A Prospective, Longitudinal Study of Endothelial Function in HIV/HCV Coinfected Subjects: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Prospective, Longitudinal Study of Endothelial Function in HIV/HCV Coinfected Subjects (NCT02597790), a registered phase not stated study. The primary outcome is Reactive Hyperemia Index (RHI) by Peripheral Arterial Tonometry (PAT).

2. Clinical Question

The clinical question has two related but distinct parts: whether cardiovascular risk measures differ between people with HIV/HCV coinfection and those with HIV alone, and how those measures change during follow-up. The registry describes measurements of endothelial function and blood biomarkers at baseline and 1 year. For participants undergoing HCV treatment during follow-up, it describes measurements 4 weeks and 24 weeks after treatment ended. These schedules do not, by themselves, establish that every participant had each assessment or that the measurements were analyzed as a particular comparison.

The primary endpoint is a baseline measure, whereas the study summary also describes longitudinal follow-up and the secondary outcomes include change in RHI. The record does not specify a primary between-group contrast, a model for repeated measures, or a result for a change over time. Consequently, the stated clinical aim should not be read as evidence that the registry establishes an effect of coinfection, or an effect of HCV treatment, on cardiovascular risk.

3. Trial Design

The study is titled A Prospective, Longitudinal Study of Endothelial Function in HIV/HCV Coinfected Subjects. Its official title describes a prospective longitudinal assessment of people coinfected with HIV and hepatitis C. The brief summary also includes people with HIV alone. The University of California, Los Angeles is listed as the sponsor. The registry records a start date of 2013-10, primary completion in 2019-01, a status of COMPLETED, and enrollment of 87.

The registry describes two groups: Group A, HIV/HCV coinfected, and Group B, HIV monoinfected. The arm descriptions are blank. Allocation is not stated, and the record identifies the study as not a randomized comparison. The groups therefore should not be treated as randomized treatment arms or assumed to be balanced in participant characteristics. The record also cautions that the arms are not a like-for-like control comparison.

Assessments were intended to include non-invasive cardiovascular risk measures, including endothelial function and blood biomarkers. The brief summary describes measurements at baseline and 1 year. For participants who underwent HCV treatment during study follow-up, it describes follow-up at 4 weeks and 24 weeks after the end of treatment. The record does not say how many participants underwent treatment, how many completed each assessment, or whether the follow-up schedule differed for other reasons.

The registry lists RHI by peripheral arterial tonometry as the primary outcome, with a baseline timeframe. Secondary outcomes include soluble biomarkers, insulin resistance by HOMA-IR, Framingham Risk Score (FRS), 10-year Risk (%), and RHI, including change in RHI. Some secondary outcome labels appear more than once in the record. The meaning of those repeated entries is not explained. Although the record lists 12 outcome measures, it lists 0 analyses. Numeric outcome results, participant flow, and a detailed statistical analysis plan are not reported in the registry record.

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

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 Reactive Hyperemia Index (RHI) by Peripheral Arterial Tonometry (PAT), measured over Baseline.

The primary endpoint is the Reactive Hyperemia Index (RHI), measured by peripheral arterial tonometry (PAT) at baseline. The registry describes it as a ratio: the average pulse wave amplitude (PWA) over a 1 minute interval starting 1 minute following cuff release divided by the pre-occlusion PWA, averaged over 3.5 minutes before cuff inflation. The endpoint is reported in ratio units, with the stated summary parameter being the median and the dispersion measure being the inter-quartile range.

In general, RHI is used as a non-invasive measure of the change in pulse wave response following temporary cuff occlusion and release. A ratio expresses the post-release response relative to the pre-occlusion reference. The median describes the middle of the observed distribution, while the inter-quartile range describes its central spread. These summaries can be useful when a distribution is not well represented by a mean and standard deviation, but the registry does not state why this summary approach was selected for this study.

The endpoint’s baseline timeframe matters for interpretation: it describes a measurement at the start of follow-up, rather than a reported change over time. The registry record does not report the median, inter-quartile range, number of participants with an available RHI measurement, or a comparison between groups. It therefore documents how the primary measure was defined, but does not provide the outcome values needed to assess the observed distribution or any difference.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the primary summary describe?

The primary outcome is specified as a median with an inter-quartile range. In general, the median is the value at the center of an ordered distribution. The inter-quartile range describes the spread of the middle half of that distribution. These summaries focus on the location and spread of observed values without requiring a symmetric distribution. They do not quantify uncertainty in a group comparison in the way a confidence interval for a contrast would. No such contrast or interval is reported in the registry record.

RHI is defined as a ratio of a post-cuff-release pulse wave amplitude measure to a pre-occlusion measure. A ratio makes the post-release response relative to a participant’s reference measurement. In general, measurement procedures and timing matter because changes in the signal can reflect both the response and the way the reference is obtained. The record specifies the measurement windows, but does not report quality-control procedures, repeatability information, or how incomplete or technically unusable measurements were handled.

What can an observational group comparison establish?

In general, an observational comparison describes associations between group membership and measured outcomes. Group membership is not randomly assigned in the study description, and the registry states that allocation is not stated. Differences in measured outcomes could therefore be associated with differences between the groups that were already present, as well as with HIV/HCV status. Random assignment can help balance measured and unmeasured factors on average; it is not described. This does not make an observational study uninformative, but it limits causal interpretation and makes the analytic approach and participant characteristics important.

The registry does not specify covariate adjustment, matching, stratification, or another approach to account for differences between groups. It also does not report a prespecified comparison or an estimated effect. It is therefore not possible to say whether any reported estimate would be unadjusted or adjusted, what factors would be included, or how the non-randomized group structure would be reflected in the analysis.

How should longitudinal measurements be understood?

In general, repeated measurements from the same participant are statistically related. An analysis of change or trajectories should account for that within-person dependence rather than treating every measurement as independent. A repeated-measures model can estimate patterns over time while representing the correlation among a participant’s observations. The choice of model depends on the outcome, timing, and estimand. The registry record does not report a longitudinal model, a definition of the primary time contrast, or an estimate of change.

Follow-up is described at baseline and 1 year, with a separate schedule of 4 weeks and 24 weeks after HCV treatment for participants who underwent treatment during follow-up. These are distinct timing descriptions, and the record does not explain how they were combined analytically. In general, differences in observation times can complicate direct comparisons. A model might use actual time, scheduled visits, or a defined contrast between selected time points, but no such choice is reported for this study.

What do the planning assumptions mean?

The registry’s sample-size assumptions are explicitly planning illustrations based on an observed effect, not the trial’s own design. They use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The planning effect is expressed as a stated fraction of the observed effect. For non-time-to-event outcomes, the illustrations are participants per arm; for time-to-event outcomes, they are total events under the Schoenfeld approach.

In general, a sample-size calculation asks how much information might be needed to detect a specified effect under stated assumptions. Its answer depends on the effect size, variability, chosen error rate, allocation, and model assumptions. It is not a measure of the probability that the completed study found a real effect. The planning illustrations should not be described as observed power, and the record does not report the study’s own sample-size justification, target power, or design calculations.

Equal allocation is an assumption for the planning illustrations, not evidence that the observed groups were equal in size. The registry gives total enrollment of 87 but not the number assigned or enrolled in either group or the number with measurements for an endpoint. The normal approximation is another planning assumption, not a statement about the distribution of the observed RHI values. The record does not provide enough information to assess whether the assumptions fit the enrolled sample.

What is absent from the reported analysis?

The registry lists 12 outcome measures and 0 analyses. It does not report test procedures, effect estimates, confidence intervals, p-values, model diagnostics, or handling of multiple outcomes. General statistical interpretation depends on these details as well as on the numerical results. Without them, the study’s planned measurements can be described, but the statistical evidence for a particular comparison cannot be evaluated.

Over-dispersion is a general concern when count data vary more than a model assumes; it can make standard errors too small if not addressed. The registry record does not report an outcome analysis based on counts or a model for which over-dispersion can be assessed. This is therefore a general statistical consideration, not a reported feature or problem in this study.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple outcome measures, including soluble biomarkers, RHI, insulin resistance by HOMA-IR, and Framingham Risk Score (FRS), 10-year Risk (%). Some outcome labels are repeated, and the record does not explain whether the repeated entries represent different groups, time points, or other distinctions. The record identifies RHI by PAT at baseline as the primary outcome, but does not describe a hierarchy among the secondary outcomes or specify which comparisons were confirmatory.

In general, when many outcomes or comparisons are examined, the chance of at least one apparently unusual result can increase. Statistical plans may address this through a prespecified hierarchy, adjustment procedures, or an explicitly exploratory interpretation. No multiplicity approach is reported in the registry record. Because outcome results and analyses are not posted, the practical effect of any multiplicity issue cannot be assessed.

Missing-data handling is also not reported in the registry record. The enrollment total does not establish how many participants had a baseline RHI measure, completed follow-up, or contributed to each biomarker outcome. The record does not report reasons for missing measurements, attrition by group, imputation, or sensitivity analyses. In general, missingness can affect estimates when the probability of an observation being missing is related to participant characteristics or outcomes. Whether that concern arose in this study cannot be determined from the registry information.

The analysis populations are not described. The record does not say whether analyses included all enrolled participants, only participants with complete measurements, or another defined population. Nor does it report whether participants were analyzed according to group membership at enrollment or according to later treatment status. These distinctions matter for interpreting an estimate, especially when follow-up timing depends on HCV treatment. Without the population definitions and analysis details, the registry record does not support a reconstruction of the statistical analysis.

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

The registry record establishes that a prospective longitudinal study was conducted in people with HIV/HCV coinfection and people with HIV alone, with planned assessment of endothelial function and blood biomarkers. It defines baseline RHI as the primary outcome and describes the measurement procedure and summary approach. It also describes follow-up assessments at baseline and 1 year, with a separate post-treatment schedule for participants who underwent HCV treatment during follow-up.

It does not report the observed RHI values, secondary outcome values, group-specific summaries, or statistical analyses. Accordingly, the record does not establish the direction or size of any difference between the groups, the amount of change over time, or the precision of an estimate. The completed status and enrollment of 87 are not substitutes for endpoint-specific results.

The study’s non-randomized group structure also limits what a comparison could establish. In general, an association between group membership and an outcome does not by itself show that group membership caused the difference. Other group characteristics may be related to both group status and cardiovascular measurements. The registry record does not report an adjustment strategy or enough participant information to assess that possibility.

The study description should not be interpreted as demonstrating an effect of HCV treatment. Treatment was not described as randomly assigned, and the record does not report how treatment decisions were made, how many participants received treatment, or a treatment-effect analysis. A post-treatment measurement schedule is a description of follow-up, not a result or causal comparison.

Finally, the sample-size illustrations are not evidence about the information achieved by the study or its likelihood of finding an effect. They are planning calculations under stated assumptions. Since the registry record does not post outcome estimates, intervals, or analyses, no conclusion about statistical significance or clinical importance is supported by this record alone. The appropriate interpretation is limited to the study design and endpoint definitions that are documented.

12. Why This Trial Matters Statistically

The study addresses a statistical problem common in clinical research: separating a group association from a causal effect when participants are not randomly assigned to groups. Comparing people with HIV/HCV coinfection with people who have HIV alone may describe differences in cardiovascular measures, but interpretation depends on who entered each group, how their characteristics differ, and how the analysis handles those differences. The registry does not report these details, which makes the distinction between a study question and a supported conclusion especially important.

It also combines a baseline primary endpoint with a longitudinal study description. Baseline RHI can characterize the distribution at one point in the measurement schedule. Longitudinal outcomes address a different question: how measurements change over time and whether patterns differ across groups. Those questions generally call for clearly defined contrasts and methods that account for repeated observations. Such analysis details and results are not reported in the registry record.

The registry includes several kinds of outcome measures, from endothelial function to biomarkers, insulin resistance, and estimated cardiovascular risk. In general, multiple outcomes can broaden the scientific picture but also create choices about outcome priority and multiplicity. A clear analysis plan helps distinguish primary tests from exploratory findings. The record names a primary endpoint but does not report how secondary outcomes or multiple comparisons were handled.

These features make the distinction between measurement, analysis, and inference central. The registry specifies what was intended to be measured and gives some timing and summary details. It does not provide the estimates needed to judge the observed data. This is a useful reminder that a registered outcome and a completed study do not, by themselves, convey the statistical evidence for a clinical claim.

13. 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 registry record leaves important design and analysis details unspecified. It does not report the number of participants in each group, group characteristics, participant flow, endpoint-specific denominators, or the number completing each scheduled assessment. Total enrollment of 87 therefore cannot be used to infer the amount of data available for any outcome.

The two groups are not described as randomized or like-for-like controls, and allocation is not stated. The record does not report a strategy for addressing baseline differences or potential confounding. Arm descriptions are blank, so the registry provides limited detail about how each group was defined beyond its HIV/HCV status.

Outcome reporting is another substantial limitation. Although 12 outcome measures are listed, 0 analyses are listed, and numerical outcome results are not reported in the registry record. The record does not provide the observed RHI median or inter-quartile range, secondary outcome estimates, uncertainty intervals, or tests. It also does not explain the repeated secondary outcome labels.

The record does not report the statistical analysis plan, missing-data methods, analysis populations, multiplicity handling, or the study’s own sample-size justification. The planning assumptions describe illustrations based on an observed effect, but the record does not state the effect values underlying them. These gaps prevent assessment of the precision, robustness, and analytic choices underlying any result.

Finally, the follow-up schedule includes both baseline and 1-year assessments and a post-HCV-treatment schedule for participants undergoing treatment during follow-up. The record does not say how these different timings were analyzed or how many participants followed each schedule. This limits interpretation of any longitudinal or treatment-related question, apart from the absence of posted estimates themselves.

14. Related Tutorials

15. Related Statistical Calculators

16. Sources

• ClinicalTrials.gov: A Prospective, Longitudinal Study of Endothelial Function in HIV/HCV Coinfected Subjects — NCT02597790.
• Registry record last updated 2022-01-20; status last verified 2021-12.
• Results first posted 2022-01-20.
• 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.

17. Record Summary

NCT02597790 is a completed prospective longitudinal study sponsored by the University of California, Los Angeles. The registry records a start date of 2013-10, primary completion in 2019-01, and enrollment of 87. The study concerned people with HIV/HCV coinfection and people with HIV alone.

The primary outcome was baseline RHI measured by PAT, summarized as a median with an inter-quartile range. The study description also includes endothelial function and blood biomarker assessments at baseline and 1 year, with assessments 4 weeks and 24 weeks after HCV treatment for participants who underwent treatment during follow-up. Listed secondary outcomes include soluble biomarkers, HOMA-IR, FRS, and RHI.

The record lists 12 outcome measures and 0 analyses. Numerical outcome results, group sizes, analysis methods, and missing-data procedures are not reported in the registry record. The documented study design and endpoint definitions therefore describe the research question and measurement plan, but do not provide statistical estimates with which to evaluate the outcomes.