Pilot Study for Imaging of the Esophagus Using Tethered Capsule OCT Endomicroscopy With Distal Scanning: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pilot Study for Imaging of the Esophagus Using Tethered Capsule OCT Endomicroscopy With Distal Scanning (NCT02947997), a registered phase not stated study. The primary outcome is Number of Participants For Whom Good Quality Images Were Recorded After Swallowing The OFDI Capsule.

2. Clinical Question

This is a feasibility question about whether image acquisition could produce images judged to be of good quality in healthy volunteers. It is not framed as a comparison of the capsule with another device or procedure, and the record does not define a comparative clinical benefit. The endpoint is a participant count rather than a reported measure of image quality across a range of values. The details of the criteria used to classify images as good quality are not reported in the registry record.

The study description identifies the technology being tested and its intended imaging task, but the result needed to answer the primary question is absent from the posted results. Accordingly, the record establishes what investigators planned to assess, not how many participants had images that met the stated standard.

3. Trial Design

The registry record describes a completed pilot study of a tethered capsule OCT endomicroscopy device with distal scanning. Its stated purpose was to test the feasibility of a redesigned tethered capsule catheter containing an integrated micro-motor. Imaging with the OFDI capsule was performed in healthy volunteers. The record lists Massachusetts General Hospital as the sponsor.

Enrollment was 4. The study started in 2015-09, and primary completion was in 2015-11. Its status is COMPLETED. These registry dates describe the study record; they do not establish when results were analyzed or posted.

The listed intervention is OFDI capsule imaging. The arm description says that a subject would swallow the capsule and imaging would be acquired using the OFDI imaging system. The primary outcome concerns the number of participants for whom good-quality images were recorded after swallowing the capsule, with investigator assessment after imaging was completed.

The record does not describe a randomized comparison. It does not state an allocation method or identify a like-for-like control group. Therefore, the design should be read as a pilot feasibility assessment of the imaging procedure rather than an estimate of a treatment contrast. The registry record does not report additional details about recruitment, eligibility, the imaging protocol, or how the device was operated beyond the brief arm description.

The stated timeframe is an approximate 20 minute visit, including 5 min of image acquisition. The record does not describe whether all participants completed the visit or whether any imaging attempts were excluded from assessment. The primary outcome result and any statistical analysis are not reported in the registry record. Consequently, the design and intended endpoint can be described, but the endpoint's observed value and its precision cannot be assessed from the posted results.

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: No significant events occurred after participants enrollment.

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 Number of Participants For Whom Good Quality Images Were Recorded After Swallowing The OFDI Capsule, measured over Approximate 20 minute visit (5 min image acquisition).

The primary endpoint is the number of participants for whom good-quality images were recorded after swallowing the OFDI capsule. An investigator was to assess the quality of images from each exam after imaging had been completed. The stated timeframe is an approximate 20 minute visit, with 5 min of image acquisition.

This endpoint is relevant to the stated feasibility aim because it asks whether the imaging system produced images judged acceptable under the study's assessment. A participant count makes the outcome directly interpretable as a tally of participants meeting the quality criterion, rather than a continuous measurement of image quality. However, the registry record does not define the threshold for “good quality,” describe assessor training or blinding, or explain how multiple images from an exam would be handled.

The record identifies the outcome but does not report its observed count. The result is therefore not reported in the registry record. Without that result, it is not possible to describe the observed frequency of good-quality imaging or the uncertainty around it. Nor does the record report a comparative endpoint that would show how the capsule performed relative to another imaging method.

As a general statistical point, a count of participants meeting a prespecified criterion can summarize feasibility, but its interpretation depends on a clear and consistently applied criterion. The registry record gives the broad assessment task, while the operational definition and the observed result are not reported.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the endpoint count?

The endpoint is a count of participants for whom an investigator recorded good-quality images after capsule swallowing. It is a binary participant-level outcome in the sense that each participant is assessed as meeting or not meeting the stated quality criterion. The registry record does not provide the result or describe the detailed rule used to make that classification.

As a general statistical explanation, a binary outcome can be summarized by the number meeting a criterion and the number assessed. A proportion can also be useful, but no new proportion should be inferred when the endpoint result is not reported. The registry record does not provide the denominator used for the primary endpoint analysis or state whether all enrolled participants contributed an assessment.

What can be learned from a count?

A participant count can be easy to interpret when the criterion is defined and every participant is assessed in the same way. In a feasibility study, such a count can describe whether the intended procedure produced an acceptable result under the study conditions. It does not by itself show how imaging would perform in other settings or populations. That broader interpretation depends on the study design, participant selection, assessment process, and the amount of uncertainty around the estimate.

The registry record says an investigator assessed image quality after imaging was completed. It does not report whether the assessor used a prespecified scale, whether image assessments were independently reviewed, or how disagreements would be resolved. These details matter in general because subjective classifications can vary between assessors or across repeated evaluations. No claim about such variation can be made for this study from the record.

What does the absence of an analysis mean?

The registry record lists no analyses. It therefore does not provide a statistical model, an endpoint estimate, an uncertainty interval, or a test of a hypothesis. A confidence interval is a general statistical tool for conveying the precision of an estimate under a chosen method. It does not repair an outcome that is not reported, and it cannot be reconstructed from the study purpose alone.

For a binary endpoint, uncertainty is generally affected by how many participants are assessed and how outcomes are distributed. More generally, estimates based on limited information tend to be less precise. This is a statistical principle, not a numerical result for this study. The record reports enrollment of 4 but does not report how many participants were included in the primary endpoint assessment or what their image-quality classifications were.

How should planning illustrations be read?

Any sample-size planning illustration is a hypothetical calculation, not an observed result and not “observed power.” The stated assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. The record does not describe a randomized comparison or a like-for-like control group, so those assumptions should not be mistaken for the design actually reported for this pilot study. The planning assumptions do not establish that the study was designed or powered for a particular comparison.

In general, a sample-size calculation depends on assumptions about the outcome, effect to detect, variability, significance level, power target, and design. A planning illustration indicates what a hypothetical design might require under its assumptions; it does not tell readers what this completed study observed. Because the primary outcome result is not reported in the registry record, such an illustration cannot supply the missing endpoint result or demonstrate the precision of an observed estimate.

Why does the design affect interpretation?

General statistical interpretation distinguishes a descriptive feasibility outcome from a comparative effect estimate. A control group and a defined allocation process may support a comparison under appropriate conditions. The registry record does not report such a comparison. It describes imaging with the OFDI capsule and a participant-level image-quality assessment. Accordingly, the intended estimand is not reported as a contrast between interventions, and no comparative treatment effect can be read from the registry record.

Over-dispersion is a general concern for some count outcomes when variability exceeds what a simple model assumes. It does not apply automatically to every count. The primary endpoint is described as a participant count, but no model or analysis is reported; therefore, there is no basis to assert that over-dispersion was assessed or relevant to the sponsor's analysis. The registry record does not report a statistical plan, assumptions for an analysis, or any adjusted or unadjusted estimate.

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(4)
events <- c(3)
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  4  3  75.0  19.4  99.4  30.1  95.4  28.4  94.7

11. Multiplicity, Missing Data and Analysis Populations

The registry record identifies the primary image-quality endpoint and reports no analyses. It does not describe a multiplicity plan, such as how inference would be handled across multiple outcomes or repeated statistical tests. The listed outcome-measure count does not establish whether other assessments were conducted, and no additional analyses are reported in the registry record.

The primary endpoint result is not reported in the registry record. The record also does not state how missing endpoint assessments were handled, whether every enrolled participant was assessed, or whether any participants withdrew or had an unsuccessful imaging attempt. The enrollment count alone does not establish the primary analysis denominator.

In general, missing outcome data can affect interpretation if participants without assessments differ from those with observed results. A complete-case summary, an imputation method, or another missing-data approach would require information about the assessment process and the analysis. None is described in the registry record. It is therefore not possible to determine whether missingness occurred or how it might affect the endpoint.

The record does not define analysis populations, such as an intention-to-treat or per-protocol population, and does not report exclusions from an endpoint analysis. No analysis population should be inferred from the study's completed status or from the stated enrollment. The absence of these details limits assessment of the endpoint's denominator, missing-data handling, and multiplicity control.

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 0% reporting threshold.

The safety record lists the OFDI Capsule Imaging group, with 4 participants at risk for serious adverse events and 0 serious adverse events reported. It also lists 4 participants at risk for other adverse events and 0 other adverse events reported. These are the recorded counts for the group; they do not describe the primary image-quality endpoint.

The deaths field is not populated with a count. Deaths are therefore not reported in the registry record, rather than reported as zero. No top serious adverse event terms are listed.

As a general statistical point, a recorded zero does not establish that the underlying risk is zero. Safety interpretation depends on the extent and duration of observation, how events were defined and collected, and how completely they were reported. The registry record gives the visit timeframe for the imaging assessment but does not describe a separate safety follow-up period or provide further event-collection details.

These figures describe what is entered in the safety record for this pilot study. They should not be used to infer safety in other populations or settings, and they do not establish the absence of unrecorded events.

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

The registry record establishes that this completed pilot study examined OFDI capsule imaging in healthy volunteers, with the stated aim of testing the feasibility of a redesigned tethered capsule catheter containing an integrated micro-motor. Its primary endpoint was the number of participants for whom an investigator recorded good-quality images after capsule swallowing. The record also specifies an approximate 20 minute visit, including 5 min of image acquisition.

The primary endpoint result is not reported in the registry record. Therefore, the posted information does not establish how many participants had images judged to be good quality, how often imaging met the intended criterion, or how precisely that outcome was estimated. The completion status does not answer those questions.

The record does not describe a like-for-like control comparison or a randomized allocation method. It cannot be interpreted as showing whether the capsule performed better or worse than another imaging approach. It also does not provide a comparative clinical outcome. The study's described focus is feasibility of image acquisition, not a reported estimate of comparative benefit.

General interpretation of feasibility findings also depends on the assessment rule and the participants studied. Here, the registry record does not detail the good-quality threshold, the image-review process, or further characteristics of the healthy volunteers. The limited enrollment reported should be understood as the scope of this pilot record, not as evidence that the findings generalize to other populations or clinical circumstances.

The safety record reports no serious or other adverse events in the listed group, while deaths are not reported in the registry record. Those entries do not answer the imaging endpoint question and should be interpreted within the available safety information.

In short, the record documents the study purpose, intervention, population, and planned assessment, but not the primary outcome result. No conclusion about observed image quality, comparative performance, or broader clinical use follows from the information reported.

14. Why This Trial Matters Statistically

This study matters statistically because a feasibility question is distinct from a comparative efficacy question. The recorded endpoint asks whether participants had images judged to be good quality after swallowing the capsule. That can be a relevant early assessment of an imaging technology, but it does not by itself estimate a difference between devices or establish performance in a broader population.

The distinction between an endpoint definition and an endpoint result is important. The registry record describes the assessment task and timeframe but does not report the resulting count. Without that value, readers cannot evaluate the observed feasibility outcome or its uncertainty. Clear reporting of the result, the number assessed, and the assessment rule would be needed to interpret the endpoint fully.

The record also illustrates why study design must guide interpretation. No randomized comparison or like-for-like control group is described. Any hypothetical planning calculation based on two arms and an observed effect is not evidence that this pilot carried out such a comparison, nor is it observed power. Planning illustrations describe assumptions; they do not replace results.

Finally, safety counts and imaging outcomes answer different questions. The recorded adverse event counts do not establish whether image acquisition was successful. Keeping these outcomes separate helps prevent a narrow set of registry entries from being read as a broader conclusion about the device. The main statistical limitation is not that a particular result is imprecise, but that the primary result needed to assess its value is not reported in the registry record.

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 interpreting this specific study is that the registry record does not report the primary endpoint result. The number of participants with good-quality images is not reported in the registry record, and no analysis or uncertainty estimate is listed. This prevents assessment of the observed feasibility outcome.

The endpoint's operational definition is also not described in detail. The record says an investigator assessed image quality after imaging was completed, but does not give the threshold for good quality, the assessment scale, or the process for resolving uncertain assessments. The number of images per exam and their handling in the participant-level classification are not reported.

The record gives enrollment of 4 healthy volunteers but does not describe participant characteristics, eligibility criteria, or the primary endpoint denominator. It does not say whether every enrolled participant completed imaging or whether any assessments were missing. Further, it does not report a control comparison, allocation method, or a statistical analysis plan. These omissions limit interpretation of both the endpoint and the study design.

The stated imaging timeframe is an approximate 20 minute visit with 5 min of image acquisition, but additional details about procedure conduct and safety follow-up are not reported in the registry record. Safety entries list event counts, while deaths are not reported. These limitations are specific to the available registry information and do not establish that unreported procedures or analyses did or did not occur.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Pilot Study for Imaging of the Esophagus Using Tethered Capsule OCT Endomicroscopy With Distal Scanning — NCT02947997.
• Registry record last updated 2023-01-17; status last verified 2023-01.
• Results first posted 2019-11-14.
• 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

NCT02947997 is a completed pilot study sponsored by Massachusetts General Hospital. It examined OFDI capsule imaging in healthy volunteers to test the feasibility of a redesigned tethered capsule catheter containing an integrated micro-motor. Enrollment was 4; the study started in 2015-09 and primary completion was in 2015-11.

The primary endpoint was the number of participants for whom good-quality images were recorded after swallowing the OFDI capsule. The assessment was to be made by an investigator after imaging, during an approximate 20 minute visit with 5 min of image acquisition. The primary result and any analysis are not reported in the registry record.

No randomized comparison or like-for-like control group is described. The safety record lists 0 serious adverse events and 0 other adverse events in the OFDI Capsule Imaging group, with 4 participants at risk for each category. Deaths are not reported in the registry record.