5% Lidocaine Ointment in the Treatment of Vulvar Vestibulitis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for 5% Lidocaine Ointment in the Treatment of Vulvar Vestibulitis (NCT00450242), a randomized phase 2 study. The primary outcome is Number of Participants Who Report the Ability to Have Intercourse.

2. Clinical Question

The clinical question concerns a patient-reported functional outcome: whether participants said they were able to have intercourse. This differs from a direct measurement of pain intensity, although pain is part of the study hypothesis and the record lists a modified pain scale among secondary outcomes. The primary outcome title does not state that it is a change score, a rate, or a comparison of responses over time. The registry lists baseline and week 8 as time points, but separate values for those time points are not reported in the registry record.

The record describes a comparison between nightly lidocaine and placebo, but the posted primary outcome does not provide a usable estimate of the contrast between arms. Its listed counts therefore cannot establish whether the groups differed, by how much they might have differed, or how precisely any difference was estimated.

3. Trial Design

The study is listed as phase 2, randomized, and double-masked. Its stated purpose was to assess whether topical lidocaine improved symptoms in women with vulvar vestibulitis compared with placebo ointment. The brief summary describes nightly use and an 8-week study duration. The intervention and arm records use both ointment and cream terminology for the treatment and placebo; additional formulation details are not reported in the registry record.

The registry record has an internal design-label tension: it lists randomized allocation and two intervention arms, but also labels the model as single group. The listed arms are 5% Lidocaine Cream and Placebo Cream. This classification cannot be resolved from the record, so the design description should retain the reported information rather than treating the single-group label as proof that there was only one arm.

The brief summary describes a planned enrollment of 28 women in each arm, for a total of 56. Actual enrollment is listed as 14, and the study status is terminated. The reason for termination is not reported in the registry record. The study start is recorded as 2006-12 and primary completion as 2009-01. These dates describe the record and do not explain the timing or reason for termination.

The primary outcome is the number of participants reporting ability to have intercourse, with baseline and week 8 listed as the timeframe. The record also names SF-12 Quality of Life Scores and the Modified Gracely Pain Scale as secondary outcomes. Four outcome measures are listed, but the posted record reports zero analyses. Thus, the design features and intended outcomes can be described, while the detailed statistical plan, analysis populations, and reasons for the gap between the planned and enrolled totals are not reported in the registry record.

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: Three lidocaine subjects and one control subject failed to complete the 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 Number of Participants Who Report the Ability to Have Intercourse, measured over baseline, week 8.

The primary endpoint is titled “Number of Participants Who Report the Ability to Have Intercourse.” It is recorded as a number of participants, and its description says that it is based on participants’ responses upon inquiry. The timeframe is baseline and week 8. The posted results list four participants in the lidocaine arm and six in the placebo arm for this outcome, with the recorded value equal to the listed group size in each arm.

In general, a participant-reported functional outcome can capture an experience that may matter directly to participants and may not be represented by a laboratory or examination measure. A count is also straightforward to describe: it records how many participants meet the stated response criterion. Those features explain why a study might select such an endpoint, but the registry does not provide a rationale for choosing it as primary.

The outcome title does not specify a scoring rule, how an ambiguous response was handled, or whether the analysis focused on baseline status, week 8 status, or change between time points. The record also does not provide separate baseline and week 8 counts. Those details are necessary to understand the endpoint’s operational definition and the intended comparison over time; they are not reported in the registry record.

Because the posted results do not provide an estimable two-arm comparison, the counts alone do not quantify a treatment contrast. They should be read as the recorded outcome counts, not as evidence of a difference between the study groups.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What kind of outcome is this?

The primary endpoint is a count of participants who reported being able to have intercourse. The registry classifies it as a binary outcome, meaning that each participant’s response is understood as belonging to one of two categories for analysis. The posted outcome is expressed as a count rather than a percentage or a comparative effect estimate. No percentage or new estimate should be inferred from the listed counts, particularly because the record notes incomplete study participation and does not spell out the analysis denominator.

In general, binary outcomes are often compared by contrasting the chance of an event between study groups. Common summaries include a difference in proportions or a ratio of proportions. These summaries answer different questions, and their interpretation depends on a clearly defined event, denominator, and analysis population. The registry does not report a usable estimate of either kind for this endpoint. It explicitly marks values as missing or not estimable for a two-arm comparison.

Why does the comparison need an estimate and an uncertainty measure?

A count in each arm is descriptive. A comparative estimate would quantify how the observed outcome differs between arms under a specified analysis. A confidence interval would show the uncertainty around that estimate. In general, the interval reflects both the observed data and the statistical method used; it is not a guarantee that the true effect lies within its limits. Neither a comparative estimate nor a confidence interval is reported for the primary endpoint, so the strength and precision of any apparent difference cannot be evaluated.

A statistical test, if reported, would address compatibility between the data and a particular null hypothesis under its assumptions. It would not by itself establish clinical importance or resolve missing-data concerns. No primary-outcome test result is posted. The record lists zero analyses, and the values needed to reconstruct a comparison are marked unavailable or not estimable. A test result should not be inferred from the raw participant counts.

What does randomization contribute?

In general, random assignment is intended to make treatment groups comparable with respect to measured and unmeasured characteristics, on average. Masking can reduce some forms of influence on participants’ reports or on outcome assessment. These design features support interpretation of an adequately conducted comparison, but they cannot replace outcome data, a defined analysis population, or a reported estimate. The registry identifies randomized allocation and double masking, while its model field says single group despite listing two arms. The record does not explain this inconsistency or provide enough detail to assess how allocation and masking were implemented.

How should missing outcomes be considered?

Missing data matter because the observed participants may not represent all randomized participants. If completion is related to symptoms, treatment experience, or the likelihood of reporting the outcome, an analysis restricted to completers can differ from an analysis that addresses all randomized participants. This is a general concern, not a claim about why participants in this study did not complete it. The record says that three lidocaine participants and one control participant failed to complete the study, but does not identify their outcome status, the analysis population, or any method for handling missing responses.

In general, approaches to missing outcomes rely on assumptions. For example, an analysis may use only observed responses, impute missing responses, or examine how conclusions change under alternative assumptions. Each approach has limitations. The registry record does not report which approach, if any, was used. Without that information, readers cannot determine how incomplete follow-up was reflected in the posted primary outcome.

What can be said about planning?

The brief summary describes a planned total of 56 participants, with 28 in each arm; actual enrollment is listed as 14. The record does not report the protocol’s sample-size justification, the effect size assumed for planning, or whether the plan changed. A planning illustration based on observed data is not observed power: it is a hypothetical calculation under specified assumptions and does not show the probability that this completed trial detected a true effect. Such illustrations should not be mistaken for evidence about the study’s actual design rationale or results.

In general, a planned sample size is chosen to target a level of precision or a chance of detecting an effect under assumptions. When enrollment differs from the plan, that can affect the amount of information available, but it does not determine the direction of an effect. No recalculated comparative estimate is available, and no sponsor analysis is posted to take precedence over a recalculation.

What about multiple outcomes?

The registry lists four outcome measures, including the primary endpoint and two named secondary outcomes: SF-12 Quality of Life Scores and the Modified Gracely Pain Scale. In general, examining multiple outcomes can increase the chance of finding at least one apparently noteworthy result by chance, especially when many tests are conducted. Statistical plans may address this through a prespecified outcome hierarchy or other methods. The registry does not report a multiplicity strategy, the analysis plan, or results for the secondary outcomes. No claim about adjustment or unadjusted testing is warranted.

Overall, the statistical record supports a narrow conclusion: descriptive arm counts are posted for the primary outcome, while the comparative analysis and essential details about missing data, analysis populations, and multiplicity are not reported in the registry record.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("5% Lidocaine Cream", "Placebo Cream")
n      <- c(4, 6)
events <- c(4, 6)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  5% Lidocaine Cream  4  4  100.0  39.8  100.0  51.0  100.0  47.8  99.5
ARM  Placebo Cream  6  6  100.0  54.1  100.0  61.0  100.0  59.0  99.6

11. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures and names two secondary outcomes: SF-12 Quality of Life Scores and the Modified Gracely Pain Scale. It reports zero analyses. Detailed results for the secondary outcomes, the number of statistical tests conducted, and any prespecified hierarchy among outcomes are not reported in the registry record. A multiplicity adjustment or other strategy for interpreting several outcomes is also not reported.

In general, multiplicity matters when researchers make inferences across several outcomes or tests: considering many results can increase the chance of at least one apparently unusual finding. That general concern does not establish that any particular analysis was performed in this study. With no posted analyses, the reader cannot assess whether multiplicity was addressed.

The record notes that three lidocaine participants and one control participant failed to complete the study. It does not say whether these participants were included in any analysis, how their missing responses were handled, or whether other outcome data were unavailable. The analysis population is not reported in the registry record. Nor does the record state whether the primary endpoint was assessed using all randomized participants, only participants who completed the study, or another defined population.

These omissions are important because missing outcome status can affect both the arm-specific counts and a comparative estimate. The posted results mark the two-arm comparison as missing or not estimable, so there is no estimate for which a missing-data method or multiplicity adjustment can be evaluated. The study’s reason for termination and the reason actual enrollment was below the planned total are also not reported in the registry record.

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 0% reporting threshold.

The posted adverse-event record lists zero serious adverse events among four participants at risk in the 5% Lidocaine Cream arm and zero among six participants at risk in the Placebo Cream arm. It also lists zero other adverse events among the participants at risk in each arm. These are the safety counts recorded for the groups shown, not evidence that no event occurred outside the record or among people not represented in those groups.

The registry does not list any serious adverse-event terms. Death counts are not reported in the registry record. The absence of a listed term or a reported death count should not be converted into a claim that a specific outcome was absent.

In general, adverse-event counts are most informative when the period of risk, event definitions, completeness of follow-up, and population monitored are clear. The record identifies the numbers at risk for these safety summaries, but does not provide further detail on collection procedures or exposure time. It also notes that some participants failed to complete the study, so the listed safety population should be read as reported rather than assumed to represent every enrolled participant.

These figures are descriptive. With the limited posted counts and no comparative safety analysis, they do not establish a difference between arms or provide a precise estimate of event risk.

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

The registry record documents a randomized, double-masked phase 2 study comparing nightly 5% topical lidocaine with placebo for vulvar vestibulitis. The primary endpoint concerns the number of participants who reported the ability to have intercourse, with baseline and week 8 listed as assessment times. The posted results give arm-specific participant counts, and the record notes that some participants did not complete the study.

What the result does mean is limited to those descriptive details. It shows what counts are recorded for the primary outcome and identifies an explicit limitation: values for a two-arm comparison are missing or not estimable. The counts do not provide a treatment-effect estimate, a confidence interval, or a statistical test. They therefore cannot establish the direction, size, or precision of a difference between lidocaine and placebo.

What the result does not mean is that the treatments are equivalent, that one is superior, or that the primary outcome improved from baseline to week 8. The registry does not report separate time-point results, a change analysis, or a comparative estimate. Nor can the posted counts establish why participants did not complete the study, whether missing responses were related to outcome, or whether the analysis represented all randomized participants.

The record lists actual enrollment of 14 and describes a planned total of 56. It is marked terminated, but the reason for termination is not reported in the registry record. These registry entries describe the scope and status of the study; they do not explain the outcome data or justify a conclusion about efficacy.

More generally, statistical evidence is evaluated using the outcome definition, analysis population, effect estimate, and uncertainty together. Here, the outcome is identified, but the comparison and several analysis details are unavailable. The appropriate interpretation is therefore cautious and descriptive. The posted results do not support a conclusion about whether lidocaine changes the primary outcome relative to placebo.

14. Why This Trial Matters Statistically

This record illustrates why a randomized label alone is not enough to interpret a clinical trial result. Randomization is intended to support a fair comparison, but readers also need outcome data for the groups, a clear analysis population, an effect estimate, and a measure of uncertainty. The registry identifies a randomized, double-masked study with two listed arms, yet the model field labels it single group and the primary outcome comparison is marked missing or not estimable.

The study also demonstrates the distinction between planned enrollment and actual enrollment. The brief summary describes 28 participants per arm and a total of 56, whereas actual enrollment is recorded as 14. The record is terminated, but its reason is not reported. These registry entries matter when judging how much information the posted results can provide. They do not, on their own, indicate the direction of an effect or why the study ended.

Incomplete follow-up is another central statistical issue. The record notes participants who failed to complete the study but does not say how their missing outcome data were handled or define the analysis population. In general, estimates may depend on how missing responses are treated, so this information is needed to understand the results rather than merely to assess presentation.

Finally, the registry lists several outcomes but posts no analyses. This highlights why outcome definitions, analysis plans, and complete results matter: without them, readers cannot assess multiplicity, compare secondary findings, or evaluate whether the stated primary question was answered. The record is useful as a case in the limits of descriptive counts when the comparative analysis and its uncertainty are 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 primary limitation is that the registry does not provide an estimable two-arm comparison for the primary endpoint. Although participant counts are listed for both arms, no comparative effect, confidence interval, or test result is posted. The endpoint timeframe includes baseline and week 8, but separate measurements or a change from baseline are not reported in the registry record.

Interpretation is further limited by incomplete follow-up. The record states that three lidocaine participants and one control participant failed to complete the study, but does not describe their outcome status or how missing responses were handled. The analysis population is not reported. The listed outcome group sizes therefore cannot be assumed to represent all enrolled or randomized participants.

The record reports actual enrollment of 14, while its brief summary describes a plan for 56 participants. It is marked terminated, with no reason for termination reported. The protocol’s sample-size justification, any changes to the planned design, and the statistical analysis plan are not reported in the registry record.

There is also a classification inconsistency: allocation is recorded as randomized and two arms are listed, while the model is labeled single group. The record does not explain this label. Intervention descriptions use both ointment and cream terminology, and further formulation details are not reported. Four outcome measures are listed, but zero analyses are posted; detailed secondary-outcome results and any multiplicity approach are unavailable. Together, these gaps prevent a full assessment of the intended analysis and the strength of evidence.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: 5% Lidocaine Ointment in the Treatment of Vulvar Vestibulitis — NCT00450242.
• Registry record last updated 2012-07-16; status last verified 2012-06.
• Results first posted 2012-07-16.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry record identifies NCT00450242 as a phase 2 study of 5% topical lidocaine for vulvar vestibulitis, sponsored by the University of North Carolina, Chapel Hill. It lists randomized allocation and double masking, two arms, actual enrollment of 14, and terminated status. The model field is labeled single group despite the listed arms and randomized allocation.

The primary outcome is the number of participants reporting ability to have intercourse, assessed at baseline and week 8. The posted counts are four for lidocaine and six for placebo. The record notes that three lidocaine participants and one control participant failed to complete the study, and marks the two-arm comparison as missing or not estimable. No analyses are posted.

The brief summary describes a planned total of 56 participants and an 8-week study. Named secondary outcomes are SF-12 Quality of Life Scores and the Modified Gracely Pain Scale. The reason for termination, analysis population, missing-data method, and detailed statistical plan are not reported in the registry record.