Sound Check-Correlation Between Transperineal and Digital Cervical Exam in 3rd Trimester Pregnancy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Sound Check-Correlation Between Transperineal and Digital Cervical Exam in 3rd Trimester Pregnancy (NCT05260333), a na na study. The primary outcome is Correlation of Cervical Dilation Via Butterfly iQ Pocket Ultrasound in Centimeters.

2. Clinical Question

The central question concerns the relationship between measurements from two examination methods, not whether one method changes a clinical outcome. Cervical dilation was assessed in centimeters on the day of the examination. The registry says a correlation coefficient was calculated, but its value and the underlying measurement results are not reported in the registry record. The degree of association between the methods therefore cannot be evaluated from the recorded outcome information.

The study also aimed to compare discomfort and determine whether patients preferred one examination method over the other. Those are patient-experience questions distinct from the measurement-correlation question. The registry lists discomfort and preference as secondary outcomes, but their results are not reported in the registry record. The record describes both examinations in sequence and says each patient served as their own control. This makes the paired nature of the intended comparison important: the observations from the two methods come from the same patients, rather than from separate randomized groups. The available record establishes the question and sequence, but not the resulting evidence about correlation, discomfort, or preference.

3. Trial Design

NCT05260333 is a completed study sponsored by Baylor College of Medicine. The registry lists an enrollment of 30, a start date of 2022-04-01, and a primary completion date of 2022-07-27. Its phase is recorded as not applicable. The study is categorized as “other,” with sequential model and no masking. Allocation is recorded as not applicable; the registry does not describe this as a randomized comparison.

The described sequence is transperineal cervical examination using Butterfly iQ ultrasound, followed by traditional digital examination by the examiner’s fingers. The primary outcome description says patients served as their own control. Thus, the intended comparison pairs measurements from the methods within patients. The registry’s adverse-event listings also display separate entries for transperineal ultrasound and digital examination, but these entries do not make the study a randomized, parallel-group comparison. The order is specified in the intervention description, and random assignment of order is not reported in the registry record.

The brief summary identifies accuracy comparison as the primary purpose and discomfort and patient preference as secondary aims. However, the primary outcome is described as a correlation of cervical dilation measurements, which evaluates association rather than, by itself, full measurement agreement or diagnostic accuracy. The detailed protocol, eligibility criteria, examiner training, device measurement procedures, and rationale for the chosen design are not reported in the registry record. Nor does the record report a sample-size justification or explain how the enrollment target was selected. The completed status indicates the study’s registry status, but does not establish that outcome results were posted.

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

Analysis population for the primary outcome, as defined in the registry: The patients served as their own control.

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 Correlation of Cervical Dilation Via Butterfly iQ Pocket Ultrasound in Centimeters, measured over 1 day.

The primary endpoint is described as the correlation of cervical dilation measured with Butterfly iQ pocket ultrasound and digital examination. Measurements are in centimeters, taken on the day of the examination, with the patient serving as their own control. The stated summary parameter is the median, with full range as the dispersion description. The endpoint description says a correlation coefficient was calculated to assess the relationship between the two examinations.

Correlation is useful for assessing whether measurements from one method tend to vary in relation to measurements from another. In general, a strong correlation can indicate that larger measurements by one method tend to accompany larger measurements by the other. Correlation alone does not show that the methods give the same measurement: a method could consistently read higher or lower and still track changes closely. Agreement questions generally require examining the size and pattern of paired differences, not only the correlation.

The registry does not identify the specific correlation coefficient, provide the paired measurement data, or report the coefficient or its uncertainty. The endpoint’s stated measurement scale and timing are documented, but the observed relationship and its precision are not reported in the registry record. Accordingly, the endpoint’s intended role is clear, while the strength and practical interpretation of the observed association cannot be determined from the recorded result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a correlation between two cervical dilation measurements made on the same day. The registry says the patient served as their own control, so the measurements are paired by patient. It also identifies the measurement unit as centimeters and states that a correlation coefficient was calculated. The coefficient type, the analysis procedure, and the numerical result are not reported in the registry record.

What does correlation describe?

In general, correlation describes the extent to which two variables move together. In this study’s context, it would describe whether patients with larger digital measurements tend also to have larger ultrasound measurements. It is a measure of association, not a direct measure of equality. Two measurement methods can be highly correlated even if one tends to give systematically larger readings. Conversely, a limited range of observed measurements can make a correlation look modest even when paired values are relatively close. These general features matter because the study summary uses the word “accuracy,” while the primary endpoint specifically names correlation.

To determine whether methods give sufficiently similar values, a reader would usually want information beyond correlation. General approaches include examining each patient’s difference between methods, checking for systematic shifts, and assessing whether differences vary across the measurement range. The registry record does not report paired differences, a measure of agreement, an acceptable-difference criterion, or the raw measurements. It is therefore not possible to assess agreement from the registered outcome description alone.

Why does pairing matter?

When each patient undergoes both methods, the two observations from that patient are related. General statistical analysis should account for this pairing. Treating each method’s measurements as if they came from unrelated patients can misrepresent the uncertainty because it discards the within-patient relationship. The registry identifies the self-control design, but does not specify how the pairing was incorporated into the correlation calculation or any other analysis. The method used to calculate the coefficient, any assumptions checked, and any uncertainty interval are not reported in the registry record.

The listed order is ultrasound followed by digital examination. General interpretation of sequential measurements should consider whether order could affect measurement or experience. For example, the first procedure could influence the circumstances of the later procedure. This is a general design consideration, not evidence that an order effect occurred. The registry does not report randomization of examination order or an analysis of order effects.

What does the summary statistic tell the reader?

The outcome describes the parameter as a median and the dispersion as full range. In general, a median gives the central ordered value and is less sensitive than a mean to extreme observations. The full range describes the spread from the smallest to the largest observed value, but it can be strongly affected by extreme observations and does not indicate how measurements are distributed between the endpoints. Those summaries do not, on their own, describe the paired relationship between the methods. The actual median, range, and correlation result are not reported in the registry record.

Uncertainty is also central to interpreting an estimate. In general, a confidence interval conveys a range of values compatible with the data under the analysis assumptions; narrower intervals indicate greater precision, while wider intervals indicate greater uncertainty. No confidence interval for the correlation is reported in the registry record. A p-value, if available, would address a specified statistical test under its assumptions, but would not by itself establish practical agreement or clinical importance. The registry does not report a primary p-value or identify a test for the correlation.

How should planning calculations be read?

The registry’s sample-size assumptions describe planning illustrations based on the observed effect, with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation. They specify that the effect to detect is a stated fraction of the observed effect. Such calculations are planning illustrations, not observed power, and do not describe the precision actually achieved in this study. The record does not report the observed effect needed to assess those illustrations, and the listed within-patient sequence should not be mistaken for evidence of a randomized, equal-allocation design. The planning assumptions are not a report of the trial’s own design justification.

The registry lists one analysis, but the analysis details are not reported in the registry record. The correlation coefficient selected, treatment of missing or unusable measurements, handling of outliers, and any adjustment for covariates are not described. These omissions do not establish that the investigators did or did not use any particular approach. They limit what can be verified from the record. The primary results and the analysis methods would be needed to evaluate the estimate, its assumptions, and its precision.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures, identifies cervical dilation correlation as the primary outcome, and names discomfort and preference as secondary outcomes. It reports one analysis, but the analysis details are not reported in the registry record. A plan for addressing multiple outcomes or multiple statistical tests is not reported in the registry record.

In general, testing several outcomes can increase the chance of observing at least one apparently unusual result by chance. A prespecified hierarchy, adjustment procedure, or clear separation between confirmatory and exploratory analyses can help readers understand how multiple results were handled. The record does not state whether any such approach was planned or used. Because the outcome results are not reported, it is also not possible to assess how multiplicity might affect interpretation of any observed findings.

Missing-data procedures are not reported in the registry record. The record does not state whether any patient lacked one of the two measurements, whether examinations were incomplete, or how missing measurements were handled. The analysis population is not described beyond the statement that patients served as their own control. It is not reported whether the primary analysis included every enrolled patient, only those with paired measurements, or another defined group. These are unknowns in the registry record, not evidence that data were missing or that a particular population was analyzed.

The registry reports enrollment of 30, but enrollment alone does not establish the number of complete pairs used in the primary analysis. The recorded outcome information does not give that analysis denominator. A reader therefore cannot assess whether missingness, exclusions, or analysis-population choices affected the reported result.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry lists serious adverse events separately for transperineal ultrasound cervical examination and digital manual cervical examination. For each listed group, 30 participants were at risk and zero serious adverse events were reported. The record also lists 30 at risk and zero affected for other adverse events in each group, and zero deaths in each group. No serious adverse-event terms are listed.

These figures describe the registry’s adverse-event entries; they do not establish that no discomfort or other experience occurred. Discomfort is listed as a secondary outcome, distinct from the adverse-event summary, and its result is not reported in the registry record. The record does not describe adverse-event definitions, ascertainment procedures, severity grading, or follow-up beyond the listed outcome entries. The timeframe for the primary measurement is 1 day, but that does not by itself define the safety-monitoring period.

The entries should not be interpreted as randomized group comparisons. The study description says patients underwent ultrasound followed by digital examination and served as their own control. The adverse-event group labels are registry categories, not evidence of independent parallel arms. Zero reported serious events is a description of the posted counts, not proof that either procedure has no risk.

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

The record describes a study intended to compare cervical dilation measurements from Butterfly iQ transperineal ultrasound with measurements from digital examination. It also identifies patient discomfort and preference as secondary questions. The examinations were described in sequence, with ultrasound first, and patients served as their own control. These details clarify the intended comparison, but they do not reveal the findings.

The primary result needed to evaluate the measurement relationship—the correlation coefficient—is not reported in the registry record. Neither are the paired measurements, an uncertainty estimate, or results describing agreement. Consequently, the record does not establish how closely measurements were associated, whether one method tended to read higher or lower, or whether differences were small enough for any particular purpose. Correlation, even if reported, would answer only the association question and would not alone demonstrate agreement or accuracy.

The discomfort and preference results are also not reported in the registry record. The stated aims should not be treated as evidence that patients preferred either examination or experienced less discomfort with one method. The adverse-event entries report zero serious events and zero deaths in the listed examination groups, but those counts do not substitute for the unreported patient-experience outcomes or establish absence of risk.

The registry status is completed, and enrollment is recorded as 30. Completion and enrollment do not supply the missing outcome estimates, analysis details, or precision measures. Planning calculations based on an observed effect are not observed power and cannot fill that evidentiary gap. The appropriate interpretation is therefore limited: the registry documents the comparison’s design and objectives, while the results needed to judge the primary and secondary questions are not reported in the registry record.

13. Why This Trial Matters Statistically

This study raises a useful statistical distinction between association and agreement. When a new measurement method is compared with an established method, a correlation can show whether values tend to move together. It cannot, by itself, show that the two methods produce interchangeable measurements. The distinction is especially relevant because the study summary frames the aim as comparing accuracy, while the registered primary endpoint is correlation of cervical dilation measurements.

The self-control design also highlights the role of paired data. Measuring each patient with both methods can make the within-patient comparison informative, but analysis must retain the pairing to characterize the relationship and its uncertainty appropriately. The registry says patients served as their own control, yet does not report the analysis details or numerical results. Readers can identify the intended structure without being able to verify how it was analyzed.

Patient experience is a separate dimension of method comparison. Discomfort and preference are named as secondary outcomes, which signals that measurement properties were not the only questions of interest. Those results are not reported in the registry record, so the stated aims cannot support conclusions about experience.

Finally, a completed registry status is not the same as a complete statistical report. The absence of the correlation estimate, uncertainty, and secondary results prevents assessment of magnitude and precision. This is a reminder that study objectives and design descriptions explain what investigators set out to learn, whereas posted estimates and their uncertainty are needed to judge what the data show.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The main limitation of the registry record for statistical interpretation is that it does not report the primary correlation coefficient or any numerical result for the primary outcome. It also does not report the paired measurements, an uncertainty interval, or a measure of agreement. This prevents assessment of the magnitude and precision of the relationship between examination methods.

The registry describes the study as sequential, with ultrasound followed by digital examination. It does not report randomized examination order or an assessment of order effects. Because both examinations are conducted in sequence, the record does not allow evaluation of whether order influenced measurement or patient experience. This is a design consideration; the registry does not establish that an order effect occurred.

The endpoint description refers to correlation, while the brief summary describes an accuracy comparison. The record does not specify the correlation coefficient, define an acceptable measurement difference, or report analyses of paired differences. Thus, the registered endpoint alone would not fully characterize agreement even if its estimate were available.

The discomfort and preference outcomes are listed but their results are not reported in the registry record. Missing-data procedures, analysis-population definitions, outcome multiplicity procedures, and detailed statistical methods are also not reported. The enrollment is recorded as 30, but the number contributing paired measurements to the primary analysis is not given. The record does not report a sample-size justification. These gaps limit assessment of precision, potential bias, and completeness of the analysis without establishing that any particular problem occurred.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Sound Check-Correlation Between Transperineal and Digital Cervical Exam in 3rd Trimester Pregnancy — NCT05260333.
• Registry record last updated 2023-11-27; status last verified 2023-11.
• Results first posted 2023-11-27.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT05260333 is a completed study sponsored by Baylor College of Medicine, with enrollment recorded as 30. The registry lists a start date of 2022-04-01 and a primary completion date of 2022-07-27. The study compared Butterfly iQ transperineal ultrasound cervical examination with digital manual examination, with ultrasound described first. Patients served as their own control.

The primary outcome was correlation between cervical dilation measurements in centimeters, recorded on the day of the examination. Discomfort and preference were listed as secondary outcomes. The primary correlation result and secondary-outcome results are not reported in the registry record. The record also does not report the analysis details needed to assess measurement agreement, uncertainty, missing data, or multiplicity. The listed adverse-event entries report zero serious adverse events and zero deaths in each examination group.