Omentectomy and Metabolic Syndrome: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Omentectomy and Metabolic Syndrome (NCT00923260), a randomized na study. The primary outcome is Components of Metabolic Syndrome (Body Mass Index).

2. Clinical Question

The question is clinically framed around the added procedure, while the posted primary outcome requires careful statistical interpretation. Both arms were scheduled to receive the same named gastric bypass procedure; the randomized contrast is whether omentectomy was also performed. A difference between arms in a baseline measure would describe the groups before the intervention could produce its intended effect. It is not evidence about a subsequent change in that measure.

The registry also lists acute phase reactants and inflammatory mediators among secondary outcomes. Baseline values are reported for interleukin-6, C-reactive protein, and tumor necrosis factor-alpha. Those measurements can describe the groups at study entry, but they do not establish how either measure changed after surgery. Follow-up outcomes relevant to the stated aim may be among the other posted secondary measures, but their individual results are not reported in the registry record in the information available for this interpretation.

3. Trial Design

This is a completed, randomized, parallel-group trial with no masking listed in the registry. One arm received laparoscopic Roux-en-Y gastric bypass with omentectomy; the other received laparoscopic Roux-en-Y gastric bypass alone. The trial enrolled 24 participants. The primary outcome and the three detailed basal inflammatory outcomes each report 11 participants per arm. Safety at-risk counts are 12 per arm. These are distinct outcome-specific counts; participant flow explaining the difference is not reported in the registry record.

The registry lists metabolic syndrome and morbid obesity as conditions. Its study summary describes an aim to evaluate the additional effect of sudden visceral fat reduction by omentectomy on metabolic syndrome, acute phase reactants, and inflammatory mediators among patients with morbid obesity undergoing laparoscopic gastric bypass. The title and intervention descriptions are consistent with a trial of the added surgical procedure, but the registry record does not provide enough detail to infer how participants were recruited, the eligibility criteria, or the precise timing of every assessment.

The primary measure is described as body mass index at baseline, in Kg/m2, with a mean and standard deviation. Its description says absolute values are presented and refers to a basal value in a previous outcome measure to determine improvement. The posted comparison therefore concerns the baseline values, not a reported change score. The registry lists the trial phase as NA. Allocation concealment, the method used to generate the random sequence, and details about blinding of outcome assessment are not reported in the registry record. Masking is listed as none.

The posted analysis for the primary outcome is a two-sided t-test, with a reported p-value of 0.79. The record does not report a corresponding confidence interval or the test’s other statistical details. The original sample-size justification, planned analysis populations, handling of missing data, and whether analyses were adjusted for other variables are not reported in the registry record. Consequently, the randomized design is clear, but several details needed to fully assess implementation and analysis are unavailable.

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

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 Components of Metabolic Syndrome (Body Mass Index), measured over Basal.

The primary outcome measures body mass index, reported in Kg/m2, as a continuous quantity. Body mass index relates weight to height and is commonly used to describe body size in clinical research. For a study focused on metabolic syndrome and obesity, it is relevant as one measure of body composition and metabolic risk, although it does not capture every component of either condition.

The registry identifies the primary time point as basal and reports absolute values. The mean was 44.9 with a standard deviation of 3.1 in the gastric bypass plus omentectomy arm, and 44.5 with a standard deviation of 4.3 in the gastric bypass alone arm. Each arm reports 11 participants for this outcome. These values describe the groups at baseline. They do not measure the effect of omentectomy after surgery, nor do they show whether either group’s body mass index improved over time.

The outcome description refers to a basal value in a previous outcome measure to determine improvement. That wording suggests that change may be evaluated using another assessment, but a post-baseline primary result and its change definition are not included in the information interpreted. The registry record does not report the details needed to establish whether the primary endpoint was intended to be a change, a follow-up value, or another comparison beyond the basal measure posted. Accordingly, the baseline result is best read as a description of the randomized groups at study entry, not as an estimate of treatment effect.

7. Results Posted in the Registry

• Roux-en-Y Gastric Bypass Alone: mean 44.50 versus 44.90 on control; difference -0.40 (95% CI -3.53 to 2.73), standardized effect d = -0.11; z-test p = 0.802.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Acute Phase Reactants and Inflammatory Mediators (Interleukine-6)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Roux-en-Y Gastric Bypass Alone: mean 8.90 versus 4.80 on control; difference 4.10 (95% CI -7.36 to 15.56), standardized effect d = 0.30; z-test p = 0.483.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Roux-en-Y Gastric Bypass Alone and the control. The interval gives the range of effects that remain compatible with the data.

Acute Phase Reactants and Inflammatory Mediators (C-reactive Protein)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Roux-en-Y Gastric Bypass Alone: mean 69.20 versus 64.50 on control; difference 4.70 (95% CI -51.23 to 60.63), standardized effect d = 0.07; z-test p = 0.869.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Roux-en-Y Gastric Bypass Alone and the control. The interval gives the range of effects that remain compatible with the data.

Acute Phase Reactants and Inflammatory Mediators (Tumor Necrosis Factor-alpha)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Roux-en-Y Gastric Bypass Alone: mean 5.70 versus 5.20 on control; difference 0.50 (95% CI -2.02 to 3.02), standardized effect d = 0.17; z-test p = 0.697.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Roux-en-Y Gastric Bypass Alone and the control. The interval gives the range of effects that remain compatible with the data.

The detailed basal inflammatory comparisons show a mixed direction of point estimates, while their recalculated confidence intervals all include zero and are broad. This pattern is compatible with considerable uncertainty about between-arm differences at baseline. It does not establish that the arms are identical, and it does not show how the measures changed after surgery.

The stated study aim includes acute phase reactants and inflammatory mediators, so these outcomes are relevant to the broader research question. However, basal measurements provide information about the groups before the intervention’s effect could be assessed. They do not serve as evidence that adding omentectomy altered inflammation or metabolic syndrome. The primary body mass index result is also basal, so it cannot be used to validate or contradict a post-procedure effect.

The registry lists 20 secondary measures. When many outcomes are examined, the chance of observing a seemingly unusual result somewhere among them can increase, even when no real effect exists. This is the general multiplicity problem. If no prespecified hierarchy or adjustment is reported, individual secondary p-values carry less confirmatory weight than a single primary analysis. The registry record does not report a multiplicity plan or enough details to determine how the secondary analyses were selected or interpreted.

Accordingly, the secondary findings should be treated as descriptive and exploratory unless a prespecified analysis plan establishes otherwise. Their value is in indicating what was measured and showing the uncertainty around the posted basal comparisons. They do not support a causal conclusion about post-operative changes, and the complete results for all listed secondary measures are not reported in the registry record.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Acute Phase Reactants and Inflammatory Mediators (Interleukine-6)
• Acute Phase Reactants and Inflammatory Mediators (Interleukine-6)
• Acute Phase Reactants and Inflammatory Mediators (Interleukine-6)
• Acute Phase Reactants and Inflammatory Mediators (Interleukine-6)
• Acute Phase Reactants and Inflammatory Mediators (C-reactive Protein)
• Acute Phase Reactants and Inflammatory Mediators (C-reactive Protein)
• Acute Phase Reactants and Inflammatory Mediators (C-reactive Protein)
• Acute Phase Reactants and Inflammatory Mediators (C-reactive Protein)

9. Statistical Interpretation

10. Statistical Methods Explained

The registry presents continuous outcomes as means and standard deviations. A mean gives the arithmetic average within an arm; the standard deviation describes how spread out individual observations are around that average. These are complementary: similar means can occur alongside different amounts of variability, and a mean alone does not show the distribution of individual values. The primary outcome reports 11 observations in each arm and gives a mean and standard deviation for baseline body mass index.

What does the mean difference represent?

The unadjusted recalculation contrasts the mean in the gastric bypass-alone arm with the mean in the gastric bypass-plus-omentectomy arm. A value below zero means the first arm’s average is lower; a value above zero means it is higher. For the primary outcome, the recalculated difference is -0.4. For the basal inflammatory comparisons, the recalculated differences are positive. These contrasts are descriptive between-arm estimates at the reported baseline time point. They are not changes from baseline, because only basal values are involved in these comparisons.

In a randomized trial, a between-arm contrast can be used to estimate the effect of assignment when it is based on an appropriate outcome measured after the intervention and the analysis respects the design. A baseline comparison instead describes the starting groups. Randomization aims to make groups comparable on average, but it does not guarantee identical baseline values in a particular small trial. A baseline difference, by itself, does not establish that randomization failed or that the procedures caused the difference.

How should the t-test and p-value be read?

The registry reports a two-sided t-test for the primary outcome and for the detailed secondary comparisons. In general, a two-sided test evaluates departures in either direction from a null difference. A t-test assesses whether the observed difference is unusual under its assumptions, including an appropriate model for the sampling variation of the means. The registry does not report further details about the test implementation, such as whether a pooled-variance or alternative version was used.

A p-value measures how incompatible the observed data are with a specified null model, assuming that model and the test assumptions apply. It is not an estimate of the magnitude of a difference and does not tell how likely the null model is to be true. A larger p-value does not establish that two groups are the same. Demonstrating equivalence would require a prespecified equivalence margin and an analysis designed for that question; neither is reported in the registry record.

The sponsor’s reported primary p-value is 0.79, while the unadjusted recalculation is 0.802. The secondary reported p-values are 0.49 for interleukin-6, 0.87 for C-reactive protein, and 0.72 for tumor necrosis factor-alpha; the corresponding recalculated values are 0.483, 0.869, and 0.697. The posted outcomes do not include confidence intervals from the registry analyses. The recalculated intervals are derived from posted summary statistics and should be distinguished from analyses reported by the trial.

Why do confidence intervals matter?

A confidence interval places an estimate in context by displaying its uncertainty. A narrow interval indicates greater precision under the method’s assumptions; a wide interval indicates less precision. An interval crossing zero means that zero difference is among the values compatible with the data at the stated confidence level. That does not imply that zero is the only plausible value, nor does it rule out differences in either direction. The primary 95% interval extends from -3.533 to 2.733, while the secondary intervals are also broad and cross zero.

General statistical principle: the precision of a mean difference depends on sample size and variability within the arms. More observations often improve precision, while greater dispersion tends to reduce it. This is particularly relevant when the outcome has a wide spread and each arm has a small number of observations. The registry does not report the original precision target or a justification for the trial’s enrollment.

What does “unadjusted recalculation” mean?

It means that the comparison is reconstructed from the posted arm-level means, standard deviations, and sample sizes, without adjustment for covariates or other model features. The recalculated result is not a replacement for the trial’s prespecified analysis. It is a straightforward way to place the posted summaries on a common scale and show an estimated difference and uncertainty. The registry does not report whether the sponsor’s own analysis used additional adjustments or other procedures; the analysis details beyond the named t-test are not reported in the registry record.

There are 20 secondary measures posted, while only a subset of basal inflammatory comparisons has detailed values in the information discussed. Multiple outcomes create a multiplicity issue: when many hypotheses are tested, the chance of seeing at least one apparently notable result can increase. General statistical practice may address this through prespecified outcome hierarchies, multiplicity adjustments, or cautious interpretation. The registry does not report a multiplicity plan, so the posted secondary p-values should not be treated as if they were a single confirmatory test.

Finally, the result summaries alone do not reveal the analysis population, exclusions, missing-data handling, or whether every randomized participant contributed to each endpoint. Those details matter because the interpretation of a randomized comparison depends on how participants are retained and analyzed. The difference between the enrollment count, outcome counts, and safety at-risk counts is visible, but the reasons for those counts are not reported in the registry record.

11. Confidence Intervals and Precision

The recalculated 95% confidence interval for the primary baseline mean difference is -3.533 to 2.733, with the contrast defined as gastric bypass alone minus gastric bypass with omentectomy. The point estimate is -0.4. Because the interval includes zero and extends in both directions, the data do not pin down the direction of the baseline difference. Its span also indicates limited precision around the estimate. This uncertainty should be considered alongside the small outcome groups and the within-arm standard deviations of 3.1 and 4.3.

For the basal inflammatory outcomes, the corresponding recalculated 95% intervals are -7.357 to 15.56 for interleukin-6, -51.23 to 60.63 for C-reactive protein, and -2.02 to 3.02 for tumor necrosis factor-alpha. Each includes zero and permits differences in either direction. The wide intervals, particularly for measures with substantial observed spread, show why point estimates alone can give a misleading impression of certainty. The intervals do not establish equivalence: that conclusion would require a defined range of differences considered unimportant, which is not reported in the registry record.

These intervals are unadjusted recalculations from the posted summaries, not confidence intervals reported by the trial. General statistical explanation: a 95% confidence interval is produced by a method that, under its assumptions, would cover the true parameter in 95% of repeated samples. It is not a statement that there is a 95% probability the fixed true value lies inside this particular interval. The registry’s reported analyses provide p-values but do not report their own confidence limits. The intervals therefore offer a useful view of the precision of the simple recalculations, while retaining the limitations of those calculations and the available summary data.

Most importantly, these are baseline contrasts. Precision about a baseline difference does not answer how precisely the treatment effect was estimated after surgery. The registry record does not report the follow-up primary contrast or its confidence interval in the material interpreted.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are illustrations based on the observed effect, not the trial’s original design calculation. For these continuous outcomes, the figures represent participants per arm, not total participants or total events. The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to the stated fraction of the observed effect. The original design assumptions and sample-size justification are not reported in the registry record.

The 80% power column gives the illustrated number of participants per arm for a design with an 80% chance of detecting the specified effect under the planning assumptions, if that effect and the other assumptions were correct. The 90% power column gives the corresponding number per arm for a design with a 90% chance. These are planning targets, not a description of how likely the completed trial was to find a result.

Rows that plan for 100%, 75%, and 50% of the observed effect illustrate how the assumed effect size changes the required enrollment. A smaller effect is harder to distinguish from sampling variation and therefore requires more participants under the same assumptions. The figures are especially sensitive to the observed effect and variability in a small trial, so they should not be interpreted as a reliable estimate of a future study’s enrollment without independent design assumptions.

This is not observed power. It is a planning illustration derived from the observed effect, and it cannot tell whether the trial was adequately designed or explain the original enrollment target.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -0.400; pooled standard deviation σ = 3.748.
2. n = 2 × (1.96 + 0.842)² × 3.748² / -0.400² = 1,378.5, rounded up to 1,379 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -0.399999999999999                      # observed difference in means
sigma <- 3.74833296279826                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(923260)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 1,379 (80% power), 1,846 (90% power)
 75% of observed effect: n per arm = 2,451 (80% power), 3,281 (90% power)
 50% of observed effect: n per arm = 5,514 (80% power), 7,382 (90% power)
power.t.test: 1379.4 
Simulated power at n = 1,379 per arm: 0.803 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

The registry reports a two-sided t-test for the primary outcome with p = 0.79. The unadjusted recalculation from the posted means, standard deviations, and sample sizes gives p = 0.802. These values are close, and the record indicates no discrepancy between the sponsor analysis and the recalculation. The primary registry analysis does not report a confidence interval, test statistic, or additional details about the test implementation.

For the three detailed basal inflammatory outcomes, the sponsor-reported p-values are 0.49, 0.87, and 0.72 for interleukin-6, C-reactive protein, and tumor necrosis factor-alpha. The corresponding unadjusted recalculated p-values are 0.483, 0.869, and 0.697. The small differences between reported and recalculated values can arise from details not recoverable from rounded summary statistics or from analysis implementation; the registry does not specify the reason. No discrepancy is flagged.

The trial’s own reported analyses remain the primary record of what the investigators analyzed. Recalculated intervals and estimates are supplementary, unadjusted summaries rather than a substitute for the sponsor’s analysis. Since the posted primary measure is basal body mass index, agreement between the p-values does not change the central interpretation: the result describes a baseline comparison rather than a post-surgical effect.

15. Multiplicity, Missing Data and Analysis Populations

The registry lists 20 secondary measures in addition to the primary outcome. Testing multiple outcomes creates a multiplicity concern: the more comparisons examined, the greater the opportunity for a nominally notable result to occur by chance. A prespecified hierarchy, a family of hypotheses, or a statistical adjustment can help control the interpretation of multiple tests. Such methods and their rationale are not reported in the registry record. The secondary p-values should therefore be interpreted cautiously rather than as independent confirmatory evidence.

The record reports a two-sided t-test for the primary comparison and the detailed secondary comparisons, but does not report the complete statistical analysis plan. It is not reported whether any analyses were adjusted for baseline covariates, whether the primary test was prespecified in the same form as posted, or whether analyses used an intention-to-treat population. An equivalence or noninferiority objective and associated margins are not reported.

Missing-data handling is not reported in the registry record. The primary outcome and detailed basal secondary outcomes each list 11 participants per arm, whereas trial enrollment is 24 and safety at-risk counts are 12 per arm. Those counts alone do not reveal whether any participants lacked an outcome, were excluded from an analysis, or contributed to a different assessment. Participant flow, reasons for unavailable measurements, and imputation methods are not reported.

Analysis populations are also not described. Without knowing whether participants were analyzed according to randomized assignment or another rule, it is difficult to assess how closely the reported comparisons preserve the benefits of randomization. Masking is listed as none, but whether outcome measurement or analysis was blinded is not reported in the registry record. These omissions limit assessment of risk of bias and reproducibility; they do not establish that a particular procedure was or was not used.

16. 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 serious adverse event terms

Serious events with the highest arm-level rate: pancreatic fistula (8.3%).

The registry lists 12 participants at risk for serious adverse events in each arm. One serious adverse event is recorded in the gastric bypass-plus-omentectomy arm, and zero in the gastric bypass-alone arm. The listed serious event term is pancreatic fistula, with 8.3% shown in the registry. No other adverse events are recorded for either arm in the posted safety counts.

These figures are counts from a small trial and should be read as a description of the events recorded, not as a stable comparison of risk between procedures. The registry does not provide enough detail to establish the event’s timing, severity beyond its serious classification, relationship to either procedure, or the method used to collect and classify events. A count of zero in one arm does not demonstrate that an event cannot occur.

Deaths are not reported in the registry record. Safety at-risk counts differ from the 11 participants per arm reported for the primary outcome; the reason for the difference is not reported. Serious adverse events and other adverse events are separate categories in the registry, so the zero counts for other adverse events should not be read as negating the listed serious event.

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

The results describe baseline measures in a randomized comparison of gastric bypass with omentectomy against gastric bypass alone. The reported body mass index means are close, and the unadjusted recalculated estimate is imprecise. The detailed basal inflammatory comparisons also have broad intervals that include zero. These observations characterize the measured groups at baseline; they do not show whether adding omentectomy changed body mass index, metabolic syndrome, or inflammatory mediators after surgery.

A non-significant p-value is not proof that the procedures have identical effects. The trial does not report an equivalence margin, and the confidence intervals permit a range of differences. Likewise, a small point estimate cannot be taken as evidence of no meaningful effect when the estimate is imprecise. The trial’s outcome counts are small, and variability is substantial for some measures, so the posted comparisons have limited precision.

The registry’s stated research aim is broader than the primary result interpreted. A valid assessment of the added procedure’s effect would require appropriately timed post-intervention outcomes, a defined comparison such as change from baseline or follow-up values, and the corresponding analysis. Those results and analysis details are not reported in the registry record for the primary endpoint.

These data therefore do not establish that omentectomy improves or worsens any clinical outcome, nor do they establish equivalent outcomes between procedures. They also do not support medical advice. They show what the registry reports about baseline measures and serious adverse events, together with substantial uncertainty and gaps in the details needed to interpret post-operative effects.

18. Why This Trial Matters Statistically

This trial is statistically instructive because the stated clinical aim focuses on an added procedure, while the posted primary endpoint is a baseline measurement. The distinction between a baseline description and a treatment-effect estimate is fundamental. A comparison before the intervention cannot, by itself, establish whether the intervention caused a later difference.

The record also illustrates why estimates and uncertainty should be read together. The means and mean differences provide a direction and scale for the observed comparison, while the confidence intervals show how imprecisely the differences are estimated. With small outcome groups and appreciable spread, the intervals allow a range of values rather than a sharply determined effect. The reported p-values alone would not communicate that full uncertainty.

Finally, the record highlights the importance of prespecification and reporting. Twenty secondary measures are listed, but a multiplicity plan, detailed analysis populations, missing-data methods, and the original sample-size justification are not reported. Without those details, readers have limited ability to distinguish confirmatory findings from exploratory ones or to assess how the analyses were carried out. Clear outcome timing and complete follow-up reporting are especially important when the research question concerns change after surgery.

19. 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 the primary result is that the posted endpoint is body mass index at baseline. It does not directly answer the study’s stated question about the additional effect of omentectomy. The description refers to a basal value in a previous outcome measure to determine improvement, but the post-baseline primary result and its analysis are not reported in the registry record.

The outcome groups are small, with 11 participants per arm for the primary and three detailed basal inflammatory measures. The estimates are consequently imprecise, and the inflammatory measures show substantial variability. The difference between total enrollment, outcome counts, and safety at-risk counts is not explained; participant flow and reasons for any differences are not reported.

Important design and analysis details are also unavailable. The method of sequence generation, allocation concealment, eligibility criteria, original sample-size justification, analysis population, missing-data handling, and any covariate adjustment are not reported in the registry record. No multiplicity strategy is reported despite the listing of 20 secondary measures. The registry lists no masking, but does not say whether outcome assessment or analysis was blinded.

Only selected secondary measures have detailed numerical results in the information interpreted here, so the overall pattern across all posted secondary measures cannot be fully assessed. Safety counts are sparse, and the record does not provide event narratives or enough information to assess attribution. These limitations restrict conclusions about comparative effects and do not, by themselves, show that the trial procedures were inadequate.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Omentectomy and Metabolic Syndrome — NCT00923260.
• Registry record last updated 2009-12-07; status last verified 2009-11.
• Results first posted 2009-06-18.
• 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.

23. Record Summary

NCT00923260 is a completed randomized, parallel-group trial titled “Omentectomy and Metabolic Syndrome.” It compared laparoscopic Roux-en-Y gastric bypass with omentectomy against gastric bypass alone among participants with morbid obesity. The registry lists an enrollment of 24 and no masking.

The posted primary outcome is baseline body mass index, with 11 participants per arm. The registry reports a two-sided t-test p-value of 0.79; the unadjusted recalculation gives a mean difference of -0.4 and a 95% confidence interval of -3.533 to 2.733. The listed basal inflammatory comparisons are also uncertain and do not measure post-surgical change.

The record lists 20 secondary measures and reports one serious adverse event in the omentectomy arm and none in the comparator arm. Several analysis and participant-flow details are not reported in the registry record. The posted baseline results do not establish the effect of adding omentectomy after surgery.