This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Evaluation of the Rectal Reflex Using Anal Acoustic Reflectometry (NCT02782377), a registered phase not stated study. The primary outcome is Opening Pressure.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02782377 |
| Phase | Phase not stated |
| Condition | Pelvic Floor Dysfunction |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 40 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Manchester University NHS Foundation Trust |
| Results posted | Yes |
2. Clinical Question
Population
People with pelvic floor dysfunction. The registry record lists an enrollment of 40.
Intervention
No treatment intervention is performed. Participants undergo anal acoustic reflectometry measurements at baseline, with a catheter alongside, and with the rectal balloon inflated.
Comparator
The primary comparison is within participants: opening pressure before rectal balloon inflation versus opening pressure after inflation. The described measurement sequence also includes a catheter-alongside assessment, but its role in the primary endpoint is not specified.
Primary question
How does opening pressure measured by anal acoustic reflectometry compare before and after 100mls air is introduced into the rectal balloon?
The study concerns the Recto-anal Inhibitory Reflex, described in the registry record as a normal response to rectal filling that involves changes in anal canal pressure. The record notes that the reflex can be absent or altered in people who have difficulty opening their bowels. It frames anal acoustic reflectometry as a way to assess the opening and closing of the anal canal, and contrasts this approach with anal manometry, which measures pressure at rest and during squeeze.
The primary question is a measurement question, not a treatment-effect question. The study description does not identify a randomized treatment or a separate control group. Instead, it describes repeated measurements in participants with pelvic floor dysfunction. The registry record does not report numerical opening-pressure results, an estimate of the pre-to-post change, or uncertainty around that estimate. It therefore does not establish from the posted results how large or consistent any change was.
3. Trial Design
The registry lists the study as completed, with a start date of 2016-02 and a primary completion date of 2016-10. The sponsor is Manchester University NHS Foundation Trust, and the recorded enrollment is 40. The listed condition is pelvic floor dysfunction. The study title is “Evaluation of the Rectal Reflex Using Anal Acoustic Reflectometry.”
The arm description characterizes the study as observational. Participants with pelvic floor dysfunction undergo three anal acoustic reflectometry measurements: at baseline, with the catheter alongside, and with the rectal balloon inflated. It states that no intervention is performed. This is not a parallel-group treatment comparison: the described measurements are taken within the same participant across different measurement conditions. Allocation is not stated in the registry record.
The primary outcome is opening pressure, measured in cmH2O. Its stated timeframe is during a single study visit, with measurement before and after balloon inflation. The endpoint description identifies baseline with the rectal balloon collapsed as Pre-RAIR and the measurement after inflation of 100mls air as Post-RAIR. The registry describes the primary outcome using a median and full range.
The registry record lists five outcome measures, but the available information does not report numerical primary endpoint results or analysis entries. It does not report a detailed statistical analysis plan, a sample-size justification for the observational study, or the handling of repeated measurements in a prespecified model. The record’s allocation field is not stated, and the study description does not identify a separate control arm. These features matter when interpreting any comparison: a within-participant measurement contrast is not equivalent to a randomized comparison between groups.
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
| Stage | Pelvic Floor Dysfunction |
|---|---|
| STARTED | 40 |
| COMPLETED | 35 |
| NOT COMPLETED | 5 |
Reasons for not completing this period:
| Reason | Pelvic Floor Dysfunction |
|---|---|
| Physician Decision | 5 |
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.
| Characteristic | Unit | Pelvic Floor Dysfunction |
|---|---|---|
| Participants analysed | 32 | |
| Age, Continuous | years | 57.5 (34 to 77) |
| Sex: Female, Male: Female | Participants | 26 |
| Sex: Female, Male: Male | Participants | 6 |
| Race and Ethnicity Not Collected | Participants | — |
| Region of Enrollment: United Kingdom | participants | 32 |
6. Primary Endpoint
The registry lists the primary outcome as Opening Pressure, measured over during single study visit- measurement taken prior to balloon inflation and post balloon inflation.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Full Range |
| Unit | cmH2O |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is opening pressure measured by anal acoustic reflectometry, in cmH2O. The registry describes measurements at baseline with the rectal balloon collapsed and after 100mls air is inflated into the rectal balloon. The measurement timeframe is a single study visit, before and after balloon inflation. The planned summary is a median with the full range.
In the study description, anal acoustic reflectometry uses sound waves and a balloon in the anal canal to assess cross-sectional area. Gradually changing balloon pressure allows measurement of the pressure at which the area starts to increase or decrease, corresponding to the canal beginning to open or close. Opening pressure is therefore used to describe one aspect of this mechanical response. The registry presents the approach as an assessment that mimics opening and closing of the anal canal, and it identifies the reflex response to rectal filling as the context for the pre- and post-inflation measurements.
A median describes the central value of observed measurements without requiring the distribution to be symmetric. The full range conveys the lowest and highest observed values, but does not by itself describe how measurements are distributed between those extremes or how precisely a pre-to-post contrast is estimated. The registry record does not report the observed median, the full range, or a numerical estimate of the change in opening pressure. It also does not report a confidence interval for the contrast.
The catheter-alongside measurement appears in the arm description, but the primary endpoint description specifies the collapsed-balloon and inflated-balloon measurements. The registry record does not report whether or how the catheter-alongside measurement contributes to the primary analysis.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central interpretive point is that the registry describes a repeated-measurement observational study, while its primary endpoint asks about opening pressure before and after rectal balloon inflation. This structure can support a within-participant description of measurements under different conditions, but it does not provide a randomized comparison of treatments. The record says no intervention is performed, and it does not identify a separate control group.
The registry record does not report the numerical primary outcome results. It gives no pre-inflation or post-inflation median, full range, paired difference, confidence interval, or p-value. It is therefore not possible to describe the size, direction, variability, or statistical precision of the observed endpoint contrast from the recorded results. The record lists five outcome measures and no analysis entries. The absence of numerical outcome results is distinct from evidence that the measurements were identical or that there was no change.
In general, a within-participant comparison can account for stable characteristics shared by the measurements from the same person. However, interpretation still depends on how measurements were collected, how repeated observations were analyzed, and whether data were missing. These details are not reported in the registry record. A difference between measurement conditions would also be a measurement finding in this study context; by itself, it would not establish a clinical benefit or prove that the method performs better than another test.
The endpoint is summarized using a median and full range. In general, the median is a measure of central location that is less influenced by extreme observations than the mean. The range communicates the endpoints of the observed values, but it is sensitive to extremes and does not quantify uncertainty in a comparison. Without the actual summaries and a measure of uncertainty, the precision of any contrast cannot be assessed. No numerical result should be inferred from the endpoint definition alone.
The record’s sample-size assumptions describe a planning illustration, not the design basis for this observational study. Those assumptions refer to 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 an observed effect. The study description instead gives a single pelvic-floor-dysfunction group with repeated measurements and says no intervention is performed. The registry record does not report the study’s own sample-size justification or make the planning assumptions a prespecified analysis plan. Such illustrations are not observed power and cannot substitute for an estimate with uncertainty.
Accordingly, the defensible reading is limited to the stated purpose and measurement design: the study examines opening pressure around rectal balloon inflation using anal acoustic reflectometry in people with pelvic floor dysfunction. How the measured pressure behaved, and how precisely any contrast was estimated, is not reported in the registry record.
9. Statistical Methods Explained
The statistical information recorded for this study is limited. The primary endpoint is opening pressure, summarized by a median and full range, and the described measurements are obtained before and after rectal balloon inflation during a single study visit. The registry record does not report numerical summaries, a numerical contrast, a confidence interval, a p-value, or an analysis entry. The concepts below explain how such information is generally interpreted; they do not describe an analysis confirmed to have been used in this study.
What does a median and full range convey?
In general, the median is the middle of the ordered observations. It can be a useful summary when measurements are skewed or include values far from the center. The full range gives the lowest and highest observed values. It shows the span of the data, but not the distribution of observations within that span. A range also changes with the number of observations and can be strongly affected by extreme values. The registry’s choice of median and full range tells readers how the primary endpoint is intended to be summarized; it does not reveal the actual values, because those results are not reported in the registry record.
Why does the repeated-measurement structure matter?
In general, measurements from the same participant are related. A paired analysis preserves that relationship by comparing each participant’s measurements across conditions, rather than treating the two sets as independent groups. This can be important because participants may differ in their typical pressure values. A comparison that ignores pairing may misrepresent the variability of the within-person contrast. The registry describes baseline, catheter-alongside, and rectal-balloon-inflated measurements, but does not report the statistical method used to account for repeated observations. It also does not specify whether the primary contrast was analyzed as paired differences or by another method.
Repeated measurements can also raise questions about measurement order and conditions. The record identifies the sequence and the primary pre- and post-inflation conditions, but does not report whether measurement order was varied, whether measurements were repeated within a condition, or how any inconsistent readings were handled. Those procedural and analytic details are not reported in the registry record and should not be inferred from the endpoint description.
What would a confidence interval add?
In general, a confidence interval expresses the statistical uncertainty around an estimate. For a pre-to-post contrast, an interval would show a range of values compatible with the data under the assumptions of the method used. A narrow interval indicates greater precision than a wide interval, though precision alone does not establish clinical importance. A confidence interval for the contrast is not reported in the registry record. The endpoint’s full range is not a substitute: it describes observed extremes, not uncertainty in an estimated contrast.
A p-value, in general, measures how compatible the observed data are with a specified null model, under the assumptions of the analysis. It does not measure the probability that a hypothesis is true, and it does not quantify the size or importance of a change. No p-value or analysis result is reported in the registry record. The record also does not state a statistical test or a model for the primary endpoint, so no inferential procedure can be attributed to the study from these details.
Why can over-dispersion matter?
In general, over-dispersion occurs when observed variability is greater than a statistical model expects. It matters especially for count outcomes when a model assumes a particular mean-variance relationship: underestimated variability can make uncertainty appear too small. The primary endpoint in this study is a pressure measurement summarized by a median and full range, not a count outcome in the stated endpoint description. The registry record does not report a count model or an over-dispersion assessment for this endpoint. This general concept should not be mistaken for a method used in this study.
How should the sample-size illustration be read?
The record’s stated assumptions describe a planning illustration computed from an observed effect. It uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is expressed as a stated fraction of the observed effect. These are assumptions for the illustration, not evidence that the observational study enrolled randomized arms or was designed around those assumptions. The arm description instead describes one pelvic-floor-dysfunction group undergoing measurements under different conditions, with no intervention.
In general, a sample-size calculation estimates how many participants might be needed to detect a specified effect under stated assumptions. Its answer depends on the effect size, variability, statistical method, significance level, and target power. When based on an observed effect, the calculation is a planning illustration and may be sensitive to how that effect was estimated. It is not observed power, and it does not show what the study’s analysis found. The registry record does not report a sample-size justification for the study’s own design, and no numerical outcome estimates are available for assessing the observed contrast.
These distinctions are especially relevant because the stated illustration assumes equal allocation between two arms while the registered study description is observational and describes measurements in participants under multiple conditions. The illustration cannot be read as proof of a two-arm trial or as a record of the actual analysis. The registry record does not explain how the illustration relates to the study’s repeated-measurement design.
What is not established by the statistical record?
The record does not report the primary outcome values, the analysis population, a method for handling missing measurements, a prespecified model, or uncertainty estimates. It therefore does not support a conclusion about the size or precision of the pre-to-post contrast. General statistical principles can clarify what such analyses would mean, but they cannot fill in unreported results or methods.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists five outcome measures. It does not report how many were designated as primary or secondary beyond the primary opening-pressure endpoint described in the record, nor does it state how multiple outcomes were handled statistically. The number of analysis entries is 0. No analysis results, p-values, or confidence intervals are recorded for assessing whether multiplicity adjustments were planned or applied.
In general, testing many outcomes can increase the chance of at least one apparently unusual result, even when no underlying effect is present. Approaches to multiplicity may include defining a primary outcome in advance, adjusting inference across outcomes, or treating additional outcomes as exploratory. Which approach was used in this study is not reported in the registry record. The presence of five listed outcome measures alone does not establish that five hypothesis tests were conducted.
The record does not report missing-data counts, reasons for missingness, imputation, or a complete-case rule. It also does not identify an analysis population or state whether all enrolled participants contributed to the primary endpoint. In general, missing measurements can affect both the precision and interpretation of a repeated-measurement comparison, particularly if availability is related to participant characteristics or measurement conditions. Without the relevant details, the direction or extent of any such effect cannot be assessed.
The registry record also does not report a statistical analysis plan specifying how the three measurement conditions were handled, whether the primary contrast was paired, or how additional analyses were selected. Those omissions limit reconstruction of the inferential strategy. They do not establish that no analyses were performed; they mean the methods and results are not reported in the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Pelvic Floor Dysfunction | 0 | 40 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Pelvic Floor Dysfunction | 0 of 40 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Pelvic Floor Dysfunction | 0 of 40 |
The registry lists 40 participants at risk for serious adverse events and 0 affected by serious adverse events. It lists 40 at risk for other adverse events and 0 affected by other adverse events. The number of deaths is 0, and no top serious adverse-event terms are listed.
These figures describe what is recorded for the study; they do not by themselves show that no adverse events of any kind occurred outside the registry’s recorded categories or reporting period. The registry record does not provide further event definitions, monitoring details, or a more detailed account of safety ascertainment. The study description says no intervention is performed, and the study is observational, so these counts should not be interpreted as evidence about the safety of a treatment.
Zero recorded events should be read as zero events reported in the registry figures, not as proof that an event is impossible. The figures also do not establish a comparison with another group: no separate control group is described. The appropriate reading is limited to the recorded at-risk counts and event counts, with the scope of safety reporting left unclear in the registry record.
12. What the Result Does, and Does Not, Mean
The study’s question is about measurement: it examines anal acoustic reflectometry opening pressure before and after rectal balloon inflation in people with pelvic floor dysfunction. The registry describes the study as observational, states that no intervention is performed, and gives a sequence of measurements within participants. The primary endpoint is expressed as a median and full range in cmH2O.
The record does not report numerical opening-pressure results, a numerical pre-to-post contrast, or an estimate of uncertainty. As a result, it cannot establish the direction or magnitude of a difference from the posted results, nor how precisely a difference was estimated. This absence of reported results is not evidence of no difference. It also prevents assessment of whether observations were consistent across participants or whether extreme values influenced the summaries.
Even if a within-participant contrast were reported, it would answer a measurement question under the conditions used in the study. It would not, by itself, show that anal acoustic reflectometry improves patient outcomes, establish a treatment effect, or demonstrate superiority to manometry. The registry’s background describes prior work and limitations of manometry, but the primary endpoint recorded for this study is opening pressure measured by anal acoustic reflectometry. A direct comparative performance result is not reported in the registry record.
The study includes 40 participants according to the enrollment field, but enrollment alone does not establish the precision of an endpoint estimate. Precision depends on the observed data and the method used to analyze them. Neither the numerical endpoint results nor an uncertainty interval is reported. The sample-size assumptions described for a planning illustration should not be treated as evidence of observed power or as confirmation that the study was designed as a two-arm comparison.
The most supportable conclusion is therefore about the study’s scope, not its unreported result: it was a completed observational evaluation of rectal-reflex measurement using anal acoustic reflectometry, with opening pressure assessed before and after inflation during a single study visit. The registry record does not provide enough outcome or analysis detail to determine what the measurements showed.
13. Why This Trial Matters Statistically
This study is statistically notable because its primary question concerns measurement under different conditions within participants, rather than an intervention tested against a control group. That distinction affects the appropriate interpretation of any contrast. Repeated measurements from the same participant are related, so an analysis ordinarily needs to account for that relationship. The registry describes the measurement sequence but does not report the method used to analyze it.
The endpoint also makes clear why the summary measure and uncertainty matter. A median and full range can describe the center and observed span of opening-pressure measurements, but they do not quantify the precision of a pre-to-post contrast. A paired estimate with an uncertainty interval would address a different question from separate medians and ranges. The numerical summaries and such an interval are not reported in the registry record, so the strength and precision of any observed pattern cannot be assessed.
The record also illustrates why planning assumptions should be separated from the design and analysis actually described. Its sample-size illustration uses equal allocation between two arms and a normal approximation, while the registered study description is observational and gives repeated measurements without an intervention. Without an explanation of how that illustration relates to the study, it should not be read as evidence of randomized allocation or as the study’s own sample-size justification.
Finally, the registry lists five outcome measures but reports no analysis entries. This leaves multiplicity, missing-data handling, and analysis populations unresolved. Those omissions are consequential for statistical interpretation: the endpoint definition can explain what was intended to be measured, but it cannot substitute for results, uncertainty, or a transparent account of analysis. The study matters statistically as an example of the need to distinguish a measurement design from a treatment comparison and a planning illustration from observed evidence.
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 registry record does not report numerical results for the primary opening-pressure endpoint. It gives no observed median or full range for either measurement condition, no numerical pre-to-post contrast, and no confidence interval or p-value. This prevents assessment of the result’s direction, magnitude, variability, and precision.
The study description is observational and reports repeated measurements in a pelvic-floor-dysfunction group, with no intervention. It does not identify a separate control group or state an allocation method. Therefore, the design as described does not support a randomized treatment comparison. The role of the catheter-alongside measurement in the primary analysis is also not reported in the registry record.
The registry record does not report the statistical method for handling within-participant measurements, the analysis population, missing-data counts, or how missing measurements were handled. It lists five outcome measures but does not describe multiplicity procedures or provide analysis entries. The record also does not report a sample-size justification for the observational study. The stated sample-size assumptions describe a planning illustration with equal allocation between two arms, which does not match the single-group repeated-measurement description without further explanation.
Safety reporting is limited to the recorded at-risk and event counts. Event definitions, monitoring details, and the scope of ascertainment are not reported in the registry record. The study’s completed status and enrollment of 40 do not resolve these outcome and methods limitations. These gaps restrict interpretation to the registered purpose and design rather than a conclusion about the observed measurement results.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Evaluation of the Rectal Reflex Using Anal Acoustic Reflectometry — NCT02782377.
- Registry record last updated 2020-12-02; status last verified 2020-11.
- Results first posted 2020-03-30.
- 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.
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18. Record Summary
NCT02782377 is a completed observational study titled “Evaluation of the Rectal Reflex Using Anal Acoustic Reflectometry,” sponsored by Manchester University NHS Foundation Trust. The registry lists pelvic floor dysfunction as the condition, enrollment of 40, a start date of 2016-02, and a primary completion date of 2016-10.
The study description says participants undergo anal acoustic reflectometry measurements at baseline, with the catheter alongside, and after rectal balloon inflation; no intervention is performed. The primary endpoint is opening pressure in cmH2O, measured before and after balloon inflation during a single study visit and summarized by a median and full range. The registry record does not report numerical primary endpoint results, an analysis method, or an estimate of uncertainty.
The safety record lists 0 serious adverse events, 0 other adverse events, and 0 deaths among the recorded at-risk groups of 40. The registry lists five outcome measures and no analysis entries. Its stated sample-size assumptions are described as a planning illustration and do not establish the study’s own design justification or observed power.