A Comparison of Body Fat Distribution in HIV-1 Infected Patients Receiving, Since the Beginning and for at Least Two Years, an Antiretroviral Therapy Based on Efavirenz or Lopinavir/Ritonavir Combined With Tenofovir + Emtricitabine or Lamivudine: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Comparison of Body Fat Distribution in HIV-1 Infected Patients Receiving, Since the Beginning and for at Least Two Years, an Antiretroviral Therapy Based on Efavirenz or Lopinavir/Ritonavir Combined With Tenofovir + Emtricitabine or Lamivudine (NCT01159743), a registered phase not stated study. The primary outcome is Total Limb Fat Mass.

2. Clinical Question

3. Trial Design

This completed study enrolled 346 participants with HIV infection. Its stated purpose was to compare body fat distribution in people receiving initial antiretroviral therapy based on efavirenz or lopinavir/ritonavir, alongside tenofovir plus emtricitabine or lamivudine. The record describes participants in both groups as having received their initial regimen for at least two years. The recorded start is 2010-07, and primary completion is 2011-09.

The two groups are identified by regimen: efavirenz and lopinavir/ritonavir. The registry record does not state how participants were assigned to them. It specifically notes that this was not a randomized comparison and that the arms are not a like-for-like control comparison. Consequently, the group labels should not be read as indicating random allocation or an otherwise balanced experimental design.

The total enrollment is 346. The record lists 237 participants at risk for adverse-event reporting in the efavirenz group and 109 in the lopinavir/ritonavir group. Those figures describe the listed safety groups; the number contributing to the primary outcome is not reported. The primary-outcome population is defined as all participants for whom data were available, without a reported count.

Total limb fat mass was the primary outcome. Secondary outcomes were distribution of body fat mass, Lipodystrophy Severity Grading Scale scores, and change over time in body fat distribution. The primary outcome was assessed at a study visit, but the record does not specify a visit timepoint or provide a detailed analysis schedule. Further design details, including the allocation process, 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

Analysis population for the primary outcome, as defined in the registry: All participants for whom data were available.

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 Total Limb Fat Mass, measured over Study visit.

Total limb fat mass measures the amount of fat in the limbs, expressed in kilograms. The registry record says it was assessed using dual energy X-ray absorptiometry (DEXA), a whole-body scanning method that uses two different low-dose x-rays to read bone mass and soft tissue mass. This makes the endpoint an instrument-based measure rather than a subjective rating.

In general, a continuous endpoint such as mass can be described by a mean and a measure of variation. A comparison of group means can summarize the average difference in the measured quantity, while a measure such as the standard deviation describes how dispersed individual measurements are around the mean. The registry record identifies the outcome parameter as a mean and its dispersion as a standard deviation.

Body fat distribution is the broader subject of the study, and total limb fat mass is the named primary measure. A single measure does not describe every aspect of body composition or distribution. The record also names other outcomes related to body fat distribution, severity grading, and change over time. Numerical results for total limb fat mass, including group means and standard deviations, are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies total limb fat mass as a continuous primary outcome, with a mean as the parameter and standard deviation as the measure of dispersion. It does not list statistical analyses or a detailed statistical analysis plan. The explanations below describe general statistical concepts; they are not claims about procedures used in this study unless the registry record explicitly says so.

What a mean and standard deviation describe

In general, the mean summarizes the average measurement in a group. The standard deviation describes the spread of individual measurements around that group average. They answer different questions: the mean locates the group’s average, while the standard deviation describes individual variability. Neither alone gives the precision of a comparison between groups. Precision depends on the amount of information available and the variability in the measurements, among other features of the analysis.

The registry record names both the mean and standard deviation for total limb fat mass, but does not include their values for either group. It therefore does not permit a reader to assess the observed group averages or the observed spread of the measurements. It also does not include a stated estimate comparing the groups.

What a comparison estimate would mean

In general, an estimate of the difference between group means expresses the contrast in average outcome between the groups being compared. Its interpretation depends on how the groups were formed and on the analysis population. For a nonrandomized comparison, an observed contrast may reflect not only the regimen groups but also other differences between their participants. The registry record states that allocation was not randomized and cautions that the arms are not a like-for-like control comparison. It does not report adjustment methods or participant characteristics that could help assess comparability.

A confidence interval, in general, represents uncertainty around an estimate under the assumptions of the statistical method used. A narrower interval indicates greater precision than a wider interval, but precision is not the same as freedom from bias. The registry record does not report a confidence interval for the primary outcome. Without one, the precision of a primary-outcome comparison cannot be evaluated from the posted results.

Why the measurement method matters

The primary outcome was assessed by DEXA. The record describes this as a whole-body scanner using two different low-dose x-rays to read bone mass and soft tissue mass. The resulting total limb fat mass is a measured quantity, rather than a clinical rating scale. In general, a measurement method determines how an outcome is operationalized; it does not by itself establish that the comparison is unbiased or that the measurement captures every aspect of the broader construct.

The outcome timeframe is described only as a study visit. No specific visit or measurement schedule is reported in the registry record. This matters because a measurement at one visit and a change measured across visits answer different questions. Although change over time in body fat distribution is named as a secondary outcome, the details of its analysis are not reported.

Nonrandomized comparisons and interpretation

In general, random assignment helps balance participant characteristics across treatment groups on average, while a nonrandomized comparison does not have that design feature. This does not establish that groups were different in this study; it means the registry record does not establish that assignment made them comparable. A statistical adjustment can sometimes address measured differences, but cannot automatically account for unmeasured factors. No adjustment strategy is reported in the registry record.

Accordingly, any group contrast, if reported elsewhere, would need to be interpreted in light of how participants entered each regimen group, which characteristics were measured, and what analysis was performed. Those details are not reported in the registry record. The record’s stated warning that the arms are not a like-for-like control comparison is central to reading the design.

Planning calculations are not trial results

In general, sample-size calculations are planning exercises: they estimate how many participants may be needed under stated assumptions to detect a chosen effect with a specified statistical procedure. They do not describe what happened in the enrolled study and are not observed power. The planning illustration associated with this study is described as based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation; it uses stated fractions of that effect. Such calculations depend on the assumptions and effect used, and do not replace reporting the actual outcome estimate and its uncertainty.

The registry record does not report the trial’s own sample-size justification or its statistical analysis plan. The planning assumptions should not be taken as evidence that the study was designed using those assumptions. In particular, an illustrative sample-size result does not supply a missing primary-outcome estimate, establish that an analysis was performed, or resolve the limitations of a nonrandomized comparison.

The registry record lists zero analyses. It does not report a test statistic, p-value, confidence interval, or adjusted estimate for total limb fat mass. General statistical explanations can clarify what these quantities would represent, but cannot recover results that the record does not report.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Efavirenz", "Lopinavir / Ritonavir")
n   <- c(232, 106)
m   <- c(8.84, 9.13)
sp  <- c(4.45, 6.26)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Efavirenz  232  8.840  4.450  8.264  9.416
CARM  Lopinavir / Ritonavir  106  9.130  6.260  7.924  10.336

11. Multiplicity, Missing Data and Analysis Populations

The primary outcome is total limb fat mass. Three secondary outcomes are named: distribution of body fat mass, Lipodystrophy Severity Grading Scale scores, and change over time in body fat distribution. Examining several outcomes can raise a multiplicity issue: in general, the more statistical tests that are performed, the greater the chance of finding an apparently notable result by chance if each is judged without regard to the others. Whether or how that issue was addressed is not reported in the registry record. No multiplicity adjustment or hierarchy of secondary analyses is described.

The primary-outcome population is defined as all participants for whom data were available. This indicates that outcome availability matters to inclusion, but the number with available data is not reported. The amount, reasons, or pattern of missing outcome data, and any method for handling missing measurements, are not reported in the registry record. No imputation or sensitivity analysis is described. It is therefore not possible to determine from the record whether participants with missing measurements differed from those with available measurements.

The record reports enrollment of 346, but does not report an analyzed sample size for the primary outcome or the secondary outcomes. It also does not describe an intention-to-treat, per-protocol, or other named analysis population. These details are important because the participants enrolled and the participants contributing to a particular analysis need not be the same. The registry record does not provide enough information to establish how the outcome population was formed beyond its available-data description.

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.

The registry record lists serious adverse events affecting 0 participants in the efavirenz group and 0 in the lopinavir/ritonavir group. It also lists other adverse events affecting 0 participants in each group. The listed at-risk counts are 237 for efavirenz and 109 for lopinavir/ritonavir. These are the event figures and group counts recorded in the registry.

The record lists no top serious-event terms. Death counts are not reported in the registry record. It does not describe the safety observation period, event-collection procedures, or additional details that would clarify how these entries were obtained. The zero counts should therefore be read as the registry’s recorded figures, not as a broader statement about every possible safety outcome or time period.

These safety entries are separate from the primary outcome, total limb fat mass. They do not provide information about body-fat measurements, and they do not resolve the design limitations of the nonrandomized comparison. The registry record does not report further safety analyses.

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

The record establishes the study’s purpose: to compare body fat distribution between HIV-1-infected participants receiving initial therapy based on efavirenz or lopinavir/ritonavir, with tenofovir plus emtricitabine or lamivudine. It also identifies total limb fat mass, assessed by DEXA, as the primary outcome. These details clarify the question the study set out to examine.

However, the registry record does not report the numerical results for total limb fat mass or the named secondary outcomes. It gives no group averages, standard deviations, comparison estimate, confidence interval, or statistical test result. The direction and size of any observed body-fat difference, and the precision of such a difference, are therefore not established by the recorded results.

The design also limits what a comparison can establish. Allocation is not stated, and the record says the study was not randomized and that the arms are not a like-for-like control comparison. In general, a difference between groups in a nonrandomized study cannot automatically be attributed to the treatment regimen; other group differences may contribute. The registry record does not report adjustment methods that would address this concern.

The listed safety counts show zero serious and zero other adverse events in each group, but the record does not give the safety observation period or further reporting details. Those entries should be understood as the recorded counts and not as a complete characterization of safety.

Thus, the record documents a completed comparison and its measurement approach, but it does not provide the results needed to judge the observed primary-outcome contrast. It does not establish that one regimen was associated with greater or lesser limb fat mass, and it does not establish the precision of any such contrast.

14. Why This Trial Matters Statistically

This study is statistically notable because its question involves comparing a measured body-composition outcome across two groups with different initial antiretroviral regimens. Total limb fat mass is a continuous measurement obtained by DEXA, while the broader study scope includes body-fat distribution, a severity grading scale, and change over time. These outcomes illustrate that a clinical question may involve more than one measurement and more than one kind of summary.

The record also makes clear why design information matters when interpreting a comparison. It does not state how participants entered the regimen groups and explicitly says that the comparison was not randomized and the arms are not a like-for-like control comparison. In general, statistical analysis cannot make a nonrandomized design equivalent to random assignment merely by comparing group averages. Interpretation depends on the allocation process and on whether relevant differences between groups were measured and addressed. The registry record does not report those details.

Another statistical issue is the distinction between naming an outcome and reporting its evidence. The primary measure and its assessment method are identified, but numerical results and analyses are not listed. Without an estimate and a measure of uncertainty, readers cannot assess the observed magnitude or precision of the comparison. This is a practical reminder that design descriptions and outcome definitions do not substitute for reporting results.

The study’s planning illustration is also distinct from an observed finding. In general, planning calculations depend on assumptions about the effect and analysis; they do not establish that the intended comparison was precise or that a result was observed. The record does not report the trial’s own sample-size justification or analysis plan. Taken together, these features make transparent reporting of allocation, outcome data, missingness, and analysis especially important for interpreting this comparison.

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 main limitation of the registry record for interpretation is that it does not report numerical results for the primary outcome or the named secondary outcomes. Group means, standard deviations, comparison estimates, confidence intervals, and p-values are not reported in the registry record. The record lists zero analyses, leaving no statistical result with which to assess the magnitude or precision of the intended comparison.

The comparison was not randomized, and the registry record cautions that the arms are not a like-for-like control comparison. Allocation is not stated. Further information about participant characteristics, group comparability, or statistical adjustment is not reported in the registry record. As a result, the recorded information does not support attributing any hypothetical difference to regimen choice.

The primary-outcome population includes participants for whom data were available, but the number included is not reported. Missing-data amounts, reasons, handling methods, and sensitivity analyses are not reported in the registry record. The outcome timeframe is described as a study visit without a more specific visit schedule. Although change over time is a named secondary outcome, its measurement and analysis details are not reported.

The registry record also does not report the trial’s own sample-size justification, full statistical analysis plan, or any approach to multiplicity across outcomes. These gaps prevent assessment of whether the reported design and analyses, if any, addressed the study’s multiple outcome questions.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Comparison of Body Fat Distribution in HIV-1 Infected Patients Receiving, Since the Beginning and for at Least Two Years, an Antiretroviral Therapy Based on Efavirenz or Lopinavir/Ritonavir Combined With Tenofovir + Emtricitabine or Lamivudine — NCT01159743.
• Registry record last updated 2013-01-24; status last verified 2013-01.
• Results first posted 2012-10-30.
• 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

This completed study enrolled 346 participants with HIV infection and compared groups receiving initial antiretroviral therapy based on efavirenz or lopinavir/ritonavir, combined with tenofovir plus emtricitabine or lamivudine. The recorded start is 2010-07, and primary completion is 2011-09.

Total limb fat mass, assessed by DEXA and summarized as a mean with standard deviation, was the primary outcome. Secondary outcomes concerned body fat mass distribution, Lipodystrophy Severity Grading Scale scores, and change over time in body fat distribution. The primary-outcome population is described as participants for whom data were available.

Allocation is not stated; the record identifies the study as nonrandomized and cautions that the arms are not a like-for-like control comparison. It lists zero serious and zero other adverse events in both groups. Numerical outcome results, analysis details, and death counts are not reported in the registry record.