Efficacy of Pegetron® Redipen™ Treatment and Treatment Compliance of Patients With Chronic Hepatitis C in Canada (P04423): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Efficacy of Pegetron® Redipen™ Treatment and Treatment Compliance of Patients With Chronic Hepatitis C in Canada (P04423) (NCT00724893), a registered phase not stated study. The primary outcome is Number of Participants Achieving Viral Response at Any Evaluation Point (Stage 1).

2. Clinical Question

The program’s broader stated aim was to assess treatment compliance and sustained virologic response rates with Pegetron Redipen. Sustained virologic response is described in the study summary as negative HCV-RNA six months after treatment. The registered primary endpoint is different in form: it counts participants with a negative result at either of the listed follow-up points, rather than reporting a rate of sustained response alone. The registry record does not report the observed primary endpoint count, compliance results, or sustained virologic response results.

3. Trial Design

This was a prospective program in Canada for treatment-naïve patients with chronic hepatitis C who were prescribed Pegetron Redipen. The registry record lists an enrollment of 2430 and a status of completed. The recorded start is 2005-08, and primary completion is recorded as 2012-08. The sponsor is Merck Sharp & Dohme LLC.

The treatment description includes peginterferon alfa-2b (PegIFN-2b) and ribavirin. Stage 1 participants received PegIFN-2b using the Redipen formulation at 1.5 mcg/kg once weekly and ribavirin capsules at 800-1400 mg daily, according to routine medical practice at participating sites. Stage 2 is described for participants with chronic hepatitis C genotype 1, with the same listed treatment and dosing description. These stage descriptions do not establish a randomized comparison between groups.

Allocation is not stated, and the record does not describe a like-for-like control arm. The program’s stated focus includes treatment compliance and sustained virologic response, while the registered primary outcome counts participants with a viral response at any evaluation point. The primary endpoint timeframe is up to 72 weeks. Its eligible population is all participants who took at least one dose of study medication, identified in the record as the ITT population.

The registry record does not report the protocol’s detailed visit schedule, how treatment compliance was measured, or the statistical plan. It also does not report a sample-size justification for the trial itself or whether interim analyses were planned. The two stage descriptions should therefore be read as descriptions of enrolled participant groups, not as evidence of treatment effects relative to one another.

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 who took at least one dose of study medication (ITT Population)

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 Achieving Viral Response at Any Evaluation Point (Stage 1), measured over Up to 72 weeks.

The primary endpoint is the number of participants achieving a viral response at any evaluation point, defined as a negative hepatitis C virus ribonucleic acid (HCV-RNA) result at either follow-up evaluation. The listed evaluations are at 12 weeks, with a window of 10-14 weeks, or at least 22 weeks after the end of treatment. The timeframe is up to 72 weeks. Participants with no viral response information were classified as having no response.

This endpoint is a count of participants, not a continuous measurement. Its “either evaluation” definition means a participant can meet the endpoint through a negative HCV-RNA result at one of the stated follow-up points. That is distinct from the study summary’s description of sustained virologic response as negative HCV-RNA six months post-treatment. The registry also lists separate secondary outcomes concerning viral response at particular follow-up times and sustained response, but does not report their results.

Binary response endpoints are commonly used to describe whether participants meet a clinically defined response criterion. As a general statistical point, a count can convey how many participants met that criterion in the analysis population, but interpretation also depends on the denominator and the handling of missing assessments. The record specifies the missing-response rule and identifies the primary population as participants who took at least one dose. It does not report the observed count or a denominator-specific response estimate, so the magnitude and precision of the endpoint cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a binary response status summarized as a number of participants. A participant is counted as having achieved viral response if HCV-RNA is negative at either of the listed follow-up evaluations. The evaluation points are 12 weeks, with a window of 10-14 weeks, or at least 22 weeks after the end of treatment. The registry gives an overall timeframe of up to 72 weeks. A participant without viral response information is classified as having no response.

What does a participant count convey?

As a general statistical explanation, a count reports the number of people meeting a defined outcome in a specified analysis population. A count alone does not describe the proportion unless its denominator is also known. Comparisons between counts also require context, such as group sizes and how participants entered each group. The registry record identifies the primary population as all participants who took at least one dose of study medication, but it does not report the primary outcome count or a corresponding denominator-specific estimate.

The endpoint uses an “either evaluation” rule: a negative HCV-RNA result at one of the specified follow-up assessments qualifies as a response. This differs from an endpoint requiring a negative result at every assessment, and it differs from a measure defined at only one time point. The summary describes sustained virologic response as negative HCV-RNA six months post-treatment. The primary endpoint’s stated rule should therefore not be treated as interchangeable with that summary definition.

Why does missing outcome information matter?

The record specifies that participants with no viral response information were considered to have no response. As a general statistical explanation, this is a conservative classification in the limited sense that missing outcomes do not count as successes under the rule; it does not establish what those outcomes would have been if measured. The number of participants with missing assessments, the reasons for missingness, and any sensitivity analyses are not reported in the registry record. Without those details and the results, the consequences of the rule cannot be quantified.

The primary population includes participants who took at least one dose. This is the population definition recorded for the endpoint; the registry does not describe further exclusions or provide the number contributing to the primary outcome. The record lists several secondary outcomes with different exclusion wording, including outcomes that exclude participants who discontinued before early virologic response evaluation and some that also exclude participants with missing data. Those differing definitions mean secondary outcome results would need to be interpreted according to their own stated populations and missing-data rules. Their results are not reported in the registry record.

What can be inferred from the analysis record?

The registry lists zero statistical analyses. No inferential procedure, adjustment method, confidence interval, hypothesis test, or effect estimate is reported. The registry record also does not report whether a prespecified statistical analysis plan existed, whether interim analyses were conducted, or how any multiplicity across outcomes was handled. Those details should not be inferred from the presence of multiple outcome definitions.

As a general statistical concept, a confidence interval expresses uncertainty around an estimate under its calculation method and assumptions. A p-value addresses compatibility of data with a specified null hypothesis under a statistical model; it is not a measure of effect size. Neither can be interpreted for this primary endpoint because the registry record reports no corresponding estimate or test. No recalculated estimate is available from the registry information in this record, and there is no reported sponsor analysis to compare with a recalculation.

The sample-size assumptions describe planning illustrations rather than the trial’s own design justification. They specify a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect to detect expressed as a stated fraction of the observed effect. The stated convention is participants per arm for outcomes other than time-to-event outcomes, for which the total number of events is used. These assumptions do not establish that the study used that allocation, that it was randomized, or that the illustrations reproduce its original planning. The record does not report the trial’s own sample-size justification. No numerical planning results are reported in the registry information.

As a general statistical explanation, over-dispersion matters when observed variation exceeds what a chosen model assumes; ignoring it can make uncertainty estimates unreliable. The primary endpoint is a participant count, but the registry record does not report a model or dispersion estimate, so over-dispersion is not an identified feature of the reported primary analysis. There are no reported analyses from which to determine whether a model-based method was used.

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("Stage 1 Participants")
n      <- c(1302)
events <- c(685)
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  Stage 1 Participants  1302  685  52.6  49.9  55.4  49.9  55.3  49.9  55.3

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary endpoint and multiple secondary outcome topics. These include treatment discontinuation due to adverse events, viral response at any evaluation point, response at 12 weeks after end of treatment, sustained virologic response, and outcomes stratified by genotype or liver fibrosis stage. Some secondary outcome descriptions apply exclusions for participants who discontinued before early virologic response evaluation; some also exclude participants with missing data. The registry record does not report results for these outcomes.

When several outcomes are assessed, multiplicity is a general statistical concern: repeated testing can increase the chance of obtaining a seemingly notable result by chance if each test is interpreted without accounting for the family of tests. The record does not report a multiplicity adjustment, a hierarchy among secondary endpoints, or a prespecified testing strategy. It also reports zero statistical analyses, so there are no registry-reported tests to interpret.

For the primary endpoint, participants with no viral response information were considered to have no response. The number of participants with missing response information and the reasons for missingness are not reported in the registry record. The secondary outcomes include some definitions that exclude participants with missing data, showing that the stated analysis populations differ by outcome; the record does not provide the counts or results for those populations.

The primary population is all participants who took at least one dose of study medication. This definition is recorded as the ITT population, but the registry does not provide a participant flow or additional details on how this population was assembled. It does not report sensitivity analyses for missing outcomes, an alternative missing-data method, or an analysis plan. Therefore, the impact of missing data, exclusions, or multiple outcome assessments cannot be quantified from the registry record.

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

The registry record describes a prospective Canadian program of Pegetron Redipen treatment and defines a primary viral-response endpoint. It does not report the primary endpoint result or the results of the listed secondary outcomes. Accordingly, the record does not establish how many participants achieved the defined response, how often sustained virologic response occurred, or what treatment compliance was observed.

The primary endpoint is a count based on a negative HCV-RNA result at either of two follow-up evaluation points. Its missing-data rule classifies participants without response information as having no response. The endpoint therefore reflects both the defined viral-response criterion and that classification rule. Without the outcome count, denominator, and information about missing assessments, neither the response frequency nor the sensitivity of the result to missing data can be evaluated.

The registry describes Stage 1 and Stage 2 groups, but does not state that allocation was randomized and does not identify a like-for-like control comparison. The two stages cannot be treated as randomized comparison arms on the basis of these descriptions. A count within a treated group, even if reported, would not by itself show what would have occurred under a different treatment or without treatment.

The study summary states an aim to assess treatment compliance and sustained virologic response. The primary endpoint is not a direct compliance measure, and its definition differs from the summary’s six-month post-treatment definition of sustained virologic response. The record’s completed status and enrollment figure describe the study record, not its outcome. No medical conclusion about treatment benefit or lack of benefit follows from the information.

13. Why This Trial Matters Statistically

This registry record is statistically useful for distinguishing an outcome definition from an outcome result. It specifies a count of participants with viral response at either of the listed follow-up evaluations, identifies the primary population as participants who took at least one dose, and states how missing response information was classified. These details clarify what the registered primary endpoint was intended to measure even though its observed result is not reported.

The record also illustrates why a study’s broad aim and its primary endpoint should be read separately. The stated program aims include treatment compliance and sustained virologic response, while the primary measure is a count of response at any evaluation point. The endpoint definitions and timeframes are not interchangeable, and the record does not report results for either the primary measure or the secondary outcomes that address related questions.

Design information is important to interpretation as well. Stage 1 and Stage 2 differ in the stated participant groups, with Stage 2 defined for genotype 1, but allocation is not stated and the record does not describe a like-for-like control comparison. This limits what can be inferred from any comparison between those groups. The registry also lists no statistical analyses, so estimates of precision and formal comparative inference are unavailable.

Finally, the record’s sample-size assumptions are identified as planning illustrations, not as the trial’s design justification. This distinction prevents planning scenarios from being mistaken for evidence about observed outcomes or statistical power. Taken together, the record supports a clear account of the registered question and analysis population, while leaving the observed response, its precision, and the trial’s inferential methods unreported.

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.

Outcome reporting is the main limitation for statistical interpretation: the registry record does not report the primary response count, a response estimate, or a confidence interval. It also does not report results for the listed secondary outcomes, including treatment discontinuation due to adverse events, response at specific follow-up times, sustained response, and outcomes by genotype or liver fibrosis stage. As a result, the magnitude and precision of the registered outcomes cannot be assessed.

The study is not described as a randomized comparison. Allocation is not stated, and the record explicitly does not establish the stages as like-for-like control groups. The Stage 1 and Stage 2 descriptions differ in their stated populations, because Stage 2 is limited to genotype 1. Any comparison between them would therefore require caution; the record does not report a comparative analysis or adjustment for group differences.

Some details needed to assess the primary outcome are absent. The record does not report the number of participants with missing viral-response information, reasons for missingness, participant flow, or sensitivity analyses. It specifies that missing response information was counted as no response, but does not provide the information needed to evaluate the practical impact of that rule. Detailed compliance measurement methods are also not reported in the registry record.

The registry reports zero statistical analyses and does not describe a statistical analysis plan, multiplicity handling, interim analyses, or the trial’s own sample-size justification. These absences prevent assessment of the planned inferential framework. The adverse-event summary lists 0 participants at risk and 0 affected in the serious and other adverse-event fields for both stage groups; deaths are not reported as a numeric value, and no top serious terms are listed. Those summary fields should not be interpreted as proof that no adverse events occurred, particularly without further results and reporting context.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Efficacy of Pegetron® Redipen™ Treatment and Treatment Compliance of Patients With Chronic Hepatitis C in Canada (P04423) — NCT00724893.
• Registry record last updated 2015-08-14; status last verified 2015-07.
• Results first posted 2013-11-20.
• 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

NCT00724893 is a completed prospective program of Pegetron Redipen treatment among treatment-naïve patients with chronic hepatitis C in Canada. The registry lists an enrollment of 2430, a start of 2005-08, and primary completion in 2012-08. Merck Sharp & Dohme LLC is listed as sponsor.

The primary endpoint counts participants with a negative HCV-RNA result at either specified follow-up evaluation, up to 72 weeks. The primary population includes participants who took at least one dose, and missing response information is classified as no response. The record describes Stage 1 participants and a Stage 2 group with genotype 1, but does not state allocation or identify a like-for-like control comparison.

The registry record does not report primary or secondary outcome results and lists zero statistical analyses. It does not report the trial’s statistical analysis plan or sample-size justification. The record therefore documents the study question and endpoint definitions, but does not provide results from which to estimate viral response, treatment compliance, or statistical precision.