Paracervical Block for Pain Associated With Laminaria Insertion: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Paracervical Block for Pain Associated With Laminaria Insertion (NCT02454296), a randomized na study. The primary outcome is Pain After Placement of Laminaria (100 mm Visual Analog Scale).

2. Clinical Question

The registry describes the purpose as assessing whether a paracervical block is effective at reducing discomfort during laminaria placement. Statistically, the posted primary outcome compares the distributions of participants’ immediate pain ratings across the two randomized groups. The posted summaries are medians with inter-quartile ranges, and the reported comparison uses a Wilcoxon (Mann-Whitney) test.

The lidocaine group’s reported median was 13.0 units, with an inter-quartile range from 2.0 to 39.0. The sham group’s median was 54.0 units, with an inter-quartile range from 27.0 to 61.0. The registry reports p = 0.01 for the comparison. These summaries describe the posted results; they do not by themselves give an adjusted effect estimate, a confidence interval for the between-group contrast, or the degree to which individual participants’ ratings overlapped.

The clinical question is therefore narrow: it concerns pain ratings taken immediately after placement in this trial, rather than pain at other times, satisfaction, or all aspects of the procedure. Those other outcomes cannot be inferred from the primary endpoint. The record lists satisfaction with overall pain control and pain associated with the block or sham block as secondary outcomes, but their numerical results are not reported in the registry record.

3. Trial Design

The registry describes a randomized, double-masked, parallel-group trial. It records enrollment of 41 and a completed status. The listed start was 2015-05 and primary completion was 2015-12. The registry names the University of Hawaii as sponsor. The phase is listed as NA.

Participants were assigned to one of two groups: paracervical block with lidocaine or sham paracervical block. The active arm description says the block was performed before laminaria placement with 1% lidocaine and sodium bicarbonate. The sham description says a capped needle was used before placement. The registry does not identify which people were masked, describe how randomization was generated or concealed, or report whether masking was assessed. Those details are not reported in the registry record.

The reported primary outcome was pain after laminaria placement, measured within 10 seconds. The registry defines the measure as a 100 mm visual analog scale, where 0 means no pain and 100 means the worst pain ever felt. The endpoint is summarized by median and inter-quartile range in each group. The posted analysis compares the groups using a Wilcoxon (Mann-Whitney) test.

The arm summaries list 20 participants for the lidocaine group and 21 for the sham group. These are the reported group sizes for the primary outcome summaries; the record does not explain whether these counts reflect every randomized participant or a particular analysis population. Eligibility criteria, recruitment details, the allocation sequence, protocol deviations, and the handling of participants without an outcome measurement are not reported in the registry record.

The registry lists two secondary outcomes: satisfaction with overall pain control on a 100 mm visual analog scale, and pain associated with the paracervical or sham block. It records three outcome measures and three analyses, but the secondary numerical results and full analysis details are not reported. The design description alone does not establish how outcomes beyond the primary endpoint were handled statistically.

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.

6. Primary Endpoint

The registry lists the primary outcome as Pain After Placement of Laminaria (100 mm Visual Analog Scale), measured over Measured within 10 seconds after placement of laminaria.

The primary endpoint is pain reported after laminaria placement. Participants were asked to rate their pain on a 100 mm visual analog scale within 10 seconds after placement. The registry describes the scale as validated and anchors it at 0 for no pain and 100 for the worst pain ever felt. The endpoint therefore captures a participant’s immediate subjective rating, rather than an objective measurement of a physical process.

Using a pain scale makes it possible to record differences in reported experience across participants and compare the distributions between randomized groups. A visual analog scale retains a range of possible ratings instead of reducing responses to a simple yes-or-no indicator. The immediate timing makes the endpoint specific to discomfort at the time of laminaria placement. It should not be read as a measure of pain later in the procedure or afterward.

The registry reports the endpoint as a median and inter-quartile range for each group. The median describes the center of the observed ratings; the inter-quartile range describes the span from the lower to the upper quartile, containing the middle half of ratings. These summaries are useful when the analysis is based on ranks or when a mean and standard deviation are not the chosen description. They do not show every participant’s rating or quantify the uncertainty in a difference between groups.

For the lidocaine group, the reported median was 13.0 and the inter-quartile range was 2.0 to 39.0. For the sham group, the median was 54.0 and the inter-quartile range was 27.0 to 61.0. The registry reports a Wilcoxon (Mann-Whitney) comparison. The numerical result for satisfaction or pain associated with the block is not reported in the registry record here, so these primary endpoint summaries should not be extended to those distinct outcomes.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the reported rank test compare?

The registry reports a Wilcoxon (Mann-Whitney) test for the primary comparison. In general, this is a rank-based method: it orders observations across groups and assesses whether ratings in one group tend to occupy different positions in that ordering from ratings in the other group. It uses the information in the observed ordering rather than relying directly on a comparison of group means.

This distinction matters because the posted group summaries are medians and inter-quartile ranges, while the test uses ranks from the underlying observations. A rank-test result cannot be reconstructed from the medians and inter-quartile ranges alone. The posted p-value is 0.01; the registry does not report a test statistic or a confidence interval for the contrast. The method is sometimes described as a test of a location difference, but interpreting it strictly as a test of medians requires assumptions about the shapes of the group distributions. The record does not report those shapes.

How should medians and inter-quartile ranges be read?

In general, the median is the central point of an ordered set of observations. The inter-quartile range runs from the lower quartile to the upper quartile and describes the middle half of the observations. These measures convey the center and spread without requiring a mean-based summary. In this trial, the lidocaine group’s median was 13.0 and its inter-quartile range was 2.0 to 39.0; the sham group’s median was 54.0 and its inter-quartile range was 27.0 to 61.0.

An inter-quartile range is not a confidence interval. It describes spread among participant ratings, whereas a confidence interval describes uncertainty about an estimated quantity. The registry’s IQRs therefore should not be read as uncertainty bounds for the difference between groups. There is no reported confidence interval for that comparison in the registry record.

What does the p-value say?

In general, a p-value summarizes how unusual data at least as incompatible with a specified null model would be if that model and the test assumptions held. Here, p = 0.01 is the registry’s result for the Wilcoxon (Mann-Whitney) comparison. It does not quantify the magnitude of the difference, the probability that one treatment is better, or the probability that the null model is true. It also does not establish whether the observed contrast is important to participants.

It is useful to read the p-value alongside the group summaries and the endpoint definition. The summaries show lower observed central pain ratings in the lidocaine group, while the test reports evidence of a group-distribution difference under its rank-based framework. A confidence interval or a clearly defined rank-based effect estimate would help convey precision and magnitude, but neither is reported in the registry record.

Why do the reported summaries not reproduce the test?

General statistical principle: summary values discard information. Many different sets of participant ratings can share the same median and inter-quartile range while having different ranks and different patterns across the groups. The Mann-Whitney calculation depends on those ranks, so it cannot be independently reproduced from the posted summaries alone. Individual observations or more detailed rank information would be needed for a direct recalculation.

The displayed summaries also do not show the distribution’s shape, tails, or possible ties. Those features can matter for understanding how a rank-based comparison behaves and for deciding whether a location-shift interpretation is appropriate. The registry does not provide participant-level observations or distribution plots in the registry record.

What does over-dispersion mean in general?

Over-dispersion is a general concern in models for count or other outcomes when observed variation exceeds what the model’s assumed distribution allows. It can make standard errors and uncertainty statements unreliable if ignored. The posted primary endpoint is a pain rating summarized by medians and inter-quartile ranges, and the reported method is a rank test. The registry does not report an over-dispersion model or indicate that over-dispersion was assessed. This concept is not a basis for adding an analysis that the record does not describe.

What is known about the analysis plan?

The registry identifies a primary endpoint, a timeframe, summaries, and a named comparison test. That is not a complete statistical analysis plan. The record does not report whether the test was specified before examining the data, whether any covariate adjustment was planned, whether there were interim analyses, or how missing ratings and protocol deviations were handled. Those details are not reported in the registry record. They should not be inferred from the fact that an analysis result is posted.

The registry lists three outcome measures and three analyses. It names two secondary outcomes, but their numerical results and the analysis methods for those outcomes are not reported. The available description therefore supports explanation of the primary rank-based comparison, but not a complete reconstruction of all analyses or of any prespecified hierarchy among outcomes.

10. Analyses Reported by the Sponsor

The registry’s own primary analysis is a Wilcoxon (Mann-Whitney) comparison, with p = 0.01. The posted group summaries are medians and inter-quartile ranges: 13.0 with an inter-quartile range of 2.0 to 39.0 for the lidocaine group, and 54.0 with an inter-quartile range of 27.0 to 61.0 for the sham group.

A rank-based test cannot be recalculated from those summaries alone, because the test depends on the ordering of participant-level ratings. No recalculated test statistic or alternative between-group estimate is reported in the registry record. Accordingly, there is no numerical recalculation to compare with the sponsor’s analysis in this account. The interpretation rests on the registry’s reported test and the posted descriptive summaries.

The registry record does not indicate a discrepancy between a sponsor analysis and a recalculation. If a recalculation from fuller data were available and differed from the sponsor’s own analysis, the sponsor’s analysis would take precedence in describing the posted trial result. The summary statistics alone cannot establish whether such a difference exists. They also cannot reproduce the rank-test p-value. The reported result should therefore be identified as the sponsor’s posted analysis, not replaced by an unsupported calculation from the summaries.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary pain outcome and two secondary outcomes: satisfaction with overall pain control on a 100 mm visual analog scale, and pain associated with the paracervical or sham block. It records three outcome measures and three analyses. The numerical results for the secondary outcomes, their analysis methods, and any ordering of primary and secondary hypotheses are not reported in the registry record.

When several outcomes or analyses are examined, multiplicity is a general statistical issue. Repeated testing can increase the chance of observing a nominally small p-value even when no underlying effects exist. Trials may address this by defining a primary endpoint, setting a hierarchy, or adjusting inference across tests. The registry record does not report whether any such approach was specified or used. It would be inappropriate to assume that the p-value for the primary endpoint was adjusted, or that the other outcomes were treated in a particular way.

The record reports group counts for the primary outcome summaries, but does not state the analysis population or whether those counts include all randomized participants. It does not report the number of missing pain ratings, reasons for missingness, or methods used to handle missing data. It also does not describe exclusions after randomization or whether participants were analyzed according to assigned group. These details are not reported in the registry record.

Missingness matters because a comparison based on observed ratings can be affected if the availability of ratings is related to participants’ pain or their assigned group. That is a general concern, not a claim that missing data occurred in this trial. Without the relevant accounting and analysis details, the posted summaries cannot establish how missing observations were handled or how sensitive the result is to those choices.

The registry also does not report an interim-analysis plan, a stopping rule, or a complete statistical analysis plan. The trial is listed as completed, but that status does not fill in these methodological details. The p-value and descriptive results can be reported as posted; conclusions about multiplicity control, the analysis population, or the impact of missing data remain limited by what the registry record documents.

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 5% reporting threshold.

The posted safety figures list 0 serious adverse events among 20 participants at risk in the paracervical block with lidocaine group and 0 among 21 participants at risk in the sham group. The figures also list 0 other adverse events among 20 and 21 participants at risk, respectively. These are counts in the registry record, not evidence that the risk of an event is absent.

With no events recorded in these groups, the posted figures do not provide an observed event rate above zero for either listed adverse-event category. They also do not establish that an event could not occur, or precisely characterize uncommon harms. A zero count in a trial of this size can coexist with uncertainty about the frequency of rare events. No confidence intervals or further safety analyses are reported in the registry record.

The deaths field is not populated with a numerical count, so deaths are not reported in the registry record; it should not be interpreted as a reported zero. The record does not list serious adverse-event terms. The safety figures should be read as limited descriptive reporting for the groups and categories shown, not as a comprehensive assessment of safety or a comparison that establishes equivalence between groups.

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

The result does mean that the registry reports lower observed median pain ratings immediately after laminaria placement in the lidocaine group than in the sham group. It also means the registry’s Wilcoxon (Mann-Whitney) comparison returned p = 0.01. The endpoint was a participant-reported 100 mm visual analog scale measured within 10 seconds after placement, with 0 defined as no pain and 100 as the worst pain ever felt.

The result does not, by itself, give a precise estimate of the magnitude of the between-group effect. The record reports group medians and inter-quartile ranges, but not a confidence interval or an effect estimate from the rank-based comparison. The p-value is not a measure of clinical importance and cannot show how much an individual participant’s experience would change. Nor does it show that every participant in one group reported less pain than every participant in the other.

The posted primary outcome is about immediate pain after placement. It does not answer questions about pain at other times, satisfaction with overall pain control, or pain associated with receiving the block or sham procedure. The registry lists those secondary outcomes but their numerical results are not reported in the registry record. The primary finding should not be used as a substitute for those unreported results.

The registry record also leaves important analytic details unavailable, including the analysis population, handling of missing ratings, and any multiplicity strategy. The group summaries and test are therefore best understood as the reported analysis rather than a complete accounting of all trial data and decisions. The safety figures show no serious or other adverse events recorded in the listed groups, but they do not establish the absence of risk.

Finally, the finding is specific to this trial’s participants, interventions, comparator, and immediate pain endpoint. The record does not provide enough information to extend the result to other settings or populations. A statistically significant comparison is evidence about the observed data under a particular test; it is not a universal conclusion about all uses of paracervical block or all experiences of laminaria placement.

14. Why This Trial Matters Statistically

This trial offers a useful example of how the choice of summary and test should be read together. The primary outcome is reported with medians and inter-quartile ranges, and the analysis is a Wilcoxon (Mann-Whitney) test. That combination highlights a common distinction in clinical research: descriptive summaries show the observed center and spread, while a rank-based test compares the ordering of observations across groups.

The distinction also explains why the posted p-value cannot be reproduced from the medians and inter-quartile ranges alone. A reader can describe the direction of the observed medians and report the test result, but cannot recover the full comparison or its precision from those summaries. The registry does not report a confidence interval for the between-group effect. This makes it important to separate evidence of a distributional difference from an estimate of its magnitude and uncertainty.

The trial also illustrates why endpoint timing and definition matter. The primary measure concerns pain reported within 10 seconds after laminaria placement, on a scale with explicit anchors. It is not interchangeable with satisfaction or pain during the block itself, both of which are listed as secondary outcomes. Keeping outcomes distinct prevents an immediate pain result from being generalized to broader aspects of the experience.

Finally, the record shows the value and limits of registry reporting. It documents the randomized, double-masked, parallel design, group summaries, test, and adverse-event counts. It does not report several details needed for a fuller audit, such as the analysis population, missing-data handling, and multiplicity approach. A statistically literate reading uses what is posted while clearly distinguishing the reported result from information that is unavailable.

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 registry record gives limited detail about the trial’s conduct beyond its randomized, double-masked, parallel design. It does not describe sequence generation, allocation concealment, which people were masked, or how masking was maintained. The description of a sham procedure using a capped needle does not establish whether participants or study personnel could distinguish group assignment. These details are not reported in the registry record.

The primary outcome summaries give group sizes, medians, and inter-quartile ranges, but no participant-level data, confidence interval, or rank-based effect estimate. This restricts assessment of precision, distribution shape, ties, and the degree of overlap between participants’ ratings. The reported p-value cannot be independently reconstructed from the summaries alone.

The registry does not report eligibility criteria, baseline characteristics, the analysis population, missing outcome counts, or the handling of missing data. It also does not describe protocol deviations or whether the analysis followed assigned groups. As a result, the reported arm counts cannot be used to establish a complete participant flow or to determine how broadly the analysis represents everyone randomized.

Although two secondary outcomes are listed, their numerical results are not reported in the registry record. The handling of multiple outcomes and analyses is also not described. The record does not report a full statistical analysis plan, interim analyses, or a sample-size justification. These omissions limit assessment of prespecification and the interpretation of the primary p-value alongside other analyses.

The safety summary reports no serious or other adverse events in the listed groups, but the deaths field is not reported as a count. The event summaries are descriptive and do not establish the absence of risk or quantify uncertainty about uncommon events. Taken together, these limitations call for a focused interpretation of the posted immediate pain comparison, rather than conclusions beyond the outcomes and analyses documented.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Paracervical Block for Pain Associated With Laminaria Insertion — NCT02454296.
• Registry record last updated 2017-04-14; status last verified 2017-03.
• Results first posted 2017-04-14.
• 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

This completed, randomized, double-masked, parallel-group trial compared paracervical block with lidocaine against a sham block before laminaria placement. The registry records enrollment of 41, a start of 2015-05, primary completion in 2015-12, and the University of Hawaii as sponsor.

The primary endpoint was pain on a 100 mm visual analog scale within 10 seconds after placement. The lidocaine group had a reported median of 13.0 and an inter-quartile range of 2.0 to 39.0; the sham group had a median of 54.0 and an inter-quartile range of 27.0 to 61.0. The registry reports a Wilcoxon (Mann-Whitney) comparison with p = 0.01.

The record lists satisfaction with overall pain control and pain associated with the block or sham block as secondary outcomes, but their numerical results are not reported in the registry record. It records 0 serious and 0 other adverse events in each listed group; deaths are not reported as a numerical count. Details on analysis populations, missing-data handling, and multiplicity are not reported in the registry record.