Optical Frequency Domain Imaging (OFDI) Surveillance and Image Guided Biopsy of the Esophagus: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Optical Frequency Domain Imaging (OFDI) Surveillance and Image Guided Biopsy of the Esophagus (NCT01439633), a na na study. The primary outcome is Number of Subjects in Which the Targeted Locations Identified Through OFDI Imaging Correlates With the Biopsies..

2. Clinical Question

3. Trial Design

The registry record describes a completed pilot study titled “Optical Frequency Domain Imaging (OFDI) Surveillance and Image Guided Biopsy of the Esophagus.” Its official title identifies it as a pilot study to evaluate OFDI surveillance and image-guided biopsy of the esophagus. Massachusetts General Hospital is listed as the sponsor. The study start is recorded as 2010-10, primary completion as 2014-05, and status as COMPLETED.

The design is single-group, with 22 participants enrolled. Allocation is listed as NA, masking as NONE, and phase as NA. The intervention is a device named MGH OFDI marking. The arm description is “OFDI imaging.” There is no parallel control arm or randomized comparison described in the registry record. Consequently, the design addresses feasibility within a single group rather than a between-group difference.

The stated aim is to assess whether locations identified as pathologic on OFDI datasets can be marked with superficial cautery marks visible during endoscopy, and whether those marks can then guide biopsy. The primary outcome is framed as a count of participants whose targeted OFDI locations correlate with biopsy findings. Its timeframe is day 1, during the diagnostic procedure.

The registry record lists one primary outcome measure and zero analyses. It does not report the observed primary outcome, a statistical analysis plan, details of participant eligibility, or how participants were selected for analysis. Those omissions limit the conclusions that can be drawn about feasibility and the precision of any estimate. The study's completed status indicates that the record marks the study as completed; it does not by itself establish that the primary outcome was achieved or analyzed.

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: Twenty two subjects were enrolled and twenty two finished completed this study

6. Primary Endpoint

The registry lists the primary outcome as Number of Subjects in Which the Targeted Locations Identified Through OFDI Imaging Correlates With the Biopsies., measured over day 1, during diagnostic procedure.

The primary endpoint is a count of participants in whom targeted locations identified through OFDI imaging correlate with biopsies. The unit is participants, and the stated timeframe is day 1, during the diagnostic procedure. The endpoint description explains a sequence: identify target locations on OFDI, mark them with superficial cautery, confirm visibility by endoscopy, use the marks to guide biopsy, and compare the images with biopsies from corresponding marked tissue.

This type of endpoint is relevant to the stated feasibility aim because it focuses on whether the imaging targets can be translated into locations that can be sampled and checked against tissue findings. It is not a measure of a between-group treatment effect, because the registry record describes a single-group study without a comparator. Nor does the endpoint definition alone establish how many participants had a successful correlation. The observed count, the criteria used to classify a correlation, and any accompanying uncertainty estimate are not reported in the registry record.

The outcome is expressed as a participant count rather than a rate or a continuous measurement. For interpretation, the count needs a clearly defined denominator and a consistent rule for what qualifies as a correlation. The record lists 22 enrolled participants, but does not report the number included in the endpoint analysis or whether all enrolled participants contributed usable imaging and biopsy data. The endpoint's purpose is therefore clear at a high level, while its result and operational details remain unavailable in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count represent?

The primary outcome is defined as a count of participants whose OFDI-identified target locations correlate with biopsy findings. A count records how many people meet an outcome definition. To interpret such a count as a proportion, an analysis also needs a denominator: the number of participants assessed under the outcome definition. The registry record lists 22 enrolled participants, but does not report the endpoint count or the number analyzed. Enrollment should not automatically be treated as the endpoint denominator, since the record does not state whether every enrolled participant had evaluable imaging and biopsy data.

The endpoint description refers to matching targeted locations on imaging with biopsies of correlated marked tissue. In general, reproducibility of this kind of outcome depends on prespecified rules for identifying a target, confirming that a mark corresponds to it, and deciding what biopsy finding constitutes correlation. The registry record describes the intended process but does not report detailed classification criteria or how ambiguous or unusable observations were handled.

What can a single-group design estimate?

A single-group design can describe outcomes observed in participants who underwent the study procedure. It does not, on its own, estimate a difference between the procedure and a comparator. Here, allocation is listed as NA, the model is single group, and no control arm is described. The study therefore frames its question around feasibility, not a randomized comparison. Its design cannot separate the experience associated with OFDI marking from differences that might be seen under another strategy.

In general, estimates from a pilot study can be imprecise, particularly when the number of participants is limited. Precision depends on the observed endpoint and the amount of usable data, as well as the analysis method. No interval estimate is reported for this outcome. A confidence interval would communicate uncertainty around an estimate, but its width and interpretation depend on the data and method; neither can be recovered from the endpoint definition alone.

What do the listed planning assumptions mean?

The registry record includes a description of a planning illustration, explicitly distinguished from the trial's own design. It specifies a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It also describes planning for a stated fraction of the observed effect. Those assumptions are associated with a hypothetical sample-size calculation, not with the single-group study design reported for this trial.

The record does not report the numerical observed effect used for that illustration, the fractions considered, or resulting participant counts. The illustration therefore cannot be interpreted as the actual enrollment target or as evidence that the study had a particular probability of detecting an effect. Sample-size calculations are planning aids based on assumed effects and methods; they are not observed power. In this case, the primary outcome result itself is not reported, so readers cannot assess the observed effect from the registry record.

A normal approximation is a general method for estimating uncertainty or planning sample sizes under specified conditions. For binary outcomes, the adequacy of an approximation can depend on the distribution of outcomes and the size of the groups. With sparse outcomes, alternative methods may be considered in general. The registry record does not identify the method used to analyze the primary endpoint, so no particular inferential method should be attributed to the study.

Why does the analysis plan matter?

Statistical interpretation depends on knowing what analysis was planned and which participants were included. The registry record lists zero analyses and does not report the primary endpoint result, inferential method, missing-data handling, or analysis population. It also does not report whether any interim analysis was planned or conducted. In general, a prespecified plan helps distinguish intended analyses from choices made after data are available, but no such details are reported.

The design has no masking, as recorded in the registry. This is a description of the trial design, not a finding about whether outcome assessment was affected. The record does not specify who interpreted images or biopsies, whether reviewers were blinded to other information, or how potential assessment differences were addressed. Such details can matter when an endpoint depends on correspondence between imaging targets and tissue samples.

Without the outcome count, denominator, criteria for correlation, and analysis details, readers should treat the registered endpoint as a planned measure rather than a reported finding. The record provides enough information to understand the general feasibility question and the single-group structure, but not enough to reproduce or independently evaluate a statistical analysis.

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("MGH OFDI Marking and Imaging")
n      <- c(22)
events <- c(22)
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  MGH OFDI Marking and Imaging  22  22  100.0  84.6  100.0  85.1  100.0  85.2  99.9

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome measure and zero analyses. It does not report a statistical analysis plan, any additional outcome analyses, or a method for addressing multiplicity. When several outcomes or statistical tests are considered, multiplicity can increase the chance of a false-positive finding if each test is interpreted separately. General approaches include defining a primary outcome in advance or adjusting inference across multiple tests. The record does not state that any particular approach was used, so no multiplicity procedure can be attributed to this study.

The endpoint result and analysis population are not reported in the registry record. The record lists 22 enrolled participants, but does not say how many had evaluable imaging and biopsy data or were included in the primary endpoint analysis. It also does not report whether data were missing, why any data might have been unavailable, or how missing observations were handled. In general, missingness can affect both the denominator and interpretation of a binary outcome; its impact depends on the amount and pattern of missing data and the assumptions used to address it.

No intention-to-treat, per-protocol, or other analysis population is described in the registry record. Those labels refer generally to defined groups of participants used for analysis, but the record does not identify such a group. It also does not report exclusions, protocol deviations, or sensitivity analyses. As a result, the enrolled count cannot be assumed to be the denominator for the primary outcome. Readers cannot assess whether the endpoint analysis included all participants or whether conclusions might change under alternative handling of unavailable data.

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 registry safety entries list the MGH OFDI Marking and Imaging group with 22 participants at risk for serious adverse events and zero affected. The same group has 22 participants at risk for other adverse events and zero affected, with zero deaths recorded. These are counts in the registry record, not estimates of comparative safety, because there is no comparator group described.

A recorded zero means that no event was entered in the relevant registry count; it does not by itself show that the risk is absent. In general, interpretation depends on how events were defined, how long participants were monitored, how events were collected, and whether all participants had complete follow-up. The registry record does not provide those details or list serious adverse-event terms.

The primary outcome timeframe is day 1, during the diagnostic procedure, but the safety entries are not accompanied by a separate detailed follow-up description. The counts should therefore be read narrowly as reported registry figures. They do not establish that every possible adverse event was assessed, nor do they support a comparison with another procedure or group.

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

The record establishes that a completed, single-group pilot study was registered to examine whether OFDI-identified target locations could be marked endoscopically and used to guide biopsy in the setting of Barrett's Esophagus. It records 22 enrolled participants and defines a primary outcome based on correlation between OFDI targets and biopsy findings during the diagnostic procedure. Those details explain what the study set out to assess.

The record does not report the observed primary outcome count, the number of participants analyzed, or an uncertainty estimate. It therefore does not show whether the proposed marking and biopsy-guidance process achieved the intended correlation in the participants studied, or how precisely that result was estimated. A registered aim and an outcome definition are not substitutes for a posted result.

The single-group design also limits interpretation. No comparator is described, so the record cannot show whether the process performed differently from another approach. No statistical analysis is reported, and no conclusion about a treatment effect or comparative performance can be drawn. The planning assumptions described for a separate sample-size illustration do not supply an observed endpoint result and should not be read as evidence of study power.

The safety counts record zero serious adverse events, zero other adverse events, and zero deaths among the listed group, with 22 at risk for each event category. These figures describe what the registry lists, but do not establish that there was no risk or that all events were captured. The record does not report detailed definitions or ascertainment procedures.

In practical statistical terms, the registry entry supports an understanding of the study question, design, endpoint definition, and recorded safety counts. It does not support a quantitative conclusion about feasibility, precision, or comparative performance. Such conclusions would require the endpoint results, denominator, and analysis details, which are not reported in the registry record.

14. Why This Trial Matters Statistically

This study illustrates why a clearly stated feasibility question and a reported endpoint result are both necessary for statistical interpretation. The registry record explains the intended chain from OFDI imaging to visible cautery marks, endoscopic verification, biopsy guidance, and comparison with tissue from the marked location. That description makes the clinical measurement goal understandable. But without the observed count and the number of participants assessed, readers cannot quantify how often the process produced the intended correspondence.

The single-group structure is also central. A feasibility count can describe experience within the enrolled group, but it is not a comparison with an alternative approach. The registry lists no allocation to separate groups and no comparator. Recognizing this prevents a within-group observation from being interpreted as evidence of superiority or a causal effect.

The record also separates the trial design from a planning illustration. The illustration's assumptions refer to equal allocation between two arms and a normal approximation, whereas the trial is registered as single group. Keeping planning assumptions distinct from the actual design avoids treating sample-size calculations as study findings or as observed power. The numeric planning results and primary endpoint result are not reported in the registry record.

Finally, the safety entries demonstrate the importance of reading zero-event counts in context. The registry records no serious adverse events, other adverse events, or deaths in the listed group, but it does not describe detailed surveillance or event definitions. A zero count is a record of observed entries, not proof of no risk. Together, the design and reporting gaps show why outcome denominators, analysis methods, uncertainty estimates, and follow-up details matter when evaluating a pilot study.

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 trial-specific limitation in interpreting the registry entry is that the primary endpoint result is not reported. The record gives the outcome definition and timeframe, but not the observed participant count, analysis denominator, or a measure of uncertainty. This prevents quantitative assessment of the stated feasibility aim.

The single-group design provides no comparator. It therefore cannot estimate a difference between OFDI-guided marking and another method. Allocation is listed as NA, and masking as NONE. The registry does not report who assessed image-biopsy correspondence or how assessment consistency was addressed. These details matter for an endpoint that depends on matching locations across imaging, markings, and tissue samples.

The registry record lists 22 enrolled participants, but does not report participant characteristics beyond the condition, eligibility criteria, or how many contributed to the endpoint. Missing data, exclusions, protocol deviations, and analysis populations are not described. The statistical analysis plan, method for estimating uncertainty, and any interim analyses are also not reported in the registry record.

Safety interpretation is limited by the absence of details about event definitions, ascertainment, and follow-up. Although the registry lists zero serious adverse events, zero other adverse events, and zero deaths, the counts alone cannot establish completeness of safety reporting or absence of risk.

Finally, a separate planning description refers to hypothetical two-arm assumptions, but the record does not report the numerical planning results or the observed effect used. Those assumptions do not supply missing trial results and do not align with the registered single-group design as a direct comparison. These limitations constrain what can be concluded from the registry entry, rather than demonstrating that the study procedures succeeded or failed.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Optical Frequency Domain Imaging (OFDI) Surveillance and Image Guided Biopsy of the Esophagus — NCT01439633.
• Registry record last updated 2019-04-10; status last verified 2019-04.
• Results first posted 2018-09-25.
• 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 pilot study sponsored by Massachusetts General Hospital, with status COMPLETED, start date 2010-10, and primary completion date 2014-05. The study concerns OFDI surveillance and image-guided biopsy of the esophagus in Barrett's Esophagus. It is registered as a single-group study, with 22 participants enrolled, allocation NA, and masking NONE.

The primary outcome is a participant count based on correlation between OFDI-identified target locations and biopsies, assessed during the diagnostic procedure on day 1. The stated aim is to evaluate marking target locations with superficial cautery marks visible by endoscopy and using those marks to guide biopsy. The primary outcome result and analysis are not reported in the registry record.

Safety entries list zero serious adverse events, zero other adverse events, and zero deaths among 22 participants at risk in the listed group. The record does not provide detailed safety ascertainment or an analysis population. It lists one primary outcome measure and zero analyses.