Gabapentin on Postoperative Pain Associated With Ureteroscopy and Stents Insertion: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Gabapentin on Postoperative Pain Associated With Ureteroscopy and Stents Insertion (NCT03151746), a randomized phase 4 study. The primary outcome is 48 Hours Morphine Equivalents Consumed..

2. Clinical Question

3. Trial Design

This was a phase 4 randomized trial with a parallel-group design and quadruple masking. The registry lists placebo and gabapentin as the two interventions. Participants assigned to gabapentin received a 1200mg pill orally one hour before the planned surgical procedure; those assigned to placebo received a placebo pill at the same stated time. Random allocation and masking are design features intended to support a fair comparison, but the record does not describe the allocation sequence, allocation concealment, masking procedures, or which people were masked.

The registry records enrollment of 20 and lists 9.0 participants in the placebo arm and 11.0 in the gabapentin arm for the primary outcome. These are the arm-specific counts attached to the posted endpoint summaries. They should not be taken as evidence about the analysis population beyond that endpoint, because the record does not specify whether all randomized participants were included in each analysis or how missing outcome data were handled.

The listed study start date is 2018-01-14, and the primary completion date is 2021-12-02. The registry status is terminated. The reason for termination, the date of termination, and whether the termination affected recruitment or follow-up are not reported in the registry record. The primary endpoint was total morphine equivalents consumed in milligrams up to 48 hours after surgery. The secondary outcomes were 24 Hour Pain Burden and QOR 40 Questionnaire Scores. The record lists three outcome measures, while the posted results identify two secondary outcomes. It does not provide a detailed protocol or statistical analysis plan.

4. Participant Flow and Accounting

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

Overall Study

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as 48 Hours Morphine Equivalents Consumed., measured over Up to 48 hours after surgery.

The primary endpoint measures the total amount of morphine equivalents, in milligrams, consumed during the first 48 hours after surgery. Morphine equivalents express consumption of opioid medications on a common scale, allowing the recorded amounts to be summarized together. The endpoint is reported as a mean for each arm, with the full range of observed values also given. In the registry, the placebo arm has a mean of 51.87 morphine milligrams and a full range from 0.0 to 204.0; the gabapentin arm has a mean of 15.71 morphine milligrams and a full range from 0.0 to 48.0.

Opioid consumption is used as a measure of postoperative medication use, alongside pain-related outcomes. It does not directly measure pain intensity, recovery quality, or the reasons for medication use. Those are distinct questions, and the registry separately names 24 Hour Pain Burden and QOR 40 Questionnaire Scores as secondary outcomes.

The mean describes the arithmetic average of the recorded consumption within an arm. The full range indicates the lowest and highest recorded values, but does not show how observations are distributed between those extremes. The registry does not report a standard deviation, confidence interval, or formal comparison for this endpoint. The arm summaries therefore describe the posted data but, on their own, do not quantify the precision of an estimated difference between groups.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary outcome as a mean and reports a full range for each arm. No formal analysis results are posted for the primary comparison. The concepts below explain how to read these statistics in general; they do not add an unreported analysis to the registry record.

What does a mean represent?

In general, a mean is calculated by adding the observed values and dividing by the number of observations. It uses every recorded value, which can make it informative as an overall summary. It can also be influenced by unusually high or low observations. For postoperative opioid consumption, a small number of high values can pull the mean upward relative to what many participants experienced. The registry gives the arm means as 51.87 morphine milligrams for placebo and 15.71 morphine milligrams for gabapentin, but does not provide individual observations or a more detailed distribution summary.

What does a full range show?

In general, the full range gives the smallest and largest observed values. The reported range is 0.0 to 204.0 for placebo and 0.0 to 48.0 for gabapentin. It conveys the span of recorded values, but not how many observations were near either end, whether values clustered around the mean, or whether there were gaps within the range. Two groups can have the same range while having very different distributions. Conversely, ranges may look different even when much of the underlying data overlap. A range is not a confidence interval and does not describe uncertainty in the estimated mean.

How should a between-arm comparison be evaluated?

In general, a comparison of means estimates how far apart the group averages are and quantifies uncertainty in that estimate. A confidence interval describes a range of values compatible with the data and the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval; an interval that includes no difference would not rule out no difference at the chosen confidence level. The registry does not report a confidence interval or a formal between-arm estimate for the primary outcome, so the precision of a comparison cannot be assessed from the posted summaries alone.

A p-value, when reported, measures how unusual data at least as incompatible with a specified null model would be under that model. It is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of an effect. No p-value for the primary comparison is reported in the registry record. The record lists zero analyses, and the available endpoint summaries do not replace an inferential analysis.

Why can distribution shape matter?

In general, analyses that assume normally distributed errors can be affected by skewed data or outlying observations. Opioid consumption can plausibly have a concentration of low values and a tail of higher values; however, the distribution in this trial is not reported, and its shape should not be guessed from the summaries. The wide span of the placebo range relative to its minimum is a reason to be attentive to distributional assumptions, not proof that a particular assumption was violated. Over-dispersion means that data vary more than a model expects. If present, it can make standard errors and confidence intervals from an overly restrictive model unreliable. The registry does not report a model or diagnostics that would establish whether over-dispersion was assessed.

What is the role of randomization and masking?

In general, random allocation aims to make treatment groups comparable on average, including with respect to factors that were not measured. Masking can reduce the influence of knowledge of assignment on care, reporting, or assessment. The registry describes this trial as randomized and quadruple masked, but does not explain the allocation implementation or identify the roles covered by masking. These design labels are relevant context; they do not eliminate random variation, missing data, or possible deviations from the intended procedures.

How should planning illustrations be read?

In general, sample-size planning asks how many participants per arm would be needed to detect a specified effect under stated assumptions. The record describes planning illustrations based on a fraction of the observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. Such illustrations are hypothetical planning exercises, not observed power and not evidence that the trial was designed to detect those effects. The registry does not report its own sample-size justification or design assumptions. Any numerical planning result should be distinguished from the observed arm summaries and from a formal analysis of the trial.

10. Multiplicity, Missing Data and Analysis Populations

The registry names 24 Hour Pain Burden and QOR 40 Questionnaire Scores as secondary outcomes, in addition to the primary measure of morphine-equivalent consumption. It does not report a multiplicity strategy, such as a hierarchy of outcomes or an adjustment for testing several outcomes. In general, when multiple outcomes or comparisons are tested, the chance of at least one apparently unusual result can increase unless the analysis plan accounts for multiplicity. This is a general statistical consideration, not evidence that any particular testing procedure was or was not used beyond what the registry reports.

Numerical results for the secondary outcomes are not reported in the registry record. No inferential results for those outcomes are posted, so their estimates and precision cannot be assessed. The record lists three outcome measures and two secondary outcomes, but does not explain the status or results of every measure.

The registry does not describe missing-data frequency, reasons for missingness, imputation, or sensitivity analyses. It also does not specify an analysis population, such as whether the reported summaries include all randomized participants or only participants with observed outcome data. The population field for the primary outcome is blank. The arm-specific counts attached to the endpoint summaries do not, by themselves, explain whether any participants were excluded or had incomplete follow-up.

These omissions matter because missing outcomes can affect both the representativeness of group summaries and the validity of a comparison, depending on why data are missing and how they are handled. Without details about missingness and analysis populations, readers cannot determine whether the posted summaries reflect the intended population or assess the robustness of the findings to alternative assumptions. A detailed statistical plan is not reported in the registry record.

11. 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 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports serious adverse events for 0 of 9 participants at risk in the placebo arm and 0 of 11 participants at risk in the gabapentin arm. It reports other adverse events for 2 of 9 participants at risk in the placebo arm and 2 of 11 participants at risk in the gabapentin arm. Deaths are reported as 0 in each arm, and no serious adverse-event terms are listed.

These are counts recorded in the safety summaries, not a complete description of every possible safety outcome. A report of zero serious adverse events means none were recorded among the stated at-risk participants; it does not prove that serious events cannot occur or that the treatments have identical safety profiles. With the arm counts reported in this trial, uncommon events may not be captured. The registry record does not provide event-level descriptions for the other adverse events, their timing, severity, or attribution. The counts should therefore be read as the posted safety information for this trial, not as a comprehensive estimate of risk.

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

The primary-outcome data describe mean morphine-equivalent consumption during the first 48 hours after surgery: 51.87 morphine milligrams in the placebo arm and 15.71 morphine milligrams in the gabapentin arm. The reported full ranges are 0.0 to 204.0 and 0.0 to 48.0, respectively. This is a descriptive pattern in the posted data. The registry does not provide a formal comparative estimate or uncertainty interval, so the reliability and precision of a between-arm difference cannot be judged from the record.

The data do not establish that assignment to gabapentin caused the difference in these summaries. Randomization is a useful design feature, but it does not make a small study immune to chance imbalance or uncertainty. Nor do these summaries establish that pain was lower, recovery was better, or that opioid consumption changed for any particular individual. The registry does not report numerical results for the named secondary outcomes, 24 Hour Pain Burden and QOR 40 Questionnaire Scores.

The trial status is terminated, but the registry record does not report the reason or its relationship to the planned enrollment, data collection, or analysis. It is not possible to infer from that status whether the decision was related to efficacy, safety, recruitment, or another consideration. The record also does not state the investigators' statistical analysis plan or sample-size rationale.

In general, a clinical trial result is best interpreted using the estimated effect, its uncertainty, the design and conduct, and the outcomes that matter to the research question. Here, the group summaries and ranges offer a limited descriptive view of opioid consumption. No formal statistical conclusion is posted for the primary comparison, and the listed secondary outcomes cannot be evaluated from the available results. The appropriate interpretation is therefore bounded: the registry records these arm-level consumption summaries, but does not establish a statistically precise or causal treatment effect.

13. Why This Trial Matters Statistically

This trial illustrates why an arm-level mean is not enough to characterize the evidence for a treatment comparison. The registry reports means and full ranges for postoperative morphine-equivalent consumption, but no formal comparison, confidence interval, or p-value. Readers can describe the observed summaries, but cannot use them alone to assess how precisely the arms differ or how compatible the data are with no difference.

The full ranges also make distributional information important. A mean may be affected by high values, while the range reveals only the endpoints and not the pattern of observations between them. More complete summaries and a prespecified analysis would help readers understand whether a mean-based comparison adequately represents the data. The record does not report those details.

The design provides useful context: the trial was randomized, placebo controlled, parallel group, and quadruple masked. Yet design labels do not substitute for a report of allocation procedures, analysis populations, missing-data handling, or statistical methods. Those details are needed to assess how the trial moved from assignment to the reported endpoint summaries.

Finally, the stated objective spans opioid use, pain, and quality of recovery, while the registry reports only primary-outcome summaries and names secondary outcomes without numerical results. That gap illustrates the importance of outcome-specific reporting. A descriptive result for consumption cannot answer questions about pain or recovery, and multiple outcomes raise questions about how analyses were prioritized. The record does not report a multiplicity plan. Statistically, the trial matters as an example of the distinction between an observed group pattern and a quantified, uncertainty-aware comparative finding.

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.

The endpoint arm counts are 9.0 for placebo and 11.0 for gabapentin. Summaries based on these group sizes may be sensitive to individual observations, particularly for a mean when the reported ranges extend from 0.0 to 204.0 and from 0.0 to 48.0. The registry does not report standard deviations, medians, interquartile ranges, individual observations, or confidence intervals, which limits assessment of distribution and precision.

No formal statistical comparison for the primary outcome is posted, and the registry lists zero analyses. The record therefore does not provide a treatment-effect estimate, a test result, or an uncertainty interval to support a comparative conclusion. It also does not report the statistical model or whether assumptions were checked.

The secondary outcomes are named, but numerical results are not reported in the registry record. The record does not describe missing outcome data, analysis populations, or how incomplete observations were handled. It does not provide a multiplicity plan, protocol, or detailed statistical analysis plan. The reason for the terminated status is not reported, and its consequences for recruitment and follow-up cannot be established.

The reported safety summaries are counts, with no serious adverse events or deaths recorded and other adverse events recorded in both arms. Event details, severity, timing, and attribution are not given. These limitations mean the posted summaries provide a narrow account of the trial rather than a complete assessment of efficacy, safety, or robustness.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Gabapentin on Postoperative Pain Associated With Ureteroscopy and Stents Insertion — NCT03151746.
• Registry record last updated 2022-07-21; status last verified 2022-07.
• Results first posted 2022-07-21.
• 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 describes a phase 4, randomized, parallel, quadruple-masked, placebo-controlled trial of preoperative gabapentin for postoperative pain associated with ureteroscopy and stent insertion. The gabapentin arm received 1200mg orally one hour before the planned procedure; the placebo arm received a placebo pill at that time. Enrollment is recorded as 20, the status is terminated, and the reason for termination is not reported in the registry record.

The primary endpoint was mean morphine equivalents consumed up to 48 hours after surgery. The registry reports a mean of 51.87 morphine milligrams and a full range of 0.0 to 204.0 for placebo, and a mean of 15.71 morphine milligrams and a full range of 0.0 to 48.0 for gabapentin. It reports no formal primary comparison or uncertainty interval. The named secondary outcomes are 24 Hour Pain Burden and QOR 40 Questionnaire Scores; numerical secondary results are not reported.