IV Acetaminophen for Postoperative Pain After Pelvic Organ Prolapse Repair: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for IV Acetaminophen for Postoperative Pain After Pelvic Organ Prolapse Repair (NCT02155738), a randomized phase 4 study. The primary outcome is Change From Baseline in Postoperative Pain.

2. Clinical Question

The primary measure is change in pain, calculated in the registry record as the 24-hour visual analog score minus the baseline score. The scale runs from 0, indicating no pain, to 100 mm, indicating the most severe pain ever; higher values indicate more pain. The trial also included vaginal and laparoscopic surgery groups, so the posted results are presented separately by surgery type and treatment. The registry record does not report a single treatment-effect estimate with a confidence interval from the sponsor’s analysis, nor does it specify how the four groups were combined in that analysis. The available results therefore address the pain question through both a reported mixed-model test across four groups and simple comparisons recalculated from posted group summaries. Those analyses have different levels of detail and should not be treated as interchangeable.

3. Trial Design

This was a randomized, triple-masked, parallel-group, phase 4 trial. The registry record lists pelvic organ prolapse as the condition and reports total enrollment of 204. Participants were assigned to intravenous acetaminophen or intravenous normal saline before anesthesia on the day of surgery. Both intervention descriptions specify administration 10-30 minutes before anesthesia induction; the placebo was 100 cc of normal saline, while the acetaminophen preparation was 100 cc at 1000mg/100mL.

The posted outcome groups distinguish vaginal surgery from laparoscopic surgery and, within each type, placebo from acetaminophen. For the primary pain outcome, the analyzed group sizes were 44 for vaginal surgery with placebo, 41 for vaginal surgery with acetaminophen, 41 for laparoscopic surgery with placebo, and 36 for laparoscopic surgery with acetaminophen. These are outcome-specific analyzed counts, not the total number enrolled. The registry record explicitly notes missing 24-hour visual analog scores and says that fewer participants were analyzed than started in each group.

The study began in 2014-07, reached primary completion on 2017-08-31, and is listed as completed. The sponsor is Halina M Zyczynski, MD. The record reports a mixed models analysis involving all four groups, but does not provide its model specification, effect estimate, confidence interval, or detailed population definition. The original sample-size assumptions, any interim analyses, and the planned handling of missing data are not reported in the registry record. The randomized and masked design supports a controlled comparison in principle, but those unreported analysis details limit how fully the posted result can be reconstructed.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The number of participants analyzed is less than the total starting the study in each group; data is missing. Missing data indicates that a 24 hour VAS was not obtained from the subject.

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: One subject in the Vaginal Surgery - Placebo group, and one subject in the Laparoscopic Surgery - IV Acetaminophen group did not complete the study. (Missing critical information: (1) information from the pharmacy regarding group assignment; (2) signed informed consent form.

6. Primary Endpoint

The registry lists the primary outcome as Change From Baseline in Postoperative Pain, measured over 24 hours.

The primary endpoint is change from baseline in postoperative pain at 24 hours. Pain was measured using a visual analog scale: a participant marked a 100mm line to indicate current pain, with 0 representing no pain and 100 representing the most severe pain ever. The endpoint subtracts the baseline score from the score taken 24 hours after the end of surgery. In this definition, a higher change indicates more pain and a lower change indicates less pain.

Using a change score places the post-surgery measurement in the context of each participant’s baseline score. It is intended to describe how pain at the specified follow-up differs from the starting measurement, rather than just comparing the 24-hour scores in isolation. The stated 24-hour timeframe also makes clear that this outcome concerns pain at a particular postoperative time, not pain across the entire recovery period.

The registry record reports means and standard deviations for the analyzed groups. It notes that some participants did not have a 24-hour visual analog score, so the primary endpoint is not available for everyone who started the study. The study summary mentions narcotic consumption as an aim, but the posted primary endpoint is pain change; a narcotic-consumption result is not reported in the registry record. Nor does the record describe the clinical importance threshold for a difference on this scale. The score’s direction is stated, but the threshold at which a difference would be considered meaningful is not reported.

7. Results Posted in the Registry

• Vaginal Surgery - IV Acetaminophen: mean 29.20 versus 20.50 on control; difference 8.70 (95% CI -2.33 to 19.73), standardized effect d = 0.34; z-test p = 0.122.
• Laparoscopic Surgery - Placebo: mean 20.70 versus 20.50 on control; difference 0.20 (95% CI -9.96 to 10.36), standardized effect d = 0.01; z-test p = 0.969.
• Laparoscopic Surgery - IV Acetaminophen: mean 20.10 versus 20.50 on control; difference -0.40 (95% CI -11.22 to 10.42), standardized effect d = -0.02; z-test p = 0.942.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Interference of Pain With Physical, Mental and Social Activities

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Vaginal Surgery - IV Acetaminophen: mean 22.00 versus 18.40 on control; difference 3.60 (95% CI -0.46 to 7.66), standardized effect d = 0.45; z-test p = 0.082.
  • Laparoscopic Surgery - Placebo: mean 22.90 versus 18.40 on control; difference 4.50 (95% CI 2.11 to 6.89), standardized effect d = 0.77; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Vaginal Surgery - IV Acetaminophen and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Laparoscopic Surgery - Placebo than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The registry lists one secondary outcome: interference of pain with physical, mental, and social activities at 1 week. Group means are posted for vaginal and laparoscopic surgery participants in both treatment groups. The numerical pattern varies across those groups, and the posted recalculated comparisons use vaginal surgery with placebo as the reference. The outcome description does not state how higher or lower values should be interpreted, so the score direction cannot safely be translated into more or less interference from the registry record alone.

These secondary observations do not replace the primary 24-hour pain endpoint. They concern a different timeframe and a different construct: reported interference with activities rather than change in pain intensity. The secondary results also do not provide a reported sponsor analysis in the registry record. They can add descriptive context about another aspect of recovery, but they do not resolve the limits in the primary analysis or supply a missing treatment-specific estimate from the mixed model.

In general, secondary outcomes are often interpreted with less weight than a prespecified primary outcome, especially when many outcomes or contrasts are examined without a reported multiplicity plan. Multiple unadjusted comparisons increase the possibility of chance findings. The registry record does not report a multiplicity strategy, a hierarchy for testing the secondary outcome, or a sponsor inferential analysis for it. The unadjusted secondary comparisons should therefore be treated as exploratory descriptions, not as independent confirmation of a treatment effect. The extent to which these measures were prespecified, and how they were intended to support the primary question, is not reported in the registry record.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Interference of Pain With Physical, Mental and Social Activities

9. Statistical Interpretation

10. Statistical Methods Explained

Several statistical ideas help distinguish what the registry reports from what can be inferred from the group summaries. The explanations below are general statistical context; the registry record does not report a complete analysis plan for this trial.

What does a mean and standard deviation describe?

A mean is the arithmetic average of the observed values in an analyzed group. Here, the primary outcome is a continuous change score, and the registry reports group means and standard deviations. The mean describes the central value of the observed changes, while the standard deviation describes how spread out individual changes are around that mean. A mean does not show the full distribution of participant outcomes. In particular, it does not reveal whether values were symmetric, whether there were outliers, or whether participants clustered into distinct patterns.

The standard deviation is not the same as the uncertainty in the mean. The standard error estimates uncertainty in a mean or contrast and depends on both variability and the number of analyzed observations. General statistical reasoning explains why estimates from smaller groups tend to be less precise when variability is otherwise similar. The posted primary groups have different analyzed counts, and some measurements were missing. The registry record does not explain whether the sponsor’s model accounted for missingness in a particular way.

What does a mean difference say?

A mean difference subtracts the mean in one group from the mean in a reference group, according to the chosen contrast. Its sign depends on the subtraction order. For the primary outcome, higher values mean a greater increase in pain, so a positive contrast in the recalculated vaginal-surgery comparison corresponds to a higher mean change in the acetaminophen group than in the placebo group. The recalculated contrast is unadjusted: it is based on the posted group summaries and does not represent a model-adjusted estimate.

Comparisons need to match the scientific question. A contrast between vaginal surgery with acetaminophen and vaginal surgery with placebo holds surgery type constant. A comparison between a laparoscopic group and the vaginal placebo group does not: it varies surgery type as well as the treatment group. Such a contrast cannot isolate the treatment difference within laparoscopic surgery. This is why the group labels and reference group matter as much as the numerical estimate.

What does a confidence interval mean?

In general, a confidence interval describes the uncertainty around an estimated effect under the assumptions of the analysis. A narrower interval indicates greater precision; a wider interval indicates less precision. An interval that includes zero for a mean difference is compatible with no difference at the confidence level used, as well as with other effects within the interval. It does not prove that the groups are identical. Interpretation also depends on whether the interval comes from the intended analysis, whether assumptions are reasonable, and whether the contrast addresses the clinical question.

The recalculated intervals are built from unadjusted summary statistics. They are not the interval from the sponsor’s mixed-model analysis. The registry record does not report a confidence level for the sponsor’s result because no sponsor interval is posted. It also does not report the prespecified clinical threshold for a meaningful difference on the pain scale.

What does a p-value say?

In general, a p-value measures how incompatible the observed data are with a specified null hypothesis under the chosen statistical model. It is not the probability that the null hypothesis is true, and it does not quantify the size or clinical importance of an effect. A small p-value can accompany an imprecise or modest estimate, while a larger p-value does not establish equivalence. Estimates and confidence intervals are needed to understand the magnitude and precision of a result.

The sponsor reports p < 0.05 for a mixed models analysis across four groups. The registry record does not state the exact null hypothesis, the model terms, or the contrasts evaluated. The recalculated p-values are unadjusted and come from pairwise summary comparisons. The two sets of p-values should not be assumed to test the same hypothesis.

Why might a mixed model be used?

In general, mixed models can represent relationships among observations and accommodate structured data, such as measurements grouped by participants or sites, through model terms that account for that structure. They can also estimate differences while including multiple factors. Whether a particular model is appropriate depends on the data structure, model specification, and assumptions. The registry record names a mixed models analysis but does not report enough detail to determine which terms were included, how surgery type was handled, or how the analysis addressed missing measurements.

Why do missing data and multiplicity matter?

Missing outcome measurements reduce the observations directly available for analysis. If missingness is related to pain or other participant characteristics, the analyzed participants may differ systematically from those without observed scores. General statistical methods can address missing data under stated assumptions, but no such method is described in the registry record. The record notes that some 24-hour VAS values were not obtained, but does not report reasons by group or a sensitivity analysis.

Multiplicity arises when multiple outcomes, contrasts, or time points are examined. As the number of statistical tests increases, the chance of at least one apparently unusual result can increase if no adjustment or prespecified testing strategy is used. The registry record lists a primary outcome, a secondary outcome, and a four-group analysis, but its multiplicity strategy is not reported. The unadjusted recalculations should therefore be read as exploratory statistical summaries rather than as a complete confirmatory testing plan.

11. Confidence Intervals and Precision

Precision is best assessed by looking at an estimate together with its confidence interval. For vaginal surgery, the recalculated mean difference comparing acetaminophen with placebo is 8.7, with a confidence interval from -2.328 to 19.73. The interval includes zero and spans effects in either direction. Thus, the summary-based estimate is not precise enough to distinguish clearly between no difference and a range of possible differences. The interval is for an unadjusted recalculation, not the sponsor’s mixed-model analysis.

The other recalculated primary comparisons use vaginal surgery with placebo as the reference. The laparoscopic placebo comparison has an estimate of 0.2, with a confidence interval from -9.963 to 10.36. The laparoscopic acetaminophen comparison has an estimate of -0.4, with a confidence interval from -11.22 to 10.42. Both intervals include zero and are wide relative to their point estimates. Because these comparisons vary surgery type as well as group assignment, they do not estimate an isolated treatment contrast within laparoscopic surgery.

In general, a confidence interval gives a range of estimates compatible with the data and the analysis assumptions, not a guarantee that the true effect lies within that range. The width reflects both the observed variability and the information in the analyzed sample. Missing 24-hour pain scores can reduce that information. The registry record does not report the sponsor’s confidence interval, so the precision of the sponsor’s mixed-model result cannot be evaluated from the posted inferential result. Nor does the record specify a threshold for a clinically important difference. Statistical precision and clinical importance are distinct questions: an interval can be narrow or wide without itself defining what size of difference matters to patients.

12. 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 illustrations based on observed effects, not the trial’s original sample-size design. The original design assumptions are not reported in the registry record. The illustrations assume a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each planning scenario uses the stated fraction of the observed effect as the effect to detect. The entries are participants per arm, not total participants or total events.

The 80% power column gives the illustrated number of participants per arm for a design with an 80% chance of detecting the chosen effect under those assumptions, if that effect and the other assumptions hold. The 90% column uses a higher target chance of detection and therefore generally requires more participants per arm. These are planning illustrations, not observed power. Observed power is not an appropriate way to reinterpret the trial’s results after the fact.

Each row varies the effect assumed for planning. Planning for 75% of the observed effect or 50% of the observed effect requires more participants than planning for 100% of the observed effect. Smaller effects are harder to distinguish from random variation, so they generally require larger samples to reach the same target power. Some recalculated contrasts have very small observed estimates and therefore produce extremely large illustrative sample sizes. Those values should not be taken as a recommendation or as evidence that the trial was designed to detect such an effect.

The planning calculations also inherit limitations of the observed estimates. The primary estimates come from small analyzed groups with missing 24-hour measurements, and some listed contrasts compare different surgery types. The illustrations do not incorporate the sponsor’s mixed-model result or establish what the original investigators considered important. For time-to-event outcomes, the planning convention would be total events, but the outcomes considered in these illustrations are continuous, so the figures are participants per arm.

13. 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 = 8.700; pooled standard deviation σ = 25.738.
2. n = 2 × (1.96 + 0.842)² × 25.738² / 8.700² = 137.4, rounded up to 138 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 <- 8.7                      # observed difference in means
sigma <- 25.7375142264014                     # 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(2155738)
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 = 138 (80% power), 184 (90% power)
 75% of observed effect: n per arm = 245 (80% power), 327 (90% power)
 50% of observed effect: n per arm = 550 (80% power), 736 (90% power)
power.t.test: 138.3 
Simulated power at n = 138 per arm: 0.798 (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.

14. Analyses Reported by the Sponsor

The sponsor’s reported result is a mixed models analysis across the four groups, labeled as a superiority analysis, with p < 0.05. The registry record does not report the model’s estimate, confidence interval, model specification, or the exact group contrast represented by that test. As a result, the reported p-value indicates that the sponsor’s analysis found a statistically significant result under its model, but it does not establish the size or direction of a specific acetaminophen-versus-placebo effect from the information posted.

The recalculations use the group means, standard deviations, and analyzed counts to form simple unadjusted comparisons. One comparison is acetaminophen versus placebo within vaginal surgery. The other listed comparisons use vaginal surgery with placebo as the reference for laparoscopic groups, so they do not isolate treatment differences within laparoscopic surgery. Their p-values and intervals therefore cannot be treated as a reproduction of the sponsor’s mixed-model test.

The registry record flags a discrepancy between the reported analysis and the recalculations. In that situation, the sponsor’s own analysis takes precedence. The recalculations remain useful as checks on the posted summaries, but they do not supersede the analysis reported by the study sponsor. Without further details on the sponsor’s model and contrasts, the difference between the results cannot be resolved from the registry record.

15. Multiplicity, Missing Data and Analysis Populations

The registry record names a primary outcome and one secondary outcome, and reports a mixed models analysis involving four groups. It does not describe a multiplicity plan: the record does not state whether the investigators adjusted for multiple outcomes or contrasts, used a testing hierarchy, or designated a single contrast within the four-group analysis as the main test. This omission matters because an analysis that considers several comparisons can produce a small p-value by chance more often than a single prespecified test. The posted unadjusted recalculations should not be read as controlling that risk.

Missing data are explicitly noted for the primary outcome. The number analyzed in each group is less than the number who started, and the record says a missing value means that a 24-hour VAS was not obtained. It does not report the reasons for missingness, whether missingness differed across groups, how the sponsor handled missing scores, or whether sensitivity analyses assessed the influence of missingness. General statistical methods for missing outcomes rely on assumptions; those assumptions and methods are not reported in the registry record.

The analysis population is also not fully described. Outcome-specific analyzed counts are posted, but the registry record does not explain whether the sponsor’s mixed-model analysis used all randomized participants, only participants with observed outcomes, or another defined population. The record does not report adherence to assigned intervention or details about exclusions. The sponsor’s model specification and the relationship between its analysis population and the posted group summaries are not reported in the registry record. These gaps limit independent assessment of the reported result and make it difficult to reconcile the mixed-model p-value with the simple summary-based comparisons.

16. 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.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: readmission within 6 weeks of surgery (6.0%).

Serious adverse events are posted by surgery and treatment group. The numbers at risk were 49 for vaginal surgery with placebo, 52 for vaginal surgery with acetaminophen, 51 for laparoscopic surgery with placebo, and 50 for laparoscopic surgery with acetaminophen. The corresponding numbers with a serious adverse event were 1, 1, 0, and 3. The registry reports no deaths in any group. It also reports zero participants with other, non-serious adverse events in each group.

The registry lists readmission within 6 weeks of surgery as a serious adverse event term and gives 6.0%. It does not provide enough information in that listing to attribute the term to a particular group or clarify how it relates to the group-level serious-event counts. These figures are descriptive. With relatively few events, they provide limited precision for comparing groups, and they do not establish that differences are caused by the assigned treatment. The registry record does not report a detailed event-level narrative or additional analysis of safety differences.

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

The registry record documents a randomized, triple-masked comparison of preoperative intravenous acetaminophen with saline placebo among women undergoing pelvic organ prolapse repair. The primary outcome measures change in pain at 24 hours, and the posted group means differ across the vaginal and laparoscopic surgery groups. A mixed models analysis across all four groups is reported as statistically significant at p < 0.05, but the record does not give its estimate or specify the contrast that produced the result.

That lack of detail is important. A significant p-value does not say how large a difference was estimated, how precisely it was estimated, or whether a particular treatment comparison drove the result. The simple unadjusted recalculation for vaginal surgery has a confidence interval that includes zero. Other recalculated comparisons use vaginal placebo as a reference for laparoscopic groups and therefore do not isolate treatment effects within laparoscopic surgery. The discrepancy flag further means that the sponsor’s own analysis takes precedence over those recalculations.

The posted record does not establish that acetaminophen changes pain for every participant or in both surgery types, nor does it establish that the groups are equivalent. A finding at one postoperative time point also does not describe pain throughout recovery. The study summary refers to narcotic consumption, but a narcotic-consumption result is not reported in the registry record. The secondary activity-interference outcome is at 1 week, but its score direction is not described and no sponsor analysis is posted.

In general, statistical evidence and clinical importance are related but distinct. The registry record does not report a threshold for a clinically meaningful change in the pain scale, so the clinical importance of any numerical difference cannot be established from these results alone. Missing primary outcome measurements and unreported analysis details add further limits. These findings describe the posted data and analyses; they do not, on their own, determine what treatment choice is appropriate for an individual.

18. Why This Trial Matters Statistically

This trial illustrates why a reported p-value should be interpreted alongside the estimate, its uncertainty, and the question the analysis actually tests. The sponsor reports a significant mixed-model result across four groups, yet the registry record does not provide the model estimate, interval, or exact contrast. Without those elements, the significance label is not enough to understand the magnitude or direction of a treatment-specific effect.

The separate surgery groups also make contrast definition important. A within-vaginal comparison addresses a different question from comparing a laparoscopic group with vaginal placebo. Simple recalculations can be useful for checking the posted summaries, but they cannot replace an analysis whose model and target contrast are not fully described. Here, the registry flags a discrepancy, reinforcing the need to distinguish the sponsor’s analysis from summary-based recalculations.

The record also shows how missing outcomes affect interpretation. Participants without a 24-hour pain score are not represented in the posted primary means, and the missing-data approach is not reported. In general, the conclusions can depend on why measurements are absent and how an analysis handles them. Finally, sample-size illustrations based on observed effects are not the same as the trial’s original design rationale or evidence of observed power. Together, these features make transparent reporting of estimands, analysis populations, missing-data methods, multiplicity plans, and confidence intervals central to a statistically useful clinical-trial record.

19. 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 limitations specific to this registry record constrain interpretation. First, the sponsor’s mixed-model result is reported only as p < 0.05 across four groups. An effect estimate, confidence interval, model specification, and exact contrast are not reported. This makes it difficult to connect the significance result to a treatment-specific question or to assess its precision.

Second, the primary endpoint has missing 24-hour VAS measurements. The record states that fewer participants were analyzed than started in each group, but does not report the reasons, group-specific missingness explanations, or the handling method. The posted group means may therefore describe a subset of those who began the trial, and the effect of missingness cannot be assessed from the record.

Third, some summary-based comparisons use vaginal surgery with placebo as the reference for laparoscopic groups. These comparisons combine surgery type and treatment group, rather than isolating the acetaminophen-versus-placebo contrast within laparoscopic surgery. The sponsor’s model may address group structure differently, but its details are not reported.

Finally, the registry does not report the original sample-size assumptions, a multiplicity plan, the analysis population definition, or a clinical-importance threshold for the VAS. A narcotic-consumption result is not reported despite being mentioned in the study summary. The secondary outcome’s score direction and sponsor inferential analysis are also not reported. These omissions limit reproducibility and narrow the conclusions that can be drawn from the posted results.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: IV Acetaminophen for Postoperative Pain After Pelvic Organ Prolapse Repair — NCT02155738.
• Registry record last updated 2018-11-19; status last verified 2018-10.
• Results first posted 2018-11-19.
• 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.

23. Record Summary

NCT02155738 is a completed, randomized, triple-masked, parallel-group phase 4 trial of preoperative intravenous acetaminophen versus intravenous normal saline in women undergoing pelvic organ prolapse repair. Total enrollment was 204. The primary endpoint was change from baseline in visual analog pain score 24 hours after surgery. The registry reports a mixed models analysis across four groups with p < 0.05, but does not post its estimate or confidence interval. The primary outcome summaries note missing 24-hour scores. Summary-based recalculations are unadjusted, and the registry flags a discrepancy; the sponsor’s own analysis takes precedence. One secondary outcome assessed pain interference at 1 week. Serious adverse events and deaths are listed by group, with no deaths reported. Important details about the sponsor’s model, missing-data handling, multiplicity, and original sample-size assumptions are not reported in the registry record.