Post Implantation/Post Market Evaluation of the Swedish Adjustable Gastric Band: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Post Implantation/Post Market Evaluation of the Swedish Adjustable Gastric Band (NCT00543140), a na phase 4 study. The primary outcome is Re-operation Rate (Band Revision, Band Replacement and Explants Resulting From Serious Adverse Device-related Event {SADE}) of Gastric Banding at 4 and 5 Years Post Implant..

2. Clinical Question

In plain terms, the study asks how often a narrowly defined, device-related re-operation was recorded in the described population after implantation. This is a question about the occurrence of a particular outcome over follow-up, not a test of whether the device performs better than another option. The registry’s brief summary says the study was designed to determine re-operation rates at 4 and 5 years. The primary outcome entry, however, gives a timeframe of 5 years. The registry record does not report the primary endpoint’s observed percentage or its confidence interval, so the result itself cannot be summarized from this record.

3. Trial Design

This is a completed phase 4, single-group device study of the REALIZE™ Swedish Adjustable Gastric Band. The registry lists enrollment of 303 and describes all subjects as having the device, with no comparator. Allocation is listed as NA and masking as none. These features make the record descriptive of outcomes in a group receiving the device; they do not support a randomized comparison with another group.

The study title and official title describe a post-implantation or post-market evaluation of safety and quality of life. The brief summary focuses on long-term safety and says the study was designed to determine re-operation rates at 4 and 5 years after implant. The primary outcome entry specifies a 5-year timeframe. The registry lists four secondary outcomes: change in HbA1c, percent change in excess body weight, and change in the physical and mental components of the SF-36 Health Survey, each at 5 years post implant. The record lists five outcome measures in total.

The registry lists a start date of 2006-08 and a primary completion date of 2015-01, and its status is completed. These dates describe the study record; they do not establish how long each individual was followed. The primary endpoint population description includes subjects implanted under protocol CI-07-0006 and subjects implanted under protocol CI-02-0006 who subsequently enrolled under protocol CI-06-0001. That population description is important when interpreting the endpoint and should not be replaced by an assumption that every enrolled subject contributed to its analysis.

The registry record does not report a detailed protocol for follow-up visits, the statistical analysis plan, the number of subjects included in the primary analysis, or a sample-size justification. A single-group design can describe the frequency of observed outcomes, but without a comparator it cannot isolate the device’s effect from other explanations for those outcomes.

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:

Analysis population for the primary outcome, as defined in the registry: Consists of subjects who had a device implanted under protocol CI-07-0006 and subjects implanted under protocol CI-02-0006 and subsequently enrolled under protocol CI-06-0001.

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.

Population: All subjects implanted with the SAGB.

6. Primary Endpoint

The registry lists the primary outcome as Re-operation Rate (Band Revision, Band Replacement and Explants Resulting From Serious Adverse Device-related Event {SADE}) of Gastric Banding at 4 and 5 Years Post Implant., measured over 5 years.

The primary endpoint is the percentage of subjects with a qualifying re-operation at 5 years post implant. The registry defines a qualifying re-operation through several conditions. It had to be an explant, band revision, or band replacement resulting from a medical condition; be an SAE or an action taken as the result of an SAE; and be related to the study device, with the relationship recorded as definite, probable, possible, or unknown. If the procedure was an action taken for an SAE, that SAE also had to be device-related. The procedure’s start date had to be strictly more than 1095 days after implantation.

The definition excludes procedures attributed to perceived failure of weight loss, subject request, or other non-medical conditions. Thus, the endpoint is narrower than a count of every re-operation or every device-related procedure. It focuses on procedures meeting the specified event, relationship, reason, and timing criteria.

General statistical context: a percentage is a way to describe how common a binary outcome is in a defined group. A re-operation endpoint can summarize the occurrence of a clinically consequential event in follow-up, while the detailed criteria determine exactly which events count. The registry record gives the endpoint definition and its timeframe, but not the observed percentage, the analysis denominator, or the stated 95% confidence interval. Those results are therefore not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies the primary outcome as a percentage of subjects and specifies a 95% confidence interval. It does not describe the statistical method used to calculate the percentage or interval, and it does not give the observed result. The discussion below explains the statistical ideas relevant to this endpoint in general; it should not be read as a claim about methods actually used in the study.

What does a percentage summarize?

General statistical explanation: for a binary endpoint, each person is classified according to whether the defined event occurred. A percentage summarizes the share of the analysis population classified as having the event. The definition of the event and the choice of denominator both matter. In this trial, the event definition is highly specific: it includes only certain procedures, with specified links to an SAE and the device, a medical reason, and a timing condition. The registry gives no primary numerator or denominator, so the percentage cannot be reconstructed from the record.

The overall enrollment of 303 is not necessarily the endpoint denominator. A study can enroll people who are not all part of a particular analysis population, and some outcomes may not be available at the relevant assessment. Those are general possibilities, not statements about what happened. The registry’s description of the primary population refers to subjects from specified protocols, but does not report its size or how it relates to the enrolled group. The endpoint analysis population is not reported in the registry record.

What would a confidence interval tell a reader?

General statistical explanation: a confidence interval communicates uncertainty around an estimate. For a percentage, the interval is intended to show how much statistical uncertainty remains about the underlying event frequency, given the data and the method used. A narrower interval generally indicates greater precision, while a wider interval indicates less precision. Interpretation also depends on the design, data completeness, and assumptions of the interval method.

The primary outcome entry names a 95% confidence interval, but the registry does not report its lower or upper limit. It also does not name the interval calculation method. It is therefore not possible to describe the estimated frequency, quantify its precision, or judge whether a particular interval method was appropriate. A stated confidence level alone is not a substitute for the estimate and interval values.

How should the timing rule be understood?

The primary endpoint requires a procedure start date strictly more than 1095 days after implantation, and the listed timeframe is 5 years. This timing rule means the endpoint does not count every qualifying procedure regardless of when it occurred. Procedures outside the rule do not meet the recorded definition, even if they otherwise resemble the specified procedures. The registry’s brief summary refers to assessment at 4 and 5 years, but the primary outcome entry gives the 5-year timeframe. The record does not explain how the timing rule was implemented in the analysis, or how subjects with different amounts of follow-up were handled.

General statistical explanation: when an outcome can occur at different times and follow-up differs among people, analysts may use methods that account for time at risk and censoring. A simple percentage and a time-to-event estimate answer different questions and rely on different assumptions. The registry record does not say whether the primary analysis used a time-to-event method, a proportion based on a defined follow-up window, or another approach. No particular method should be attributed to the study based on the endpoint wording alone.

What does the sample-size illustration represent?

The planning illustrations are calculated from an observed effect under stated assumptions, rather than being the study’s original design justification. They use a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect to detect expressed as a fraction of the observed effect. The illustrations are hypothetical planning quantities, not observed power and not evidence that the trial had a particular power.

Those assumptions describe a two-arm planning scenario, but this registry study is single-group and has no comparator. The illustrated equal allocation therefore does not describe the actual trial design. The registry does not report the original sample-size justification, the effect size used in planning, or a trial-specific power calculation; these details are not reported in the registry record. Planning numbers should be read as illustrations for a hypothetical comparison, not as a property of the study’s actual enrollment or as confirmation that the primary endpoint was adequately powered.

What can the design estimate?

General statistical explanation: a single-group study can describe outcomes observed among its participants, subject to the endpoint definition, follow-up, and available data. A comparator is needed for a direct estimate of how outcomes differ between groups. Even an accurately estimated event percentage in one group cannot by itself separate the contribution of the intervention from other influences, such as participant characteristics or the course of events over time.

For this record, the registry supplies the design description, enrollment, endpoint definition, and some safety counts, but not the primary percentage or its confidence limits. It also does not report the analysis method, analysis denominator, or handling of missing outcomes. Statistical interpretation must therefore stay at the level of what the record documents, rather than infer an unreported calculation.

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("REALIZE™ Adjustable Gastric Band")
n      <- c(303)
events <- c(27)
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  REALIZE™ Adjustable Gastric Band  303  27  8.9  6.0  12.7  6.2  12.7  6.2  12.7

11. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures in total: the primary re-operation endpoint and four secondary outcomes concerning HbA1c, excess body weight, and the physical and mental components of the SF-36 Health Survey. It does not report whether statistical testing was performed for each outcome, how outcomes were ordered or prioritized beyond their primary and secondary labels, or whether any adjustment for multiple testing was planned. A multiplicity strategy is not reported in the registry record.

General statistical context: when several outcomes are tested, the chance of obtaining at least one apparently notable result can increase if each is interpreted separately. Analysts may address this with prespecified hierarchies, adjusted thresholds, or other approaches, depending on the study question. The record does not state whether any such approach was used, so no conclusion about multiplicity control is possible.

The record also does not report the amount of missing endpoint or secondary-outcome data, the reasons for missingness, or the method used to handle it. It gives no description of imputation, complete-case analysis, or sensitivity analyses. These methods are not reported in the registry record; their use should not be assumed.

The primary population is described as subjects from specified implantation and enrollment protocols, but the number included in the analysis and the rules for inclusion are not given. No intention-to-treat, per-protocol, or other named analysis population is reported. Consequently, readers cannot establish from this record whether the reported enrollment of 303 matches the analysis population for any endpoint, or assess how missingness and population selection may affect the posted results.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: device migration (9.2%), catheter related complication (5.0%), cholelithiasis (4.3%), cholecystitis (2.6%), gastric dilatation (2.3%).

The registry safety summary lists 303 subjects at risk for serious adverse events, with 138 affected, and 303 at risk for other adverse events, with 302 affected. These figures describe the numbers of subjects recorded in each category. They are not the primary re-operation endpoint, which has a separate definition based on procedure type, medical reason, SAE and device relationship, and timing after implantation.

The listed serious-event terms include device migration at 9.2%, catheter related complication at 5.0%, cholelithiasis at 4.3%, cholecystitis at 2.6%, gastric dilatation at 2.3%, and osteoarthritis at 2.0%. These are the terms and percentages shown in the registry summary. The record does not provide further details about event counts, repeated events, timing, or whether each term represents affected subjects or events. The listed percentages should therefore be read as reported, without assuming a different denominator or adding them together.

The deaths field has no value; deaths are not reported in the registry record. General statistical context: safety summaries depend on how events are defined, collected, and grouped, and the number of people affected is distinct from the number of events. The listed counts alone do not establish cause or comparative risk, particularly in a single-group study without a control arm.

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

This registry record documents a completed, single-group evaluation of the REALIZE™ Swedish Adjustable Gastric Band and defines a primary endpoint for qualifying re-operations at 5 years post implant. It also reports safety counts for subjects affected by serious and other adverse events, along with a list of serious-event terms and percentages. These are descriptive features of the posted record.

The record does not report the observed primary endpoint percentage, its analysis denominator, or the limits of the stated 95% confidence interval. It therefore does not provide enough information to describe the frequency or precision of the primary re-operation result. The safety figures are not a substitute for that result and do not answer the endpoint question by themselves.

The design also sets a boundary on interpretation. All subjects had the device, and there was no comparator. The record can describe outcomes observed in the study group, but it cannot show how those outcomes compare with an alternative group under the same study conditions. General statistical context: an outcome observed after an intervention does not, on its own, establish that the intervention caused the outcome or changed its frequency.

The endpoint definition further limits what counts. It excludes some reasons for re-operation and applies a timing condition, so it should not be treated as a count of every procedure or every device-related concern. The primary population description also refers to subjects enrolled under specified protocols; the registry does not report the number of subjects included in the endpoint analysis.

Accordingly, the meaning of the record is chiefly methodological and descriptive: it states what the primary outcome was intended to capture and provides some safety summaries. The primary numerical result, its uncertainty, the analysis population, and several analysis choices are not reported in the registry record. No conclusion about a comparative effect or the primary endpoint estimate can be drawn from the information.

14. Why This Trial Matters Statistically

This trial matters statistically because it illustrates how strongly interpretation depends on a precise endpoint definition. The primary outcome is not simply any re-operation. It combines procedure type, a medical reason, an SAE condition, a device-relationship category, and a timing rule. These details define the outcome being counted and determine which procedures fall outside it. Readers need the definition before interpreting any eventual percentage.

It also highlights the distinction between enrollment and analysis population. The record lists enrollment of 303, while the primary endpoint population is described using implantation and enrollment protocols. Without a reported analysis denominator, readers cannot tell how many subjects contributed to the endpoint estimate or whether it represents the whole enrolled group. This is central to understanding any percentage and its uncertainty.

The single-group design is another important statistical feature. It can describe outcomes in the observed group, but it does not offer a concurrent comparator for estimating a difference between treatment strategies. The record’s sample-size illustrations are based on hypothetical two-arm planning assumptions, whereas the actual study has no comparator. Keeping those purposes separate prevents a planning illustration from being mistaken for a trial result or an observed-power claim.

Finally, the record shows why a named confidence interval is not enough for interpretation. The primary endpoint specifies a 95% confidence interval, but the limits and estimate are not reported. Without them, neither the event frequency nor its precision can be assessed. The missing analysis details also matter: missing-data handling, multiplicity methods, and the analysis population are not reported in the registry record. Together, these omissions restrict what can responsibly be concluded from the posted information.

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 interpreting this particular record is that it does not report the primary endpoint result. The primary outcome is defined and a 95% confidence interval is named, but the percentage, numerator, denominator, and interval limits are not reported in the registry record. Readers therefore cannot assess the observed frequency or its precision.

The study is single-group, with no comparator. This limits the questions that can be answered: the design does not provide a like-for-like comparison against another treatment or a control group. The reported safety counts and any eventual endpoint percentage would describe the study population, not a comparative difference.

The population description for the primary endpoint refers to subjects implanted under protocol CI-07-0006 and subjects implanted under protocol CI-02-0006 who subsequently enrolled under protocol CI-06-0001. The registry also lists overall enrollment of 303, but it does not report how many subjects met the endpoint analysis criteria or how that population relates to the total enrollment. This leaves the endpoint denominator unclear.

The registry’s brief summary refers to 4- and 5-year re-operation rates, while the primary outcome entry lists a 5-year timeframe. The record does not provide an analysis output that clarifies the results at each time point or how follow-up was handled. It also does not report methods for missing data, analysis-population definitions, multiplicity, or the primary statistical calculation. These details are not reported in the registry record, and should not be inferred from the outcome description.

Lastly, the safety summary does not provide further context about event timing, repeated events, or cause. The listed serious-event terms and percentages should be read as registry summaries rather than as a complete account of each event or as evidence of comparative risk.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Post Implantation/Post Market Evaluation of the Swedish Adjustable Gastric Band — NCT00543140.
• Registry record last updated 2016-03-09; status last verified 2016-02.
• Results first posted 2016-03-09.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry record describes a completed phase 4, single-group evaluation of the REALIZE™ Swedish Adjustable Gastric Band, with enrollment of 303. All subjects had the device, and there was no comparator. The study’s stated focus includes long-term safety, quality of life, and re-operation after implantation.

The primary endpoint is the percentage of subjects with a qualifying re-operation at 5 years post implant. Its definition requires specified procedures, a medical reason, an SAE and device relationship, and a procedure start date strictly more than 1095 days after implantation. The registry does not report the primary percentage, analysis denominator, or confidence interval limits.

The safety summary lists 138 of 303 subjects affected by serious adverse events and 302 of 303 affected by other adverse events. It also lists serious-event terms and percentages. Methods for missing data, multiplicity, and the endpoint analysis population are not reported in the registry record. The findings are therefore descriptive, with no comparator-based estimate.