This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for An Observational Study of Pegasys (Peginterferon Alfa-2a) Plus Copegus (Ribavirin) in Participants With Chronic Hepatitis C (CHC), Genotype 2, 3, 1 or 4, Undergoing Opioid Maintenance Therapy (NCT01416610), a registered phase not stated study. The primary outcome is Percentage of Participants With Sustained Virological Response 24 Weeks After Completing Treatment (SVR24).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01416610 |
| Phase | Phase not stated |
| Condition | Hepatitis C, Chronic |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 88 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Hoffmann-La Roche |
| Results posted | Yes |
2. Clinical Question
Population
Participants had previously untreated chronic hepatitis C, with genotype 2, 3, 1 or 4, and were undergoing opioid maintenance therapy. The registry records enrollment of 88 participants. It does not give further detail in the primary population field.
Intervention
Participants received Pegasys (peginterferon alfa-2a) plus Copegus (ribavirin), as prescribed by their treating physician. The study was observational, so the record does not describe treatment assignment by the study team.
Comparator
No like-for-like control group is described. The registry lists one group, “All Participants,” and does not state an allocation method. The treatment outcomes therefore cannot be read as a randomized comparison against another treatment or against no treatment.
Primary question
The primary endpoint was the percentage of participants with undetectable HCV RNA 24 weeks after completing treatment, called SVR24. The registry defines the measure and its handling of missing observations, but the primary result is not reported in the registry record.
The clinical question is therefore descriptive: among participants with the stated hepatitis C genotypes who were receiving opioid maintenance therapy and treated with the combination as prescribed by their physician, what percentage had the defined virological response after treatment and follow-up? The study also listed outcomes concerning SVR 12, end-of-treatment response, virological relapse, health status, fatigue, complaints and depression. Their results are not reported in the registry record.
Because the study did not describe a control group or random allocation, it cannot by itself isolate the effect of the medicines from other influences on outcomes. Its focus on a population receiving opioid maintenance therapy is part of the study question, but the registry does not provide enough outcome information to quantify response in that population.
3. Trial Design
This was a prospective, multicenter, non-interventional study sponsored by Hoffmann-La Roche. Its title and description identify a study of combination therapy with Pegasys (peginterferon alfa-2a) and Copegus (ribavirin) in people with chronic hepatitis C undergoing opioid maintenance therapy. Eligible participants had previously untreated hepatitis C and genotype 2, 3, 1 or 4. The registry lists 88 participants enrolled.
The study was observational: participants received treatment as prescribed by their treating physician. The registry describes one group, “All Participants,” rather than separate treatment arms. It does not state an allocation method, and it does not describe a randomized comparison. The study’s design can document outcomes among treated participants, but it does not create a concurrent control comparison that would separate treatment effects from other differences between participants or changes over time.
The planned observation included treatment and a treatment-free follow-up period of 24 weeks. The primary endpoint timeframe is described as 24 weeks after treatment completion, within 3 years, 6 months. The study record gives a start of 2010-04, a primary completion of 2014-10 and a status of COMPLETED. These registry entries describe the study’s recorded timing and status; they do not establish that every participant completed treatment or follow-up.
The registry identifies SVR24 as the primary outcome and lists additional outcomes relating to virological response and patient-reported measures. It does not report results for those outcomes in the record represented. It also does not report the study’s sample-size justification, planned interim analyses or a detailed statistical analysis plan. The enrollment figure is not a substitute for those design details, and it does not establish the precision achieved for the primary outcome.
The safety record uses a Safety Population of 86 participants. That differs from the stated enrollment of 88, but the reason for the difference is not reported in the registry record. The record does not provide enough information to determine who was excluded from the safety population or how that population relates to the primary endpoint analysis population.
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
| Stage | All Participants |
|---|---|
| STARTED | 88 |
| Intention to Treat | 88 |
| Safety Population | 86 |
| Per Protocol | 83 |
| Completed Treatment | 47 |
| Completed Follow-up | 45 |
| COMPLETED | 45 |
| NOT COMPLETED | 43 |
Reasons for not completing this period:
| Reason | All Participants |
|---|---|
| Adverse Event | 4 |
| Adverse Event -Patient decision | 3 |
| Lack of Efficacy | 4 |
| No reason given | 5 |
| Withdrawal by Subject | 13 |
| Lost to Follow-up | 7 |
| Sufficient treatment duration (PCR neg.) | 7 |
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.
| Characteristic | Unit | All Participants |
|---|---|---|
| Participants analysed | 88 | |
| Age, Continuous | years | 34.6 (SD 8.5) |
| Sex: Female, Male: Female | Participants | 24 |
| Sex: Female, Male: Male | Participants | 64 |
| Region of Enrollment: Austria | participants | 88 |
6. Primary Endpoint
The registry lists the primary outcome as Percentage of Participants With Sustained Virological Response 24 Weeks After Completing Treatment (SVR24), measured over 24 weeks after completing treatment, within 3 years, 6 months.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | percentage of participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the percentage of participants with sustained virological response 24 weeks after completing treatment, abbreviated SVR24. The registry defines SVR24 as undetectable hepatitis C virus ribonucleic acid (HCV RNA) at that follow-up time. This is a binary outcome at the participant level: a participant either meets the stated definition or does not, subject to the registry’s handling of missing observations.
A response measured after treatment has ended is used to describe whether the virological result is sustained through the specified follow-up interval. That makes the timing part of the endpoint definition: the registry is not asking only whether HCV RNA was undetectable during treatment or at the end of treatment. General interpretation of such an endpoint depends on the definition, the assessment time and the population included in the denominator.
The record specifies a last observation carried forward (LOCF) approach and says the percentage is based on the number of non-missing observations, identified as total. It does not report the resulting percentage, its confidence interval, or the number of participants contributing to the primary analysis. The description gives a 95% confidence interval as the measure of dispersion, but no interval limits are reported in the registry record.
SVR24 is one of several listed outcomes. The registry also names SVR 12, end-of-treatment response and virological relapse, as well as measures of health status, fatigue, complaints and depression. Those outcomes capture different timepoints or domains and should not be treated as interchangeable with the primary endpoint. Their results are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a clinically defined primary outcome, but it does not report the observed SVR24 percentage or its 95% confidence interval. Consequently, the posted information does not establish the proportion of participants who met the primary definition or how precisely that proportion was estimated. A study status of COMPLETED and a stated enrollment of 88 do not fill in those missing outcome results.
The distinction between a defined outcome and a reported result matters. The endpoint description states what would count as SVR24, when it would be assessed and how missing observations would be handled. It does not state how many participants met the definition. The 95% confidence interval is named as the dispersion measure, but without its limits there is no numerical estimate of sampling uncertainty to interpret.
The design also limits what a response estimate could mean. This was an observational study in which treatment was prescribed by the treating physician. The record describes no control group and no randomized allocation. If an outcome percentage were available, it would describe the observed participants under the recorded care context; it would not, by itself, show what would have happened to comparable participants under another treatment or without treatment. Differences in participant characteristics, care and follow-up could affect observed outcomes, and the registry does not describe methods that would address such differences.
The registry lists enrollment of 88 and a Safety Population of 86. The reason for the difference is not reported in the registry record. These figures refer to different recorded quantities, and the primary analysis population is not stated in the population field. It would therefore be inappropriate to assume that all enrolled participants contributed to the endpoint estimate or to use the safety count as the primary denominator.
There are no analysis entries reported in the registry record. The record also does not provide results for the listed secondary endpoints. This means that no claims about the observed virological response, patient-reported outcomes or associations between these outcomes can be drawn from the recorded results. The absence of reported results is not evidence that an outcome was absent; it means the registry record does not give the estimate.
The safety information is also descriptive. It lists participants at risk and affected for serious and other adverse events in the Safety Population, along with several serious-event terms and their percentages. These figures do not establish that the study treatment caused the events. The record does not report deaths in the adverse-event data shown, so deaths should not be interpreted as zero. Together, the available information supports a reading of the study’s design and outcome definitions, not a conclusion about treatment efficacy or safety.
9. Statistical Methods Explained
The statistical methods described in the registry are limited. The primary outcome is a percentage, the stated dispersion measure is a 95% confidence interval, and the endpoint definition uses last observation carried forward. No detailed analysis plan, analysis entries or primary result are reported in the registry record. The concepts below explain how these methods are generally interpreted; they do not fill in missing study-specific details.
What does a percentage measure?
For a binary outcome such as whether HCV RNA is undetectable at the specified follow-up, a percentage expresses the number meeting the endpoint relative to the analysis denominator. Interpreting it requires knowing both the endpoint definition and which participants contribute to the denominator. The registry says that the primary percentage is based on non-missing observations, identified as total, but it does not give the number of participants in that analysis or the observed percentage. Enrollment alone does not determine the endpoint denominator.
A percentage is descriptive of the analyzed participants. In an observational study, it does not automatically estimate a causal treatment effect. A causal comparison requires a suitable contrast and assumptions about how participants came to receive the treatments being compared. The registry describes one participant group and no like-for-like control comparison, so a percentage for this cohort would not, on its own, quantify the effect of treatment relative to an alternative.
How should a confidence interval be read?
A confidence interval communicates uncertainty around an estimate under the statistical method used. In general, a 95% confidence interval is produced by a procedure designed to cover the underlying quantity in 95% of repeated samples under its assumptions. It is not a guarantee that the particular interval contains the true value, nor does it address every source of uncertainty, such as bias from selection or incomplete follow-up.
For a percentage, the width of the interval reflects statistical precision: a narrower interval indicates greater precision under the calculation’s assumptions, while a wider interval indicates less. The registry names a 95% confidence interval for the primary endpoint but does not report its limits. Its precision therefore cannot be assessed from the record. Nor can an interval be reconstructed without the required outcome and denominator information.
What does LOCF do?
Last observation carried forward is a missing-data procedure that uses a participant’s last recorded value in place of an unavailable later value, according to the endpoint’s analysis rule. The registry states that the SVR24 definition uses LOCF and that the percentage is based on non-missing observations. It does not give further operational details about which values were carried forward, how many observations were missing, or how the procedure was applied to individual participants.
As a general statistical matter, LOCF does not recover an unobserved outcome. It substitutes an earlier measurement and therefore relies on assumptions about how the outcome would have behaved after that measurement. If a participant’s status changes between the last observed assessment and the target time, carrying the earlier value forward may not represent the status at the target time. The direction and size of any resulting bias depend on the missingness and outcome patterns; they cannot be determined from the registry description alone. Sensitivity analyses can examine whether conclusions change under alternative assumptions, but such analyses are not reported in the registry record.
Why does the observational design matter?
In an observational study, treatment is not assigned through randomization by the study. Here, the registry says that treatment was prescribed by treating physicians. General statistical interpretation must therefore distinguish an observed outcome during treatment from a treatment effect. Participant characteristics, clinical decisions and follow-up could be related both to treatment and to outcomes. A comparison that does not control for relevant differences may be confounded. The registry does not report a control group, adjustment analyses or other methods for addressing confounding.
Because allocation is not stated and the record identifies only one participant group, there is no recorded randomized, like-for-like comparison to use as a causal contrast. Even a precisely estimated response percentage would describe the study population and conduct, not establish what the same participants would have experienced under a different care strategy. The record does not provide analyses that could support a stronger causal interpretation.
What can sample-size planning illustrations tell readers?
Planning illustrations are not observed study outcomes and are not observed power. The stated assumptions for the illustrations include a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation and an effect to detect expressed as a fraction of the observed effect. The illustrations are not the trial’s own design rationale. The trial record describes one observational group, so a hypothetical two-arm planning setup should not be mistaken for the actual allocation or study design.
Sample-size calculations depend on their assumptions, including the target effect and design. They can illustrate the scale of a future study under those assumptions, but they do not show that the completed study had a given probability of finding an effect. The registry does not report its sample-size justification, and the primary outcome result is not reported in the registry record. The planning assumptions therefore cannot supply an efficacy estimate or substitute for the missing analysis.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists eight outcome measures overall and names secondary outcomes for SVR 12, end-of-treatment response, virological relapse, SF-36 scores by visit, FSS score by visit, BL score by visit and BDI score by visit. The primary outcome is SVR24. These endpoints involve more than one outcome domain and, for the patient-reported measures, repeated visits. When many outcomes are examined, the chance of at least one apparently unusual result can increase. General approaches include prespecifying a hierarchy or adjusting for multiple comparisons. The registry record does not report a multiplicity procedure, a testing hierarchy or a detailed statistical analysis plan.
The primary endpoint definition specifies LOCF for missing observations and says the percentage is based on non-missing observations. The record does not state how much data were missing, the number included in the primary analysis, or whether additional missing-data methods or sensitivity analyses were used. LOCF is a rule for handling missing follow-up measurements; it does not remove uncertainty about the unobserved outcome. The assumptions and potential effect of the rule cannot be evaluated without information about the missing data and analysis.
The record lists 88 enrolled participants and a Safety Population of 86, but does not report why those counts differ. The primary analysis population field is blank, so the endpoint population cannot be assumed to match either figure. The record also has no analysis entries. As a result, the registry does not permit assessment of exclusions, endpoint denominators, outcome-specific missingness or the consistency of analysis populations across outcomes.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Safety Population | 14 | 86 | 16.3% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Safety Population | 60 of 86 |
Most frequent serious adverse event terms
| Event term | Organ system | Safety Population |
|---|---|---|
| Anaemia | Blood and lymphatic system disorders | 2 of 86 |
| Drug withdrawal syndrome | General disorders | 2 of 86 |
| Abscess limb | Infections and infestations | 1 of 86 |
| Erysipelas | Infections and infestations | 1 of 86 |
| Herpes zoster | Infections and infestations | 1 of 86 |
| Pneumonia | Infections and infestations | 1 of 86 |
| Anorexia nervosa | Psychiatric disorders | 1 of 86 |
| Withdrawal syndrome | Psychiatric disorders | 1 of 86 |
| Cholelithiasis | Hepatobiliary disorders | 1 of 86 |
| Osteoarthritis | Musculoskeletal and connective tissue disorders | 1 of 86 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Safety Population |
|---|---|---|
| Fatigue | General disorders | 42 of 86 |
| Depression | Psychiatric disorders | 23 of 86 |
| Anaemia | Blood and lymphatic system disorders | 15 of 86 |
| Decreased appetite | Metabolism and nutrition disorders | 15 of 86 |
| Influenza like illness | General disorders | 14 of 86 |
| Headache | Nervous system disorders | 14 of 86 |
| Nausea | Gastrointestinal disorders | 13 of 86 |
| Pyrexia | General disorders | 10 of 86 |
| Alopecia | Skin and subcutaneous tissue disorders | 9 of 86 |
| Weight decreased | Investigations | 8 of 86 |
Serious events with the highest arm-level rate: anaemia (2.3%), drug withdrawal syndrome (2.3%), abscess limb (1.2%), erysipelas (1.2%), herpes zoster (1.2%).
For the Safety Population, the registry lists 86 participants at risk for each of the serious and other adverse-event groupings. It records 14 affected for serious adverse events and 60 affected for other adverse events. These are descriptive counts in the registry record; no additional percentage has been calculated. The safety population is distinct from the 88 participants listed as enrolled, and the reason for that difference is not reported in the registry record.
The listed serious-event terms and percentages are anaemia, 2.3%; drug withdrawal syndrome, 2.3%; abscess limb, 1.2%; erysipelas, 1.2%; herpes zoster, 1.2%; and pneumonia, 1.2%. The record does not give further event-level context in these entries, such as timing or whether an event was considered related to study treatment. A serious adverse event is not, by its classification alone, proof that treatment caused it.
The deaths field does not contain a reported value. That is not the same as a reported count of zero; deaths are not reported in the registry record. These safety entries should be read as recorded descriptive information, not as a causal comparison or a complete account of each participant’s risk.
12. What the Result Does, and Does Not, Mean
The record establishes that a prospective, multicenter observational study was conducted among participants with previously untreated chronic hepatitis C, specified genotypes and opioid maintenance therapy. It also establishes how the registry defines its primary endpoint: undetectable HCV RNA 24 weeks after completing treatment, with LOCF used for missing observations. The study status is COMPLETED, and enrollment is listed as 88.
Those design details do not establish the observed SVR24 result. The registry record does not report the primary percentage, the confidence interval limits or the number of participants included in the primary analysis. It also does not report results for the listed secondary outcomes. Therefore the posted information cannot show how many participants achieved SVR24, how precise the estimate was, or how outcomes changed across the other measures.
Even if a cohort response estimate were available, the observational design would shape its interpretation. Participants received treatment as prescribed by treating physicians, and the registry describes no comparator group or randomized allocation. A result in this cohort would not, on its own, show what would have occurred under another treatment or establish that the treatment caused the observed outcome. General concerns include selection, confounding and incomplete follow-up; the registry record does not report methods that would resolve them.
The safety counts and listed serious-event terms describe recorded events in the Safety Population. They do not establish causation, and the record does not report a death count. The difference between enrolled and safety-population counts is not explained. These details call for caution about denominators and completeness rather than an assumption that all enrolled participants contributed to every analysis.
In short, the record supports understanding the study question, design, endpoint definition and some safety reporting. It does not support a numerical conclusion about the primary response, a comparison of treatment strategies, or a conclusion about the treatment’s efficacy or safety. Those conclusions would require outcome results and analysis details not reported in the registry record.
13. Why This Trial Matters Statistically
This study is statistically notable because it focuses on a defined clinical population receiving opioid maintenance therapy while examining hepatitis C treatment outcomes. Its observational, multicenter design reflects treatment as prescribed by clinicians rather than an allocation process described as randomized. That context matters: estimates from such a cohort can characterize observed outcomes, but comparisons and causal claims require methods and data beyond a simple outcome percentage.
The primary endpoint is clearly framed around a specified virological status and follow-up time. The registry also names patient-reported measures and other virological outcomes, indicating that the study’s questions extended beyond a single endpoint. However, the registry record does not report outcome results or analysis entries. This illustrates why a well-defined endpoint and a completed study status are not substitutes for a posted estimate, denominator and measure of precision.
Missing-data handling is another important statistical feature. LOCF is explicitly part of the SVR24 definition, yet the record does not report missingness amounts or sensitivity analyses. A reader cannot assess how the rule affected the estimate without those details. Similarly, the enrollment count and safety-population count differ, but the record does not explain the analysis populations.
The study’s value for statistical interpretation therefore lies partly in the questions it raises about design, denominators, missing data and causal inference. Its record identifies the intended outcome and population, while leaving important result and analysis details unreported. That distinction is useful for clinical researchers: conclusions should match the evidence actually recorded, and uncertainty about missing information should remain explicit rather than being filled by assumptions.
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.
Several trial-specific limitations follow directly from the registry record. First, it describes an observational study with treatment prescribed by the treating physician, one listed participant group and no stated allocation method. There is no recorded like-for-like control comparison. The design therefore does not provide a randomized contrast, and the record does not report adjustment methods for confounding.
Second, the primary SVR24 result and its 95% confidence interval are not reported in the registry record. No primary analysis denominator is given, and the population field for the primary endpoint is blank. Although enrollment is 88, the Safety Population is 86; the reason for the difference is not reported. These details prevent a reader from establishing which participants contributed to the primary analysis or assessing its precision.
Third, LOCF is specified for the primary endpoint, but the record does not describe the extent or pattern of missing data, provide sensitivity analyses, or give further operational detail about the procedure. The registry also does not report an analysis plan, sample-size justification or interim-analysis approach. The absence of these details limits assessment of how the analyses were selected and how robust the results would be to alternative assumptions.
Finally, the secondary outcomes are named but their results are not reported. The registry does not describe multiplicity handling, and the safety record does not report a deaths value or provide further context for the listed events. These gaps limit interpretation of both efficacy and safety; they should not be replaced by assumptions about unreported results.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: An Observational Study of Pegasys (Peginterferon Alfa-2a) Plus Copegus (Ribavirin) in Participants With Chronic Hepatitis C (CHC), Genotype 2, 3, 1 or 4, Undergoing Opioid Maintenance Therapy — NCT01416610.
- Registry record last updated 2017-04-10; status last verified 2017-03.
- Results first posted 2015-12-09.
- 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.
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18. Record Summary
The registry describes a completed prospective, multicenter, non-interventional study sponsored by Hoffmann-La Roche. It enrolled 88 participants with previously untreated chronic hepatitis C, genotype 2, 3, 1 or 4, who were undergoing opioid maintenance therapy. Participants received Pegasys plus Copegus as prescribed by their treating physician, with a treatment-free follow-up period of 24 weeks.
The primary outcome was SVR24, defined as undetectable HCV RNA 24 weeks after treatment completion, using LOCF. The record specifies a 95% confidence interval but does not report the primary estimate or interval. It lists 8 outcome measures and gives no analysis entries. The Safety Population was 86; the reason it differs from enrollment is not reported. Safety entries include 14 affected for serious adverse events and 60 affected for other adverse events, with no deaths value reported.
The record does not describe a randomized comparison, report secondary outcome results, or provide a detailed statistical plan. The available information supports interpretation of the study design and endpoint definitions, but not a numerical conclusion about the primary outcome.