Effectiveness and Safety Study of LAP-BAND Treatment in Subjects With BMI >/= 30 kg/m2 and < 40 kg/m2: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effectiveness and Safety Study of LAP-BAND Treatment in Subjects With BMI >/= 30 kg/m2 and < 40 kg/m2 (NCT00570505), a na na study. The primary outcome is Percent of Subjects Attaining Clinically Successful Weight Loss ( ≥ 30% EWL) at 1 Year Post LAP-BAND Implantation.

2. Clinical Question

The stated purpose was to assess whether the LAP-BAND System was safe and effective in subjects in the specified BMI range. Statistically, the primary endpoint is a binary outcome: each subject either attained the defined weight-loss threshold by the stated assessment time or did not. The intended summary is the percentage of subjects meeting that threshold in the intent-to-treat population.

Because the record describes one group without a control arm, the primary question is descriptive for the treated study group. It does not estimate a randomized contrast between the device and another treatment or no treatment. A comparison with a benchmark would require a stated benchmark and an analysis; neither is reported in the registry record. The endpoint result itself is also not reported, so the record does not establish how many subjects met the threshold or how precisely the percentage was estimated.

3. Trial Design

This was a completed, single-group study sponsored by Apollo Endosurgery, Inc. The record lists enrollment of 151 and identifies the study condition as obesity. The intervention was the LAP-BAND System. The arm description states that all subjects in the LapBand group received the device. Allocation is listed as NA, masking as NONE, and phase as NA.

The study began in 2007-11, and primary completion is recorded as 2009-10. These dates describe the study record; they do not establish the follow-up duration for every participant. The primary endpoint has a one-year timeframe after implantation, but the record does not report individual follow-up completeness or how missing one-year assessments were handled.

There is no randomized control group described. The record itself cautions that this is not a randomized comparison and that the arms are not a like-for-like control comparison. Since only one group is described, the study design supports reporting outcomes among those enrolled and treated, but does not by itself separate the intervention’s effects from other explanations for observed changes.

The listed secondary outcomes are percent weight loss, change in comorbid conditions related to obesity, and change in quality of life. The record lists eight outcome measures and zero analyses. It does not report the study’s protocol-based sample-size justification, details of any interim analyses, or a statistical analysis plan. Those omissions limit what can be concluded about how the study was planned and how its outcomes were intended to be evaluated.

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: 155 Subjects were enrolled per protocol (defined as signing the informed consent). After enrollment, 4 subjects withdrew consent prior to treatment, and 2 subjects were not implanted due to ineligibility discovered during screening. This resulted in 149 subjects starting the study and receiving treatment with the LAP-BAND System.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Intent-to-treat (ITT)

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 Percent of Subjects Attaining Clinically Successful Weight Loss ( ≥ 30% EWL) at 1 Year Post LAP-BAND Implantation, measured over One year.

The primary endpoint is the percentage of subjects attaining clinically successful weight loss one year after LAP-BAND implantation. The record defines success as at least 30% excess weight loss. Excess weight loss is defined as weight loss divided by excess weight, multiplied by 100. The endpoint population is intent-to-treat.

This is a binary endpoint at the participant level: the criterion is either met or not met at the specified assessment. Reporting a percentage gives a direct description of how common that defined outcome was in the study population. A threshold-based measure can be easier to interpret than a continuous average when the clinical question is framed around the proportion reaching a specified target. It also discards information about how far each person’s result lies above or below the threshold, so it should not be confused with the full distribution of weight changes.

The endpoint is specifically tied to one year after implantation. The record does not report the number meeting the criterion, the resulting percentage, a confidence interval, or a statistical test. Consequently, the endpoint definition is available, but the primary result and its precision are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What kind of outcome is the primary endpoint?

The endpoint is binary at the participant level because it classifies each subject according to whether at least 30% excess weight loss was attained at one year. The group-level result would ordinarily be expressed as a percentage of participants meeting the criterion. In general, a binary outcome simplifies a potentially continuous measurement into a yes-or-no classification. That can make the target straightforward to communicate, but it also means that distinct weight-loss amounts on the same side of the threshold receive the same classification.

The definition is important to interpretation. The record defines excess weight loss using weight loss divided by excess weight, multiplied by 100, and uses the threshold of at least 30% to define clinical success. It does not report further operational details about how excess weight was calculated for each subject or how measurements were collected. Such details are not reported in the registry record.

What can a one-group estimate tell readers?

In general, a one-group estimate describes the outcome frequency in the group studied. It does not, on its own, show what would have happened to the same participants under a different intervention or without the intervention. A randomized comparison is one way to estimate a between-group contrast while reducing systematic differences between groups. This record describes no randomized comparison; allocation is NA and the design is single group. Therefore, even if the endpoint percentage were reported, it would be a group outcome rather than a randomized treatment contrast.

The registry record identifies the primary population as intent-to-treat. In general, an intent-to-treat approach aims to analyze participants according to their assigned study group, regardless of treatment adherence. In a single-group study, the practical details of how that population was defined and how participants with missing endpoint measurements were handled remain important. Those details are not reported in the registry record.

How should precision be understood?

In general, a point estimate is an estimate from the observed study data, while a confidence interval conveys uncertainty around that estimate under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, but does not by itself resolve limitations such as missing data or lack of a comparator. The registry record does not report the primary endpoint estimate or its confidence interval, so no numerical statement about its precision can be made.

A p-value, when reported, addresses how compatible the observed data are with a specified statistical null model. It does not measure the size or clinical importance of an outcome. No primary endpoint test or p-value is reported in the registry record. It is therefore not possible to characterize statistical evidence for the endpoint from the posted results.

What do the sample-size assumptions mean?

The record describes planning illustrations using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says that the effect used for planning is a stated fraction of the observed effect. These are planning assumptions, not a description of this study’s design: this trial is listed as a single-group study, not a two-arm randomized comparison. The record does not report a protocol-based sample-size justification for the trial. Any planning sample sizes based on an observed effect are illustrations and should not be read as observed power or as evidence that the study was adequately or inadequately sized.

In general, sample-size calculations depend on the outcome, design, target effect, statistical error rates, and analysis assumptions. A planning calculation describes what a hypothetical design might require under those assumptions; it does not establish what was observed. The registry record does not report the primary endpoint result from which such an observed-effect illustration could be evaluated.

How do adverse-event summaries differ from comparative analyses?

The safety record gives participant counts at risk and affected, as well as selected serious adverse-event terms with percentages. These quantities describe reported events in the study group. In general, counts of participants affected differ from counts of event episodes: one participant can potentially experience more than one event, and an event listing does not necessarily tell readers whether categories overlap. The registry record does not provide enough detail to determine the relationship among categories, the event-level counting rules, or the duration of safety follow-up.

Because there is no comparator group, the safety summaries do not estimate a relative risk against another treatment. A percentage listed for a serious-event term should be read as a reported registry figure, not as a comparative effect or a causal estimate. Further details about event adjudication, exposure time, and statistical testing are not reported in the registry record.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("LapBand")
n      <- c(143)
events <- c(120)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  LapBand  143  120  83.9  76.9  89.5  77.0  89.0  77.0  89.0

11. Multiplicity, Missing Data and Analysis Populations

The record lists three secondary outcome topics: percent weight loss, change in comorbid conditions related to obesity, and change in quality of life. It also lists eight outcome measures overall. The primary endpoint is the percentage meeting the defined excess-weight-loss threshold at one year. The record lists zero analyses, and it does not report statistical tests for the primary or secondary outcomes.

When multiple outcomes or multiple statistical tests are considered, the chance of at least one apparently notable result can increase. In general, multiplicity methods may be used to control that risk, or outcomes may be designated as descriptive or exploratory. The registry record does not report a multiplicity strategy, a hierarchy for secondary outcomes, or which analyses, if any, were confirmatory. No conclusions about adjustment or prespecification can be drawn from the listed outcome names alone.

The primary population is identified as intent-to-treat, but the handling of missing endpoint data is not reported in the registry record. The record does not state how many subjects had an observed one-year measurement, how missing values were treated, or whether any sensitivity analyses were planned or performed. In general, missingness can affect the estimated percentage if participants without measured outcomes differ from those with observed outcomes. Without the missing-data details, the potential effect cannot be assessed.

The registry record also does not report a statistical analysis plan, interim analyses, or a protocol-based sample-size justification. These omissions mean that the analysis choices and their timing cannot be evaluated from the record. They should not be filled in by assuming a conventional approach.

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 1% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: gastric outlet obstruction (3.4%), gastric prolapse (2.7%), band slip (2.7%), band erosion (1.3%), abdominal cavity abscess (0.7%).

The safety summary reports that 149 subjects were at risk for serious adverse events and 18 were affected. For other adverse events, 149 were at risk and 145 were affected. These are participant counts, not necessarily counts of distinct event episodes. The record does not provide the safety follow-up duration or explain whether a participant could be counted in more than one event category.

The listed serious adverse-event terms include gastric outlet obstruction at 3.4%, gastric prolapse at 2.7%, band slip at 2.7%, band erosion at 1.3%, abdominal cavity abscess at 0.7%, and abdominal Pain at 0.7%. These percentages are reported as registry figures. The record does not provide their event-count denominators or additional detail about how terms were selected for listing.

The serious-event figures describe reported experience in the single study group. Without a comparator, they do not establish whether event rates are higher or lower than those under another treatment. Deaths are not reported in the registry record; a blank death entry should not be interpreted as a reported count of zero.

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

The record establishes that the study assessed the LAP-BAND System in subjects with obesity and a BMI at least 30 kg/m2 and under 40 kg/m2. It identifies the primary outcome as attainment of at least 30% excess weight loss one year after implantation and gives the endpoint population as intent-to-treat. It also reports selected serious adverse-event figures and lists secondary outcome topics.

Those details do not amount to a reported primary efficacy result. The registry record does not state the percentage or number of subjects reaching the weight-loss threshold, and it does not provide an interval or statistical test for that endpoint. As a result, readers cannot determine from this record how often the threshold was met or how precisely that frequency was estimated.

The design also limits comparative interpretation. The study is single group, with no randomized comparator described. An outcome observed in the treated group would not, by itself, quantify how outcomes differ from an alternative. The registry record does not provide a benchmark against which to assess the primary endpoint.

The safety figures provide counts and selected event-term percentages for the study group. They can be read as descriptive reports, but they are not comparative estimates and do not indicate how risks would differ under another intervention. The record does not report the duration of safety follow-up or enough detail to reconstruct event-level rates.

In short, the registry record defines what was studied and how the principal endpoint was framed, but leaves the main endpoint result and key analysis details unreported. It supports a description of the study design and recorded safety summaries, not a conclusion about comparative benefit or harm.

14. Why This Trial Matters Statistically

This study raises several statistical issues common to device studies with threshold-based outcomes. The primary endpoint translates a continuous weight-loss measure into a binary criterion: at least 30% excess weight loss at one year. This makes the intended outcome easy to state, but it can conceal variation among subjects who fall on the same side of the threshold. The definition and timing therefore matter when interpreting any reported percentage.

The single-group structure is another central issue. A group-level percentage can describe the outcomes observed among participants, but a causal or comparative claim requires a meaningful reference. The registry record describes no randomized comparator and explicitly notes that this is not a randomized comparison. That distinction should remain clear even if a primary result is available elsewhere.

Reporting completeness matters as much as the choice of outcome. Here, the endpoint definition and intent-to-treat population are recorded, while the observed endpoint result, confidence interval, analysis, and missing-data handling are not reported in the registry record. Without those elements, neither the size nor the precision of the primary estimate can be evaluated from the record.

The safety summaries also illustrate why denominators and context matter. The record reports participants at risk and affected, alongside selected percentages for serious-event terms, but does not report follow-up duration or a comparison group. Those figures are useful as descriptive entries, yet cannot be interpreted as relative safety effects.

For clinical researchers and biostatisticians, the key lesson is to distinguish an endpoint definition from an endpoint result, a descriptive cohort outcome from a comparative effect, and planning assumptions from the study’s actual design. Each distinction constrains what can responsibly be inferred.

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 statistical interpretation is that the registry record does not report the primary endpoint result. Although the outcome is defined as attaining at least 30% excess weight loss at one year, the number and percentage attaining it are absent. No confidence interval or statistical test is reported, so the result’s magnitude and precision cannot be assessed.

The single-group design provides no concurrent control arm. The record lists allocation as NA and masking as NONE, and it states that this is not a randomized comparison. Consequently, the study description does not support a direct estimate of how outcomes differ from another treatment or from no intervention.

Although the primary population is labeled intent-to-treat, the record does not report endpoint completeness or missing-data procedures. It does not say how many participants contributed an observed one-year outcome or how incomplete follow-up was addressed. The statistical impact of missing information is therefore unknown.

The registry record lists eight outcome measures and zero analyses, but does not report an analysis plan, multiplicity strategy, interim analyses, or a protocol-based sample-size justification. It is not possible to assess whether outcome analyses were prespecified or how multiple outcomes were handled.

For safety, the record reports participant counts and selected serious-event terms, but does not state the follow-up duration, event-counting rules, or whether categories overlap. The death entry is not reported in the registry record. These details limit interpretation of the safety summaries beyond their descriptive form.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Effectiveness and Safety Study of LAP-BAND Treatment in Subjects With BMI >/= 30 kg/m2 and < 40 kg/m2 — NCT00570505.
• Registry record last updated 2015-03-17; status last verified 2015-03.
• Results first posted 2012-12-03.
• 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

NCT00570505 is a completed, single-group study sponsored by Apollo Endosurgery, Inc. It enrolled 151 subjects with obesity and evaluated the LAP-BAND System in subjects with a BMI at least 30 kg/m2 and under 40 kg/m2. The primary endpoint was the percentage attaining at least 30% excess weight loss one year after implantation, in an intent-to-treat population.

The registry record does not report the primary endpoint result, a confidence interval, or an analysis. It lists percent weight loss, changes in obesity-related comorbid conditions, and quality of life among secondary outcomes, with eight outcome measures and zero analyses listed. Safety summaries report 18 of 149 subjects affected by serious adverse events and 145 of 149 affected by other adverse events. The study has no randomized comparator, and its record does not report missing-data procedures or a protocol-based sample-size justification.