Study to Image the Esophagus Using the OFDI Capsule: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study to Image the Esophagus Using the OFDI Capsule (NCT02204150), a na na study. The primary outcome is Feasibility of OFDI Imaging in Subjects Swallowing the OFDI Capsule.

2. Clinical Question

In practical terms, this is a procedural feasibility question: can imaging of the esophagus be acquired following capsule swallowing, according to the study's quality criterion? The record describes the intended imaging session as taking an average of 5 minutes. It does not define the quality threshold in further detail or report how the image-quality judgment was made.

The study is described as a pilot and includes no control arm. Therefore, its primary question concerns the imaging procedure within the enrolled group, rather than a comparison of outcomes between interventions. The posted record does not report a treatment-effect estimate or a statistical comparison. It also does not provide the number of enrolled participants who completed imaging or the number included in the endpoint assessment. Those details are not reported in the registry record.

3. Trial Design

This is a completed, single-group pilot study registered as NCT02204150, with the title “Study to Image the Esophagus Using the OFDI Capsule.” The official title is “Pilot Study for Imaging of the Esophagus Using an OFDI Capsule.” Massachusetts General Hospital is listed as the sponsor. The phase is recorded as NA, allocation as NA, and masking as none.

The record lists an enrollment of 56 and identifies Barrett's Esophagus and Eosinophilic Esophagitis as conditions. The intervention is the OFDI Capsule, classified as a device. Its arm description states that the subject will swallow the capsule and imaging will be acquired using the OFDI Imaging system. Because the model is single group, no separate control arm or randomized allocation is described.

The brief study summary gives feasibility and tolerability as the main purpose. The primary outcome is the number of subjects from whom quality OFDI imaging was obtained. Its timeframe is the imaging session, which the record says should take an average of 5 minutes. The registry record does not report the primary outcome count, a statistical analysis, or an analysis population.

The study start is recorded as 2012-02, primary completion as 2015-07-31, and status as completed. These dates describe the registry record's study timeline; they do not provide further information about participant follow-up or the timing of individual assessments. The record does not report additional protocol detail on recruitment, eligibility criteria, image assessment, or handling of participants whose imaging could not be completed.

With no randomized comparison, the design can describe the imaging experience in the study group but cannot provide a controlled estimate of how imaging outcomes differ from another procedure or group. The registry record does not report any comparative analysis.

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: In this feasibility study we try to establish the overall number of participants who are able to swallow the capsule and provide us with quality imaging using this new technology. At this point we do no distinguish tolerability separately in each of the three groups and are treating them as one.

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.

6. Primary Endpoint

The registry lists the primary outcome as Feasibility of OFDI Imaging in Subjects Swallowing the OFDI Capsule, measured over Images will be acquired during the OFDI imaging session which should take an average of 5 minutes.

The primary endpoint is the number of participants from whom quality OFDI imaging was obtained. It is recorded as a count of participants, with the imaging session as the assessment timeframe. This directly addresses the study's stated feasibility aim: whether the capsule imaging procedure can yield images judged to meet the study's quality criterion.

A count is a straightforward way to describe how many participants reached a defined procedural outcome. However, interpretation depends on knowing both the count meeting the criterion and the number assessed. The record lists enrollment of 56, but does not report the primary endpoint count or clarify how many participants were evaluated for image quality. It also does not specify the quality threshold or the method used to judge image quality. These details are not reported in the registry record.

The endpoint is not a measure of diagnostic accuracy, clinical benefit, or a comparison with another imaging method. No such endpoint or comparison is reported. Nor does the count alone describe tolerability; although tolerability is part of the study's stated purpose, the primary endpoint is image acquisition quality. The registry record does not report a separate tolerability outcome.

For a binary outcome, each assessed participant can be classified as either meeting or not meeting the criterion, and the count records those meeting it. Without the number assessed and the result count, neither the observed fraction nor its precision can be described. No such result is reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The methods that can be described are limited to the design and endpoint information in the registry record. This is a single-group study with allocation recorded as NA and masking recorded as none. The primary outcome is a count of participants from whom quality OFDI imaging was obtained. The record lists zero analyses, so no inferential statistical method or endpoint estimate is reported.

What does a single-group design tell us?

In a single-group design, outcomes are observed among participants who receive or undergo the study procedure, without a separate concurrent control group. Such a design can describe whether a procedure was carried out and what outcomes were recorded in the study group. It does not, by itself, estimate a contrast against another procedure or establish that observed outcomes differ from what would have happened under a comparator. Here, the registry record identifies the OFDI capsule imaging procedure and does not report a comparator.

How should a count endpoint be read?

A count of participants meeting a criterion records the number of people classified as having the outcome. For interpretation, it is important to know the number who were assessed as well as the number who met the criterion. The record reports enrollment of 56 but does not state how many participants were assessed for the primary endpoint or how many had quality images. Thus the count and the denominator for an endpoint rate are not reported. A proportion, interval estimate, or test cannot be reconstructed from the registry record.

In general, a confidence interval describes the statistical uncertainty around an estimate under the assumptions of the method used. It does not account automatically for all sources of bias, such as an unclear outcome definition or incomplete outcome assessment. No confidence interval is reported for this endpoint, and the registry record does not identify an inferential procedure used to calculate one.

Why does the endpoint definition matter?

The endpoint depends on what qualifies as “quality OFDI imaging.” A clear operational definition can help determine whether different assessments classify images consistently. The record states the outcome's general meaning but does not report a threshold, grading approach, assessor information, or adjudication process. These details are not reported in the registry record, so the meaning and reproducibility of the quality classification cannot be evaluated from the entry.

What is over-dispersion, and does it apply?

In general, over-dispersion describes more variability in data than a particular statistical model expects. It can matter for count outcomes when a model assumes a specific relationship between the mean and variance. This endpoint, however, is defined as a count of participants with a binary event, and the record reports no fitted model or analysis. There is no basis in the registry record for assessing over-dispersion or stating that a count model was used.

How should planning illustrations be understood?

General sample-size planning uses assumptions about the target effect, variability, significance level, allocation, and statistical method. Such calculations describe a planned design under assumptions; they are not observed results and do not measure the probability that a completed study has demonstrated an effect. The registry record includes a generic planning description based on a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of an observed effect. It also distinguishes total events for time-to-event outcomes from participants per arm for other outcomes.

Those assumptions describe a two-arm planning illustration, whereas this registry entry describes a single-group study. The record does not report numeric planning outputs or a study-specific sample-size justification. It also does not report an observed primary endpoint effect from which to interpret such an illustration. No conclusion about this study's planned power or adequacy of enrollment can be made from the available 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("OFDI Capsule Imaging")
n      <- c(56)
events <- c(56)
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  OFDI Capsule Imaging  56  56  100.0  93.6  100.0  93.6  100.0  93.7  100.0

11. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when a study conducts multiple statistical tests or evaluates multiple outcomes in ways that increase the chance of a chance-positive finding. The registry record lists one outcome measure and zero analyses. It does not report multiple endpoint tests or any adjustment for multiplicity. A multiplicity strategy is not reported in the registry record.

The absence of a reported analysis means it is not possible to establish whether a statistical test was conducted, whether the primary endpoint was analyzed as planned, or whether additional analyses were performed outside the posted record. The record does not report a statistical analysis plan, interim analyses, or a testing hierarchy.

Missing data are also important for interpreting a count of participants with quality imaging. A reader would need to know how many participants underwent the procedure, how many had images available for assessment, and how non-evaluable or incomplete imaging was classified. The registry record reports enrollment of 56 but does not report endpoint completeness, exclusions, withdrawals, or a missing-data method. These details are not reported in the registry record.

The analysis population is not stated. The record does not say whether the endpoint was assessed in all enrolled participants, only those who swallowed the capsule, or another defined group. Nor does it report whether participants with unsuccessful or incomplete imaging were counted as not meeting the quality criterion. Without these definitions and counts, the endpoint denominator and handling of missing observations remain unclear.

These are reporting gaps rather than evidence that any particular method was or was not used. No assumptions about an analysis population, missing-data procedure, multiplicity correction, or interim monitoring can be made from the registry entry.

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 0% reporting threshold.

The adverse-event record lists the OFDI Capsule Imaging group with 56 participants at risk for serious adverse events and 56 at risk for other adverse events. It reports zero affected participants in both categories and zero deaths. No top serious adverse-event terms are listed.

These figures describe what is posted in the registry record. They should not be treated as a complete characterization of tolerability: the record does not state the event definitions, the period of safety observation, the method of collection, or whether every enrolled participant contributed to each safety category. The at-risk counts are recorded as 56, but further detail about exposure or follow-up is not reported in the registry record.

A zero count in a posted category means that no affected participants are entered for that category in this record; it does not quantify the uncertainty around the frequency of events or establish that other symptoms or procedural difficulties did not occur. The record does not report a separate tolerability endpoint or broader safety analysis. Because there is no comparator group, these safety entries also do not support a controlled comparison of event frequency.

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

The registry record identifies a pilot study intended to test the feasibility and tolerability of tethered capsule OFDI imaging. Its primary endpoint is the count of participants from whom quality imaging was obtained. That definition makes the central question clear, but the posted record does not give the endpoint count. Therefore, the primary feasibility result cannot be quantified from this entry.

The record also does not report the number of participants whose images were assessed, an endpoint rate, an uncertainty interval, or an analysis. Enrollment of 56 is not a substitute for those results. It cannot show whether all enrolled participants completed the procedure or had evaluable images. The criteria for image quality and the handling of incomplete imaging are not reported in the registry record.

The single-group design means that any observed imaging outcome would describe the study group rather than provide a randomized comparison with another method. The registry record does not report such a comparison. It also does not report a diagnostic-accuracy endpoint or evidence about clinical outcomes. The study's stated focus is imaging feasibility and tolerability, not a comparative estimate of clinical benefit.

The safety entries list zero affected participants in the serious and other adverse-event categories and zero deaths, among 56 at risk in each category. These entries are relevant to how the record reports safety, but without event definitions and observation details they cannot establish the absence of every possible tolerability issue.

Accordingly, the record documents a completed pilot study and its intended endpoint, but it does not contain the primary result necessary to judge how often the image-quality criterion was met. It does not establish superiority, equivalence, or a treatment effect. Those conclusions are not reported in the registry record.

14. Why This Trial Matters Statistically

This study is statistically notable because its main question is procedural feasibility, while the registry record does not post the count that would answer that question. In a feasibility study, a clearly defined outcome and a transparent denominator are essential: readers need to know how many participants were assessed and how many met the criterion. The entry defines the outcome in broad terms but reports neither the count nor the endpoint denominator.

The single-group design is also central to interpretation. Without a separate comparator, the record can describe the imaging procedure as studied but cannot provide a controlled estimate of differences against another approach. This is not a flaw in every pilot study; it is a boundary on the conclusions the design can support. The registry record does not report a comparative analysis.

The distinction between a stated objective and a posted result matters. The brief summary identifies feasibility and tolerability as the purpose, and the primary outcome is an image-quality count. But the record lists zero analyses and no primary result. The absence of a reported estimate is not evidence that imaging failed or succeeded; it means the registry entry does not quantify the outcome.

Finally, the record's generic planning assumptions concern a two-arm illustration, while this study is recorded as single group. Planning illustrations depend on assumptions and should not be confused with observed evidence. No numeric planning results or study-specific sample-size justification are reported in the registry record. Keeping design, planning, and outcome reporting separate helps prevent claims that go beyond the available statistical 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 primary limitation for interpretation is that the registry record does not report the result for its primary endpoint. Although the outcome is defined as the number of participants with quality OFDI imaging, the count and the number assessed are absent. As a result, feasibility cannot be summarized quantitatively from the registry entry.

The endpoint's operational details are also limited. The record does not report the image-quality threshold, assessment procedure, assessor training, or whether image judgments were independently reviewed. It does not explain how unsuccessful, incomplete, or non-evaluable imaging was classified. Those details are not reported in the registry record.

Enrollment is recorded as 56, but the record does not describe participant flow, completion of the imaging procedure, withdrawals, or the analysis population. It is therefore unclear whether the primary endpoint would have been assessed among all enrolled participants or a subset. No statistical analysis, uncertainty estimate, or missing-data approach is posted.

The design is single group, with no randomized comparator. This constrains interpretation to the studied procedure and group and does not permit a controlled estimate against another method. The record also does not report a separate tolerability outcome, despite tolerability being part of the stated purpose.

Safety interpretation is limited by the absence of reported event definitions, observation period, collection methods, and further detail about the at-risk population. The posted zero counts should be read within those reporting limits. Finally, a study-specific sample-size justification and interim analysis information are not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Study to Image the Esophagus Using the OFDI Capsule — NCT02204150.
• Registry record last updated 2019-04-30; status last verified 2019-04.
• Results first posted 2019-04-23.
• 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

NCT02204150 is a completed, single-group pilot study sponsored by Massachusetts General Hospital. It evaluates an OFDI capsule imaging procedure in participants with Barrett's Esophagus or Eosinophilic Esophagitis. Enrollment is listed as 56; allocation is NA and masking is none.

The primary outcome is the number of participants from whom quality OFDI imaging was obtained during an imaging session expected to take an average of 5 minutes. The registry record does not report the outcome count, its denominator, or an analysis. The adverse-event entries list zero affected participants for serious events, zero for other events, and zero deaths, with 56 at risk in each category.

The entry documents the study purpose and design but does not provide the primary feasibility result or further detail on image-quality assessment, missing observations, or the analysis population.