Sonographic Evaluation of Visceral Fat After Bariatric Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Sonographic Evaluation of Visceral Fat After Bariatric Surgery (NCT01285791), a registered phase not stated study. The primary outcome is Decrease in the Visceral Fat Layer Measured by Ultrasound a Day Before and a Year After Surgery..

2. Clinical Question

The scientific rationale in the record is that visceral fat is associated with metabolic syndrome and may change after weight loss. The study focuses on measuring that layer of fat rather than using weight loss itself as the primary endpoint. Its stated hypothesis favors sleeve gastrectomy and gastric bypass over adjustable gastric banding, on the basis of the proposed distinction between restrictive and malabsorptive procedures. That is a hypothesis in the registry description, not a result.

The primary question is therefore about change in an ultrasound measurement and whether that change differs by procedure. The registry also lists change in glucose and triglyceride blood levels as secondary outcomes. It does not report values for the primary or secondary outcomes, or analyses comparing the procedures. Consequently, the record does not establish the direction, size, or precision of any observed difference.

3. Trial Design

The registry record describes a completed clinical study sponsored by Hadassah Medical Organization. Its title concerns sonographic evaluation of visceral fat after bariatric surgery; the official title also refers to subcutaneous fat. The condition listed is morbid obesity. Enrollment is recorded as 39. The study start is listed as 2011-01 and primary completion as 2014-01. The status is COMPLETED.

The three procedure groups are laparoscopic adjustable gastric banding, laparoscopic sleeve gastrectomy, and laparoscopic gastric bypass. The group descriptions say that ultrasound assessment is performed before surgery and one year after surgery to determine the amount of visceral fat-layer decrease. These descriptions establish the intended measurement schedule, but the registry record does not supply group-specific outcome values or a detailed account of how observations were collected.

This is not described as a randomized comparison: allocation is not stated, and the arms are flagged as not being a like-for-like control comparison. The record does not explain how people were assigned to a procedure, whether allocation followed clinical choice, or what other factors may have influenced procedure selection. As a result, a difference between groups, if reported, would not by itself establish that procedure choice caused the difference.

The primary endpoint is a continuous measure: mean decrease in the visceral fat layer, measured in centimeters by ultrasound. The endpoint description specifies ultrasound one day before surgery and one year after surgery, while the stated primary-outcome timeframe is 18 months. This timing discrepancy is not explained in the registry record. The listed secondary outcomes are changes in glucose and triglyceride blood levels. The record lists 2 outcome measures and 0 analyses; numerical results and a statistical analysis plan are not reported.

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 Decrease in the Visceral Fat Layer Measured by Ultrasound a Day Before and a Year After Surgery., measured over 18 months.

The primary endpoint concerns the decrease in the visceral fat layer measured by ultrasound. The registry describes measurements before surgery and one year after surgery, with the primary endpoint expressed as mean reduction in centimeters. It identifies the outcome as a continuous measure and specifies the mean as its summary statistic, with standard error as the stated measure of dispersion. No endpoint values are reported in the registry record.

Ultrasound is the measurement method selected for this study. The registry’s rationale describes it as a way to assess the visceral fat layer and notes that the investigators aimed to use it to compare changes after the different procedures. The endpoint is therefore a measurement of change in a particular fat layer, not a direct measure of overall body fat, weight loss, metabolic syndrome, or a clinical event. The listed secondary outcomes—change in glucose and triglyceride blood levels—are separate measures and should not be treated as substitutes for the primary endpoint.

In general, a pre-surgery and follow-up measurement can be used to describe change within a group. Comparing those changes among procedure groups addresses whether the measured reduction differs by procedure. Such a comparison depends on the measurement schedule, the availability and quality of paired measurements, and the analysis method. The record does not state how the change was calculated, whether all participants had both assessments, or how measurement variability was handled. It also gives a timeframe of 18 months for the primary endpoint despite describing assessment one year after surgery; that inconsistency is not resolved in the record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The endpoint is continuous: it is a mean decrease in an ultrasound-measured layer of fat, expressed in centimeters. The registry names standard error as the measure of dispersion but does not report an estimate. No statistical analyses are listed. The following concepts explain how results of this type are generally interpreted; they do not describe an analysis confirmed by the registry record.

What does a mean change describe?

For a continuous outcome, a mean summarizes the observed measurements in a group. If each person has a pre-surgery measurement and a follow-up measurement, change can be described using the difference between those measurements for each person, then summarized across the group. The registry says that the endpoint is a mean decrease, but does not specify the exact calculation convention or provide the underlying measurements. It is therefore not possible to reconstruct the endpoint or verify how it was calculated.

A group mean is a summary, not a description of every participant’s response. Participants can have different changes, and a mean alone does not show that distribution. The registry’s specified standard error describes uncertainty in an estimated mean under the relevant statistical model; it is not the same as the spread of individual measurements. Neither the standard error value nor a measure of participant-level variability is reported.

How should a comparison be read?

A comparison of procedures might focus on average changes within each group or on differences between those average changes. In general, an estimated difference describes the observed contrast, while an uncertainty interval shows how precisely that contrast has been estimated. A p-value, when used, measures how compatible the data are with a specified null hypothesis under the assumptions of the analysis; it is not the probability that the null hypothesis is true. The registry record lists 0 analyses and reports no estimates, intervals, or p-values, so none of these interpretations can be applied to a posted comparison.

Because the study has three procedure groups, the analysis plan would need to clarify what comparisons were intended. A global test of whether any group differs answers a different question from selected pairwise comparisons. If multiple comparisons are made, multiplicity procedures can control the risk of false-positive findings across those tests. The registry record does not state which contrasts were planned or how multiplicity was handled. It would be inappropriate to infer a testing strategy from the study aim alone.

Why does allocation matter?

Random allocation, when used and implemented appropriately, can help balance measured and unmeasured baseline characteristics across groups on average. The registry does not describe this study as randomized; allocation is not stated, and the arms are flagged as not being a like-for-like control comparison. In a nonrandomized comparison, differences in baseline characteristics, clinical decisions, or other factors may affect both procedure choice and outcome. Statistical adjustment can sometimes address measured differences, but cannot automatically remove unmeasured confounding. The record does not report whether adjustment was planned or performed.

Baseline outcome values also matter when interpreting change. Groups may start at different levels, and comparisons based only on change can have different interpretations from comparisons that adjust follow-up values for baseline. The registry gives no baseline values and does not state which approach was used. The measurement schedule is described as one day before surgery and one year after surgery, but the primary-outcome timeframe is listed as 18 months. This inconsistency remains unexplained.

What does a planning illustration mean?

The sample-size assumptions describe a planning illustration calculated from an observed effect, rather than the trial’s own design. The stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the target effect is a stated fraction of the observed effect. In general, such calculations estimate the number of participants per arm for 80% power or for another stated power, under the chosen assumptions. They are planning scenarios, not observed power, and they do not show that a study had a particular chance of finding an effect after the data were collected.

These assumptions do not establish that the actual study used equal allocation or a two-arm design: the registry describes three procedure groups and does not state its allocation method. The record does not report a sample-size justification from the investigators, the effect estimate used for planning, or further calculation details. Any planning illustration should therefore be read as conditional on its stated assumptions, not as a description of the trial’s conduct or evidence of an observed treatment effect.

More generally, normal-approximation calculations rely on assumptions about the sampling distribution of the estimator. Departures from those assumptions can affect the accuracy of a calculation. The record does not report diagnostics or alternative calculation methods, so no further assessment of those assumptions is possible.

What can be learned from the listed analyses?

The registry lists 0 analyses. That does not mean that no analysis occurred outside the registry; it means that no analysis is reported in this record. Without an analysis description, it is not possible to establish whether the results were analyzed as paired measurements, whether group comparisons were adjusted, how missing follow-up measurements were treated, or which statistical tests were used. In general, these decisions affect the meaning and reliability of estimates, and should be stated alongside numerical results.

For the same reason, the named standard error cannot be used to infer a confidence interval or significance test when no numerical estimate is reported. A confidence interval is often useful because it presents both the estimated effect and its precision on the outcome’s scale. A p-value alone would not communicate the size or clinical meaning of an effect. Neither type of result appears in the registry record.

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("Patients Undergoing Laparoscopic Adjustable Gastri", "Patients Undergoing Laparoscopic Sleeve Gastrectom", "Patients Undergoing Laparoscopic Gastric Bypass")
n   <- c(11, 15, 13)
m   <- c(3.6, 7.1, 5.6)
sp  <- c(0.8, 0.5, 0.6)
sd  <- sp * sqrt(n)      # standard errors converted to SDs
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  Patients Undergoing Laparoscopic Adjustable Gastri  11  3.600  2.653  1.817  5.383
CARM  Patients Undergoing Laparoscopic Sleeve Gastrectom  15  7.100  1.936  6.028  8.172
CARM  Patients Undergoing Laparoscopic Gastric Bypass  13  5.600  2.163  4.293  6.907

11. Multiplicity, Missing Data and Analysis Populations

The record lists a primary endpoint and secondary outcomes for change in glucose and triglyceride blood levels. It does not state which comparisons were planned among the three procedure groups, whether the secondary outcomes were formally tested, or how multiplicity was handled. When several outcomes or contrasts are tested, the chance of at least one apparently positive result can increase. In general, a prespecified analysis plan can clarify which comparisons are primary and whether adjustments are used. No such plan or adjustment method is reported in the registry record.

Missing-data handling is also not reported. The group descriptions specify ultrasound assessment before surgery and one year after surgery, but the record does not say whether all participants completed both measurements, how unavailable follow-up measurements were addressed, or whether any imputation was used. Without that information, the potential effect of missing follow-up on the estimated changes cannot be assessed.

Analysis populations are not described. The record does not state whether analyses included everyone enrolled, only participants with measurements at both time points, or another defined population. It also does not describe exclusions, protocol deviations, or a rule for assigning participants to procedure groups for analysis. These details matter because different analysis populations can produce different estimates, particularly in a nonrandomized comparison.

The registry reports 0 analyses and no numerical outcome results. Therefore, it is not possible to evaluate whether the observed data, any adjustments, and the handling of missing measurements were consistent with an intended plan. These elements are not reported in the registry record.

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 safety record lists serious adverse events and other adverse events by procedure group. For laparoscopic adjustable gastric banding, the listed at-risk population is 11 and the listed serious and other adverse event counts are both 0. For laparoscopic sleeve gastrectomy, the listed at-risk population is 15 and both event counts are 0. For laparoscopic gastric bypass, the listed at-risk population is 13 and both event counts are 0. These are the recorded counts in the registry.

These entries should be read as reported event counts, not as proof that no adverse events occurred outside the definitions, collection period, or reporting process used for the registry. The record does not describe the adverse-event observation window, event ascertainment methods, or completeness of reporting. It also does not provide further event terms; no top serious-event terms are listed. Death counts are recorded as null, which means they are not reported in the registry record, not that the recorded value is 0.

In general, a zero count does not establish that an event is impossible or that procedures have equivalent safety. Interpretation depends on how events were defined and collected, the time observed, and the precision of the resulting estimates. The registry’s safety entries are descriptive and do not include a comparative safety analysis. They should not be used alone to rank the procedures or make treatment decisions.

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

The record establishes that investigators intended to measure visceral fat by ultrasound before surgery and one year after surgery in groups undergoing laparoscopic adjustable gastric banding, laparoscopic sleeve gastrectomy, or laparoscopic gastric bypass. It identifies a continuous primary outcome expressed as mean decrease in centimeters and lists changes in glucose and triglyceride blood levels as secondary outcomes. It also records the study as COMPLETED.

Those design and status details do not reveal the study’s findings. The registry record does not report the primary endpoint values, group comparisons, uncertainty estimates, or statistical analyses. It therefore does not show whether visceral fat decreased, how large any change was, or whether the changes differed among procedures. The stated hypothesis favoring sleeve gastrectomy and gastric bypass remains a hypothesis in the absence of reported results.

The record also does not establish a causal effect of procedure choice. Allocation is not stated, and the groups are not described as a like-for-like control comparison. In general, differences between nonrandomized groups may reflect characteristics related to both procedure selection and outcome. The registry does not report adjustment methods that could help account for measured differences, and adjustment cannot be assumed.

The safety entries list 0 serious and 0 other adverse events in each group, with the listed at-risk populations shown in the registry. These counts are not a comparative safety analysis, and the reporting period and ascertainment details are not stated. Death counts are not reported in the registry record.

Accordingly, the posted record supports a description of the intended question, measurements, and recorded safety counts, but not a conclusion about comparative benefit, harm, or effectiveness. The absence of registry results should not be interpreted as evidence of no change or no difference.

14. Why This Trial Matters Statistically

This study illustrates the statistical distinction between defining a measurable endpoint and reporting evidence about that endpoint. The registry specifies ultrasound-measured mean decrease in visceral fat, a unit, a dispersion measure, and a measurement schedule. Those details help identify the intended outcome. Without numerical results and an analysis, however, readers cannot assess the magnitude or precision of the measured changes or compare procedures.

The design also highlights why a comparison’s allocation method matters. The record describes three procedure groups but does not state allocation and flags the arms as not being a like-for-like control comparison. In general, a difference in group averages is not automatically a causal effect when groups may differ in other ways. Transparent reporting of group characteristics, methods of allocation, adjustment decisions, and uncertainty would be important to interpret such a comparison.

The record identifies an additional issue for statistical interpretation: the endpoint description specifies measurement one year after surgery, whereas the primary-outcome timeframe is 18 months. Clear timing is needed to know which observation contributes to the endpoint and how follow-up was defined. The discrepancy is not resolved in the registry record.

Finally, the record shows how planning calculations should be kept separate from observed findings. The stated assumptions describe a sample-size planning illustration, not observed power and not necessarily the design actually used. A planning scenario cannot replace reported estimates, uncertainty intervals, or a transparent analysis plan. In this case, the registry lists 0 analyses and does not report outcome results, so the statistical question remains unanswered by the posted record.

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 for interpretation is that no numerical outcome results or analyses are reported in the registry record. The primary endpoint is described, but its group-specific values, uncertainty, and comparisons are absent. The listed secondary outcomes likewise have no reported results. The study’s completion status does not resolve this lack of findings.

Allocation is not stated, and the arms are identified as not being a like-for-like control comparison. The record does not describe how procedure choice was determined, provide baseline characteristics, or report adjustment for potential confounding. This limits interpretation of any between-group contrast, even if one were available.

The measurement timing is not fully consistent: the endpoint description refers to ultrasound one day before surgery and one year after surgery, while the primary timeframe is 18 months. The registry does not explain how these descriptions relate. The record also does not specify the ultrasound measurement protocol, assessor procedures, or how measurement variability was evaluated.

Other relevant design details are not reported in the registry record. These include detailed eligibility criteria, missing-data handling, analysis populations, prespecified contrasts, multiplicity procedures, and the statistical methods used. The sample-size description is a planning illustration based on an observed effect, but the record does not give the effect estimate or investigators’ own sample-size justification. The safety entries do not state the observation period or event ascertainment method, and death counts are not reported.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Sonographic Evaluation of Visceral Fat After Bariatric Surgery — NCT01285791.
• Registry record last updated 2016-03-16; status last verified 2016-02.
• Results first posted 2016-03-16.
• 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

The registry record describes a completed study sponsored by Hadassah Medical Organization, with enrollment of 39 and status COMPLETED. Its stated aim is to compare ultrasound-measured visceral fat reduction after laparoscopic adjustable gastric banding, laparoscopic sleeve gastrectomy, and laparoscopic gastric bypass. The endpoint is a mean decrease in centimeters, with assessment described before surgery and one year afterward. The primary-outcome timeframe is listed as 18 months, a discrepancy not explained in the record.

Change in glucose and triglyceride blood levels is listed as a secondary outcome. The registry lists 0 analyses and does not report numerical primary or secondary results. Allocation is not stated, and the arms are not described as a like-for-like control comparison. Safety entries list 0 serious and 0 other adverse events in each group; death counts are not reported in the registry record. The stated hypothesis is not a reported finding.