Pen/Rebetol group, the registry lists 597 participants at risk for serious adverse events and 20 participants with a serious adverse event. For other adverse events, it lists 597 participants at risk and 100 participants with an event. These counts are separate safety summaries. They should not be combined or treated as treatment-completion outcomes.

The listed serious adverse event terms are hepatic neoplasm malignant (0.3%), hospitalisation (0.3%), pancytopenia (0.2%), diarrhoea (0.2%), vomiting (0.2%), and injection site reaction (0.2%). These are the terms and percentages recorded; the registry entries do not specify whether the percentages refer to participants, events, or another reporting convention. The record does not state that these events were caused by treatment, and the listings alone do not establish causation.

Deaths are not reported in the registry record. The record does not provide further details about event timing, severity grading, relationship assessment, or how recurrent events were counted. Safety summaries describe what was recorded in the stated group; without a concurrent comparator and additional methods, they do not establish comparative safety.

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

The registry record establishes that a completed study enrolled 601 participants and described treatment with PegIntron Pen/Rebetol alongside a patient assistance program at sites in Austria. Its primary question concerned the number of participants completing treatment over 24 or 48 weeks, depending on genotype, with 24 weeks of follow-up. The record does not report the completion count. It therefore cannot show the observed extent or precision of treatment completion.

The design information also defines the limits of interpretation. This was not a randomized comparison, and allocation is not stated. No concurrent comparator group is described. Even if the completion result were available, a single-group result would describe the participants and setting studied; it would not by itself demonstrate what completion would have been under another support program or without one. The registry’s stated intention to compare with similar studies from other clinics was to inform future comparative phase IV studies, not a reported randomized comparison in this study.

The safety entries document adverse-event counts and listed serious adverse event terms for the PegIntron Pen/Rebetol group. They do not establish causation or comparative safety. The record does not report deaths, event timing, or more detailed safety analysis. The safety population and primary endpoint population are not reconciled in the available information.

More broadly, the registry record does not report the statistical analysis plan, endpoint estimate, confidence interval, missing-data procedures, multiplicity approach, or sample-size justification. The sample-size illustrations are planning calculations under stated hypothetical assumptions, not observed power and not evidence about the primary result. These boundaries mean that the record supports a description of the study’s intent, design, and selected safety counts, but not a conclusion about comparative effects or the precision of treatment completion.

14. Why This Trial Matters Statistically

This study is statistically important as an example of the difference between documenting an outcome question and reporting an outcome estimate. The registry defines treatment completion as its primary endpoint, identifies the timeframe, and describes the participant group and support arrangement. But the primary count is not reported. Without the result and its denominator, the central descriptive question remains unanswered in the registry record.

The record also illustrates why study design determines the claims a result can support. It describes a single group and explicitly says the study is not a randomized comparison. Its stated interest in experience from other clinics is connected to designing future comparative phase IV studies. That distinction matters: cross-study context can motivate later research, but it is not equivalent to a concurrent randomized control group within this study.

Finally, the record makes visible several elements needed to assess statistical credibility: a defined analysis population, clear endpoint rules, missing-data methods, prespecified analyses, and a justified sample size. Some details are stated, such as the primary population label and treatment timeframe, while many analysis details and the endpoint result are not reported. The sample-size illustrations use hypothetical assumptions and should remain separate from the actual study design. Keeping these distinctions clear helps prevent planning calculations, safety entries, or enrollment counts from being mistaken for evidence about the primary endpoint.

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.

Important limitations specific to this study follow from the registry entries and omissions. The record describes one group receiving PegIntron Pen/Rebetol with a patient assistance program and states that this was not a randomized comparison. No concurrent control arm is described, and allocation is not stated. The design therefore does not provide a within-study comparison between assistance strategies.

The primary outcome is named, but its observed count is not reported. The endpoint definition beyond the word “complete,” the endpoint denominator, and the handling of participants with unknown or incomplete status are not reported in the registry record. The primary population is listed as all participants, but the relationship between that population and the safety population is not explained. Enrollment is reported as 601, while the safety group lists 597 at risk; the record does not explain the difference between those entries.

The intervention setting is described as sites in Austria, but the number of sites and details of participant selection are not reported in the registry record. The treatment timeframe varies by genotype, and no results by genotype or duration are included. The record also does not report adherence measurement methods, the second outcome’s content, the analysis plan, missing-data methods, multiplicity handling, or sample-size justification.

Safety reporting is limited to the listed at-risk and affected counts, serious adverse event terms, and term percentages. Deaths and other details about event timing, attribution, and counting are not reported. These limitations constrain interpretation of both effectiveness-related outcomes and safety; they do not establish what unreported results would have shown.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Adherence in Patients Receiving PegIntron Pen/Rebetol for Hepatitis C in Conjunction With a Patient Assistance Program (Study P04281)(COMPLETED) — NCT00704522.
• Registry record last updated 2015-10-06; status last verified 2015-10.
• Results first posted 2010-05-17.
• 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 of PegIntron Pen/Rebetol administered with a patient assistance program to patients with hepatitis C at sites in Austria. It reports enrollment of 601 participants and a primary endpoint of treatment completion, assessed over 24 or 48 weeks depending on genotype and followed by 24 weeks. The record identifies the study as not a randomized comparison and describes no concurrent comparator group.

The primary endpoint result and the statistical analyses are not reported in the registry record. The safety listing reports 20 serious adverse events among 597 participants at risk and 100 other adverse events among 597 at risk. It lists serious adverse event terms and percentages; deaths are not reported. The stated purpose was to compare experience with similar studies from other clinics to inform future comparative phase IV studies. The record does not provide the statistical analysis plan, missing-data approach, multiplicity method, or sample-size justification.