Pioglitazone Before Peginterferon and Ribavirin for Hepatitis C Infection in HIV/HCV-Coinfected Patients With Insulin Resistance: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pioglitazone Before Peginterferon and Ribavirin for Hepatitis C Infection in HIV/HCV-Coinfected Patients With Insulin Resistance (NCT00665353), a na phase 2 study. The primary outcome is The Proportion of All Subjects With HCV Viral Load < 60 IU/mL at Week 24 of Step 2..

2. Clinical Question

The clinical question is whether a period of pioglitazone before HCV therapy, followed by continued pioglitazone alongside peginterferon and ribavirin, is associated with the specified virologic endpoint in this selected population. The registry’s background describes insulin resistance as common in people with HIV/HCV coinfection and as associated with poor HCV treatment responses. It gives the study rationale as evaluating whether pioglitazone before HCV treatment is safe and effective in improving treatment outcome among people for whom prior peginterferon and ribavirin treatment was unsuccessful.

The endpoint is measured after step 2 has begun, rather than at the end of pioglitazone-only step 1. It is a binary outcome: each participant either meets the specified viral-load threshold at the stated time or does not. The registry record does not report the number meeting that threshold, the denominator included in the actual analysis, or reasons any enrolled subject might be absent from an endpoint assessment. The study therefore frames a question about response in a narrowly described group, but its record does not provide the result needed to quantify that response.

3. Trial Design

The registry identifies this as a Phase 2, completed, single-group study with an enrollment of 19. Its condition is HIV-1 and hepatitis C coinfection. The official title further specifies HCV genotype 1, insulin resistance, and prior nonresponse to peginterferon and ribavirin. The study began in 2009-03, and primary completion is listed as 2011-05. The sponsor is Advancing Clinical Therapeutics Globally for HIV/AIDS and Other Infections.

The regimen was sequential. In step 1, all participants received pioglitazone for 24 to 28 weeks. In step 2, participants continued pioglitazone and added peginterferon and ribavirin for up to 48 additional weeks. Thus, the treatment sequence includes a period before the HCV drugs are added and a period of combined treatment. The registry does not report further dosing details in the record.

Allocation is listed as not applicable, masking is listed as none, and the model is single-group. These design features mean the study does not include a concurrent randomized control arm. The primary endpoint is the proportion of all enrolled subjects with HCV viral load < 60 IU/mL at Week 24 of step 2. A secondary outcome concerns the proportion with HCV viral load < 60 IU/mL at Week 72 of step 2. Other listed secondary outcomes include safety and tolerability, changes in AST and ALT, HOMA-IR, fasting total cholesterol, and triglycerides.

Because every participant followed the same planned treatment sequence, the record can describe outcomes during that sequence but cannot directly compare the regimen with an untreated, usual-care, or alternative-treatment group. The registry record does not report the rationale for the enrollment target, a statistical analysis plan, or methods for estimating treatment effects. Completion status indicates the trial is marked completed; it does not itself establish that results were posted for every endpoint.

4. Participant Flow and Accounting

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

Before assignment: A5239 was a single-arm study which enrolled prior nonresponders to peginterferon (PEG-IFN) and ribavirin (RBV)\> therapy with documented insulin resistance. 31 potential subjects failed to meet all inclusion/exclusion criteria. 22 of these potential subjects did not meet the HOMA-IR criterion (\> 2.5 within 42 days prior to study entry).

Study Step 1

Reasons for not completing this period:

Study Step 2

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All enrolled subjects.

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 The Proportion of All Subjects With HCV Viral Load < 60 IU/mL at Week 24 of Step 2., measured over Week 24 of Step 2.

The primary endpoint is the proportion of all enrolled subjects with HCV viral load < 60 IU/mL at Week 24 of step 2. It records whether participants have reached the stated threshold at a specified assessment point during the period when pioglitazone is continued and peginterferon and ribavirin have been added. The endpoint is binary at the participant level, then expressed as a proportion for the study population.

General: a threshold-based virologic endpoint can make a treatment outcome interpretable as the share of participants meeting a prespecified laboratory criterion at a defined time. It is different from measuring the average change in viral load: it classifies participants according to whether their value is below the threshold, rather than describing how far values changed. The result depends on the threshold, assessment time, and population included in the calculation.

The registry record identifies the endpoint population as all enrolled subjects and specifies a 90% confidence interval as its dispersion measure. A confidence interval describes uncertainty around an estimated proportion; it is not a guarantee that the true proportion lies within the reported interval. The registry record does not report the observed proportion or the interval limits, so neither the estimated response frequency nor its precision can be stated from this record.

The endpoint is clinically relevant to the study’s stated objective of evaluating HCV treatment outcome in people with prior nonresponse, but the registry record alone does not establish that any observed outcome was caused by pioglitazone or by the combined regimen. The absence of a concurrent comparator limits causal interpretation, and the missing result prevents even a descriptive estimate of how many participants met the endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical interpretation begins with the study structure. This was a single-group study with no masking and no concurrent randomized comparator. The endpoint is a proportion, not a difference between treatment arms. That distinction determines what can be estimated directly: the study can describe the fraction meeting a criterion in its enrolled population, but its design does not provide a like-for-like control comparison. The registry record does not report an adjusted treatment-effect model or a causal analysis.

What does the primary proportion represent?

The primary endpoint classifies each enrolled subject according to whether HCV viral load was < 60 IU/mL at Week 24 of step 2. A proportion is formed by relating the number meeting the criterion to the population counted in the analysis. The registry names all enrolled subjects as the population, but it does not report the endpoint numerator, the analyzed denominator, or the observed proportion. It also does not say how a participant without a Week 24 measurement was handled. Those omissions prevent reconstruction or verification of the endpoint estimate.

General: a proportion is a natural summary when an outcome has two categories, such as meeting or not meeting a threshold. It is easy to interpret as a frequency in the analyzed group, but it compresses information. Participants just above the threshold and participants with much higher viral loads both fall outside the endpoint category. The measure also depends on the chosen threshold and assessment time; changing either could change the classification.

How should the confidence interval be read?

The endpoint specifies a 90% confidence interval. General: a confidence interval expresses the statistical uncertainty associated with an estimate, reflecting that an estimate from a sample may differ from the value in a broader population. A narrower interval generally indicates greater precision under the method used, while a wider interval indicates less precision. The interval does not represent the range of individual participant outcomes, and it does not mean that the estimate has a 90% probability of being correct.

The confidence interval limits are not reported in the registry record. The interval method is also not reported, so it is not possible to assess whether the calculation used a particular formula or model. With a proportion, the method matters especially when the number of observations is limited or when the estimate is near the boundaries of the possible range. No alternative interval or sensitivity analysis is reported in the registry record.

What does the design permit?

The single-group structure permits descriptive analysis of participants’ outcomes under the treatment sequence. It does not permit a direct comparison with a parallel control group because none is described. Comparing a participant’s outcome after step 1 with an outcome after step 2 would not by itself solve this problem: the treatment components differ between steps, and time also passes between assessments. The registry record does not report a design or analysis that separates the effects of the individual drugs or the sequence.

General: random assignment to concurrent groups can help balance measured and unmeasured factors on average, supporting a more direct treatment comparison. Without that design feature, observed changes can have more than one explanation. This is a limitation on causal interpretation, not a claim that a change did or did not occur. Since primary results are not reported, the registry record does not establish even the size or direction of a change in the primary endpoint.

What do the planning assumptions mean?

The record describes sample-size planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It states that the effect to detect is a stated fraction of the observed effect. These are planning assumptions, not evidence about the trial’s observed power. The actual study is single-group, so an equal-allocation, two-arm illustration describes a hypothetical design rather than the study’s enrolled structure. No sample-size justification for the trial is reported in the registry record.

General: a planning calculation estimates the sample size that a hypothetical study might need under specified assumptions. Its output depends on the assumed effect, variability or event frequency, significance level, power target, and design. Such an illustration is not an observed result and cannot establish that an analysis was adequately powered. The numerical planning outputs are not reported in the registry record, and the effect estimate on which the illustrations are said to be based is not reported there either.

What analysis details remain unknown?

The registry record does not report the statistical test or estimation procedure used for the primary endpoint, whether any adjustment was planned, or whether analyses were conducted according to an intention-to-treat principle. It also does not report the handling of missing endpoint measurements, protocol deviations, or changes to the planned analysis. Without these details, the endpoint definition can be understood, but the analysis producing a result cannot be independently evaluated.

General: missing outcome data can affect a proportion if participants with unavailable measurements are omitted, counted as not meeting the criterion, or handled through another method. Different choices can produce different estimates. An analysis population also defines whose outcomes contribute to the result. Clear reporting of both matters for assessing how well an estimate corresponds to the stated population. The registry specifies all enrolled subjects as the primary population but does not report how that population was implemented in analysis.

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("PIO (Step 1) Then PIO+PEG-INF+RBV (Step 2)")
n      <- c(19)
events <- c(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  PIO (Step 1) Then PIO+PEG-INF+RBV (Step 2)  19  0  0.0  0.0  17.6  0.0  16.8  0.1  16.8

11. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple outcomes: safety and tolerability, a later HCV viral-load threshold outcome, and changes in AST, ALT, HOMA-IR, fasting total cholesterol, and triglycerides. It does not report how many analyses were performed for each outcome, which were considered confirmatory, or whether any procedure was used to account for multiple statistical tests. The registry record therefore does not establish how multiplicity was addressed.

General: when many outcomes or comparisons are examined, the chance of at least one apparently unusual result can increase, even if there is no underlying effect. Multiplicity procedures can help control that risk, but the appropriate approach depends on the analysis plan and the role of each outcome. Without a reported plan, individual secondary findings should not be treated as though they were the sole prespecified test.

The primary endpoint population is described as all enrolled subjects. The registry record does not report the number with an available Week 24 of step 2 viral-load measurement, the number included in the analysis, or how missing values were treated. It also does not report whether participants who did not reach that assessment were counted as not meeting the threshold, excluded, or addressed using another strategy. Those choices can affect a proportion and its confidence interval.

The registry record does not report whether the analysis followed an intention-to-treat principle, whether exclusions were made after enrollment, or how protocol deviations were handled. These are not details that can be inferred from the stated population label. Nor does the record report a prespecified missing-data sensitivity analysis. As a result, the endpoint population is described, but the completeness and analysis handling of that population are not reported in the registry record.

General: transparent reporting of the analysis population, missing-data rules, and multiplicity approach helps readers understand which question an estimate answers and how robust it may be to analytic choices. Here, the absence of both the endpoint result and these analysis details means the primary estimate cannot be interpreted for precision or sensitivity to missing data.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pancreatitis (5.3%), pneumocystis jiroveci pneumonia (5.3%), pneumonia aspiration (5.3%).

The registry lists 2 affected participants in the serious-adverse-event category among 19 at risk, and 18 affected participants in the other-adverse-event category among 19 at risk. These are separate registry categories; they should not be added together to infer a combined number of affected participants. The record does not report whether the same participants appear in both categories, and no combined count is stated.

The listed serious adverse-event terms are pancreatitis, Pneumocystis jiroveci pneumonia, and pneumonia aspiration, each with a reported frequency of 5.3%. These are registry-reported event terms and frequencies. The record does not provide enough detail to infer from these entries whether an event was judged related to a study drug, how events were adjudicated, or whether the frequency refers to a participant with an event or repeated event occurrences. The death count is not reported in the registry record.

General: adverse-event summaries describe events observed or reported during a study; they do not, on their own, establish causation. A single-group study has no concurrent comparator for estimating whether an event frequency differs from what would otherwise have occurred. The listed safety figures should therefore be read as descriptive registry data, not as a comparative safety estimate. The registry does not report further detail on severity grading, timing, exposure-adjusted rates, or attribution.

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

The registry record defines a clinically focused question in a selected population: whether participants with HIV/HCV coinfection, insulin resistance, and prior nonresponse meet a specified HCV viral-load threshold after pioglitazone is given before, and then alongside, peginterferon and ribavirin. It also records a single-group study structure, enrollment of 19, and a primary endpoint at Week 24 of step 2.

What the record does not report is the primary endpoint estimate. There is no reported proportion, confidence interval limit, or endpoint count from which the response frequency or its precision can be assessed. The study’s status as completed does not fill that gap. Therefore the registry record cannot quantify how often the endpoint was met in this cohort.

Even if the primary result were available, this design would support a descriptive account of outcomes under the treatment sequence, not a direct causal comparison against another regimen. No concurrent control group is reported. Because peginterferon and ribavirin were added after pioglitazone-only step 1, any change across the sequence could not be attributed to pioglitazone alone from the design information given. Other influences, including time and participant characteristics, would not be separated by randomization against a control group.

The safety entries describe reported event categories and terms. They do not establish that a study drug caused an event, and they do not provide a comparative estimate of risk. The registry record also leaves the analysis population, missing-data handling, multiplicity approach, and detailed statistical methods unreported. These omissions limit how fully any numerical result could be evaluated, even apart from the absent primary estimate.

In practical statistical terms, the record identifies what investigators intended to measure and how treatment was sequenced, but it does not provide the result needed to judge the endpoint’s observed frequency. It can inform discussion of study design and reporting completeness; it cannot, on its own, establish the size, precision, or cause of a treatment outcome.

14. Why This Trial Matters Statistically

This trial matters statistically because it illustrates the distinction between a treatment sequence and a controlled treatment comparison. Pioglitazone was given first, then continued when peginterferon and ribavirin were added. The design can describe outcomes within that sequence, but the registry reports no concurrent comparator group. This distinction is important whenever a study question asks whether a preparatory treatment improves a later outcome: a single-group sequence does not isolate the contribution of the preparatory treatment.

It also illustrates why endpoint definitions and endpoint results must be considered separately. The primary outcome is specific: the proportion of all enrolled subjects with HCV viral load < 60 IU/mL at Week 24 of step 2. A clearly stated threshold and time point make the intended measure understandable. But the registry record does not report the observed proportion or its 90% confidence interval, so the definition cannot tell readers what occurred or how precisely it was estimated.

The enrollment of 19 makes transparent reporting of the analyzed population and uncertainty especially relevant, but the record does not state how many participants contributed an endpoint measurement or how missing measurements were handled. General: smaller studies commonly yield estimates with substantial uncertainty, and interval estimates help make that uncertainty visible. The actual precision in this trial cannot be assessed without the result and interval limits.

The listed planning assumptions also highlight a design distinction: an equal-allocation, two-arm sample-size illustration is hypothetical when the recorded trial itself is single-group. Planning calculations can inform future study design, but they are not observed power and do not substitute for a concurrent comparison. The record does not report the trial’s own sample-size justification.

Finally, the safety entries are descriptive. Without a comparator, attribution details, and further event information, they do not establish comparative risk or causation. Together, these features make the record useful for understanding what was planned and what was reported, while underscoring the limits imposed by missing outcome results and unreported analysis details.

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 principal trial-specific limitation in interpreting the registry record is that it does not report the primary endpoint estimate, its confidence interval limits, or the underlying endpoint counts. As a result, the planned virologic outcome cannot be quantified from the record. Completion status does not provide those missing results.

The single-group design has no concurrent randomized comparator, and masking is listed as none. The design therefore does not support a like-for-like treatment contrast. It cannot isolate the contribution of pioglitazone from the subsequent addition of peginterferon and ribavirin, or distinguish treatment effects from changes over time and other influences. This is a design limitation, not evidence for or against a treatment effect.

The enrolled population is narrowly described: people with HIV-1 and HCV genotype 1 coinfection, insulin resistance, and prior nonresponse to peginterferon and ribavirin. Findings, if reported, would pertain most directly to that population; the record does not establish applicability to people outside those criteria. The registry does not report additional demographic or clinical characteristics that would help assess how representative the enrolled group was.

The registry record does not report the analysis population used, the number assessed at the primary time point, missing-data handling, protocol deviations, or the statistical procedure for the endpoint. It also does not report multiplicity handling across the listed secondary outcomes, detailed safety-event attribution, or a sample-size justification. These gaps prevent a complete assessment of robustness and precision.

The primary endpoint is assessed at Week 24 of step 2, while a secondary threshold outcome is listed at Week 72 of step 2. The record does not report either endpoint result. The duration of treatment in step 1 is specified as 24 to 28 weeks, and step 2 treatment is described as lasting up to 48 additional weeks; the record does not provide further information about individual exposure or assessment completion. These limits should be kept in view when interpreting the study description.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Pioglitazone Before Peginterferon and Ribavirin for Hepatitis C Infection in HIV/HCV-Coinfected Patients With Insulin Resistance — NCT00665353.
• Registry record last updated 2018-10-12; status last verified 2018-09.
• Results first posted 2012-09-13.
• 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

NCT00665353 is a completed Phase 2, single-group study with an enrollment of 19. It concerns people with HIV-1 and HCV genotype 1 coinfection, insulin resistance, and prior nonresponse to peginterferon and ribavirin. The study began in 2009-03, with primary completion listed as 2011-05.

Participants received pioglitazone for 24 to 28 weeks, then continued pioglitazone and added peginterferon and ribavirin for up to 48 additional weeks. The primary endpoint is the proportion of all enrolled subjects with HCV viral load < 60 IU/mL at Week 24 of step 2, with a 90% confidence interval specified. The registry record does not report the primary result or interval limits.

Safety entries list 2 affected participants in the serious-adverse-event category and 18 in the other-adverse-event category, each among 19 at risk. Listed serious-event terms each have a reported frequency of 5.3%. The record does not report a comparator group, detailed analysis methods, missing-data procedures, or the death count.