Observational Study of Anti-Reflux Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Observational Study of Anti-Reflux Surgery (NCT01624506), a registered phase not stated study. The primary outcome is Gastroesophageal Reflux Disease Health Related Quality of Life Outcome (GERD-HRQL).

2. Clinical Question

3. Trial Design

This is the Observational Study of Anti-Reflux Surgery, a registry study sponsored by Torax Medical Incorporated. The registry describes two care groups: magnetic sphincter augmentation using the LINX Reflux Management System, and laparoscopic fundoplication. Its stated purpose is to collect information on these anti-reflux surgical options in everyday clinical practice and follow the clinical course from pre-operative assessment to three years post-surgery.

The record lists an enrollment of 760. The study start is recorded as 2010-01, and primary completion as 2015-01. The status is COMPLETED. These registry fields describe the study record; they do not establish that every enrolled subject completed follow-up or contributed to the primary outcome. The primary outcome population is specifically limited to enrolled subjects who completed the 3-year visit and responded to the GERD-HRQL questionnaire.

The allocation method is not stated, and this is not a randomized comparison. The treatment groups should therefore not be treated as interchangeable groups created by random assignment. Treatment selection may be associated with patient characteristics, clinical decisions, or other factors that the registry record does not describe. This limits how confidently an observed difference could be attributed to treatment rather than to differences in who received each procedure.

The record lists one outcome measure and reports no analyses. It does not report a statistical analysis plan, sample-size justification for the study design, interim analyses, adjustment methods, or a prespecified approach to confounding. Those omissions prevent a detailed assessment of how the primary question was intended to be tested. The registry record also does not report the reasons participants may have been lost to follow-up or excluded from the outcome 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: Not required

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Enrolled subjects who completed the 3-year visit and responded to the Gastroesophageal Reflux Disease Health Related Quality of Life Outcome (GERD-HRQL) questionnaire are included in the analysis.

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 Gastroesophageal Reflux Disease Health Related Quality of Life Outcome (GERD-HRQL), measured over 3 years post-surgery.

The primary endpoint is the Gastroesophageal Reflux Disease Health Related Quality of Life Outcome, or GERD-HRQL, measured at 3 years post-surgery. It is a continuous score reported as a mean with standard deviation. The registry describes a total score from 0-50, based on 10 questions, each rated from 0-5. Lower scores indicate better health-related quality of life; higher scores indicate worse health-related quality of life.

A patient-reported quality-of-life measure can capture how a condition affects a person's experience, rather than relying only on clinical events or procedure-related observations. In general, using a defined questionnaire also gives investigators a consistent outcome to collect across participants and treatment groups. The GERD-HRQL score is relevant to the study's stated interest in the clinical course after anti-reflux surgery, but its meaning depends on who completed the questionnaire and how the responses were handled.

The registry record defines the analysis population as enrolled subjects who completed the 3-year visit and responded to the questionnaire. It does not report group means, standard deviations, sample counts for this endpoint, or a treatment contrast. Consequently, the endpoint's recorded definition is available, but the observed outcome and its precision are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry characterizes the primary measure as continuous and reports it as a mean with standard deviation. A mean describes the central value of a set of scores. A standard deviation describes how spread out the scores are around that mean. Together, these summaries can help readers understand both the typical score and variability among respondents, but they do not show the distribution's full shape or the influence of unusual values. Neither group's mean nor standard deviation is reported in the registry record.

What would a comparison of means tell the reader?

In general, a comparison of group means estimates how far apart the average scores are in the populations represented by the groups. For GERD-HRQL, the direction of an observed contrast would need to be interpreted using the scale's stated direction: lower scores indicate better quality of life. An estimated contrast alone would not show its precision. A confidence interval is a general statistical way to express the range of effects compatible with the data and analysis assumptions. The registry record reports no mean contrast, confidence interval, or inferential analysis for this endpoint.

Why does the observational design matter?

In a randomized trial, allocation by chance is intended to reduce systematic differences between treatment groups. In this study, allocation is not stated, and the record identifies the study as observational. In general, patients who receive different procedures may differ before treatment or may be treated in different clinical circumstances. Such differences can confound an outcome comparison: an apparent association between procedure and score may partly reflect other characteristics associated with treatment choice and outcome. Statistical adjustment can address measured confounders under suitable assumptions, but it cannot guarantee removal of unmeasured confounding. The registry record does not report which covariates, if any, were included in an adjusted analysis.

The record does not report whether the planned primary comparison was unadjusted or adjusted, which model was used, or how uncertainty was calculated. It also does not report diagnostic checks, sensitivity analyses, or a method for addressing differences in follow-up. Those details are important because the validity of statistical conclusions depends not only on the endpoint but also on the design, analysis choices, and assumptions.

What does the standard deviation not show?

In general, a standard deviation describes variation in individual scores, not the uncertainty of the estimated mean. The uncertainty of a mean depends on both score variability and the number of observations contributing to that estimate. The record does not report the endpoint-specific group counts, so readers cannot assess the precision of group means from the registry entries. Nor can the listed enrollment be assumed to equal the number who completed the visit and questionnaire, because the endpoint population is restricted to completers and respondents.

How should planning calculations be understood?

General sample-size planning asks how many participants would be needed to detect a chosen effect under stated assumptions about the design and analysis. The study record describes planning illustrations based on the observed effect, a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is described as a fraction of the observed effect. The record also distinguishes planning outputs for time-to-event outcomes from those for other outcomes. These assumptions describe planning illustrations, not the study's own design or observed power. The numerical planning estimates and the observed effect used as their basis are not reported in the registry record. Without those values, no planning result can be interpreted.

In general, over-dispersion is extra variability beyond what a chosen statistical model expects. If present and not accounted for, it can make standard errors too small and confidence intervals too narrow. This is a general consideration for model-based analyses, not a reported feature of this study. The registry record does not identify a model or report whether over-dispersion was assessed, so it is not possible to say whether it was relevant to the primary endpoint analysis.

Likewise, a p-value is a measure tied to a specified statistical test and its assumptions; it is not a measure of effect size or clinical importance. No p-value or test for GERD-HRQL is reported. With no effect estimate or uncertainty interval, readers cannot use inferential statistics to judge how compatible the results are with a range of possible effects.

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("Magnetic Sphincter Augmentation", "Fundoplication")
n   <- c(328, 97)
m   <- c(4.2, 4.9)
sp  <- c(5.7, 7.8)
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  Magnetic Sphincter Augmentation  328  4.200  5.700  3.581  4.819
CARM  Fundoplication  97  4.900  7.800  3.328  6.472

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure, the GERD-HRQL score at 3 years post-surgery. It reports no analyses. A single listed primary outcome does not establish that investigators collected or examined only one measure, conducted only one analysis, or followed a prespecified hierarchy of outcomes. The analysis plan, any secondary outcomes, and any multiplicity-control strategy are not reported in the registry record.

In general, multiplicity arises when several outcomes, time points, subgroups, or statistical tests are examined. If many tests are considered, the chance of at least one apparently notable result can increase unless the analysis accounts for that testing or interpretation is appropriately cautious. No information is reported about such procedures for this study. Because the registry record contains no primary outcome results or analyses, the impact of multiplicity on any reported inference cannot be evaluated.

The endpoint population includes subjects who completed the 3-year visit and responded to the questionnaire. The registry record does not report how many subjects contributed scores in each group, how much outcome data were missing, or why data were missing. It does not describe imputation, other missing-data methods, or sensitivity analyses. In general, analyzing only respondents can produce a biased estimate if the likelihood of completing follow-up is related to the score or other relevant characteristics. The extent or direction of any such bias cannot be determined from the registry record.

The record does not specify an intention-to-treat or other analysis population for a randomized assignment, and the study is observational with allocation not stated. It does define the primary endpoint population, but does not report whether additional populations were used for other analyses. No conclusion about the consequences of missing data or selection into the outcome population is possible from the information reported.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

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: dysphagia (1.9%), worsening of gerd (1.1%), heartburn (0.6%), gastritis (0.4%), hypertension (0.4%).

The registry lists serious adverse events for the Magnetic Sphincter Augmentation group as 22 affected among 530 at risk, and for the Fundoplication group as 4 affected among 230 at risk. It lists other adverse events as 98 affected among 530 at risk for Magnetic Sphincter Augmentation, and 30 affected among 230 at risk for Fundoplication. Deaths are listed as 1 and 0, respectively. These are the registry's group entries; they should not be converted into a comparative risk estimate without a defined analysis.

The registry also lists serious adverse event terms and percentages: Dysphagia, 1.9%; Worsening of GERD, 1.1%; Heartburn, 0.6%; Gastritis, 0.4%; Hypertension, 0.4%; and Pneumonia, 0.4%. The record does not specify in these entries how events were attributed, whether an individual could contribute more than one event, the observation period for each person, or whether events were adjusted for differences in follow-up. It also does not report a statistical comparison of safety between groups.

In general, event counts and at-risk figures are descriptive unless accompanied by clear definitions and an appropriate comparative analysis. The observational allocation also means group differences cannot be assumed to result from treatment. These entries should be interpreted as reported safety information, not as proof of comparative harm or safety.

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

The record establishes the study's observational purpose, treatment groups, follow-up intent, and primary endpoint definition. It indicates that GERD-HRQL was intended to describe health-related quality of life at 3 years post-surgery among enrolled subjects who completed the visit and answered the questionnaire. It also reports descriptive adverse-event entries for both groups. These details identify the questions the study was designed to address in clinical practice.

The record does not report group-level GERD-HRQL results, a difference in mean scores, or uncertainty around any comparison. Therefore, it does not show whether the groups had similar or different quality-of-life scores, how large a difference might have been, or how precisely an effect was estimated. It also cannot establish whether any observed difference would be clinically important. The direction of the scale is clear, but the outcome values are not reported in the registry record.

The study is not a randomized comparison, and allocation is not stated. Accordingly, even a descriptive difference between groups would not automatically be a causal treatment effect. In general, treatment choice and outcome may both be associated with baseline or clinical characteristics. The registry record does not report an adjusted analysis that could help address measured differences, and adjustment would still depend on assumptions.

The safety counts describe events recorded in each group, but the record does not provide the event definitions, timing, exposure-adjusted analyses, or inferential comparisons needed to interpret them as relative risks. The counts do not establish that one procedure causes more or fewer adverse events. Similarly, the enrollment figure and at-risk counts do not reveal how many participants contributed to the primary questionnaire analysis.

Overall, the record is informative about the intended outcome and the scope of follow-up, but it does not report the primary numerical results or the analyses needed to support a comparative conclusion. It should not be read as demonstrating that either procedure does or does not improve outcomes.

14. Why This Trial Matters Statistically

Observational studies can describe outcomes in routine clinical practice, where treatment is selected in ordinary care rather than assigned through a randomized protocol. That setting can be useful for understanding how procedures are studied outside a randomized comparison. This record's stated aim—to collect data on magnetic sphincter augmentation and fundoplication and follow patients from pre-operative assessment through three years post-surgery—makes the handling of group comparability and follow-up especially important.

The primary endpoint also illustrates how interpretation depends on more than a scale definition. GERD-HRQL has an explicit score range and direction, but readers still need the group summaries, endpoint-specific counts, and uncertainty estimates to assess the observed outcomes. The registry record gives the endpoint definition and target population but does not report these numerical results. That gap distinguishes a specified outcome from a reported analysis.

The study is also a useful example of why design labels matter. An observational comparison may describe associations between treatment group and outcome, but allocation not stated and lack of randomization limit causal interpretation. Statistical adjustment can be relevant, but readers need to know which factors were measured, how they were modeled, and whether assumptions were checked. These analysis details are not reported in the registry record.

Finally, the record illustrates the importance of transparent outcome follow-up. The primary measure includes only subjects who completed the 3-year visit and answered the questionnaire. Without group-specific completion and missingness information, the representativeness of those scores cannot be assessed. A clear account of who contributed data, alongside effect estimates and uncertainty, would be necessary for a fuller statistical interpretation.

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 central limitation for interpretation is that the registry record does not report GERD-HRQL results or analyses, despite identifying the outcome as primary. Group means, standard deviations, endpoint-specific counts, an estimated contrast, and uncertainty measures are not reported. This prevents assessment of the observed outcome, its precision, or its statistical significance.

The nonrandomized design is another important limitation. Allocation is not stated, and there is no reported adjustment strategy for possible differences between patients receiving the two procedures. The record therefore does not support a causal comparison. Any differences in clinical practice, participant characteristics, or follow-up could matter, but the registry does not describe them.

The outcome is restricted to subjects who completed the 3-year visit and responded to the questionnaire. The number of such respondents in each group, reasons for noncompletion, amount of missing data, and missing-data methods are not reported. Selection into this outcome population may limit how well the results represent all enrolled subjects, although the extent of any effect is unknown.

Safety reporting is also limited in the registry entries. Event definitions, timing, repeated events, person-time, attribution, and comparative methods are not reported. The listed at-risk counts and affected counts should not be treated as adjusted rates or as evidence of a causal difference. The record does not report interim analyses, the detailed statistical plan, or a sample-size justification for the study design. These gaps constrain evaluation of both the intended and reported analyses.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Observational Study of Anti-Reflux Surgery — NCT01624506.
• Registry record last updated 2021-06-08; status last verified 2021-05.
• Results first posted 2021-06-08.
• 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 observational study of anti-reflux surgery sponsored by Torax Medical Incorporated. It lists an enrollment of 760 and two treatment groups: magnetic sphincter augmentation using the LINX Reflux Management System and laparoscopic fundoplication. The study's stated purpose was to collect data in everyday clinical practice and follow patients from pre-operative assessment to three years post-surgery.

The primary outcome is mean GERD-HRQL score at 3 years post-surgery, among subjects who completed the visit and responded to the questionnaire. Lower scores indicate better quality of life. The registry record lists adverse-event counts and serious event terms, but does not report primary outcome results, statistical analyses, or a comparative safety analysis. Allocation is not stated, and the groups are not randomized. The available record therefore describes the study and its outcome definitions but does not establish a comparative treatment effect.