Clinical and Economic Outcomes in Laparoscopic Sleeve Gastrectomy Versus Roux-en-Y Gastric Bypass Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Clinical and Economic Outcomes in Laparoscopic Sleeve Gastrectomy Versus Roux-en-Y Gastric Bypass Surgery (NCT01754194), a registered phase not stated study. The primary outcome is Quality of Life (QOL) in First Postoperative Year According to EuroQol-5 Dimensions-5 Levels (EQ-5D-5L).

2. Clinical Question

3. Trial Design

This was an observational study of two surgical procedures for morbid obesity: gastric sleeve resection and Roux-en-Y gastric bypass. The official title describes an evaluation in clinical and health-economic terms. The registry record reports enrollment of 293 and a completed status. It lists the study start as 2012-04 and primary completion as 2013-09.

The record does not state how participants were allocated to the procedures. It therefore does not establish that treatment assignment was random, nor does it describe a randomized control comparison. As an observational comparison, differences between groups could reflect which patients received each procedure, along with other differences in clinical circumstances. The record does not report baseline characteristics or an adjustment strategy that would show whether such differences were addressed.

The stated objectives included generating local clinical, health-related quality-of-life and health-economic data, as well as supporting multidisciplinary bariatric sites in Germany through structured procedure guidelines and training. These objectives provide context for the evaluation, but do not establish that training changed outcomes or that one procedure was superior.

The primary outcome was quality of life during the first postoperative year, assessed with EQ-5D-5L and summarized over 12 Months. Listed secondary outcomes included excess weight loss, duration of surgery, recovery time, transfer to intensive care or another special unit during hospitalization, and surgical complications. Although the record lists 8 outcome measures, it reports 0 analyses. Statistical methods for comparing the procedures, participant flow, group sizes, and details of follow-up 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.

Before assignment: Use or preference of surgical procedure was at the discretion of the surgeon. For each patient, the study consisted of three phases: Screening/Baseline; Surgery; Post-operative observation for up to 12 months. Data were gathered per SoC (Standard of Care) at each of the three study phases.

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 Quality of Life (QOL) in First Postoperative Year According to EuroQol-5 Dimensions-5 Levels (EQ-5D-5L), measured over 12 Months.

The primary endpoint is quality of life during the first postoperative year, measured with EQ-5D-5L and reported in Score*months over 12 Months. The registry description says that the measure includes a descriptive system covering mobility, self-care, usual activities, pain or discomfort, and anxiety or depression. Each dimension has five response levels, ranging from no problems to extreme problems. It also describes an EQ visual analogue scale, on which patients mark their health from 0 (worst health imaginable) to 100 (best health imaginable) on a 20 cm vertical scale.

The registry record describes a global score at each timepoint that combines the five dimensions and the VAS according to a specific algorithm. It then describes an area-under-the-curve summary intended to combine repeated quality-of-life measurements taken at flexible intervals between 0 and 12 months after the procedure. In general, an area-under-the-curve measure can represent the level of an outcome across a period rather than at only one assessment. The record states that a higher value represents better quality of life.

This type of summary can be useful when repeated measurements are collected over time, but interpretation depends on the scoring algorithm, measurement schedule, and handling of missing assessments. Those details, along with the observed group values and their uncertainty, are not reported in the registry record. The endpoint definition alone therefore does not indicate which procedure had a higher score or how precisely any group difference was estimated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies the study as observational and does not state how participants were assigned to gastric sleeve resection or Roux-en-Y gastric bypass. This distinction is central to interpreting a comparison. In a randomized study, random assignment is intended to balance measured and unmeasured characteristics across groups on average. In an observational study, procedure selection may be related to patient characteristics or clinical decisions. As a result, an observed group difference may reflect both procedure choice and differences between the people who received each procedure.

What does an unadjusted comparison represent?

In general, an unadjusted comparison contrasts outcome summaries between groups without accounting for other variables. It describes the difference observed in those groups, but does not by itself show that the procedure caused the difference. An adjusted analysis can account for measured characteristics using a specified statistical model, but it cannot automatically remove bias from unmeasured factors or incorrect model assumptions. The registry record does not report whether the primary comparison was adjusted, which variables might have been included, or what model was used.

How should a continuous outcome be read?

The primary outcome is described as a mean of a continuous measure, with standard deviation as the dispersion measure. A mean gives a summary of the observed scores; a standard deviation describes how spread out scores are around that mean. They answer different questions: the mean concerns the average outcome level, while the standard deviation concerns variation among observations. The registry record does not report the group means or standard deviations, so neither the average quality-of-life level nor its variability can be assessed from the posted results.

In general, a comparison of means is most informative when accompanied by an estimate of the difference and its uncertainty. A confidence interval communicates precision as well as the range of effect values compatible with the data and model. A p-value, if reported, addresses compatibility with a specified null hypothesis under statistical assumptions; it does not measure clinical importance or the probability that a hypothesis is true. No primary comparison estimate, confidence interval, or p-value is reported in the registry record.

What does the area-under-the-curve endpoint add?

The registry description says the EQ-5D-5L outcome combines repeated measurements collected at flexible time intervals between 0 and 12 months after surgery into one area-under-the-curve value. In general, this approach can summarize both the level and persistence of an outcome across follow-up. It may be more informative than relying on a single timepoint when the question concerns the experience across a period. However, a single summary can hide the timing of changes: similar overall values could arise from different patterns of improvement or decline.

Interpretation also relies on how the score is calculated and how observations at different timepoints contribute to it. The registry record describes a composite involving the five descriptive dimensions and the VAS, but does not provide the scoring algorithm or details of how the area was calculated. The schedule of assessments, rules for irregular measurements, and handling of missing observations are also not reported in the registry record.

Why does over-dispersion matter in general?

For count outcomes, over-dispersion means that the observed variation is greater than expected under a simple model such as a Poisson model. If it is ignored, standard errors can be too small and confidence intervals too narrow. This is a general statistical consideration, not a claim about this study: the registry record does not describe a count-outcome analysis or report a model for the listed secondary outcomes. For continuous outcomes such as the stated primary measure, the relevant model assumptions and diagnostics would depend on the analysis actually used, which is not reported.

What can the planning illustration say?

The record describes a planning illustration based on a fraction of the observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation. It specifies participants per arm for non-time-to-event outcomes and a total event count for time-to-event outcomes. Such calculations are planning scenarios, not observed power and not evidence that the original study was designed around those assumptions. The registry record does not report the resulting planning values or the trial's own sample-size justification. The planning description also does not resolve the interpretation of an observational comparison or replace an analysis of the posted outcomes.

More broadly, statistical methods are only interpretable when linked to the endpoint, analysis population, missing-data approach, and group estimates. These details are not reported in the registry record. The available description therefore allows the endpoint and general methodological issues to be explained, but does not support reconstruction of the study's analysis.

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("Procedure Type I", "Procedure Type II")
n   <- c(169, 124)
m   <- c(3, 3)
sp  <- c(0.1, 0.1)
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  Procedure Type I  169  3.000  0.100  2.985  3.015
CARM  Procedure Type II  124  3.000  0.100  2.982  3.018

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists 8 outcome measures, including the primary quality-of-life endpoint and secondary outcomes related to excess weight loss, health-resource use, and surgical complications. It reports 0 analyses. The record does not explain whether the outcomes were tested in a prespecified hierarchy, whether adjustment for multiple comparisons was used, or how the primary outcome was distinguished from exploratory analyses. Without this information and the outcome estimates, the chance of selective emphasis across outcomes cannot be assessed.

In general, testing multiple outcomes can increase the chance of observing at least one apparently notable result even when no underlying differences exist. Methods that control or otherwise address multiplicity can help, but the suitable approach depends on the study questions and analysis plan. No such approach is reported in the registry record. The stated primary outcome identifies the endpoint of principal interest, but by itself does not establish how multiplicity was handled.

The registry record does not report missing-data counts, completeness of follow-up, reasons for missing assessments, or an approach to handling missing EQ-5D-5L measurements. These details are important for an area-under-the-curve endpoint based on repeated observations: incomplete follow-up could affect both the calculated summary and which participants contribute to an analysis. The record also does not report the analysis population, such as which participants were included in each outcome analysis or how exclusions were handled.

Allocation to procedures is not stated, and the record identifies the arms as not being a like-for-like control comparison. Without reported baseline information, missing-data handling, analysis populations, and adjustment methods, readers cannot assess whether the compared groups and analyzed participants were sufficiently comparable for the intended interpretation.

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

The registry record establishes that an observational evaluation compared gastric sleeve resection with Roux-en-Y gastric bypass and identified quality of life during the first postoperative year as its primary outcome. It also defines the intended EQ-5D-5L summary and lists clinical and health-economic outcomes. Those details clarify the research question, but they do not reveal the findings.

No outcome estimates or statistical comparison results are reported in the registry record. It is therefore not possible to say from the posted information which procedure group had a higher quality-of-life summary, whether any apparent difference was large or small, or how precisely it was estimated. The same limitation applies to the listed secondary outcomes. The study's completed status does not establish that a result favored either procedure.

Even if a numerical difference were available, an observational comparison would require careful interpretation. Because allocation is not stated, the registry record does not show that groups were made comparable through randomization. Differences in patient characteristics or procedure selection could contribute to observed outcome differences. An association between procedure and outcome would not, on its own, establish that the procedure caused the association.

In general, statistical significance and clinical importance are distinct. A small difference may be estimated precisely, while a potentially important difference may be estimated imprecisely. Assessing either requires effect estimates and uncertainty, as well as context for interpreting the scale. The registry record reports neither the primary comparison estimate nor its uncertainty, so neither judgment can be made.

The study's stated objectives include generating local clinical, quality-of-life, and economic data and supporting bariatric sites in Germany. These are aims, not evidence that the objectives were achieved or that the procedures had particular effects. The record supports understanding what was intended to be evaluated; it does not support a treatment recommendation or a conclusion that one procedure works better.

13. Why This Trial Matters Statistically

This study raises a useful statistical question: how should quality of life across a postoperative period be compared when the data come from an observational evaluation of two procedures? The chosen EQ-5D-5L area-under-the-curve endpoint is intended to combine repeated assessments across the first postoperative year. This reflects a question about the course of quality of life, rather than only a score at one follow-up point.

The observational design also illustrates why the label of a comparison is not enough to interpret it. When allocation is not stated and the record flags that the arms are not a like-for-like control comparison, differences in observed outcomes may have multiple explanations. Baseline characteristics, procedure selection, and analytical adjustment would be relevant to judging comparability, but those details are not reported in the registry record.

The record further distinguishes outcomes of different kinds. Quality of life is a continuous patient-reported measure; the listed secondary outcomes include resource-use measures and surgical complications. Different outcomes call for different summaries and potentially different analytical assumptions. Definitions alone do not show what was observed, and a list of outcomes does not reveal how multiplicity, missing measurements, or analysis populations were handled.

Finally, the registry record demonstrates the limits of interpreting a completed study from an outcome description alone. Without estimates and uncertainty, readers cannot judge the magnitude or precision of a comparison. Statistical interpretation depends not only on the study question and endpoint, but also on transparent reporting of the analysis and results.

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 available registry information leaves important details about design and execution unreported. Although enrollment is listed as 293, the record does not give the number of participants in each procedure group, explain the allocation process, or report baseline characteristics. Allocation is explicitly not stated, and the arms are identified as not being a like-for-like control comparison. These gaps limit assessment of group comparability and confounding.

The primary endpoint is described, but its score construction is not fully reproducible from the record. The EQ-5D-5L description refers to a specific algorithm combining the five dimensions and VAS, and to an area-under-the-curve summary across flexible measurement times. The algorithm, assessment schedule, calculation details, and missing-measurement rules are not reported in the registry record.

Outcome estimates and analysis details are also absent. The record lists 8 outcome measures and 0 analyses, but does not report group results, uncertainty estimates, statistical tests, covariate adjustment, multiplicity procedures, or the analysis population. It therefore does not permit evaluation of the magnitude, precision, or robustness of the comparisons.

The adverse-event fields list 0 participants at risk and 0 affected for serious and other events in each procedure group. These entries do not establish that no events occurred: the record does not explain the zero at-risk entries, and death counts are not reported in the registry record. The listed secondary outcome of surgical complications likewise has no reported findings. These reporting limitations make it inappropriate to interpret the adverse-event fields as evidence of safety or absence of complications.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Clinical and Economic Outcomes in Laparoscopic Sleeve Gastrectomy Versus Roux-en-Y Gastric Bypass Surgery — NCT01754194.
• Registry record last updated 2017-07-07; status last verified 2017-04.
• Results first posted 2017-07-07.
• 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

NCT01754194 is a completed observational study titled “Clinical and Economic Outcomes in Laparoscopic Sleeve Gastrectomy Versus Roux-en-Y Gastric Bypass Surgery.” It concerns people with morbid obesity and lists gastric sleeve resection and Roux-en-Y gastric bypass as the procedures evaluated. The sponsor is Medtronic - MITG. Enrollment is listed as 293; the study start is 2012-04 and primary completion is 2013-09.

The primary outcome is quality of life assessed with EQ-5D-5L over 12 Months and summarized as Score*months using an area-under-the-curve approach. Secondary outcomes include excess weight loss, surgery duration, recovery time, transfers to intensive care or another special unit during hospitalization, and surgical complications. The study objectives also describe local clinical, quality-of-life, and health-economic data generation and support for multidisciplinary bariatric sites in Germany.

Allocation is not stated, and the record cautions that the arms are not a like-for-like control comparison. Although outcome measures are listed, the record reports 0 analyses and no outcome estimates. Group results, analysis methods, missing-data handling, and the analysis population are not reported in the registry record.