Self-administered Intravaginal 2% Lidocaine Gel Prior to Intrauterine Device Insertion in Nulliparous Women: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Self-administered Intravaginal 2% Lidocaine Gel Prior to Intrauterine Device Insertion in Nulliparous Women (NCT01534520), a randomized na study. The primary outcome is Change in Pain From Baseline to IUD Insertion.

2. Clinical Question

3. Trial Design

The registry describes a randomized, triple-masked, parallel-group trial, with intravaginal 2% lidocaine gel compared with intravaginal placebo gel before IUD insertion. The trial is marked completed. The registry lists enrollment of 61 and records the study start as 2012-06 and primary completion as 2013-05. The phase is listed as NA. These registry fields describe the trial's design and status, but do not establish how randomization was generated, how allocation was concealed, or who was masked. Those details are not reported in the registry record.

The two intervention descriptions specify 4mL of gel in each group. The placebo is identified as K-Y Jelly. The primary outcome concerns pain change from baseline to IUD insertion, assessed with a VAS from 0 mm, meaning no pain, to 100 mm, meaning the worst pain in the patient's life. The primary values are summarized as medians with interquartile ranges. No primary-outcome analysis comparing the groups is posted in the registry record.

Secondary outcomes listed in the record concern the experience of self-inserting the study gel, physicians' assessment of whether IUDs were easy to insert, and the need for pain medication up to 7 days. A result for pain-medication use is posted, while the specific outcome values and analyses for the other listed secondary outcomes are not reported in the registry record. The registry does not report a sample-size justification, a detailed protocol, or a statistical analysis plan. The listed enrollment should therefore be read as the trial's recorded enrollment, not as evidence of the assumptions used to choose that number.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: * 2 patients were removed from the study. Patients were considered screen failures before randomization to an arm. * 18 declined participation; 10 (56%) reported "time concerns" as their primary reason for declining.

Overall Study

Reasons for not completing this period:

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: Randomization is blinded.

6. Primary Endpoint

The registry lists the primary outcome as Change in Pain From Baseline to IUD Insertion, measured over change in pain score from baseline (before IUD insertion) to time of IUD insertion.

The primary endpoint measures the change in pain from before IUD insertion to the time of insertion. Pain was assessed using a visual analog scale ranging from 0 mm, no pain, to 100 mm, the worst pain in the patient's life. The endpoint is a change score, rather than a pain assessment at only one time point. It is intended to describe how participants' reported pain differed between the baseline assessment and insertion.

The registry reports the endpoint using a median and an interquartile range for each group. The lidocaine group has a median of 61.0 and an interquartile range of 53.0 to 71.0; the placebo group has a median of 68.0 and an interquartile range of 58.0 to 80.0. These summaries describe the observed distributions and their middle portions. An interquartile range gives the range from the 25th to the 75th percentile; it is not a confidence interval for the median and does not, by itself, quantify uncertainty in the difference between groups.

A before-and-after change outcome can characterize pain over the period relevant to insertion, but its interpretation depends on how the change was defined and analyzed. The registry describes the baseline and insertion assessments but does not report further details about the calculation or statistical analysis of the primary change score. In particular, a formal estimate and uncertainty interval for the between-group primary effect are not reported in the registry record. The posted medians should therefore be read as descriptive summaries, not as a complete comparative analysis.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical interpretation depends on matching each summary to the question it can answer. For the primary outcome, the registry reports a median and interquartile range in each arm. A median is the center of the observed ordered values: half of the observations lie at or below it and half at or above it, subject to ties. The interquartile range describes the middle half of the observed values. These summaries are useful when an outcome is not well represented by a mean and standard deviation, or when a protocol chooses a robust summary. The registry does not explain why the median was selected, and it does not report the underlying participant-level scores.

What does a confidence interval describe?

In general, a confidence interval expresses the uncertainty associated with an estimate under a specified statistical procedure. It is not a range that contains a fixed proportion of individual participant outcomes. For the secondary risk difference, the unadjusted recalculation is -0.164, with a 95% confidence interval from -0.323 to -0.005. Interpreted in the direction used for that calculation, a risk difference below zero indicates a lower observed risk in the lidocaine group than in the placebo group. The interval gives a range of values compatible with the calculation's assumptions; it does not address bias, missing outcomes, or the consequences of examining multiple outcomes.

The risk ratio and odds ratio are alternative ways to compare binary outcomes. A risk ratio compares the probabilities of an outcome between groups. An odds ratio compares odds, which are not the same as probabilities. The posted risk ratio is 0.830, with a 95% confidence interval from 0.684 to 1.006, and the posted odds ratio is 0.148, with a 95% confidence interval from 0.017 to 1.32. Their different numerical scales do not mean they contradict the risk difference; each expresses the comparison differently. When an outcome is common, odds ratios can look further from 1 than risk ratios, so interpretation should stay tied to the measure being reported.

How should the p value be read?

In general, a p value describes the compatibility of observed data with a null hypothesis under a specified test and its assumptions. It is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of an effect. The unadjusted p value for the medication comparison is 0.055. The registry does not report the test used, and a p value alone cannot resolve uncertainty about the endpoint definition or the analysis population. The registry's planning illustration names a two-sided significance level of 0.05, but it does not establish that this was the prespecified testing threshold for every outcome.

Why do analysis choices matter?

For binary outcomes, the analysis can depend on how the outcome is defined, which participants are included, and how missing responses are handled. The medication result has posted denominators of 30 in the lidocaine group and 28 in the placebo group. The primary endpoint lists 30 and 29 participants, respectively. Reasons for these denominators and any missing-data approach are not reported in the registry record. A calculation from group counts is necessarily limited to the counts and definitions available; it cannot account for unreported participant-level information or adjusted analyses.

Over-dispersion is a general concern when data vary more than a model's assumed distribution allows. It can make standard errors too small if a model assumes less variability than is actually present. The registry's primary summary is a median and interquartile range, and the posted secondary outcome is binary; no model specification or assessment of over-dispersion is reported. This general issue should not be mistaken for evidence that over-dispersion occurred in this trial.

What do the sample-size illustrations mean?

The planning illustration is based on the observed effect for the medication outcome, not on a reported design justification for the trial. Under its stated assumptions of a two-sided significance level of 0.05, equal allocation, and a normal approximation, it gives participants per arm for 80% and 90% power at several fractions of that observed effect. Planning for 100% of the observed effect gives 60 participants per arm for 80% power and 79 for 90% power. Planning for 75% of the observed effect gives 90 and 120 participants per arm, respectively; planning for 50% gives 164 and 219 participants per arm. These are planning illustrations only, not observed power and not a reconstruction of the trial's intended enrollment target. Smaller assumed effects require larger illustrative group sizes under the stated approach.

10. Multiplicity, Missing Data and Analysis Populations

The registry names a primary pain-change outcome and three secondary outcomes. The posted results include the primary group summaries and a numerical comparison for pain-medication use, but the registry records no reported analyses. A prespecified statistical analysis plan, including the testing sequence and any method for controlling multiplicity, is not reported in the registry record. It is therefore not possible to determine whether the medication comparison was planned as confirmatory, exploratory, or subject to an adjustment for other outcomes.

Multiplicity matters when several endpoints or analyses are examined. In general, each additional statistical test creates another opportunity for a result to appear unusual under a null hypothesis. An adjustment can help control the overall false-positive rate, while a prespecified hierarchy can clarify which comparisons are intended to carry the strongest evidential weight. These are general principles; the registry does not report whether either approach was used in this trial. The unadjusted medication result should consequently be interpreted with that limitation in mind.

Missing-data methods and analysis populations are also not reported in the registry record. The primary endpoint lists 30 participants in the lidocaine arm and 29 in the placebo arm; the medication outcome lists 30 and 28. The record does not explain the differences in denominators, state whether all randomized participants were analyzed, or describe imputation or other handling of missing observations. It would be inappropriate to infer a reason for those counts from the values alone.

Other details important to a full assessment—including the sample-size justification, the statistical plan for the primary endpoint, interim analyses, and any sensitivity analyses—are not reported in the registry record. The planning illustration is based on the observed secondary effect and should not be mistaken for the trial's original sample-size rationale. These reporting gaps limit the ability to assess how closely the posted analyses reflect the intended trial design and how robust the conclusions would be under alternative analytic choices.

11. 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 1% reporting threshold.

Most frequent non-serious adverse event terms

The registry's serious adverse event figures list 0 affected participants among 29 at risk in the placebo group and 0 among 30 at risk in the study-drug group. These entries indicate that no serious adverse events are recorded in the posted figures for either group. The record's serious-event terms list is empty, so no specific serious event categories are named.

A zero count in a trial of this size is not proof that a serious event cannot occur. It describes the events recorded among the participants included in these safety figures, during the safety observation period used by the registry. That period and the methods for collecting or classifying events are not reported in the registry record. The deaths fields are null, so death counts are not reported in the registry record.

The record also lists 1 other adverse event among 29 at risk in the placebo group and 0 among 30 at risk in the study-drug group. These are counts of participants affected as recorded, not a complete account of event type, severity, timing, or attribution. Further details about these other events are not reported in the registry record. Safety figures should be read as descriptive registry entries, not as a comparative statistical analysis of safety.

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

The registry supports a description of the trial's design, primary outcome summaries, and selected secondary and safety entries. It records a randomized, triple-masked, parallel-group comparison of intravaginal 2% lidocaine gel with placebo gel in nulliparous women undergoing IUD insertion. For the primary pain-change endpoint, it reports medians and interquartile ranges in each group. It does not report a formal between-group estimate or uncertainty interval for that primary outcome. The descriptive values alone cannot establish the precision of a treatment contrast.

For pain-medication use up to 7 days, the record includes group counts and an unadjusted comparison. That result is one secondary outcome, not a substitute for the unreported primary comparison. It also needs to be interpreted in light of the unreported testing plan, multiplicity approach, analysis population, and missing-data handling. A p value or confidence interval cannot remove those uncertainties, and neither is a direct measure of clinical importance.

The results do not establish why participants experienced the recorded pain changes or whether the observed group summaries would be similar in other settings or populations. Information about participant characteristics, study setting, eligibility details, and the timing of gel administration is not reported in the registry record. The record also does not provide enough detail to reconstruct the randomization procedure, masking roles, or full statistical plan.

Accordingly, the posted material should be understood as a limited statistical account of one completed trial. It allows readers to see the endpoint definitions and recorded group summaries, but it does not support a complete assessment of the primary comparative effect. It should not be read as proof of benefit or lack of benefit, nor as a definitive account of safety. Those conclusions would require fuller outcome reporting and information about the planned and conducted analyses.

13. Why This Trial Matters Statistically

This trial illustrates why a registry result needs more than a pair of group summaries to answer a comparative clinical question. Medians and interquartile ranges show the distributional summaries recorded for each arm, but do not quantify uncertainty in the difference between arms. A primary endpoint can be clearly defined and still be difficult to interpret comparatively when the registry does not report an effect estimate, confidence interval, or statistical test for that outcome.

It also demonstrates the importance of distinguishing a primary endpoint from secondary measures. Pain change at insertion and subsequent medication use address related but distinct questions. An unadjusted secondary comparison can be informative as a descriptive result, yet multiple outcomes, unspecified analysis choices, and missing multiplicity information constrain its evidential weight. The distinction between descriptive evidence and confirmatory inference is central to clinical trial reading.

The sample-size illustration offers another statistical lesson. A planning calculation based on an observed effect is not the same as the original design rationale and cannot establish the power of the completed trial. The illustration shows how its stated target group sizes vary with the assumed fraction of the observed effect, but the original assumptions and justification are not reported in the registry record. Treating such calculations as observed power or as proof that the trial was adequately planned would misrepresent their purpose.

Finally, differences in posted denominators and sparse safety counts emphasize the value of transparent reporting about analysis populations, missing observations, follow-up, and outcome definitions. These details help readers judge whether the numbers answer the stated question and how much uncertainty remains. The record offers a useful example of how registry entries can convey design and summary data while leaving key parts of statistical interpretation unresolved.

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.

Several trial-specific details that would help interpret these results are not reported in the registry record. The enrollment is 61, while the primary endpoint lists 30 participants in the lidocaine group and 29 in the placebo group. The medication outcome lists 30 and 28, respectively. The record does not explain the differences among these denominators, identify an analysis population, or describe how missing data were handled. Therefore, the reason each outcome has its recorded count cannot be determined from the registry entries.

The primary endpoint is reported by group as a median and interquartile range, but a between-group analysis is not reported. Further details about how the change score was calculated, whether baseline values were used in an adjusted analysis, and how uncertainty was estimated are not reported in the registry record. Without these details, the endpoint summaries cannot provide the same information as a comparative estimate with its precision.

The record does not provide detailed eligibility criteria, participant characteristics, study setting, gel administration timing, allocation procedures, or the roles of the people masked. It also does not report a sample-size justification, interim analyses, a full statistical analysis plan, or sensitivity analyses. These omissions limit assessment of trial conduct, generalizability, and the robustness of the reported outcomes.

Finally, the secondary outcomes are not all accompanied by posted numerical results or reported analyses. The medication comparison is unadjusted, and the registry does not report whether multiplicity was considered. Safety entries are sparse and do not include detail about the other adverse event or the observation period. These are limits on interpretation of the registry record, rather than evidence that any particular unreported procedure or event occurred.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Self-administered Intravaginal 2% Lidocaine Gel Prior to Intrauterine Device Insertion in Nulliparous Women — NCT01534520.
• Registry record last updated 2016-12-22; status last verified 2016-10.
• Results first posted 2016-12-22.
• 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

The registry record describes a completed randomized, triple-masked, parallel-group trial of self-administered intravaginal 2% lidocaine gel versus intravaginal placebo gel before IUD insertion in nulliparous women. Enrollment is listed as 61, and the primary endpoint is change in VAS pain score from baseline to insertion. The primary values are reported as group medians and interquartile ranges, without a posted between-group analysis.

A secondary comparison is recorded for pain-medication use up to 7 days, with an unadjusted recalculation and planning illustrations based on the observed effect. Other listed secondary outcomes do not have numerical results reported in the registry record. The registry also records no serious adverse events among participants listed at risk in either group. Key details about the statistical plan, analysis populations, missing data, and sample-size justification are not reported in the registry record.