Retrospective TIF Study for Treatment of Gastroesophageal Reflux Disease (GERD). The RetroTIF Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Retrospective TIF Study for Treatment of Gastroesophageal Reflux Disease (GERD). The RetroTIF Study (NCT01327963), a na na study. The primary outcome is Typical and Atypical Gastroesophageal Reflux Disease (GERD) Symptom Elimination.

2. Clinical Question

In practical terms, the registered question is descriptive: among participants assessed after TIF, how many met the stated symptom criteria? The outcome description names GERD-HRQL, GERSS, and RSI questionnaires, each addressing symptom measures. The registry does not clearly specify a combined rule for deciding whether an individual meets the overall primary endpoint, beyond the scale-specific criteria described. It also does not report the distribution of questionnaire scores before or after the procedure. Therefore, the stated research question can be identified, but the result cannot be reconstructed from this record.

3. Trial Design

This was a retrospective, open-label, post-market, single-group study of Transoral Incisionless Fundoplication. The intervention was identified as the TIF 2.0 technique iteration, using the EsophyX device. The registry record lists an enrollment of 110 and identifies GERD as the condition. The record describes the intended setting as high-volume centers across the United States.

The record lists the study start as 2010-09 and primary completion as 2014-02. Its status is TERMINATED. These registry entries establish the recorded study timeline and status; they do not explain why the study was terminated or whether all planned follow-up and analyses were completed. That explanation is not reported in the registry record.

Retrospective data collection means the study evaluates information gathered from past care rather than describing a prospectively assigned intervention in the record. Open-label indicates that masking was listed as NONE. Allocation is listed as NA, consistent with the single-group model and absence of a randomized comparator. These features matter when interpreting outcomes: a before-and-after description can document participants' observed status, but without a control group it cannot isolate the procedure's contribution from other influences or changes over time.

The record lists a primary symptom outcome and secondary outcomes concerning serious adverse events and unanticipated adverse device effects, PPI use, healing of reflux esophagitis, persistence of reduced hiatal hernia, and impedance/pH findings. It does not describe the criteria for inclusion in each analysis, the data sources used, or the statistical methods for comparing observations. A protocol, sample-size justification, interim-analysis plan, and reasons for termination 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.

Overall Study

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: Baseline population is 110 of 124 who were eligible. 110 signed informed consent to participate in the study.

6. Primary Endpoint

The registry lists the primary outcome as Typical and Atypical Gastroesophageal Reflux Disease (GERD) Symptom Elimination, measured over median 7 months (range 5-17 months).

The primary endpoint is a count of participants described as experiencing typical and atypical GERD symptom elimination. The registry identifies follow-up at a median of 7 months, with a range of 5-17 months. It describes symptom assessment using three questionnaires: GERD-HRQL for typical symptoms, GERSS for atypical symptoms, and RSI for atypical laryngopharyngeal symptoms.

The scales capture different aspects of symptoms. GERD-HRQL has nine questions, each scored from 0-5; the registry says scores are considered normalized when every score is 0. GERSS measures severity and frequency on scales of 0-3 and 0-4, respectively, with a total scale of 0-60; a score below 18 is described as expected in patients with controlled reflux symptoms. RSI has nine questions scored from 0-5, a maximum of 45, and a normality threshold of 13 or lower.

Using symptom questionnaires allows a study to represent patient-reported experiences rather than relying only on a technical or physiological measure. In general, a prespecified threshold can turn a score into a count of participants who meet an endpoint, which is straightforward to describe. However, the registry record does not report the number meeting the primary endpoint, the score distributions, or a precise rule showing how the three questionnaire criteria combine into a single participant-level outcome. The recorded endpoint definition therefore gives context for the intended measure, but not an observed result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record reports no statistical analyses for the listed outcomes. It does not describe a statistical analysis plan, a model, a hypothesis test, an uncertainty interval, or adjustments for potential confounding. The methods below are general statistical context for understanding the kinds of data described; they should not be read as methods that this study is known to have used.

What a participant count conveys

The primary outcome is framed as a count of participants who meet a symptom-elimination definition. A count is a direct way to express how many people satisfy a criterion. To interpret it, readers also need the relevant denominator: for example, whether the count is among everyone enrolled, everyone eligible for follow-up, or only those with completed questionnaires. If the denominator changes because some records are unavailable, the apparent frequency can depend on how missing participants are handled. The denominator for the primary endpoint is not reported in the registry record.

In general, when a participant is classified as either meeting or not meeting an endpoint, the result can be represented as a binary outcome. A statistical interval around the corresponding proportion can describe sampling uncertainty. Such an interval does not account automatically for selection bias, measurement problems, missing outcomes, or unmeasured differences among participants. No primary endpoint count, proportion, or interval is reported in the registry record, so none can be interpreted for this study from the posted result fields.

Questionnaire thresholds and measurement

The outcome description names three symptom questionnaires and includes scale ranges and threshold language. A scale can preserve more detail than a simple yes-or-no classification because it records degrees of symptom severity or frequency. A threshold makes an endpoint easier to express as a participant count, but it also discards information about how close a score is to the threshold and how scores are distributed within each category.

In general, a threshold-based endpoint is clearest when the analysis specifies in advance which score or combination of scores qualifies a participant, how scores are treated when items are incomplete, and which follow-up observation is used. The registry provides scale descriptions and some criteria, but the precise combined rule for the primary endpoint and the handling of incomplete questionnaires are not reported in the registry record. No item-level or total-score results are reported either.

Single-group evidence and causal interpretation

In general, a single-group study can describe observed outcomes in the group under study, but it does not by itself estimate a contrast against a concurrent control. A change from an earlier measurement, if reported, could reflect the intervention as well as other influences, such as the natural course of symptoms, changes in co-interventions, participant selection, measurement timing, or regression toward typical values after unusually severe symptoms. These are general interpretive concerns, not findings established for this study.

Retrospective data collection can also make completeness and consistency dependent on existing records. For a clinical outcome, it is useful to know whether the same measurement procedures were used for all participants, how follow-up was obtained, and whether assessors were aware of the intervention. The record identifies the study as retrospective and open-label, but does not give these operational details. They are not reported in the registry record.

Uncertainty, tests, and models

In general, a confidence interval describes statistical uncertainty around an estimate, conditional on the assumptions used to calculate it. A p-value addresses compatibility between observed data and a specified null model; it is not the probability that a hypothesis is true and does not convey the size or clinical importance of an outcome. Neither an interval nor a p-value can be interpreted without an identified estimate, analysis population, and method. The registry record reports no analyses for the outcomes, so it provides no such results.

For a binary outcome, possible statistical methods depend on the study question and data structure. A one-group descriptive analysis differs from a comparison between groups, and a repeated-measures analysis differs from an analysis of one follow-up observation. The registry record does not identify which approach, if any, was used. No model, covariate adjustment, or handling of center-level variation is reported. It would not be appropriate to infer an analysis method from the endpoint label alone.

Planning assumptions are not study results

General sample-size planning asks how much information may be needed to detect a specified effect under stated assumptions. Planning output depends on choices such as the target effect, error rate, allocation, and calculation method. Such an illustration is not an observed outcome, and a planned sample size does not establish that a study had adequate precision for every endpoint. The record does not report the trial's own sample-size justification or design rationale. Any planning illustration associated with the posted statistical materials should not be interpreted as observed power or as a result of the trial.

Because the record contains no reported outcome analysis, there is no basis for evaluating whether a chosen model fit the data, whether assumptions were checked, or whether estimates were adjusted. Those details, along with any analysis of repeated observations or differences across centers, are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The record lists a primary endpoint and several secondary outcomes, spanning symptom measures, safety events, PPI use, healing of reflux esophagitis, hiatal hernia status, and impedance/pH testing. When a study examines multiple outcomes, the chance of at least one apparently unusual result can increase if each is tested separately. In general, a prespecified hierarchy or multiplicity adjustment can help define how multiple tests should be interpreted. The registry record does not report a multiplicity plan, a testing hierarchy, or adjusted results.

The registry record lists 0 analyses. It does not provide outcome-specific estimates, confidence intervals, or p-values. The analysis population for each endpoint, including the number with available follow-up data, is not reported in the registry record. Nor does the record explain whether all registered outcomes were analyzed, whether any analyses were omitted, or whether any outcomes were added after data collection.

Missing-data handling is not reported in the registry record. This matters because incomplete questionnaires or unavailable follow-up could affect which participants contribute to a symptom count. In general, complete-case analysis uses only participants with the required data, while other approaches make additional assumptions about missing outcomes. No method can be attributed to this study from the record.

The record also does not describe an intention-to-treat population or another analysis-population definition. Because the design is retrospective and single-group, readers would need clear accounting of who was assessed, who had data for each outcome, and how incomplete records were treated to evaluate the representativeness of the analysis. These details, the multiplicity strategy, and any missing-data sensitivity analyses are not reported in the registry record.

11. 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 0% reporting threshold.

The posted safety entries report 0 serious adverse events among 110 at risk, 0 other adverse effects among 110 at risk, and 0 deaths. These are counts in the registry record; they are not a comparative risk estimate because the study has no control group. The record does not provide an uncertainty interval for these counts or describe how safety events were collected and adjudicated.

A zero count means that no affected participants are recorded in that entry. In general, it does not prove that the underlying event risk is zero. The interpretation depends on the amount and completeness of observation, the event definitions, and how consistently events were sought and recorded. The registry record does not report enough detail to evaluate those factors for the safety outcomes.

The secondary safety outcome names serious adverse events and unanticipated adverse device effects. The posted safety summary does not list any serious event terms. This should be read as the reported summary, not as evidence that every possible adverse event was assessed or that unlisted events could not have occurred. Follow-up duration for safety assessment and the completeness of safety reporting are not reported in the registry record.

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

The registry record gives a clear outline of the study question: it was a retrospective, open-label, single-group assessment of TIF for GERD, with symptom elimination as the primary outcome. It also identifies the questionnaire measures and gives a follow-up timeframe. The posted safety entries record no serious adverse events, other adverse effects, or deaths among the listed at-risk participants.

However, the primary symptom outcome result is not reported in the registry record. There is no reported count of participants meeting the endpoint, no denominator for the primary analysis, and no estimate of uncertainty. The record therefore does not establish the frequency of symptom elimination in the analyzed group. It also does not report outcome estimates for the listed secondary measures.

Even if a single-group symptom result were available, it would describe what was observed among participants with analyzed data, not a causal comparison with another treatment or with no intervention. The design has no concurrent control group, and the registry provides no randomized contrast. Differences in participant characteristics, follow-up, other care, measurement, and data completeness could shape an observed outcome. The record does not provide information sufficient to separate those influences.

The safety counts should be interpreted narrowly as registry-recorded counts. Without more detail on event ascertainment and follow-up completeness, zero posted events should not be equated with proof of no risk. Likewise, the listed enrollment does not establish how many participants contributed to each endpoint analysis.

Accordingly, the record supports a description of the planned focus, design, follow-up, and posted safety counts. It does not support a conclusion about the size or precision of the primary symptom outcome, a comparison against alternatives, or a causal claim about the procedure. Those outcome analyses are not reported in the registry record.

13. Why This Trial Matters Statistically

This study illustrates a common statistical distinction between a stated research objective and an analyzable result. The registry describes symptom elimination as the primary endpoint and identifies the instruments and follow-up timeframe, but the primary count and its analysis are not reported. Without an estimate and denominator, readers cannot assess either the observed frequency or its precision.

Its single-group, retrospective structure also makes the distinction between description and comparison especially important. A cohort description may characterize the outcomes recorded in routine practice, but it does not provide the same evidence as a randomized comparison. The absence of a control group limits causal interpretation regardless of how clearly an outcome is defined. This is a design feature, not a numerical result.

The endpoint combines patient-reported measures with different scales and threshold descriptions. That raises a general statistical issue: translating multiple measures into a single binary endpoint requires an explicit participant-level rule. Readers also need to know how incomplete questionnaires and different follow-up times were handled. Those details are not reported in the registry record, so the intended endpoint cannot be fully reconstructed from the description alone.

The safety summary provides counts, but sparse or zero event counts still require context about observation and event ascertainment. In general, counts without a defined analysis population or uncertainty estimate may be difficult to compare with other evidence. Here, the record reports no comparison and no analysis results.

The statistical lesson is that registration details, outcome definitions, and posted results serve different purposes. The record identifies what was to be assessed, but the absence of outcome analyses prevents an evidence-based account of the primary endpoint's magnitude or uncertainty. This distinction helps prevent study aims and safety summaries from being mistaken for complete 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 main limitation for interpreting results is that the registry record does not report the primary outcome count or any statistical analyses. It therefore gives no estimate of symptom elimination, no uncertainty interval, and no account of the denominator used for that outcome. The analyses for the secondary outcomes are also not reported.

The single-group design has no concurrent comparator, and allocation is listed as NA. As a result, the design cannot provide a direct treatment contrast. The retrospective, open-label nature of the study may also raise general concerns about data completeness, measurement consistency, and assessment, but the registry record does not provide details to determine how these issues were addressed.

The record describes several questionnaire scales and thresholds but does not clearly specify the combined rule for classifying a participant as having primary endpoint symptom elimination. It also does not report how incomplete questionnaire items, unavailable follow-up, or differing follow-up times were handled. The primary timeframe is a median of 7 months, with a range of 5-17 months, but the record does not state the number assessed at each time or the analysis population.

The study status is TERMINATED, but the reason for termination and whether all planned outcomes were collected are not reported in the registry record. A protocol, sample-size justification, statistical analysis plan, interim-analysis details, and multiplicity strategy are also not reported. These omissions limit the ability to judge planned versus reported analyses or assess whether the posted results represent all intended outcomes.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Retrospective TIF Study for Treatment of Gastroesophageal Reflux Disease (GERD). The RetroTIF Study — NCT01327963.
• Registry record last updated 2020-12-03; status last verified 2020-11.
• Results first posted 2020-12-03.
• 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.

18. Record Summary

The registry record describes NCT01327963, titled “Retrospective TIF Study for Treatment of Gastroesophageal Reflux Disease (GERD). The RetroTIF Study.” Its official title concerns long-term outcomes after TIF performed in routine clinical practice. The study was retrospective, open-label, post-market, and single-group, with an enrollment of 110. The recorded start is 2010-09, primary completion is 2014-02, and status is TERMINATED.

The intervention was Transoral Incisionless Fundoplication using the TIF 2.0 technique iteration. The primary outcome was a count of participants with typical and atypical GERD symptom elimination, assessed at a median of 7 months, with a range of 5-17 months. Secondary outcomes included safety, PPI use, esophagitis healing, hiatal hernia status, and impedance/pH measures.

The registry record reports 0 serious adverse events, 0 other adverse effects, and 0 deaths among the listed at-risk participants. It does not report the primary endpoint result, outcome analyses, a comparator, or key analysis details.