Myocardial Function & FFA Metabolism in HIV Metabolic Syndrome: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Myocardial Function & FFA Metabolism in HIV Metabolic Syndrome (NCT00656851), a randomized na study. The primary outcome is Myocardial Glucose Utilization Rate.

2. Clinical Question

3. Trial Design

This study is listed as randomized, with a parallel model and no masking. The two named intervention arms are pioglitazone and exercise training. The registry record gives an enrollment of 24 and a completed status. It lists the phase as NA. The start is recorded as 2005-09, and primary completion as 2009-08.

The pioglitazone arm is described as receiving 30mg/day for 16 weeks. The exercise arm is described as cardiorespiratory and resistance exercise training 3days/wk for 16 weeks. The registry record does not describe the sequence-generation method, allocation concealment, the process used to assign participants, adherence monitoring, or whether participants could receive both interventions. Further protocol details are not reported in the registry record.

The population of interest is described in the study summary as HIV-positive people with metabolic syndrome. The record lists HIV infections, cardiovascular disease, insulin resistance, HIV lipodystrophy and the metabolic syndrome among the conditions. Those listings do not specify that every participant had each condition, and detailed enrollment criteria are not reported in the registry record.

The primary outcome is myocardial glucose utilization rate, with a stated timeframe of Weeks 0 and 16. Nine outcome measures are listed, including secondary measures of myocardial contractile function during diastole and systole, fasting lipids and lipoproteins, and fasting glucose, insulin and HOMA. The registry record does not provide a statistical analysis description, an analysis population definition, or results for the outcomes. It also does not report whether there were interim analyses or how missing measurements were handled.

4. Participant Flow and Accounting

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

Before assignment: Exclusion criteria: medications or dietary supplements that affect metabolism (β-blocker, β-agonist, Ca2+ channel blocker, corticosteroid), neuromuscular disorder that affects metabolism or ability to exercise, consumed \>3 alcohol drinks/wk, active Hep C or B, recreational-anabolic -appetite stimulant drugs, regular physical exercise.

Overall Study

Reasons for not completing this period:

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 Myocardial Glucose Utilization Rate, measured over Weeks 0 and 16.

Myocardial glucose utilization rate is intended to quantify how rapidly glucose is taken up and metabolized in the left ventricle. The registry description says it is measured using radio-tracer 11C-glucose and positron emission tomography. It defines the rate as glucose leaving the blood, entering left-ventricular muscle cells and undergoing metabolism, including processes related to ATP generation, glycolysis, glycogenolysis or lactate production. The stated unit is nmol glucose/g heart muscle/min.

This endpoint is relevant to the study’s biological question because it measures myocardial glucose handling directly, rather than relying only on a circulating glucose measurement. In general, a physiological measurement can help characterize a proposed mechanism, but a change in such a measure does not by itself establish a change in clinical health or patient experience. The other listed outcomes include measures of myocardial contractile function and fasting metabolic measures, which address related but distinct aspects of the study question.

The endpoint is specified at Weeks 0 and 16, but the registry record does not report the values, estimates of change, standard errors, or a between-arm estimate. It describes the outcome parameter as a mean and its dispersion as a standard error. Because no endpoint results are reported in the registry record, the magnitude, direction and precision of any observed change cannot be assessed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The methods described in the registry record are limited. It identifies randomized allocation, a parallel design and no masking, and it defines the primary outcome and measurement time points. A detailed statistical analysis plan, including the specific outcome model and contrast, is not reported in the registry record. The following statistical explanations are general and do not imply that these methods were used for this study.

What does randomization contribute?

In general, randomization assigns participants to study groups through a chance-based process. When implemented appropriately, it can reduce systematic differences between groups in measured and unmeasured characteristics at the time of assignment. It does not guarantee that groups will be identical, especially in a small study. The registry record does not describe the randomization sequence, allocation concealment, or how assignment was carried out. Those details are important for judging how well the process protected against predictable assignment.

A parallel design means that participants are assigned to a group and followed within that group rather than switching between interventions as part of a crossover design. Here, the record names pioglitazone and exercise training as the two arms. It does not describe a separate placebo or usual-care arm. Without a specified control condition or a reported analysis contrast, the record cannot clarify what causal comparison was intended beyond the existence of the two named randomized arms.

What do the mean and standard error describe?

The primary outcome is characterized as a continuous measure summarized by a mean, with standard error as the stated dispersion. A mean describes the central level of a set of measurements. A standard error describes the estimated uncertainty in a mean, rather than the spread of individual participant values. In general, a standard deviation is used to describe variation among observations, while a standard error concerns precision of an estimate. These quantities serve different purposes and should not be treated as interchangeable.

To interpret change from baseline, an analysis would need to define how measurements at Weeks 0 and 16 are compared. For example, an analysis might estimate change within each arm or compare groups at follow-up while accounting for baseline values. These approaches can yield different estimates and rely on different assumptions. The registry record does not report which method was used, whether adjustment was planned, or what the resulting estimates were. No method should be inferred from the endpoint definition alone.

Why does the choice of contrast matter?

A within-arm comparison asks whether the measurement changed over time among participants in a given arm. A between-arm comparison asks whether the outcomes differ between randomized groups. In general, a change within one arm is not by itself evidence that its intervention caused that change: changes over time can also reflect background trends, measurement variation or other influences. A randomized between-arm contrast is usually the relevant comparison for assessing differences attributable to assigned groups, provided the analysis and conduct support that interpretation.

The registry record specifies measurements at two time points but does not provide a single primary comparison. It records that the primary outcome has several categories or time points and was not reduced to one comparison. Therefore, the record does not establish whether a reported analysis would compare endpoint means, changes from baseline, or another contrast. No numerical result is available to evaluate.

How should uncertainty be considered?

General statistical interpretation considers the estimated effect alongside its uncertainty. A confidence interval conveys the precision of an estimate by expressing values compatible with the observed data under the chosen model and assumptions. A p-value, if reported, addresses how unusual the data would be under a specified null hypothesis and analysis. Neither measure tells readers the clinical importance of an effect on its own. The registry record reports no confidence interval or p-value for the primary outcome, so statistical evidence and precision cannot be assessed.

In general, estimates from small studies can be imprecise, but the amount of uncertainty must be judged from the actual data and analysis. The enrollment of 24 does not itself determine the precision of the primary outcome estimate; the number with usable measurements, variability and analysis method also matter. Those outcome-specific details are not reported in the registry record. The safety denominators should not be assumed to represent the endpoint analysis sample.

What do the planning assumptions mean?

General sample-size planning asks how many participants may be needed to detect an effect under specified assumptions. The stated planning assumptions refer to a two-sided significance level of 0.05, equal allocation between arms, a normal approximation and an effect defined as a stated fraction of the observed effect. Such calculations are planning illustrations, not observed outcomes and not evidence that a study had a particular probability of success. They cannot replace an effect estimate or uncertainty interval.

The record does not report an observed primary effect or a single comparison from which to interpret a planning illustration. It also does not report the protocol’s sample-size justification. Thus, no conclusion about the trial’s original power calculation or design target can be drawn from the planning assumptions. The stated sample-size assumptions should not be described as the trial’s own design rationale.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists nine outcome measures and identifies several secondary outcomes, but it does not report a multiplicity strategy. With multiple outcomes or multiple time-point comparisons, repeated testing can increase the chance of a nominally notable result arising by chance. General approaches may define one primary contrast in advance, adjust for multiple testing, or organize outcomes hierarchically. The registry record does not say whether any such approach was planned or used. Because no outcome analyses are reported, the effect of multiplicity on the findings cannot be assessed.

Missing-data handling is not reported in the registry record. The record does not state how many participants completed each assessment, how missing scans or other measurements were treated, or whether any imputation or sensitivity analyses were performed. In general, missing data can affect estimates when the likelihood of missingness is related to participant characteristics or outcomes. The extent and direction of any effect cannot be determined without information about missing observations and the analysis approach.

Analysis populations are also not defined. The record does not state whether the primary analysis included everyone as randomized, only participants with observed endpoint measurements, or another group. The enrollment count is 24, while the safety denominators are 12 for pioglitazone and 8 for exercise training; these figures do not establish the primary-outcome analysis population. No intention-to-treat analysis, per-protocol analysis or other population definition is reported in the registry record.

The primary outcome is described at Weeks 0 and 16, but the record does not give a single comparison or explain how multiple measurements were incorporated. Together, the lack of a stated analysis population, missing-data method and multiplicity plan limits reproducibility and makes it difficult to assess how robust any potential outcome analysis would be.

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 1% reporting threshold.

The registry record lists serious adverse events as 0 among 12 participants at risk in the pioglitazone arm and 0 among 8 participants at risk in the exercise-training arm. It also lists 0 other adverse events among the same respective at-risk denominators. These are the figures recorded for the listed groups; the record does not provide event terms or further details about collection and reporting.

The safety denominators are not the same as the total enrollment of 24, and the registry record does not explain this difference. They should not be treated as the numbers included in the primary-outcome analysis or as proof that every enrolled participant was assessed for adverse events. The record lists deaths as null for both groups, so deaths are not reported in the registry record; null should not be interpreted as a confirmed count of zero.

In general, a recorded count of zero means no event was recorded in the stated denominator, not that an event is impossible or that all relevant harms have been ruled out. Safety interpretation depends on how events were defined, monitored, attributed and reported, as well as the amount of observation. Those details are not reported in the registry record. The figures therefore describe the registry’s posted counts and do not establish the complete safety profile of either intervention.

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

The record establishes that a randomized parallel-group study was conducted with pioglitazone and exercise-training arms in a population described as people with HIV and metabolic syndrome. It identifies myocardial glucose utilization rate as the primary outcome, measured at Weeks 0 and 16, and describes a radio-tracer and positron emission tomography method. These details show what the study set out to measure; they do not show what the measurements found.

The primary outcome results are not reported in the registry record. There are no reported group means, changes, between-arm estimates, standard errors, confidence intervals or test results from which to assess direction, magnitude or precision. The results therefore do not establish that myocardial glucose utilization increased, decreased or remained unchanged. They also do not establish that one intervention differed from the other.

The study summary describes hypotheses about heart metabolism, heart function, insulin resistance and potential effects of the interventions. These are research questions, not demonstrated findings. The listed secondary outcomes indicate additional domains of interest, but their results are not reported in the registry record. Likewise, the posted adverse-event counts are limited to the stated denominators and do not provide a complete account of safety monitoring or events.

In general, a physiological outcome can inform understanding of a biological process without answering every question about clinical benefit or harm. Even a precise change in a metabolic measure would not, by itself, establish a lasting effect on cardiovascular events, symptoms or quality of life. This record does not report such clinical outcomes or results from the listed secondary measures. The appropriate conclusion is therefore about the information available: the registry documents the trial design, interventions and endpoint definition, but does not report the outcome evidence needed to judge effects.

13. Why This Trial Matters Statistically

This trial is statistically interesting because it connects an intervention study with a mechanistic measurement. The primary outcome is a rate of glucose utilization in heart muscle, assessed with radio-tracer imaging, rather than a simple clinical event count. Such measures can address biological questions, but they also require careful attention to measurement precision, analysis choices and the distinction between a mechanism and a patient-centered outcome.

The randomized parallel design is relevant because comparisons between assigned groups can, in general, help separate intervention-related differences from changes that occur over time in both groups. However, the registry record does not identify a separate control condition or report the primary between-arm estimate. It also does not report how repeated measurements were analyzed. The design label alone cannot answer whether the analysis produced an interpretable intervention contrast.

The enrollment of 24 and the safety denominators of 12 and 8 illustrate why population definitions matter. Enrollment, safety monitoring and endpoint analysis can involve different sets of participants. Without a reported analysis population and participant flow, the numbers cannot be linked confidently to the primary outcome estimate. The record also does not report missing-data handling or outcome-specific completion.

Finally, the record lists multiple outcomes and time points without a reported multiplicity plan or single primary comparison. In general, this makes a prespecified analysis strategy important for interpreting a family of results. Here, no results or detailed analysis plan are reported, so statistical evidence, precision and robustness cannot be evaluated. The trial’s statistical importance lies in the questions it frames and in the need for transparent outcome reporting, not in a result that the registry record does not contain.

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 main limitation for interpreting this trial is that the registry record does not report outcome results. The primary endpoint’s means, standard errors and comparative estimates are absent, as are confidence intervals and test results. Without those quantities, no estimate of effect or precision can be assessed. The record notes measurements at Weeks 0 and 16 but does not provide a single primary comparison.

Important design and analysis details are also not reported in the registry record. These include detailed eligibility criteria, the randomization procedure, allocation concealment, adherence, the statistical analysis plan, the primary analysis population and missing-data methods. The record does not describe a separate placebo or usual-care arm. It is therefore not possible to determine from the record alone how the randomized comparison was operationalized or analyzed.

The record lists nine outcome measures and several secondary outcomes, but does not explain how multiplicity was addressed. It also does not report participant flow or the number with usable measurements for each outcome. The enrollment count of 24 and the safety denominators do not resolve those questions. The safety entries list no affected participants in the stated denominators, but do not describe monitoring duration, event definitions or completeness of reporting; deaths are recorded as null rather than a numeric count.

Finally, the study summary frames physiological and metabolic hypotheses, while the listed primary measure is a mechanistic endpoint. The record does not report clinical outcome results that would establish whether any measured change corresponded to a difference in health outcomes. These limitations restrict interpretation to the study’s stated design and measurement aims, rather than its effects.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Myocardial Function & FFA Metabolism in HIV Metabolic Syndrome — NCT00656851.
• Registry record last updated 2013-08-28; status last verified 2013-08.
• Results first posted 2013-08-20.
• 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.

18. Record Summary

NCT00656851 is listed as a completed, randomized, unmasked, parallel study with enrollment of 24. Its two named arms are pioglitazone and exercise training. The record describes pioglitazone as 30mg/day for 16 weeks and exercise training as cardiorespiratory and resistance training 3days/wk for 16 weeks.

The primary outcome is myocardial glucose utilization rate, measured at Weeks 0 and 16 using radio-tracer 11C-glucose and positron emission tomography. Nine outcome measures are listed, including secondary measures of myocardial contractile function and fasting metabolic measures. The registry record does not report primary or secondary outcome results, an analysis plan, missing-data methods or analysis populations.

Safety entries list 0 serious and 0 other adverse events among 12 at risk in the pioglitazone arm and among 8 at risk in the exercise-training arm. Deaths are not reported in the registry record. The available information defines the design, interventions, endpoint and posted safety counts, but does not establish intervention effects or their precision.