A Collaborative Trial in Injectors of Individualized Treatment for Genotype 2/3: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Collaborative Trial in Injectors of Individualized Treatment for Genotype 2/3 (NCT01364090), a non-randomized phase 4 study. The primary outcome is Treatment Efficacy.

2. Clinical Question

3. Trial Design

This was a Phase IV, open-label, multicentre, international, parallel trial with non-randomized allocation. The registry lists 93 participants enrolled and the study status as completed. The listed sponsor is the Kirby Institute. Treatment combined directly observed pegylated interferon alfa 2b with self-administered ribavirin.

Treatment duration depended on HCV RNA results at week 4. Participants with non-quantifiable or undetectable RNA were assigned to the shortened treatment-duration group and continued treatment through week 12. Participants with quantifiable or detectable RNA were assigned to the standard treatment-duration group and continued through week 24. The descriptions also specify follow-up for 24 weeks after treatment completion, making the total durations described 36 weeks and 48 weeks, respectively.

The adverse-event record also lists participants who discontinued before RVR as a separate group. The registry does not explain further how this group relates to the treatment-duration groups or to the primary outcome population. The trial’s stated purpose was to assess whether shortening treatment for people responding well early in treatment was feasible, safe and effective. Those aims describe the question being studied; they are not themselves findings.

Since allocation followed week-four response, the two duration groups differed by a characteristic used to determine treatment duration. Their results cannot be interpreted as if participants had been randomly assigned to 12 or 24 weeks. The registry record does not report a randomized control group, masking, or a detailed statistical analysis plan.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

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

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 Treatment Efficacy, measured over 36 weeks.

The primary endpoint is the number of participants with undetectable HCV RNA 12 weeks after the end of treatment, described as SVR12. The registry gives a 36-week timeframe and lists the primary outcome population as ITT. It defines the duration strategy according to the week-four RNA result: 12 weeks of therapy for participants whose RNA was non-quantifiable or undetectable, and 24 weeks for participants whose RNA was quantifiable or detectable.

A sustained virologic response endpoint records whether viral RNA is undetectable at a specified point after treatment ends. In general, this kind of endpoint captures a post-treatment response rather than only a measurement taken during therapy. The count format gives the number of participants meeting the endpoint; without the endpoint result and its denominator, it does not show how frequently the outcome occurred.

The registry record supplies the endpoint definition but no observed count, denominator, estimate of uncertainty, or analysis result for SVR12. It therefore does not establish from the posted results how many participants met the primary endpoint or how precisely any treatment-strategy outcome was estimated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Several statistical ideas help distinguish the design and outcome definition from evidence about treatment effects. In general, a trial’s design determines what comparisons its data can support, while an endpoint definition says what is counted. Neither is a substitute for reporting the observed outcomes and their uncertainty.

What does non-randomized allocation imply?

In a randomized comparison, allocation is determined by a chance process, which can help make treatment groups comparable on average. This trial instead used week-four RNA response to guide duration. Participants with early non-quantifiable or undetectable RNA received the shortened duration, while those with quantifiable or detectable RNA received the standard duration. Early response is therefore tied to group membership. A comparison of the groups would combine differences in early response with differences in treatment duration. The registry itself flags that the arms are not a like-for-like control comparison.

Adjustment for measured characteristics can sometimes address some observed group differences, but it cannot automatically remove unmeasured differences or eliminate the design’s limitations. Whether adjusted analyses were conducted, which variables might have been included, and what methods were used are not reported in the registry record. No effect estimate should be inferred from the allocation descriptions alone.

What does a count endpoint convey?

The primary outcome is a count of participants who meet the SVR12 definition. A count is an understandable summary of how many people had the specified outcome. To interpret it as a rate or compare it across groups, the relevant denominator and a clearly defined analysis population are also needed. The registry lists ITT as the primary outcome population, but does not report the endpoint count, denominator, or resulting analysis. No rate or comparison can therefore be described from the outcome definition alone.

In general, a confidence interval expresses the uncertainty around an estimate under the assumptions of the method used. A narrow interval indicates greater precision than a wide interval, while neither width nor position establishes causality by itself. No confidence interval for the primary outcome is reported in the registry record. The result’s precision is therefore not available for interpretation.

How should the planning illustrations be read?

Planning sample sizes are not observed trial outcomes. The record describes its sample-size illustrations as based on the observed effect, with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation; the illustrated effect is a stated fraction of the observed effect. For non-time-to-event outcomes, those illustrations are expressed as participants per arm for 80% or 90% power; time-to-event illustrations use a total event count. These are planning assumptions, not evidence that the completed study had a particular probability of finding a result or that a result was observed. The numerical planning values and the observed effect are not reported in the registry record, so no specific illustration can be interpreted from the information available.

In general, power calculations depend on assumptions about the effect to detect, variability or event frequency, significance level, and analysis method. If those assumptions differ from what occurs, the calculation may not describe the precision or sensitivity of the completed study. A planning calculation is also distinct from a post-study claim of observed power; it cannot replace an effect estimate with an interval.

Why does the allocation rule matter for analysis?

Because duration was assigned according to an early response, the duration groups are not exchangeable by design. A simple comparison of their outcomes would be descriptive unless supported by additional assumptions and an appropriate analysis. The registry record reports zero analyses, and does not describe a model, adjustment strategy, or inferential test for the primary endpoint. It is not possible to attribute a group difference to treatment duration from the design description alone.

General statistical interpretation should therefore keep three questions separate: what outcome was defined, what outcome was observed, and what causal comparison the design supports. In this record, the outcome is defined, but its observed primary result is not reported; the design supports description of a response-guided strategy, not a randomized duration comparison.

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("Standard Treatment Duration (24 Weeks)", "Shortened Treatment Duration (12 Weeks)", "Discontinued Prior to RVR")
n      <- c(26, 61, 6)
events <- c(10, 51, 0)
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  Standard Treatment Duration (24 Weeks)  26  10  38.5  20.2  59.4  22.4  57.5  22.4  57.6
ARM  Shortened Treatment Duration (12 Weeks)  61  51  83.6  71.9  91.8  72.4  90.8  72.3  90.8
ARM  Discontinued Prior to RVR  6  0  0.0  0.0  45.9  0.0  39.0  0.4  41.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures and names secondary topics covering treatment adherence, treatment response (ETR and SVR24), and behavioral and quality of life. It does not report how many hypotheses were tested, which outcomes were designated secondary in a statistical analysis plan, or whether any adjustment for multiple comparisons was planned or used. When several outcomes are examined, the chance of at least one apparently notable result can increase; in general, multiplicity methods are used to manage that issue. No particular method should be assumed.

The primary outcome population is listed as ITT. The record does not explain the operational definition of ITT, who was included in the analysis, how participants without an endpoint measurement were handled, or whether there were departures from the intended population. Missing-data methods, imputation rules, and sensitivity analyses are not reported in the registry record. The numbers enrolled alone do not establish how many participants contributed a primary outcome result.

The registry reports zero analyses. It does not provide a statistical analysis plan, model specifications, adjustment variables, interim-analysis information, or inferential results for the primary endpoint. These details are not reported in the registry record. Consequently, neither multiplicity control nor the effect of missing data on the endpoint can be assessed from the posted information.

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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: road traffic accident (16.7%), toxicity to various agents (3.8%), vascular pseudoaneurysm (3.8%), pneumonia (3.8%), abscess (3.8%).

The serious adverse-event figures are reported as affected participants alongside participants at risk for each group. The standard treatment-duration group has 4 affected participants among 26 at risk; the shortened treatment-duration group has 6 among 61; and the group discontinued prior to RVR has 1 among 6. The record also gives counts for other adverse events: 26 among 26, 60 among 61, and 5 among 6, respectively. These are descriptive group-specific counts, not a randomized comparison.

The registry lists Road Traffic Accident at 16.7% among the top serious-event terms. Toxicity to various agents, Vascular pseudoaneurysm, Pneumonia, Abscess, and Suicidal ideation are each listed at 3.8%. The record does not describe the event-term denominator or explain whether events were considered related to treatment. These percentages and counts should not be interpreted as evidence of causation. Death counts are not reported in the registry record. Differences in group size and the response-guided allocation also limit direct comparison of the groups’ safety counts.

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

The registry record supports a description of a Phase IV, open-label, non-randomized trial that assigned treatment duration according to HCV RNA response at week 4. It also supports reporting the primary endpoint definition and the listed serious adverse-event counts and terms. These registry entries describe the study and what the record contains; they do not establish the size or direction of a treatment effect.

The primary outcome is SVR12, but its observed result is not reported in the registry record. There is no reported primary endpoint estimate or confidence interval with which to assess the result’s precision. The record also does not report results for the listed secondary outcomes. It is therefore not possible to state from this information how participants’ outcomes compared with any benchmark or how the strategies differed.

The trial’s non-randomized design is important to the meaning of any descriptive contrast. People receiving shorter treatment had a different week-four response criterion from people receiving standard duration. A difference between these groups would not, by itself, isolate the effect of duration. Conversely, the absence of a reported result in the registry record is not evidence that an outcome did or did not occur.

The safety counts describe reported events in groups with different sizes and selection criteria. They do not by themselves establish whether an event was caused by treatment or permit a controlled comparison of risk. The registry record does not supply the attribution details needed for that interpretation.

In general, a clinical trial result is interpreted using the endpoint estimate, its uncertainty, the analysis population, and the design that generated the comparison. Here, the endpoint and design are described, but the main efficacy estimate and its uncertainty are not. The available record therefore supports a limited account of the trial’s question and reporting, rather than a conclusion about whether either treatment duration is preferable.

14. Why This Trial Matters Statistically

This trial is statistically notable because treatment duration was linked to an early response measure rather than assigned randomly. That design directly reflects a response-guided strategy, but it makes a simple comparison of the 12-week and 24-week groups difficult to interpret as an effect of duration alone. The distinction between describing outcomes in response-defined groups and estimating a causal treatment effect is central to reading the record.

The endpoint also illustrates why a clear definition is not enough for statistical interpretation. The record defines SVR12 and identifies ITT as the primary population, yet does not report the endpoint count, an estimate, or uncertainty. Without those results, readers cannot assess the observed response or its precision. The outcome topics and safety counts add context, but they cannot replace the missing primary efficacy result.

The sample-size material is identified as planning illustration based on an observed effect, with stated assumptions. Such calculations concern what a study might be designed to detect under assumptions; they are not observed outcomes and should not be treated as post-study evidence. The numerical planning values are not reported in the registry record, and the primary result needed to assess the trial’s findings is also absent.

For researchers, the record underscores the value of making allocation rules, analysis populations, missing-data handling, and endpoint results transparent. These details determine what comparisons can be made and how much uncertainty surrounds them. In this case, the design and intended question are legible, while the posted efficacy analysis is not available for interpretation.

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.

The most important trial-specific limitation for interpreting efficacy is the non-randomized, response-guided allocation. Participants entered different treatment-duration groups according to HCV RNA status at week 4. This means the groups differed by the criterion that determined their duration, and they are not a like-for-like control comparison. A contrast between them would not isolate the effect of treatment duration without additional analytic assumptions.

The registry record gives no observed primary endpoint result, uncertainty interval, or statistical analysis. It therefore does not permit assessment of the magnitude or precision of SVR12. Although the primary population is listed as ITT, the record does not define how that population was implemented or describe missing endpoint data and their handling. It also does not report analyses of the secondary outcome topics.

The record describes a group that discontinued prior to RVR in the safety information but does not clarify its role in efficacy analyses. The serious-event categories and event-term percentages are listed without reported attribution methods or fuller analytic context. These counts should therefore remain descriptive.

The posted information does not report a detailed statistical plan, multiplicity procedures, model specifications, adjustment variables, or interim-analysis details. These omissions limit assessment of how analyses were selected and conducted. They are limitations of what is reported in the registry record; no assumptions about unreported procedures can resolve them.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Collaborative Trial in Injectors of Individualized Treatment for Genotype 2/3 — NCT01364090.
• Registry record last updated 2019-11-18; status last verified 2019-11.
• Results first posted 2017-10-18.
• 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 NCT01364090, a completed Phase IV, open-label, non-randomized, parallel trial sponsored by the Kirby Institute. It lists 93 participants enrolled and evaluates response-guided treatment durations using pegylated interferon alfa 2b and ribavirin for chronic HCV genotype 2 or 3 among people with injection drug use.

Week-four RNA status determined whether participants followed the 12-week or 24-week treatment-duration group. The primary endpoint is the count of participants with undetectable HCV RNA 12 weeks after treatment, identified as SVR12, with a 36-week timeframe and an ITT population. The endpoint result and its statistical analysis are not reported in the registry record.

Safety counts are listed for the two duration groups and for participants discontinued prior to RVR. The record also names secondary outcome topics, but does not report their results. Its non-randomized allocation limits direct interpretation of the duration groups as a controlled comparison.