Paracervical Block During Office Hysteroscopy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Paracervical Block During Office Hysteroscopy (NCT00811187), a randomized phase 2 study. The primary outcome is Assessment of Pain on a 10-point Visual Analog Pain Scale During the Procedure..

2. Clinical Question

3. Trial Design

The registry describes a randomized, parallel-group, placebo-controlled trial of paracervical block during office hysteroscopy. It identifies the study as Phase 2 and reports that it is completed. The recorded enrollment is 80. The posted primary-outcome data list 37 participants for the lidocaine group and 37 for the saline placebo group; the registry record does not explain how these outcome counts relate to the enrollment figure.

The active intervention was lidocaine paracervical block, described as 5cc 1% lidocaine injected in each paracervical region. The comparator was saline placebo injection, described as 5cc Normal Saline in each region. The brief summary says subjects would be randomized to one of these groups, have pain assessed throughout the procedure, and remain blinded along with physicians. The registry classifies masking as quadruple, but the identities of all masked parties are not reported in the registry record.

The stated purpose was to determine the effectiveness of paracervical block for pain relief in office hysteroscopy, particularly with placement of the Essure device. The primary endpoint was pain on a 10-point visual analog scale during the procedure. The record specifies assessment at each step that could potentially elicit pain, particularly during direct physical manipulation. It does not fully describe how those step-specific assessments were combined into the posted mean outcome.

The registry lists one primary outcome measure and one analysis. The sponsor’s reported analysis is described as linear regression, with a net mean difference and a superiority analysis. Further details of the regression model, covariates, coding, or analysis assumptions 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.

Before assignment: Of the 80 patients that met inclusion and exclusion criteria, only 74 completed either the lidocaine or saline placebo single-injection. Patients were randomized 1:1.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Intent to Treat Population (all participants assigned to lidocaine or saline).

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 Assessment of Pain on a 10-point Visual Analog Pain Scale During the Procedure., measured over During Procedure.

The primary endpoint is pain during the procedure, measured using a visual analog scale from 0, minimum pain, to 10, maximum pain. The registry says the scale was measured as centimeters, and that a higher score indicates more pain and therefore a worse outcome. Pain was assessed at procedural steps considered potentially painful, specifically when there was direct physical manipulation. The listed population is the intent-to-treat population: all participants assigned to lidocaine or saline.

Pain is the outcome of interest because the study’s stated purpose is to evaluate pain relief during office hysteroscopy, particularly in connection with placement of the Essure device. A continuous scale can retain gradations in reported pain rather than reducing responses to a simple yes-or-no outcome. The posted endpoint is summarized as a mean, with standard deviation as its measure of spread.

The registry does not report whether the posted mean represents an average across assessment steps, a particular procedural moment, or another summary of the repeated assessments. It also does not describe the handling of incomplete pain assessments. These details matter for interpreting exactly what the group means represent. The endpoint’s direction is clear: lower values indicate less reported pain, while higher values indicate worse pain.

7. Results Posted in the Registry

• Lidocaine Group: mean 4.15 versus 3.38 on control; difference 0.77 (95% CI -1.21 to 2.75), standardized effect d = 0.18; z-test p = 0.446.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: a score on a visual analog pain scale. The registry summarizes it using a mean and standard deviation. A mean describes the group’s average score, while the standard deviation describes how dispersed individual scores are around that average. These summaries are understandable, but they do not show the full distribution of scores or explain how repeated measurements at different procedural steps were handled.

What does a mean difference represent?

A mean difference compares the average score in one group with the average score in another. For the unadjusted recalculation, the reported direction is lidocaine minus saline. On this scale, a positive difference means a higher average score in the lidocaine group, which corresponds to more pain; a negative difference means a lower average in that group. The recalculated estimate is 0.77. The direction must be interpreted together with the scale definition, not as a generic improvement or worsening label.

The sponsor reports a net mean difference of -2.03 from linear regression. A regression-based contrast may be adjusted or defined differently from a direct comparison of the two posted means, but the registry does not report enough detail to determine why these estimates differ. The sign convention and model specification are also not described. It is therefore not appropriate to attribute the conflict to any particular adjustment, coding choice, or analysis population. The sponsor’s own analysis takes precedence when the record flags a discrepancy.

What does the confidence interval tell us?

A confidence interval gives a range of values that are reasonably compatible with the data and the method used, under the method’s assumptions. The recalculated 95% interval runs from -1.209 to 2.749. It includes zero and spans values on both sides of zero. That breadth means the unadjusted estimate is imprecise: the summary data do not tightly locate the group difference. The interval is for the recalculation, not the sponsor’s regression result. A confidence interval for the sponsor analysis is not reported in the registry record.

What does the p-value tell us?

The recalculated unadjusted p-value is 0.446. The sponsor reports p <.001 for the regression analysis. A p-value measures how unusual the observed data, or more extreme data, would be under a specified null hypothesis and analysis model. It does not measure the size or clinical importance of a difference, and it is not the chance that a result is due to chance. The two p-values relate to analyses that do not agree, so they should not be presented as interchangeable estimates of one result.

The reported analysis method is linear regression, and the effect parameter is labeled a net mean difference. Regression can estimate a group contrast while accounting for variables included in a model. However, the registry record does not report the model covariates, functional form, diagnostics, treatment of repeated pain scores, or any other modeling details. No reconstruction of that model is possible from the posted summary.

Why can spread matter?

Variation affects how precisely a group mean and a between-group contrast can be estimated. When scores vary substantially, the observed mean is less informative about where individual participants’ scores tend to fall. The saline standard deviation is 5.84, compared with 1.9 for lidocaine, on a scale bounded from 0 to 10. The pronounced difference in reported spread warrants verification of the summary statistics and clarification of how the endpoint was formed. It does not by itself establish why the groups differ in spread.

For continuous outcomes, statistical procedures often rely on assumptions about the distribution of errors and the relationship between the outcome and explanatory variables. General statistical practice is to examine whether those assumptions are adequate and whether influential observations affect the estimate. Such checks and the results of any checks are not reported in the registry record. The group summaries alone cannot establish that the assumptions were met.

The simple recalculation is explicitly unadjusted and uses the posted group summaries. It is useful as a transparent comparison of the displayed means, but it is not a substitute for the sponsor’s regression analysis. Because the discrepancy is substantial and its source is not explained, the recalculation should be treated as a check on the summary figures, not as a replacement for the sponsor’s analysis.

10. Confidence Intervals and Precision

The unadjusted recalculated mean difference is 0.77, with a 95% confidence interval from -1.209 to 2.749. In plain terms, the interval expresses uncertainty around the estimated difference using the posted group summaries and the recalculation method. It includes zero and values in both directions, so this unadjusted comparison does not pin down whether the mean score was higher or lower in the lidocaine group in the wider population represented by the analysis.

The interval is also wide relative to the point estimate. This indicates limited precision for the unadjusted contrast: the data are compatible with a range of possible differences, rather than concentrating closely around 0.77. This does not establish equivalence or show that any difference is unimportant. Equivalence would require an appropriate design and margin, neither of which is reported in the registry record.

The interval belongs to the simple recalculation only. The sponsor’s regression analysis reports a net mean difference of -2.03 and p <.001, but no confidence limits for that estimate are reported in the registry record. The sponsor and recalculated results conflict, and the record does not explain the reason. Given the discrepancy, the sponsor’s own analysis takes precedence; however, the lack of a reported confidence interval for that analysis limits direct assessment of its precision.

Confidence intervals describe statistical uncertainty under the chosen method. They do not account automatically for every source of uncertainty, such as uncertainty about endpoint construction, missing observations, model choice, or generalizability. The registry record does not provide enough detail to evaluate those additional sources for this outcome.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm, not total events. The registry’s planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to a stated fraction of the observed effect. These are planning illustrations based on the observed effect, not the trial’s original design assumptions; those original assumptions are not reported in the registry record.

The 80% power column gives the number of participants per arm that the planning calculation estimates would be needed for an 80% chance of detecting the specified effect under those assumptions. The 90% power column gives the corresponding number per arm for a 90% chance. These are target detection probabilities under the calculation’s assumptions, not guarantees that a future study will produce a statistically significant result.

The planning rows consider 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. The figures increase as the assumed effect becomes smaller: detecting a smaller difference generally requires more participants because it is harder to distinguish from random variation. The displayed numbers should be interpreted as illustrative planning estimates, not as a recommendation for a new study design.

This is not observed power. It is a forward-looking calculation based on an effect estimate from the trial, and the recalculated effect is itself uncertain. The discrepancy between the unadjusted recalculation and the sponsor’s analysis makes particular caution appropriate when interpreting illustrations tied to the observed effect. The planning figures do not resolve that discrepancy or establish what sample size the trial originally intended to use.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 0.770; pooled standard deviation σ = 4.343.
2. n = 2 × (1.96 + 0.842)² × 4.343² / 0.770² = 499.3, rounded up to 500 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 0.77                      # observed difference in means
sigma <- 4.34255685052021                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(811187)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 500 (80% power), 669 (90% power)
 75% of observed effect: n per arm = 888 (80% power), 1,189 (90% power)
 50% of observed effect: n per arm = 1,998 (80% power), 2,674 (90% power)
power.t.test: 500.2 
Simulated power at n = 500 per arm: 0.807 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Analyses Reported by the Sponsor

The sponsor’s reported analysis is a linear regression with a net mean difference of -2.03, a p-value of <.001, and a superiority classification. The registry does not report confidence limits for this estimate. The simple recalculation from the posted group means gives a mean difference of 0.77, a 95% confidence interval from -1.209 to 2.749, and an unadjusted p-value of 0.446.

These results are not in agreement: the estimated direction differs, and the p-values lead to different statistical interpretations. The record identifies a discrepancy but does not report enough about outcome coding, model specification, adjustment variables, or analysis details to explain it. It would be speculative to assign the disagreement to a particular cause.

The recalculation is a direct, unadjusted comparison of the posted summary statistics. It should not be treated as a reproduction of the sponsor’s regression model. Because the discrepancy is flagged, the sponsor’s own analysis takes precedence. Readers should distinguish that reported analysis from the unadjusted recalculation and note that the registry record does not supply the additional model detail or confidence interval needed to assess the sponsor estimate’s precision fully.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure and one analysis, and it reports no posted secondary outcomes. This does not establish that no other analyses were conducted; it describes what is listed in the registry record. No multiplicity adjustment, hierarchy of outcomes, or plan for handling multiple comparisons is reported in the registry record.

Multiplicity is a general statistical concern when many outcomes, time points, subgroups, or analysis choices are examined. The more opportunities there are to identify a result that appears unusual, the more difficult it can be to interpret an isolated p-value without knowing what was planned. In this trial, pain was assessed at each step that could potentially elicit pain, but the registry does not describe whether the sponsor’s analysis used step-specific results, a combined measure, or another summary. The count and handling of these assessments are not reported in the registry record.

The listed analysis population is intent to treat, described as all participants assigned to lidocaine or saline. The posted outcome summaries list 37 participants per group, while registry enrollment is 80. The record does not explain this difference, indicate whether the outcome summaries include everyone assigned, or describe exclusions from the analysis. It also does not report how missing pain assessments were handled, whether any imputation was used, or how incomplete procedural data were treated.

These omissions constrain interpretation. Missing outcome data can affect an estimated group contrast if the likelihood of a missing assessment is related to pain or differs between groups. General statistical practice is to report the amount and pattern of missingness and to explain the analysis approach, but those details are not available in the registry record. No conclusion about the presence or absence of missing data should be inferred from the group summaries alone.

The registry describes randomization and a parallel design, but does not report the randomization procedure, allocation concealment details, or a prespecified statistical analysis plan. These elements are not needed to describe the posted outcome, but they would help assess how the analysis was planned and whether the reported result followed that plan.

15. 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 reports zero serious adverse events among 37 participants at risk in the lidocaine paracervical block group and zero among 37 participants at risk in the saline placebo group. It also lists zero other adverse events in each group and zero deaths in each group. These are the adverse-event figures recorded for the study.

Zero reported events means that no events were recorded in these categories for the participants listed as at risk; it does not prove that the interventions have no risks. The registry record does not provide event descriptions, a detailed surveillance method, or additional context about how adverse events were collected. The absence of listed serious adverse event terms should therefore be read as a feature of the posted record, not as evidence that all possible harms were excluded.

The safety figures are descriptive and should not be used to make a broad comparison of safety. The study’s posted adverse-event counts are limited, and the registry record does not report a statistical analysis of these outcomes. No inference about risk beyond the reported trial data is warranted.

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

The registry record describes a randomized comparison of lidocaine paracervical block with saline placebo during office hysteroscopy, with pain during the procedure as the primary outcome. The posted means are 4.15 for lidocaine and 3.38 for saline on a scale where higher scores indicate worse pain. The simple unadjusted recalculation estimates a difference of 0.77, with a 95% confidence interval from -1.209 to 2.749 and p = 0.446.

The sponsor’s reported regression analysis gives a different result: a net mean difference of -2.03 and p <.001, labeled superiority. The discrepancy in direction and statistical result is central to interpretation. Because the registry record flags the discrepancy, the sponsor’s analysis takes precedence over the recalculation. At the same time, the record does not give the model details or confidence interval needed to understand the sponsor estimate fully, nor does it explain why it differs from the posted means.

These findings do not establish that the treatments are equivalent, nor do the posted summaries alone settle the direction of the group contrast. They describe results recorded for this trial and cannot, without further information, answer whether the same result would apply to other populations, procedures, or settings. The stated focus on office hysteroscopy, particularly placement of the Essure device, should be kept in mind when considering the scope of the record.

The primary endpoint is described as pain assessment at potentially painful steps, especially direct physical manipulation. The registry does not explain how those measurements were summarized for the reported mean or how incomplete assessments were handled. The posted saline standard deviation of 5.84 is large on a scale bounded from 0 to 10 and merits verification. These gaps, together with the analysis discrepancy, make a cautious reading important.

The appropriate statistical takeaway is not a treatment recommendation. It is that the registry contains conflicting representations of the primary comparison, and the available record does not fully resolve or explain that conflict. The sponsor’s reported analysis is the controlling analysis under the discrepancy flag, while the unadjusted recalculation remains a useful check on the displayed group summaries.

17. Why This Trial Matters Statistically

This trial is statistically notable because the sponsor’s reported primary analysis conflicts with a straightforward recalculation from the posted group means. The recalculated contrast is 0.77 in the direction of higher pain scores in the lidocaine group, with a confidence interval spanning both negative and positive values. The sponsor reports a net mean difference of -2.03 and p <.001. The registry identifies a discrepancy, but does not explain it.

Such a mismatch matters because interpretation depends on more than a p-value. Direction, effect estimate, uncertainty, outcome definition, and analysis method all shape the statistical conclusion. When those elements are not aligned across the posted summaries and the sponsor analysis, readers need to keep the results separate and avoid choosing whichever estimate appears more persuasive. The record specifies that the sponsor’s own analysis takes precedence in this situation.

The outcome also involves pain assessments at procedural steps that could elicit pain. The registry’s description makes clear that measurements occurred throughout the procedure, but it does not explain how those assessments became the single reported mean outcome. That detail can affect what the mean represents and how a model should account for the observations.

Finally, the pronounced difference between the reported group standard deviations, and the saline value on a bounded scale, highlights the importance of checking summary statistics and endpoint construction. The case illustrates why transparent reporting of analysis methods, confidence intervals, missing-data handling, and outcome aggregation is important for clinical researchers interpreting trial results.

18. 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 reporting gaps limit interpretation. Although the endpoint is described as being assessed at pain-eliciting procedural steps, the registry does not state how those step-level measurements were combined into the posted mean. It is not clear whether the outcome represents an average across steps, a selected assessment, or another summary. The record also does not describe how many assessments were available for each participant or how incomplete assessments were handled.

The posted standard deviations are 1.9 for lidocaine and 5.84 for saline, despite the pain scale’s stated bounds of 0 to 10. The saline spread is large relative to the scale and should be checked against the underlying data and the method used to form the outcome. The registry does not provide distributions or participant-level data that would allow this check.

The sponsor’s regression analysis conflicts with the simple recalculation in both direction and statistical result. The regression specification, covariates, coding, and confidence interval are not reported in the registry record, so the disagreement cannot be resolved from the listed information. The discrepancy means that the unadjusted calculation should not be substituted for the sponsor analysis.

The registry reports enrollment of 80, while the outcome summaries list 37 participants in each group. It does not explain how those figures relate or confirm the number included in the sponsor’s model. The intent-to-treat population is named, but the record does not detail missing data, exclusions, or departures from that population.

Further information about the original sample-size assumptions, statistical analysis plan, allocation procedures, and masked parties is not reported in the registry record. These omissions do not change the recorded results, but they restrict assessment of planning, analysis conduct, and the extent to which the posted findings can be generalized.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Paracervical Block During Office Hysteroscopy — NCT00811187.
• Registry record last updated 2019-12-11; status last verified 2019-12.
• Results first posted 2019-12-11.
• 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.

22. Record Summary

The registry describes a completed Phase 2 randomized, parallel-group, quadruple-masked, placebo-controlled trial of lidocaine paracervical block during office hysteroscopy. The intervention was 5cc 1% lidocaine in each paracervical region; the comparator was 5cc Normal Saline in each region. The stated focus included pain relief, particularly during placement of the Essure device.

The primary outcome was mean pain on a 0-to-10 visual analog scale during the procedure, with higher scores indicating worse pain. The posted group means were 4.15 for lidocaine and 3.38 for saline. The unadjusted recalculation conflicts with the sponsor’s reported linear regression result of -2.03 and p <.001. Under the registry’s discrepancy flag, the sponsor’s analysis takes precedence, although its model details and confidence interval are not reported. The registry records zero serious adverse events, other adverse events, and deaths in each group.