Tipranavir/Ritonavir Low Dose Pharmacokinetics in Treatment Naive Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Tipranavir/Ritonavir Low Dose Pharmacokinetics in Treatment Naive Patients (NCT00530920), a registered phase 2 study. The primary outcome is Viral Load (log10 Copies/mL) Change From Baseline (Last Observation Carried Forward (LOCF)).

2. Clinical Question

The broader study question was dose-finding: the brief summary says the aim was to identify an optimal combination of tipranavir and ritonavir that could be used in a pivotal trial. That aim ties together pharmacokinetic measurements and short-term efficacy and safety observations. Pharmacokinetic outcomes include measures of drug exposure, concentration, clearance, distribution, and timing. They can describe how the studied regimens behave in the body, but they do not by themselves establish a clinical benefit.

The clinical question is consequently narrower than whether treatment improves health outcomes. The listed primary endpoint captures an early viral-load change over a short interval, while the registry record also lists numerous pharmacokinetic outcomes. Longer-term outcomes and results from a later pivotal trial are not reported in the registry record. The posted information does not contain the primary endpoint estimates needed to describe the observed viral-load changes or compare the regimens on that outcome.

3. Trial Design

The registry identifies this as a phase 2, parallel-group study, with a listed enrollment of 85. Its status is completed. The official title describes a multicenter, randomized, open-label clinical trial, and the study dates are listed as starting in 2007-10 with primary completion in 2008-05. However, the registry record does not state the allocation method. The three regimens are listed as separate groups, but no formal control arm or prespecified pairwise comparison is identified in the record available for this analysis.

The regimens were tipranavir with ritonavir at 500 mg/200 mg once daily, 250 mg/100 mg twice daily, or 500 mg/100 mg twice daily. The stated intent was to assess steady-state pharmacokinetics together with short-term efficacy and safety in treatment-naive patients with HIV-1. An open-label design means that treatment assignment was not masked as described in the title; the registry does not provide details about any masking of outcome assessment.

The primary outcome is viral-load change from baseline (Day 0) to the final assessment (Day 14), expressed in log10 copies/mL and summarized as a median with an inter-quartile range. The stated analysis population is the Treated Set, defined as randomized participants documented to have taken at least one dose of investigational treatment. The record lists 17 outcome measures and 3 analyses. It also lists pharmacokinetic outcomes such as apparent oral clearance, area under the curve, post-dose concentrations, trough and maximum concentrations, volume of distribution, terminal half-life, and time to maximum concentration.

The registry record does not give a sample-size justification, a detailed analysis plan, or the method used to allocate participants. Although the stated enrollment and arm-level safety denominators are available, the record does not provide enough information to reconstruct the flow of participants through screening, assignment, treatment, and analysis. The completed status indicates that the study has ended; it does not establish that every planned analysis or result is posted.

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: Treated Set, includes all patients that were randomized and were documented to have received at least one dose of investigational treatment

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.

Population: Treated Set, includes all patients that were randomized and were documented to have received at least one dose of investigational treatment

6. Primary Endpoint

The registry lists the primary outcome as Viral Load (log10 Copies/mL) Change From Baseline (Last Observation Carried Forward (LOCF)), measured over Baseline (Day 0) to Final (Day 14).

The primary endpoint is the change in viral load, measured in log10 copies/mL, from baseline on Day 0 to the final assessment on Day 14. Viral load is a measure of the amount of HIV-1 genetic material detected in a sample. Expressing it on a logarithmic scale represents changes in orders of magnitude rather than equal absolute changes in copies. The endpoint therefore describes short-term change in a laboratory marker, not a long-term clinical outcome.

The registry specifies a median and an inter-quartile range. The median describes the middle of the observed distribution and is less influenced by unusually high or low values than the mean. The inter-quartile range describes the spread of the central portion of observations. These summaries can be useful when outcome distributions are skewed or contain extreme values, although the record does not state why these summaries were selected.

The endpoint uses last observation carried forward (LOCF) for the final assessment. Under this approach, an earlier observed value may be used in place of a missing final value. This defines how some missing endpoint values are handled, but the record does not state how many values were missing or when observations were carried forward. The endpoint definition is reported, but the median changes and their inter-quartile ranges for the groups are not reported in the registry record. As a result, the size and precision of the observed short-term changes cannot be described from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical information recorded for this study is limited but includes useful details about the endpoint summary, missing-data convention, and analysis population. The distinction between a stated method and a reported result is essential: the record describes how the primary endpoint was intended to be expressed, but does not give the endpoint estimates needed to judge the observed pattern.

What does a median and inter-quartile range describe?

The median is the central value when observations are ordered. It is a measure of location, not a measure of precision. The inter-quartile range describes the spread of the central portion of the observations, leaving the tails outside that range. Together, these summaries can give a useful picture of a distribution when a mean and standard deviation might be sensitive to extreme observations or skewness.

These summaries do not, on their own, provide a confidence interval for the population effect. A confidence interval is a range of values compatible with the observed data under a specified statistical procedure; it communicates uncertainty in an estimate. The registry record does not report confidence intervals for the primary outcome. Nor does it provide the group-specific medians and inter-quartile ranges. Consequently, neither the central observed changes nor their precision can be evaluated from the posted primary outcome information.

How should the change score be understood?

The endpoint is a change from baseline to the final assessment, rather than a final viral-load value alone. A change score expresses how an individual or group moved relative to its starting measurement. The endpoint is on the log10 copies/mL scale, so interpreting it requires attention to the logarithmic scale. No conversion to an absolute number of copies is necessary to understand the registry’s stated measure, and no such conversion is reported.

A group-level change does not by itself show how individual participants changed. A median can conceal variation in the direction and size of individual responses, which is one reason the accompanying spread measure matters. A comparison of group changes would also require a defined analysis and uncertainty estimate. The registry record does not state a formal comparison for the primary endpoint or report inferential results.

What does LOCF do?

Last observation carried forward uses a participant’s last available measurement as a substitute for a missing later measurement. It creates a complete value for the specified endpoint under that convention, but it does not recover an unobserved measurement. The approach can be problematic when the unobserved value would likely differ from the earlier one, or when missingness is related to participants’ outcomes. The assumption behind carrying a value forward is not tested merely by applying the method.

The registry record specifies LOCF but does not report how many final observations were missing, how many values were carried forward, or the reasons for missingness. It also does not report a sensitivity analysis using a different missing-data approach. Therefore, the impact of LOCF on the endpoint estimates cannot be assessed. A missing-data method is part of the analysis definition, but it cannot substitute for reporting the missingness pattern and the resulting estimates.

What is the Treated Set?

The primary outcome population is defined as participants who were randomized and documented to have received at least one dose of investigational treatment. This definition excludes people who were randomized but did not receive treatment, if any such participants existed. The record does not report how many participants were excluded on that basis or give a participant flow for the primary analysis.

Analysis populations answer different questions. A population based on treatment received can differ from one that retains participants according to their assigned group, especially when treatment is not started or is discontinued. The registry record defines the Treated Set but does not report a separate intention-to-treat analysis or explain whether any other populations were used for efficacy or pharmacokinetic outcomes.

What can planning calculations say?

A sample-size planning illustration can show how a hypothetical future study might be sized under stated assumptions. The assumptions recorded for such an illustration include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is expressed as a stated fraction of an observed effect. These are planning assumptions, not evidence about the original trial’s design.

Such calculations depend on the selected effect size and statistical assumptions. They do not establish that the study had a particular probability of detecting an effect, and they are not observed power. The registry record does not report the original sample-size justification or the assumptions used to plan this trial. Planning counts should therefore be interpreted only as illustrations for a hypothetical design, not as results from the trial or proof that a clinical effect was present.

Why does over-dispersion matter in general?

In general, over-dispersion occurs when observed variability is greater than a statistical model expects. If a model assumes less variation than the data contain, standard errors can be too small and uncertainty can be understated. The registry information available for this analysis does not identify an over-dispersion model or indicate that over-dispersion was assessed. This concept is relevant only when a model’s assumptions and outcome type call for it; it should not be presumed to apply to this study’s median-based primary endpoint.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists 17 outcome measures and 3 analyses. It does not report a multiplicity adjustment, a hierarchy of outcomes, or a complete prespecified statistical analysis plan. When a study evaluates multiple outcomes or makes multiple comparisons, the chance of at least one false-positive finding can increase if each result is interpreted in isolation. Adjustment strategies or a clearly defined hierarchy can help address that issue, but their use in this study is not reported in the registry record.

The primary outcome is identified as viral-load change from baseline to Day 14, while a range of pharmacokinetic outcomes is also listed. The record does not explain whether these outcomes were tested inferentially, which analyses were considered confirmatory, or whether comparisons between the three regimens were prespecified. Without those details, the relative emphasis placed on any reported result cannot be determined. The available information does not support treating any one result as statistically definitive based on a multiplicity strategy.

For missing data, the primary endpoint specifies LOCF. The record does not report the amount or pattern of missingness, reasons for missing measurements, or sensitivity analyses. It also does not say whether other outcomes used the same missing-data approach. These omissions limit assessment of whether the reported analysis population and endpoint handling could affect the interpretation of results.

The primary population is the Treated Set, defined by randomization and receipt of at least one dose. The record does not report a participant flow or results for any alternative analysis population. A reader therefore cannot determine how closely this population corresponds to all randomized participants or whether analyses using different population definitions would lead to similar conclusions. Neither the original sample-size justification nor a detailed interim-analysis plan is reported in the registry record.

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

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: alanine aminotransferase increased (3.6%), aspartate aminotransferase increaset (3.6%).

The serious adverse-event counts are listed by regimen among participants at risk. In the 500 mg/200 mg once-daily group, 0 of 30 participants were affected; in the 250 mg/100 mg twice-daily group, 0 of 25 were affected; and in the 500 mg/100 mg twice-daily group, 1 of 28 was affected. These counts describe participants with at least one serious adverse event according to the registry summary. They do not describe the total number of serious events or their duration.

Other adverse events affected 17 of 30 participants in the once-daily group, 9 of 25 in the 250 mg/100 mg twice-daily group, and 15 of 28 in the 500 mg/100 mg twice-daily group. These are counts, and the record does not provide a formal statistical comparison of the regimens. The counts alone cannot establish that one regimen is safer or less safe than another.

The registry lists alanine aminotransferase increased and aspartate aminotransferase increaset among the leading serious-event terms, each at 3.6%. The spelling of the latter term follows the registry listing. Deaths are not reported in the registry record. Further detail about event timing, severity, recurrence, and treatment-relatedness is not reported in the registry record, so these summaries should be read as limited descriptive safety information.

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

This study addresses a defined dose-finding question in treatment-naive patients with HIV-1: it evaluates three tipranavir and ritonavir regimens with attention to pharmacokinetics and short-term efficacy and safety. Its primary endpoint is a short-term change in viral load, summarized as a median and inter-quartile range using LOCF. The registry record also identifies a set of pharmacokinetic outcomes and provides limited adverse-event counts.

The endpoint definition does not reveal the outcome. The group-specific viral-load changes, their inter-quartile ranges, and inferential results are not reported in the registry record. Consequently, the posted results available for this analysis do not show whether viral load changed in any particular direction, how large any change was, or how the regimens compared. Pharmacokinetic estimates are also not reported in the record available for this analysis, so the dose regimens cannot be ranked by exposure or other pharmacokinetic properties from these details.

Likewise, the adverse-event counts do not establish comparative safety. They are descriptive summaries from a short-term study, and the record does not report a formal safety comparison or the detail needed to characterize all events. The absence of a reported serious event in a group is not proof that no such risk exists; it is a count from the recorded study population and follow-up. Deaths are not reported in the registry record.

The study’s design description and its incomplete details also limit causal interpretation. The official title calls the study randomized, but allocation is not stated in the registry record, and no formal like-for-like control comparison is defined. The available information therefore does not support a claim that one regimen caused a better or worse outcome than another. Nothing in these findings establishes long-term effects, results beyond the listed short-term endpoint, or whether any regimen should be used in practice.

13. Why This Trial Matters Statistically

The study is statistically informative as an example of the difference between a clearly defined research question and a fully interpretable result. The registry identifies a dose-finding objective, three regimens, a primary endpoint, a summary measure, a missing-data convention, and an analysis population. Those elements help a reader understand what was intended to be measured. Yet without the endpoint estimates, uncertainty measures, and a stated comparison plan, the central efficacy question remains unanswered in the posted registry information.

The study also combines distinct kinds of evidence. Pharmacokinetic outcomes describe drug exposure and related characteristics, while viral-load change is a short-term biological outcome and adverse-event counts describe safety observations. Each has a different interpretation and may require different statistical methods. Their inclusion in one trial does not make them interchangeable, and a pharmacokinetic finding would not by itself establish a clinical outcome.

Multiplicity and missing data matter because the record lists several outcomes and analyses, and specifies LOCF for the primary endpoint. The absence of a reported multiplicity plan, missingness pattern, and sensitivity analyses makes it difficult to assess robustness. The Treated Set definition also clarifies that the primary analysis concerns participants who received treatment, while the record does not report the flow needed to evaluate how that set relates to all randomized participants.

Finally, this study illustrates why planning calculations must be separated from observed evidence. A hypothetical sample-size illustration can support design discussions under stated assumptions, but it cannot fill gaps in a trial’s posted results or demonstrate that an effect was detected. Statistical interpretation depends on the estimates, uncertainty, analysis choices, and design details; the registry record reports some of these elements, but not all of them.

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 primary limitation for interpreting efficacy is that the registry record defines the viral-load endpoint but does not report its group-level values. The median change and inter-quartile range are not available in the information for this analysis, and no confidence interval or p-value is reported. Thus the central endpoint cannot be interpreted quantitatively, and the three regimens cannot be compared on the primary outcome.

The design description leaves important details unresolved. The official title describes a randomized study, but the registry record does not state the allocation method. It also does not define a formal comparator or pairwise analysis. The study is open label according to its title, while further information about outcome assessment is not reported in the registry record. These details constrain how confidently differences between regimen groups could be attributed to treatment, even if group-level outcomes were available.

The registry record does not report the original sample-size justification, a detailed statistical analysis plan, or a multiplicity strategy. Although the record lists 17 outcome measures and 3 analyses, it does not explain which comparisons were prespecified or how multiple outcomes were handled. Nor does it report whether interim analyses were conducted. The missing-data information is also limited: LOCF is specified for the primary endpoint, but the amount and pattern of missingness and any sensitivity analyses are not reported.

The safety summaries are limited to counts of participants affected and a short list of leading serious-event terms. Event-level context, follow-up detail, and deaths are not reported in the registry record. The listed enrollment and safety denominators do not, by themselves, describe participant flow or establish the analysis sample for each endpoint. These limitations mean that the available registry information supports description of the study’s stated aims and selected safety counts, but not a complete statistical assessment of efficacy, pharmacokinetics, or comparative safety.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Tipranavir/Ritonavir Low Dose Pharmacokinetics in Treatment Naive Patients — NCT00530920.
• Registry record last updated 2014-06-06; status last verified 2014-05.
• Results first posted 2009-07-08.
• 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

NCT00530920 is a completed phase 2, parallel-group study sponsored by Boehringer Ingelheim. The official title describes a multicenter, randomized, open-label trial of three tipranavir and ritonavir regimens in treatment-naive patients with HIV-1. Listed enrollment is 85; the study start is 2007-10 and primary completion is 2008-05. The registry record does not state the allocation method.

The primary endpoint is median change in viral load, in log10 copies/mL, from Day 0 to Day 14, using LOCF in the Treated Set. The endpoint results and pharmacokinetic estimates are not reported in the registry record. Safety summaries list serious adverse events affecting 0, 0, and 1 participants across the three regimen groups, and other adverse events affecting 17, 9, and 15 participants. The record lists 17 outcome measures and 3 analyses, but does not report the original sample-size justification, a full statistical plan, or a multiplicity strategy.