Study of HCV Genotype 1 Patients in the UK Treated With ViraferonPeg and Rebetol (Study P05269)(COMPLETED): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study of HCV Genotype 1 Patients in the UK Treated With ViraferonPeg and Rebetol (Study P05269)(COMPLETED) (NCT00724373), a registered phase not stated study. The primary outcome is Participants With Treatment Success.

2. Clinical Question

The study’s stated aim was to characterize subgroups of genotype 1 participants in routine care and examine factors associated with response and treatment outcomes. Its broader aim included developing predictive models of responsive or refractory phenotypes to inform understanding of HCV treatment, management, and drug development. These are research objectives, not findings: the registry record does not report subgroup estimates, model results, or a count of participants with treatment success.

The registry lists 442 participants as enrolled. That enrollment figure does not, by itself, establish how many records had complete outcome information, how many participants were included in a particular analysis, or what proportion achieved sustained virological response. Those details are not reported in the registry record. Because there is no described control group, the central question is descriptive and associational rather than a comparison of treatment against an alternative.

3. Trial Design

This is described as a retrospective data study and a non-interventional review of medical records. The records were drawn from specialist secondary and tertiary care centers across the United Kingdom that specialize in hepatitis C treatment. Participants had genotype 1 HCV infection and had been treated with pegylated interferon alfa-2b and ribavirin in the preceding 48 months. The listed enrollment is 442, and the study status is completed.

The study period is listed as starting in 2007-11, with primary completion in 2009-02. The registry describes collection of data from the start of participants’ first exposure to the combination therapy. For participants who successfully completed treatment, the specified follow-up period was at least 24 weeks. The registry does not provide more detail about how records or centers were selected, how treatment exposure was verified, or how follow-up information was obtained.

The record lists peginterferon alfa-2b and ribavirin as the interventions, but describes a single participant group rather than treatment arms designed for comparative analysis. It explicitly does not describe a randomized comparison, and the listed design does not provide a like-for-like control group. The objective was to identify subgroups and examine relationships between subgroup characteristics and response in real-world care.

There is one listed outcome measure and no analyses listed in the registry record. Allocation details, a formal statistical analysis plan, a sample-size justification, interim analyses, and analysis populations are not reported in the registry record. The planning assumptions attached to any sample-size illustrations are not a description of this study’s actual design: equal allocation between two arms is not the design described for this retrospective review.

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: Number of participants who had treatment success.

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 Participants With Treatment Success, measured over Data will be collected from the start of first exposure to pegylated interferon alfa-2b and ribavirin combination therapy. Participants who have successfully completed treatment will have data collected for a follow-up period of at least 24 weeks..

The primary outcome is titled Participants With Treatment Success and is recorded as a number of participants. Treatment success is defined as achieving sustained virological response: undetectable viraemia 24 weeks after therapy completion. This definition places the endpoint after treatment rather than measuring a response during treatment. The specified follow-up for participants who completed treatment was at least 24 weeks, consistent with the timing used in the endpoint definition.

A count is a direct way to describe how many participants met the stated outcome definition. Interpreting a count as a response rate would also require an appropriate denominator: for example, the number of participants with an outcome assessment in the relevant analysis. That denominator and the primary outcome count are not reported in the registry record, so a response rate cannot be read from this record.

In general, sustained virological response is used as an outcome because it captures virological status after treatment has ended. The registry’s stated rationale was to study response rates, treatment outcomes, and participant characteristics associated with response. Although the endpoint is defined, the record does not present its observed result, subgroup results, or a measure of precision such as a confidence interval. The definition therefore explains what would count as success, but does not establish how many participants met it.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The methods information in the registry is limited. It characterizes the work as a retrospective, non-interventional medical-record review, identifies the primary outcome as a count of participants, and states the endpoint definition. It does not report the analysis procedures used to produce outcome or subgroup estimates. The following concepts explain how such data are generally interpreted; they are not claims about analyses performed in this study.

What does a participant count represent?

A binary outcome classifies each participant into one of two states for the endpoint: meeting the definition of treatment success or not meeting it. The registry records the primary endpoint as the number of participants with success. A count can describe the observed number in an analyzed group, but it is not a rate unless the relevant denominator is also known. In a medical-record review, the number enrolled and the number with complete, usable outcome data need not be identical. The registry record does not report the primary outcome count, the analysis denominator, or how participants without a recorded outcome were handled.

In general, uncertainty around a binary outcome can be expressed with a confidence interval. A confidence interval describes the range of values reasonably compatible with the data and the statistical method used; it is not a guarantee that the true value lies within that range. No confidence interval for treatment success is reported in the registry record. Without the estimate, denominator, and method, neither the magnitude nor precision of the primary result can be assessed.

What does retrospective design imply?

In general, retrospective studies use information that was recorded before the research analysis was undertaken. They can describe characteristics and outcomes in the records available to investigators, but the information may have been collected for clinical rather than research purposes. Definitions, timing, and completeness of recorded measurements can vary. This makes clear outcome definitions and transparent reporting of missing information especially important. The endpoint definition is stated in this record, but the procedures for checking, harmonizing, or adjudicating medical-record data are not reported in the registry record.

Non-interventional data do not establish that an observed association was caused by treatment or by a particular participant characteristic. Differences between subgroups may reflect other differences between participants, selection into care, or the availability of recorded data. General methods such as adjustment for measured characteristics can address some observed differences when appropriately planned and reported, but they cannot automatically remove unmeasured confounding. The registry does not report whether adjustment was performed or what variables were included.

How should subgroup and prediction aims be assessed?

Subgroup analysis asks whether outcomes differ across categories or levels of participant characteristics. Predictive modeling seeks to combine characteristics into estimates of outcome for individuals or groups. In general, interpreting either requires knowing how subgroups were defined, which variables were considered, how model fit and performance were evaluated, and how uncertainty was quantified. A model developed in one set of records may not perform similarly in other settings; validation is relevant to judging whether predictions generalize. The registry states an aim to identify subgroups and provide predictive models, but it does not report subgroup estimates, model specifications, validation procedures, or performance results.

Over-dispersion is a general issue for count outcomes when the variability in counts exceeds what a chosen model assumes. It can make standard errors too small if the model does not account for the extra variation. The primary endpoint is a participant count for a binary outcome, but the record does not report a count model or any dispersion assessment. This concept therefore explains a possible modeling consideration, not a method known to have been used in this study.

What do the planning illustrations mean?

Sample-size calculations are planning tools: they show how many participants might be needed under specified assumptions to detect an effect of a chosen size with a chosen statistical procedure. They do not report observed treatment effects and are not observed power. The stated illustration assumptions include a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a fraction of the observed effect. These assumptions do not match the retrospective single-group design described in the registry, and the record does not report the study’s own sample-size justification. No numeric planning result or observed effect is included in the registry information used for this account.

For time-to-event planning, the stated convention is to express the total number of events; other planning outputs are expressed as participants per arm. Those are general distinctions about how planning quantities may be reported. They do not turn this study into a two-arm trial or supply an unreported endpoint result. The registry record does not report time-to-event analyses for the primary outcome.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and no analyses. It does not report whether additional outcomes, subgroup comparisons, or model-building analyses were specified outside the registry, or whether any statistical multiplicity procedure was used. Multiplicity is a general concern when many hypotheses are tested: the chance of at least one apparently notable result can increase as the number of tests grows. Methods for controlling or interpreting that issue depend on the number and purpose of the analyses. No such plan is reported in the registry record, so the degree of multiplicity cannot be assessed.

The primary endpoint definition is available, but the primary outcome count and its denominator are not. The record does not describe the extent or pattern of missing medical-record information, missing endpoint data, or any method for handling missingness. In general, missing data can affect interpretation when participants without recorded outcomes differ from those with observed outcomes. Whether that issue arose in this study, and how it was addressed, is not reported in the registry record.

The registry does not identify an intention-to-treat, per-protocol, complete-case, or other analysis population. Because this is a retrospective review rather than a randomized comparison, labels used for randomized trials may not map directly onto its data handling. What matters for interpretation is a clear description of which eligible records and participants contributed to each analysis. That description is not reported. The enrollment of 442 should therefore not be taken to mean that every participant was included in every outcome or subgroup analysis.

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 5% reporting threshold.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: anaemia (0.9%), acute psychosis (0.9%), neutropenia (0.5%), suicide attempt (0.5%), angina pectoris (0.2%).

The safety summary lists 442 participants at risk for the serious-event reporting and 17 affected by serious adverse events in the pegylated interferon alfa-2b and ribavirin group. It lists 442 at risk and 0 affected for other adverse events. These are registry entries, not a comparative safety analysis; the study description does not include a control group for like-for-like comparison. The record does not state whether the event counts refer to participants with at least one event or to event episodes, so the figures should be read using the registry’s labels rather than as a detailed event-level account.

The listed serious-event terms and percentages are anaemia, 0.9%; acute psychosis, 0.9%; neutropenia, 0.5%; suicide attempt, 0.5%; angina pectoris, 0.2%; and supraventricular tachycardia, 0.2%. The record does not provide event narratives, timing, severity breakdowns, or a method for attributing events to treatment. The deaths value is not reported in the registry record. These entries describe what the safety summary records; they do not establish comparative risk or explain the primary treatment-success outcome.

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

The record supports a limited, precise description of the study’s purpose and structure: a retrospective review of UK medical records for participants with genotype 1 HCV treated with pegylated interferon alfa-2b and ribavirin. The primary endpoint is defined as the number of participants achieving sustained virological response, with success requiring undetectable viraemia 24 weeks after therapy completion. The enrollment is 442, and the record includes a safety summary for the treatment group.

However, the posted registry information does not report the number achieving the primary endpoint or the denominator needed to interpret that number as a rate. It also does not report subgroup results, predictive-model results, or precision estimates. The study’s aims therefore should not be confused with demonstrated findings. The registry makes clear what investigators intended to examine, but not what the outcome analysis found.

Nor does the described design establish a treatment effect relative to another option. No randomized comparison or like-for-like control group is described. In general, an outcome observed in a treated group cannot by itself distinguish treatment effects from participant characteristics, care setting, selection, or other influences. The registry record does not provide the information needed to make those distinctions or draw causal conclusions.

The safety figures are also descriptive. They record serious adverse events and other adverse events in the treatment group, but do not provide a comparator or detailed attribution analysis. Their interpretation is bounded by the safety summary’s definitions and reporting, which are not elaborated in the record. Overall, this record documents a clinically defined endpoint and a real-world research question, but the missing outcome and analysis results prevent conclusions about response frequency, subgroup patterns, model performance, or comparative benefit and harm.

13. Why This Trial Matters Statistically

This study is statistically relevant because it illustrates the difference between a well-defined research question and a reported estimate that can answer it. The endpoint has a clear clinical definition: sustained virological response, specified as undetectable viraemia 24 weeks after therapy completion. Yet a definition alone does not show how often the outcome occurred. A count, its denominator, and an account of analyzed records are necessary to interpret the endpoint quantitatively.

The study also raises a common challenge in real-world evidence: participant characteristics and outcomes may be available from clinical records, but retrospective data can be affected by how care was delivered and how information was documented. Associations between characteristics and outcomes can be useful for forming or evaluating hypotheses, but they do not automatically represent causal effects. Clear reporting of selection, missing data, analysis populations, subgroup definitions, and adjustment methods is essential to judge the strength and limits of such evidence. Those details are not reported in the registry record.

Its stated interest in subgroup identification and predictive models underscores the distinction between finding patterns in a dataset and demonstrating that a model is reliable. Model estimates, uncertainty, and evaluation in relevant data are needed to understand predictive performance. None of those results are listed. Likewise, a planning illustration based on hypothetical assumptions does not establish that the study was adequately powered or that an effect was observed.

The record is therefore a useful example of why statistical interpretation depends on more than enrollment and an endpoint label. Without observed results and methods, readers cannot assess the size, precision, or robustness of the primary finding. Transparent registry reporting allows those gaps to be identified rather than filled by assumption.

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 trial-specific limitation in the registry record is that the primary outcome is defined but no result is reported. The count of participants with treatment success, the denominator used for that outcome, and any estimate of uncertainty are not reported in the registry record. Enrollment of 442 does not establish the number with evaluable follow-up, so it cannot substitute for an outcome denominator.

The retrospective, non-interventional design relies on medical records from specialist secondary and tertiary care centers. The record does not describe how centers or records were selected, whether the included records represent all eligible patients in those settings, or how missing or inconsistent information was handled. These unknowns limit assessment of selection and information bias. Findings from specialist centers may also not describe other settings; the record does not report evidence about generalizability beyond the stated UK care context.

No comparator group is described, and the record explicitly does not present a randomized comparison or like-for-like control comparison. Therefore, the design as recorded cannot support a comparative treatment-effect estimate. The subgroup and predictive-model objectives are not accompanied by reported definitions, estimates, model details, or validation results. It is not possible to judge whether those objectives were achieved.

Further methodological details are not reported in the registry record, including the statistical analysis plan, sample-size justification, interim analyses, analysis populations, and procedures for multiplicity or missing data. The deaths value in the safety summary is also not reported. These gaps do not show that particular procedures or data were absent; they mean that the registry record does not allow those aspects to be evaluated.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Study of HCV Genotype 1 Patients in the UK Treated With ViraferonPeg and Rebetol (Study P05269)(COMPLETED) — NCT00724373.
• Registry record last updated 2015-09-25; status last verified 2015-09.
• Results first posted 2010-06-07.
• 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

This completed, non-interventional retrospective study concerns participants with genotype 1 HCV treated with pegylated interferon alfa-2b and ribavirin in the UK. The registry lists enrollment of 442, a start date of 2007-11, and primary completion in 2009-02. The sponsor is Merck Sharp & Dohme LLC.

The primary outcome is the number of participants with treatment success, defined as sustained virological response 24 weeks after therapy completion. The record lists one outcome measure and no analyses. It does not report the primary outcome count, denominator, subgroup findings, model results, or uncertainty estimates. A safety summary records 17 participants with serious adverse events among 442 at risk and 0 with other adverse events among 442 at risk; deaths are not reported in the registry record.