Truvada Plus Raltegravir for Nonoccupational Post-exposure Prophylaxis (nPEP): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Truvada Plus Raltegravir for Nonoccupational Post-exposure Prophylaxis (nPEP) (NCT01214759), a na phase 4 study. The primary outcome is Efficacy as Assessed by the Number of Participants Who Were HIV Positive at 6 Months.

2. Clinical Question

The clinical question is therefore descriptive: among the study population defined by completion of all visits, what number of participants was recorded as HIV-positive at the six-month assessment after the 28-day drug course? The registry’s purpose statement focuses on safety and tolerability as well as prevention of HIV infection. Those aims are not interchangeable. The count of participants with a six-month HIV-positive result addresses the stated prevention outcome, while clinical or laboratory abnormalities and completion of the course address tolerability and safety.

Without a concurrent comparator, this study cannot directly estimate how the outcome differs from what would have occurred under another prophylaxis strategy or no prophylaxis. The primary measure can describe outcomes among participants in this arm, but it cannot by itself establish a treatment effect. The record does not report the number of HIV-positive participants, the number assessed for the primary outcome, or a statistical estimate for the outcome. Those missing results prevent a quantitative answer to the primary question from the registry record alone.

3. Trial Design

The registry identifies NCT01214759 as a completed Phase 4 study sponsored by The University of Texas Health Science Center, Houston. The recorded enrollment is 103. The study start is listed as 2011-05 and primary completion as 2013-12. These record details describe the registered study; they do not supply results for its primary outcome.

The design is single-group, with Truvada and raltegravir listed together as the intervention. The arm description calls this a single arm. Allocation is recorded as not applicable, and masking is recorded as none. There is therefore no randomized allocation or masked comparison described in the registry record. The study summary says that the combination was given for 28 days to evaluate safety and tolerability for HIV prevention following exposure.

The primary outcome is the number of participants who were HIV-positive at six months. Its listed population is all who completed all study visits. Two secondary outcomes are also listed: participants exhibiting clinical or laboratory abnormalities resulting from the 28-day exposure, and participants who completed the 28-day course. The record states that there are three outcome measures in total, including the primary measure.

A single-group design can record outcomes observed after treatment, but it does not supply a concurrent counterfactual. Without a control arm, differences from an untreated or alternative-treatment group are not measured within this study. The lack of masking may also matter when interpreting outcomes that involve judgment or reporting, although the registry does not describe how outcome assessments were conducted. Details of eligibility, recruitment, follow-up procedures, and the methods used to verify HIV status are not reported in the registry record.

The registry records no analyses. It does not report an analysis population beyond the primary outcome’s description of participants who completed all visits, or explain how other participants were handled. The recorded enrollment, design, and outcome definitions therefore establish the setting and intended questions, but they do not fill in the missing outcome counts or analysis details.

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: All who completed all study visits

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: All who were enrolled

6. Primary Endpoint

The registry lists the primary outcome as Efficacy as Assessed by the Number of Participants Who Were HIV Positive at 6 Months, measured over 6 months.

The primary endpoint is the number of participants who were HIV-positive at six months. The registry describes it as an assessment of whether the Truvada and raltegravir combination prevents HIV acquisition among HIV-negative people exposed to HIV. The stated population is all who completed all study visits. The endpoint is a binary event at the participant level: a participant is counted according to whether the specified HIV-positive outcome is present at the six-month assessment.

Using a defined assessment time gives the outcome a consistent point of reference. In general, a binary endpoint can be summarized by the number of participants with the event and the number assessed, and may also be expressed as a proportion or modeled with methods for binary data. Those summaries need an explicit denominator and a clear account of missing assessments. The registry record does not report the primary event count, the number assessed, or an estimate with uncertainty, so none of these quantities can be described for this study.

The endpoint is relevant to the stated prevention question, but its interpretation depends on how the six-month status was determined and which participants were included. Those procedures are not reported in the registry record. The listed analysis population includes only those who completed all study visits, which is narrower than an analysis of everyone enrolled if some participants did not complete follow-up. The record does not state whether any additional analyses used a different population.

This endpoint describes observed HIV status in the study arm. Because the study has no concurrent comparator, the endpoint alone cannot show how the outcome would compare under another strategy. It also should not be confused with the secondary measures of clinical or laboratory abnormalities and completion of the 28-day course; those address different aspects of the study aims.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The design information supports a limited set of statistical interpretations. The study is described as single-group, with allocation not applicable and no masking. A single-group study records outcomes in participants who receive the intervention but does not create a concurrent comparison group. Random allocation, when present, is a method for making comparison groups more alike on average with respect to both known and unknown factors. That feature is not described. Thus, a comparison of observed outcomes with an external expectation would require information and assumptions beyond the registered design.

What does a binary endpoint represent?

The primary endpoint counts participants with a specified event: HIV-positive status at six months. Binary outcomes distinguish whether an event is present or absent for each assessed participant. Common descriptive summaries include the event count and the denominator, along with a proportion. If the outcome is modeled, the choice of effect measure and model should match the scientific question and study design. A single-group binary outcome may be described as an observed event frequency, but without a comparator it is not a between-group treatment effect.

For this endpoint, both the numerator and denominator are needed for a meaningful frequency. The record does not report either the six-month event count or the number assessed. The enrollment recorded as 103 cannot be assumed to be the denominator: the primary outcome population is stated as participants who completed all study visits, and the number completing visits is not reported. No proportion should be inferred from the enrollment figure.

How should uncertainty be understood?

A point estimate is an estimate of an underlying quantity from observed data. A confidence interval expresses uncertainty around an estimate under specified statistical assumptions; it is not a guarantee that the true value lies within the interval. For a binary event, uncertainty depends on the event count, the number assessed, and the method used to form the interval. The registry record reports no primary estimate or confidence interval, so the precision of the outcome cannot be evaluated.

Hypothesis tests and p-values address compatibility between data and a stated null model under the assumptions of the test. Their interpretation requires knowing the hypothesis, analysis population, model, and testing plan. None of these primary-outcome analysis details is reported in the registry record, and the record lists zero analyses. No conclusion about statistical significance can be drawn from an absent analysis.

Why does the single-group design matter?

In a randomized comparison, treatment groups can be compared using an analysis that reflects the allocation and the chosen outcome measure. In this study, only one arm is listed. Any observed event count would describe that arm during the defined follow-up, but would not directly estimate a contrast against another approach. Historical or external comparisons can be informative in some settings, but they require comparable populations, outcome definitions, follow-up, and other assumptions. No external comparator or such analysis is described in the registry record.

No masking is recorded. In general, masking can reduce the influence of knowledge of treatment assignment on some outcome assessments and participant reports. Its relevance depends on how an outcome is measured. The registry record does not describe assessment procedures for HIV status or adverse outcomes, so the practical effect of the absence of masking cannot be evaluated.

What do the planning assumptions mean?

The registry’s sample-size assumptions describe a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. These are assumptions for planning illustrations, not evidence that the trial itself used that design. The registered study is single-group, so the equal-allocation, two-arm illustration does not describe its actual allocation. The record does not report a trial-specific sample-size justification or the resulting planning values. Such planning values are not observed power and do not establish the probability that a completed study detected an effect.

Planning illustrations are conditional on their assumptions. A target effect, significance level, allocation, and statistical approximation determine the interpretation of a calculated sample-size requirement. If the effect used for planning is estimated from observed data, that estimate itself can be uncertain. A planning calculation cannot replace reporting the observed outcome, its denominator, and its uncertainty. The record does not explain a sample-size rationale for this study or identify an analysis that would connect the illustration to the registered single-group design.

How do missing outcomes affect interpretation?

When some participants do not have an outcome assessment, the observed cases may differ from those without an assessment. The effect of missing data depends on why information is missing and on the analysis strategy. Good reporting distinguishes enrollment, follow-up completion, and the population included in each analysis. Here, the primary outcome population is described as participants who completed all visits, but the count in that population and the handling of other participants are not reported. No imputation, sensitivity analysis, or missing-data assumption is described.

Over-dispersion is a general concern for some count outcomes: observed variability can exceed what a simple model assumes, affecting standard errors and intervals. It is not a feature that can be assessed from the primary endpoint as described, which is a participant count for a binary status, and no model or analysis is reported. The registry does not report a statistical plan sufficient to determine the methods used for any endpoint. Interpretation should therefore remain descriptive and limited to the information actually recorded.

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("Truvada and Raltegravir")
n      <- c(55)
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  Truvada and Raltegravir  55  0  0.0  0.0  6.5  0.0  6.5  0.0  6.4

11. Multiplicity, Missing Data and Analysis Populations

The registry lists the primary HIV-positive outcome at six months and two secondary outcomes: clinical or laboratory abnormalities from the 28-day exposure, and completion of the 28-day course. Considering multiple outcomes can raise multiplicity concerns. In general, when several hypotheses are tested, the chance of at least one apparently positive result may increase if each is assessed independently at a conventional threshold. Analysis plans may address this through a hierarchy of outcomes or other methods, but no such plan is reported in the registry record.

The record lists zero analyses and does not report p-values, confidence intervals, adjustment procedures, or a testing hierarchy. It is therefore not possible to determine whether any multiplicity strategy was prespecified or used. The absence of reported tests also means there are no reported significance findings to interpret across the outcomes.

Missing-data handling is likewise not reported. The primary outcome population is described as all who completed all study visits, but the number who completed visits, the number with six-month status, and reasons for any missing assessments are not reported. The registry does not state whether participants without complete follow-up were excluded, included through another method, or examined in sensitivity analyses. The enrollment figure alone cannot identify the denominator for the primary result.

Analysis populations are not described beyond the primary outcome population statement. The record does not specify whether safety outcomes were analyzed among all enrolled participants, participants who received treatment, or another group. It also does not state how protocol deviations or incomplete treatment courses were handled. These omissions limit reproducibility and make it difficult to judge whether each outcome reflects the same participants. They also prevent evaluation of possible bias from excluding people without complete follow-up.

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 non-serious adverse event terms

The safety display records the Truvada and raltegravir arm with 85 participants at risk in the serious category and 0 participants affected. It also records 85 participants at risk in the other category and 8 participants affected. These are participant counts as entered in the registry record; the categories should not be treated as interchangeable with the primary HIV outcome or with the separately listed secondary outcomes.

The record does not provide serious-event terms, and the list of top serious terms is empty. It does not explain the event definitions, collection window, severity grading, or whether the counts refer to participants with at least one event. The death count is null, which means deaths are not reported in this record; it should not be read as a reported count of zero. The display also does not give details about the other events or their relationship to treatment.

These figures are limited to the recorded safety categories and do not establish the absence of all adverse effects. They cannot be used to compare safety with another regimen because the study has no concurrent comparator. The registry’s secondary outcomes describe clinical or laboratory abnormalities and course completion, but their results are not reported in the record. The safety counts should therefore be read as narrow descriptive entries, not as a complete account of tolerability or a comparative safety estimate.

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

The registry record establishes that a completed Phase 4, single-group study evaluated Truvada plus raltegravir as a 28-day post-exposure prophylaxis course. It specifies a six-month outcome based on the number of participants who were HIV-positive and describes the relevant population as those completing all study visits. It also identifies safety, tolerability, and completion outcomes. These details describe what the study set out to assess.

The record does not report the primary outcome count, the number assessed at six months, or an estimate of uncertainty. It therefore does not establish from the posted results how many participants were HIV-positive at the assessment or how precise an estimate would be. The completed status and recorded enrollment do not supply those missing results. Nor do the safety counts answer the primary prevention question.

The study design also constrains what can be concluded. A single arm without a concurrent comparator can describe observed outcomes in that arm, but it cannot measure a direct difference against another prophylaxis approach or a control condition. A treatment effect requires a comparison and assumptions about how groups relate to each other. No comparative analysis is reported in the registry record.

These limitations do not show that the intervention did or did not prevent HIV infection. They mean that the registered information available for this analysis is insufficient to make a quantitative claim about that outcome or a comparative claim about benefit. The distinction is important: an aim to assess prevention is not itself an outcome result, and an unreported result should not be interpreted as no events.

The available safety entries are also limited. The record reports participants affected in serious and other categories, but does not give terms for serious events or report deaths as a numeric count. It does not provide the fuller outcome results needed to assess safety and tolerability. Readers should interpret the record as a description of the design and selected recorded counts, not as a comprehensive efficacy or safety conclusion.

14. Why This Trial Matters Statistically

This study illustrates why a registered objective, a design, and a result are different kinds of evidence. The registry identifies HIV status at six months as the primary outcome and gives a target population description, but does not report the observed outcome. Without the count and denominator, a reader cannot estimate the event frequency or its precision. Without a comparator, even a fully reported count would remain a description of one study arm rather than a direct estimate of a difference between strategies.

The design also makes the distinction between prevention intent and causal inference visible. A treatment may be studied with the goal of prevention, but estimating how outcomes differ because of treatment generally requires a suitable comparison and an analysis aligned with that design. The record’s single-group structure does not provide an internal comparison. This does not invalidate descriptive information; it defines the question that the design can answer.

Reporting matters for safety as well as efficacy. The registry gives participant counts for serious and other categories, but does not report serious-event terms, a numeric death count, or the results of the listed course-completion and clinical or laboratory abnormality outcomes. Such omissions limit readers’ ability to understand what the recorded counts represent and how completely outcomes were captured.

Finally, the record illustrates the importance of analysis transparency. It lists no analyses and does not report how missing follow-up, multiple outcomes, or analysis populations were handled. Statistical interpretation depends on these choices, not only on a study’s title or stated aim. Clear outcome counts, denominators, uncertainty estimates, and prespecified analysis details would be needed for a fuller assessment. In their absence, the disciplined interpretation is to distinguish what is registered from what remains unreported.

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.

Several limitations are specific to the information recorded for this trial. First, the primary endpoint result is absent: the registry record gives neither the number HIV-positive at six months nor the number assessed. Although enrollment is recorded as 103, the primary population is defined as people who completed all visits, and its size is not reported. This prevents calculation or assessment of the primary event frequency.

Second, the single-group design has no concurrent comparator. The record therefore cannot provide a randomized, like-for-like estimate of how outcomes differed from another strategy. Allocation is not applicable, and masking is listed as none. The record does not describe how outcome assessment was conducted, so the implications of the lack of masking cannot be further evaluated.

Third, the registry lists secondary safety and completion outcomes without reporting their results. The serious-event display has no listed serious terms, while the death count is not reported. The meaning and collection rules for the other category are also not specified. These gaps limit interpretation of the selected safety counts and do not permit a comprehensive account of tolerability.

Finally, the record does not report a statistical analysis plan, details of missing-data handling, an outcome hierarchy, or the analysis populations beyond the primary outcome’s completion-based description. It lists zero analyses. The planning assumptions describe a two-arm illustration, while the registered trial is single-group; no trial-specific sample-size justification is reported. These limitations leave the primary result, its precision, and the rationale for its analysis unclear in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Truvada Plus Raltegravir for Nonoccupational Post-exposure Prophylaxis (nPEP) — NCT01214759.
• Registry record last updated 2016-02-08; status last verified 2016-01.
• Results first posted 2016-02-08.
• 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.

19. Record Summary

NCT01214759 is a completed Phase 4, single-group study sponsored by The University of Texas Health Science Center, Houston. The registry records enrollment as 103, a start date of 2011-05, and primary completion in 2013-12. The intervention was Truvada plus raltegravir, described as a 28-day course for post-exposure prophylaxis. Allocation is not applicable, and masking is listed as none.

The primary outcome is the number of participants HIV-positive at six months among those who completed all study visits. Two secondary outcomes concern clinical or laboratory abnormalities and completion of the 28-day course. The primary result and secondary outcome results are not reported in the registry record. The safety display records 0 participants affected in the serious category and 8 in the other category, with deaths not reported. The record lists zero analyses and provides no concurrent comparator.