LapBand Adjustment to Improve Early Weight Loss: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for LapBand Adjustment to Improve Early Weight Loss (NCT01060592), a non-randomized phase 2, phase 3 study. The primary outcome is %Excess Weight Loss 4-6 Weeks After Surgery (Large and Small Bands).

2. Clinical Question

3. Trial Design

The registry classifies this completed study as phase 2/3, nonrandomized, unmasked, and single-group. Enrollment is recorded as 35. The record describes a group receiving stoma adjustment during surgery and a historical reference based on weight-loss records from patients treated after surgery. These features mean the comparison is not a randomized, concurrent control comparison, even though the record describes both intervention and historical groups.

For the intervention, the first band adjustment was made during surgery. The EndoFLIP device was used to set the stoma to 7mm. The summary says that a chart relating stoma size to band fill was created during surgery and would guide later adjustments at routine follow-up visits. The historical description says the first adjustment was not made until 3-4 weeks after surgery and that later adjustments were made heuristically using the surgeon’s experience.

The registry lists the study start as 2009-10, primary completion as 2010-12, and status as completed. These dates describe the record’s study timeline; they do not establish when an analysis was conducted or whether all planned outcomes were collected. The protocol’s allocation rationale, recruitment details, follow-up completeness, and statistical analysis plan are not reported in the registry record. The record also does not explain how the historical patients were selected or how their records were aligned with the intervention group.

The historical arm description refers to 50 patients, whereas the serious-adverse-event record lists 49 at risk in that arm. Those entries are not reconciled in the registry record. They should be read as distinct reported details rather than treated as interchangeable descriptions of the same analysis population.

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: N/A - Single arm non-randomized study

4-6w

12m

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 %Excess Weight Loss 4-6 Weeks After Surgery (Large and Small Bands), measured over 4-6 weeks post surgery.

The primary endpoint is the mean percentage of excess weight lost, expressed as %EWL, at 4-6 weeks after surgery. It is specified for large and small bands. In general, an excess-weight-loss measure describes weight change relative to a reference amount of weight above a chosen target; however, the exact calculation and reference-weight definition are not given in the registry record.

A mean summarizes the average outcome in a group, while the standard deviation describes how spread out individual measurements are around that average. Reporting both can help readers distinguish the group’s central outcome from the variability among participants. The registry identifies the primary measure as a mean with standard deviation, but it does not report either value for either group.

The early measurement is relevant to the stated hypothesis because the intervention changes the timing of the first adjustment. It provides an outcome at 4-6 weeks, rather than a direct measure of longer-term weight loss. The registry separately lists the number of band adjustments required in the first year as a secondary outcome. Neither the clinical importance threshold for %EWL nor a target difference between groups is reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the endpoint’s summary measure?

The primary endpoint is a continuous measure, %EWL, summarized as a mean and standard deviation at 4-6 weeks after surgery. In general, a mean is the arithmetic center of observed measurements, and a standard deviation describes their dispersion. A mean can be useful for comparing group averages, but it does not show the full distribution: participants may have outcomes that vary substantially even when the group mean is similar. The registry does not give the group means or standard deviations, so neither the average outcome nor its variability can be assessed from this record.

The endpoint title specifies large and small bands, but does not define those categories or report results separately for them. The exact formula for %EWL, including its reference weight, is also not reported in the registry record. These definitions matter for reproducibility: different choices about a reference weight or subgroup classification can affect how a continuous endpoint is interpreted.

What does a group comparison require?

In general, a comparison of means estimates how far apart the group averages are, while a confidence interval describes the uncertainty around that estimated contrast. A narrow interval indicates greater precision than a wide interval, but its interpretation depends on how the estimate was produced and on the study design. No mean contrast or confidence interval for %EWL is reported in the registry record. No p-value or other inferential result for the primary endpoint is reported either.

A randomized comparison can, on average, balance measured and unmeasured characteristics between groups through the allocation process. This study is classified as nonrandomized and single-group, and its comparator is historical. General methodological caution therefore applies: differences between records can reflect factors other than the timing of band adjustment. Examples in general include differences in patient characteristics, clinical practice, follow-up, or outcome recording. Whether any of these occurred in this study, and whether an analysis addressed them, is not reported in the registry record.

Why does the historical comparator matter?

The intervention group received its first adjustment during surgery, while the historical description places the first control adjustment 3-4 weeks after surgery. This makes the timing contrast part of the intended question, but also means that treatment group and historical period may be linked. Without a concurrent comparison, it is not possible from the registry description alone to distinguish a timing-related difference from other changes over time. The historical records are described as heuristic adjustments guided by the surgeon’s experience, whereas the intervention summary describes a chart to guide later adjustments. The record does not report whether other care or measurement procedures were similar.

The historical arm description cites 50 patients, while the adverse-event information lists 49 at risk. The registry does not explain the difference. Nor does it state whether the same records or analysis populations were used for the primary endpoint and safety summaries. These uncertainties limit interpretation of denominators and comparability.

How should planning calculations be read?

The registry’s sample-size assumptions describe planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. In general, a sample-size calculation asks how many participants per arm might be needed under assumed conditions to detect an effect of a chosen size with a chosen level of power. The assumptions describe illustrative calculations, not the trial’s own design justification. They are not observed power, and they do not show that a result was found or that an analysis was performed.

The registry record does not report the effect estimate on which those illustrations were based, nor a sample-size justification established before the study. It also reports zero analyses. Thus, the planning assumptions cannot substitute for an outcome estimate, uncertainty interval, or description of the analysis actually used.

What is not established about the statistical approach?

The registry identifies five outcome measures and lists the number of analyses as zero, but it does not describe an analysis plan for the primary endpoint. It does not state whether comparisons were adjusted, how missing observations were handled, which participants were included in each analysis, or whether any interim analyses were planned or conducted. Those methods should not be inferred from the endpoint definition or from the study hypothesis. In general, transparent reporting of these choices helps readers understand the population, assumptions, and uncertainty behind an estimate. They are not reported 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("Historic", "Stoma Adjustment at Surgery")
n   <- c(39, 23)
m   <- c(15.63, 20.8)
sp  <- c(8.9, 10.8)
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  Historic  39  15.630  8.900  12.745  18.515
CARM  Stoma Adjustment at Surgery  23  20.800  10.800  16.130  25.470

11. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures, identifies %EWL at 4-6 weeks as the primary endpoint, and names the number of band adjustments in the first year as a secondary outcome. It does not describe how multiple outcomes or comparisons were handled statistically. The number of analyses is recorded as zero, and no endpoint-specific results or analysis plan are reported in the registry record.

In general, testing several outcomes or subgroups can increase the chance of finding an apparently notable result by chance. A prespecified hierarchy or adjustment strategy can clarify how multiple tests are interpreted. No such strategy is reported. The primary endpoint title refers to large and small bands, but the registry does not say whether these were planned as separate analyses, how they were defined, or whether any multiplicity approach applied.

Missing-data methods and analysis populations are also not reported in the registry record. There is no account of participants with unavailable %EWL measurements, incomplete follow-up, or exclusions from an analysis. The record does not specify whether all enrolled participants were intended for the primary analysis or whether a different population definition was used. These omissions matter because missing outcome data can affect both the estimate and its precision, especially when the reasons for missingness are related to the outcome or treatment.

The registry describes the intervention enrollment as 35 and lists 35 at risk for the safety record. It describes a historical profile of 50 patients, while the safety record lists 49 at risk. The record does not explain how these figures relate to endpoint-specific analysis populations. No assumptions about missing data, exclusions, or population membership can be established from these entries.

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 serious-adverse-event record lists 0 affected among 49 at risk in the historical group and 0 affected among 35 at risk in the group receiving stoma adjustment at surgery. These are reported counts, not evidence that the risk was exactly zero. The registry does not provide a confidence interval or other measure of uncertainty for these observations.

The historical arm description refers to 50 patients, whereas the serious-adverse-event record lists 49 at risk. The reason for this difference is not reported in the registry record. The recorded number at risk should therefore be read as the denominator attached to the safety entry, not as a resolution of the historical group’s size across all outcomes.

The record does not list serious adverse-event terms, and death counts are not reported in the registry record. It also does not explain the safety-event collection period, definitions, or completeness of reporting. General caution is warranted when reading zero-event counts: they describe what was recorded for the stated at-risk groups, and do not alone establish the absence of all safety events or quantify the uncertainty around risk.

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

The record establishes the intended comparison: adjustment of the gastric band during surgery, with the stoma set to 7mm using EndoFLIP, versus a historical pattern in which the first adjustment was made 3-4 weeks after surgery. It defines early %EWL at 4-6 weeks as the primary endpoint and identifies first-year band adjustments as a secondary outcome. These details describe the research question and measurement plan, not the observed results.

No primary endpoint values, variability estimates, group contrast, or inferential result are reported in the registry record. The record therefore does not allow readers to determine the observed early weight-loss profile or the precision of a comparison. It also does not report the secondary outcome result for the number of adjustments. The study hypothesis that an earlier adjustment could promote earlier weight loss and reduce later adjustments should not be read as evidence that either outcome occurred.

Even if outcome estimates were available, the nonrandomized historical comparison would call for caution. Differences between groups could reflect factors beyond adjustment timing, and the registry does not report an analysis addressing such differences. The record also does not explain the difference between the historical group’s 50 patients in the arm description and 49 at risk in the safety record.

The serious-adverse-event entries show zero affected in each listed group, but the associated denominators and absent event definitions limit what can be concluded. These entries are not a substitute for complete safety reporting or a comparison with quantified uncertainty. Overall, the registry record documents a completed study and its intended question, but does not provide the outcome evidence needed to judge the magnitude, precision, or robustness of the primary comparison.

14. Why This Trial Matters Statistically

This study raises a useful statistical issue: an intervention’s timing can be compared with historical care, but such a comparison does not have the same basis for causal interpretation as random assignment with concurrent groups. The record explicitly classifies the study as nonrandomized and single-group, while describing a historical reference. Readers therefore need to distinguish the study’s hypothesis from what its design can establish and from what its reported results actually show.

The endpoint is also time-specific. Mean %EWL at 4-6 weeks focuses on early weight change, while the study’s stated rationale also concerns the number of adjustments over the first year. Those are distinct outcomes and time horizons. A result for one would not automatically answer the other. The registry identifies both, but does not report outcome estimates for either.

The record illustrates why denominators and analysis populations should be clear. The historical description refers to 50 patients, yet the safety record lists 49 at risk. Without an explanation, readers cannot assume that those counts refer to identical populations or that one is an error. Similarly, a zero-event count needs its denominator, event definitions, and reporting period to be fully interpretable.

Finally, planning illustrations and observed results answer different questions. A calculation based on an observed effect does not establish that the study had adequate design-stage planning, and it is not observed power. Here, the outcome estimate underpinning the illustrations is not reported in the registry record. The example underscores the importance of reporting the estimate, its uncertainty, the analysis population, and the methods used to make a comparison.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The principal limitation for interpretation is that the registry record does not include the primary endpoint results. There are no reported group means, standard deviations, effect estimate, confidence interval, or test result for %EWL at 4-6 weeks. Results for the listed secondary outcome, the number of band adjustments in the first year, are also absent. The registry records zero analyses.

The design is nonrandomized and uses historical controls, so the groups may differ for reasons other than when the first adjustment occurred. The historical adjustments were described as heuristic and based on the surgeon’s experience; the intervention summary describes a chart to guide later adjustments. The registry does not report whether patient characteristics, clinical practices, follow-up, or measurement procedures were comparable, or whether statistical adjustment was attempted.

The record does not define the calculation of %EWL, explain the large- and small-band categories, or report endpoint-specific denominators. It does not describe missing-data handling, analysis populations, multiplicity methods, or a statistical analysis plan. The historical arm is described as 50 patients, while 49 are listed at risk for serious adverse events; that difference is unexplained. Safety-event definitions, collection period, and death counts are not reported in the registry record.

These limitations mean that the record supports a description of the study question and design, but not a quantitative assessment of the primary comparison or its precision.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: LapBand Adjustment to Improve Early Weight Loss — NCT01060592.
• Registry record last updated 2013-04-08; status last verified 2013-04.
• Results first posted 2013-04-04.
• 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

NCT01060592 is a completed phase 2/3 study sponsored by Crospon, with a registry start of 2009-10 and primary completion of 2010-12. It is classified as nonrandomized, unmasked, and single-group, with enrollment recorded as 35. The intervention involved making the first gastric-band adjustment during surgery, using EndoFLIP to set the stoma to 7mm. The comparator is described through historical records in which the first adjustment was delayed until 3-4 weeks after surgery.

The primary endpoint is mean %EWL at 4-6 weeks after surgery, identified for large and small bands. The number of band adjustments in the first year is listed as a secondary outcome. The record does not report results for these endpoints or an analysis of the comparison. Serious adverse events are recorded as 0 among 49 at risk in the historical group and 0 among 35 at risk in the intervention group; death counts are not reported in the registry record. The historical arm description refers to 50 patients, a difference the record does not explain.