Preoperative Gabapentin for Post-tonsillectomy Pain in Children: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Preoperative Gabapentin for Post-tonsillectomy Pain in Children (NCT01707420), a randomized na study. The primary outcome is Total Oral Analgesia Consumption.

2. Clinical Question

The registry also lists self-report pain scores at rest and when swallowing as secondary outcomes. These outcomes describe different aspects of post-operative pain, while the primary outcome concerns analgesic consumption. Neither secondary outcome has a reported result in the registry record. The stated rationale notes that post-operative pain control can be challenging and that the study was intended to evaluate a single preoperative dose; that rationale is not evidence of a trial effect. Without posted outcome estimates, the direction, size, and precision of any group difference cannot be assessed.

3. Trial Design

The registry identifies this as a randomized, quadruple-masked, parallel-group study. Randomization assigns participants to treatment groups by chance, while a parallel design keeps each participant in the assigned group rather than having participants receive both study interventions. The record does not specify which roles were included in quadruple masking, so the exact masking arrangements cannot be described. Nor does the registry record explain how the randomization sequence was generated or how assignment was concealed.

The active intervention was gabapentin, 20 mg/kg, as a single dose 60 min before surgery. The comparator was a single liquid placebo dose of 0.4 mL/kg, also given 60 min before surgery. The enrollment is recorded as 36. For the adverse-event entries, 18 were listed as at risk in each arm; the registry does not provide a participant flow account that would explain how those figures relate to enrollment at other stages of the study.

The study is marked completed, and the registry lists its start as 2012-08 and primary completion as 2015-12. The phase is recorded as NA. The sponsor is University of Colorado, Denver. These administrative details describe the registered study but do not substitute for a report of its clinical outcome estimates.

The primary outcome is continuous: cumulative hydrocodone dose in mg/kg, summarized as a mean with standard deviation. Its timeframe is up to 36 hours after surgery, and the description refers to measurements at nine time points between 0 and 36 hrs post operatively. The registry treats the outcome as involving multiple time points and does not reduce it to a single comparison. Consequently, the choice of a summary or model for the repeated measurements cannot be inferred from the registered endpoint description. The registry record does not report the analysis method used for the primary outcome.

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: Healthy children aged 5 - 16 years old.

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 Total Oral Analgesia Consumption, measured over Up to 36 hours.

The primary endpoint is total oral analgesia consumption, described as the total mean oral analgesic requirement measured by cumulative hydrocodone dose in mg/kg. It covers the period up to 36 hours after surgery, with the description referring to nine time points within that period. Hydrocodone dose is a measure of analgesic use rather than a direct pain rating. The endpoint therefore addresses whether the amount of oral analgesia recorded differs between the randomized groups.

A continuous outcome such as dose can be summarized by a mean, which describes the arithmetic average, and a standard deviation, which describes the spread of individual measurements around that mean. These summaries can help characterize both the typical recorded amount and variability among participants. The registry identifies mean and standard deviation as the endpoint’s parameter and dispersion, but does not report the group means, standard deviations, or a comparison estimate.

The stated study purpose also includes post-operative pain scores and analgesic use. Self-report pain scores at rest and when swallowing are listed as secondary outcomes, but the primary endpoint is analgesic consumption. The endpoint description does not say how values from its multiple time points were combined or modeled, and the registry does not report whether the analysis used all time points jointly or selected a particular summary. Without those details and the observed results, the endpoint definition alone cannot show whether the groups differed or how precisely any difference was estimated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a randomized parallel-group trial with quadruple masking. In general, random allocation is intended to reduce systematic differences between groups at the time of assignment. Masking is intended to limit the influence of knowledge of assigned treatment on care, reporting, or assessment. The registry does not describe the sequence-generation procedure, allocation concealment, or which roles were masked, so those design features cannot be evaluated from the record. Randomization and masking labels do not by themselves demonstrate that these procedures were implemented successfully.

What does the primary measure represent?

The primary measure is continuous: cumulative hydrocodone dose in mg/kg, summarized as a mean and standard deviation. A mean gives the average recorded dose, while a standard deviation describes how dispersed the measurements are around that average. In general, these summaries are useful for describing a continuous outcome, but they do not fully describe its distribution. If observations are strongly skewed or include unusual values, the mean and standard deviation can be influenced by those features. The registry does not provide the observed distributions or summary statistics needed to assess this for the trial.

The primary outcome description refers to nine time points between 0 and 36 hrs post operatively. Repeated measurements from the same participant are generally related rather than independent. In general, an analysis that treats all repeated observations as independent can misrepresent uncertainty. Appropriate approaches may account for within-participant correlation, or may define a prespecified summary across time. Which approach was used, and how the cumulative dose was constructed, are not reported in the registry record. The record’s note that the outcome has several categories or time points and was not reduced to one comparison reinforces that a single primary estimate is not available in the posted outcome information.

How should uncertainty be assessed?

In general, a confidence interval combines an estimated effect with information about its uncertainty. A narrow interval indicates greater precision under the analysis assumptions, while a wide interval indicates less precision. A confidence interval can also show which effect directions remain compatible with the data. No interval or estimate for the primary outcome is reported in the registry record, so precision cannot be judged. The registry also gives no primary-outcome test statistic or p-value. A reader should not treat the trial’s enrollment alone as evidence that a particular difference was detected or ruled out.

Over-dispersion is a general concern when observed variation is greater than an analysis model assumes. If that occurs and is not accommodated, standard errors may be too small and inferential results may appear more certain than warranted. The primary measure is described as continuous with a standard deviation; the registry record does not report an analysis model or enough outcome data to determine whether over-dispersion was relevant. This is a general statistical consideration, not a claim about what occurred in this trial.

What can the planning assumptions tell us?

The registry describes sample-size illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. The intended effect to detect is described as a stated fraction of the observed effect; the illustrations are expressed as participants per arm. These are planning illustrations, not observed power. A planning calculation estimates the sample size that might be needed under its assumptions; it does not show the probability that the completed trial detected an effect. The posted record does not include the observed primary effect needed to interpret or reproduce such illustrations, and the primary outcome is not reduced to a single comparison. The registry also does not report the trial’s own sample-size justification. The planning assumptions therefore should not be presented as the trial’s protocol or as evidence of its design rationale.

General interpretation of a normal approximation depends on assumptions about the outcome and the sampling distribution of the estimator. Whether those assumptions were suitable for the repeated cumulative-dose outcome cannot be evaluated without the analysis specification and observed data. Similarly, equal allocation is stated for the planning illustration; it does not establish the allocation procedure or actual analyzed group sizes for the efficacy outcome.

What does the registry leave unresolved?

The registry does not report the primary analysis method, the treatment-effect estimate, its standard error or confidence interval, or a test result. It does not report how repeated measurements were handled, whether the analysis was adjusted for covariates, or what analysis population was used. No missing-data strategy or sensitivity analysis is described. These omissions prevent a full assessment of the statistical model, its assumptions, and the robustness of any result. General methodological explanations can clarify what these choices mean, but cannot identify which choices were made in this study.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome with several time points and two secondary pain-score outcomes: self-report pain at rest and when swallowing. Testing or estimating multiple outcomes can raise multiplicity concerns because the overall chance of a chance-positive finding may differ from that for a single prespecified comparison. In general, a statistical plan may address this by identifying a primary comparison, specifying an order of testing, or adjusting for multiple comparisons. The registry record does not report a multiplicity strategy, and the primary outcome is explicitly not reduced to one comparison. It is not possible to determine from the record whether or how multiplicity was handled in the trial’s analysis.

The registry lists zero analyses in the outcome summary and does not post estimates for the primary or secondary outcomes. This means there are no reported analysis results to evaluate for consistency or selective reporting. It does not establish why results are absent or whether analyses were performed outside the registry record.

Missing-data handling is not reported in the registry record. There is no description of missing outcome observations, exclusions, imputation, or sensitivity analyses. The analysis population is also not reported: the record does not say whether the primary analysis included all randomized participants or used another population definition. Without those details, the effects of missingness or analysis-set choices cannot be assessed. The registry’s enrollment and adverse-event risk counts do not provide a participant flow account for the efficacy endpoint.

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’s adverse-event entries list 18 participants at risk in the placebo arm and 18 in the gabapentin arm. It records zero serious adverse events in each arm and zero deaths in each arm. For other adverse events, the recorded figures are 3 in the placebo arm and 9 in the gabapentin arm. These are descriptive registry entries; the record does not provide event definitions, timing, severity details, or a statistical comparison.

The serious-event figures should be read as the counts recorded in this registry summary, not as proof that serious risks were absent. A zero count means no serious event is listed for the corresponding arm in this entry; it does not establish that an event is impossible or that the study could rule out uncommon harms. The other-event counts likewise do not establish a causal effect of either intervention. The registry does not specify whether these figures represent numbers of events or affected participants in a way that permits further interpretation, so they should not be converted into rates or comparative measures.

These safety entries do not answer the primary efficacy question about cumulative hydrocodone consumption, nor do they provide the pain-score results. They should be considered separately from the unreported efficacy analyses.

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

The record describes a trial designed to examine whether a single preoperative dose of gabapentin was associated with differences in post-operative analgesic consumption and pain scores in children undergoing tonsillectomy or adenoidectomy. The primary measure was cumulative hydrocodone dose in mg/kg up to 36 hours. The design was randomized, parallel-group, and quadruple-masked, with liquid placebo as the comparator. These details establish the question and the registered design, not the result.

The central limitation for interpretation is that the registry record does not report the primary outcome values or a treatment-effect estimate. It also does not report results for self-report pain at rest or when swallowing. Consequently, the record cannot establish the direction or size of any difference, its precision, or whether the observed data were compatible with a range of effects. The absence of reported efficacy results should not be read as a finding of no effect or equivalence.

In general, a trial result is interpreted by considering the estimated effect, its uncertainty, the outcome definition, and the analysis methods. Those pieces are not available for the primary comparison in this record. The described sample-size illustrations are planning calculations based on an observed effect and specified assumptions, not observed power and not a substitute for outcome estimates. The registry does not state the study’s own sample-size justification or analysis plan.

The adverse-event entries give a separate, limited descriptive account: the registry lists no serious adverse events or deaths in either group, and lists other adverse events in both groups. They do not determine efficacy and do not by themselves establish comparative safety. More broadly, the record can inform readers about the registered population, interventions, outcomes, and design, but it cannot answer whether the intended outcomes differed between groups. A conclusion about the trial’s clinical effect would require outcome data and analysis information that are not reported in the registry record.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the distinction between a registered question and a reported result. The record provides a defined population, two randomized interventions, a continuous primary outcome, and secondary pain measures. Yet it does not post the primary comparison or the secondary outcome results. A detailed design description cannot replace effect estimates and uncertainty when the goal is to understand what the trial’s data show.

The primary endpoint also illustrates an analytical issue common to clinical research: a measure recorded across multiple time points needs a clearly described summary or repeated-measures analysis. The registry refers to nine time points between 0 and 36 hrs post operatively and notes that the outcome has not been reduced to one comparison. Without a reported analysis method, readers cannot tell how those repeated observations contributed to an overall estimate or how their dependence was handled.

The record also distinguishes planning assumptions from findings. Sample-size illustrations are based on an observed effect and assumptions about significance level, allocation, and approximation. Such calculations can support planning, but are not observed power and cannot replace the completed trial’s actual estimates. Because the relevant outcome result is not posted, those illustrations cannot resolve the clinical question.

Finally, the safety figures demonstrate why descriptive counts require careful framing. The registry lists serious events, other events, and deaths separately, but does not provide the detail or inferential analysis needed to make strong comparative claims. Taken together, the record is useful for understanding what was intended and what was registered, while also showing why transparent reporting of outcome estimates, analysis choices, and uncertainty is essential to statistical interpretation.

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 principal trial-specific limitation for interpreting the registry record is the absence of posted efficacy results. The primary outcome is described, but its group values and comparative estimate are not reported in the registry record. The secondary pain outcomes are named without results. As a consequence, neither the magnitude nor precision of the intended comparisons can be assessed.

The primary endpoint involves multiple time points, and the registry indicates that it has not been reduced to one comparison. The record does not explain how cumulative hydrocodone consumption was summarized across those times or how repeated observations were analyzed. This prevents evaluation of the statistical approach and its assumptions.

The record also does not report participant flow for the efficacy analysis, an analysis population, missing-data handling, a multiplicity strategy, or the primary statistical model. Randomized, quadruple-masked, and parallel-group are recorded design labels, but implementation details such as sequence generation, concealment, and which roles were masked are not described. The registry does not report the trial’s own sample-size justification.

The adverse-event summary is limited to recorded counts and does not describe event definitions, detail, or comparative statistical analysis. It cannot fill the gap in efficacy reporting or establish a complete safety profile. These limitations concern what can be learned from the registry record; they do not establish what analyses or additional information may exist outside that record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Preoperative Gabapentin for Post-tonsillectomy Pain in Children — NCT01707420.
• Registry record last updated 2021-01-15; status last verified 2020-12.
• Results first posted 2021-01-15.
• 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 identifies a completed randomized, quadruple-masked, parallel-group study sponsored by University of Colorado, Denver. It records enrollment of 36, a start of 2012-08, primary completion of 2015-12, and phase NA. The intended population was healthy children aged 5 - 16 years old undergoing tonsillectomy or adenoidectomy.

The intervention was gabapentin, 20 mg/kg, once 60 min before surgery; the comparator was liquid placebo, 0.4 mL/kg, once at the same stated time. The primary outcome was mean cumulative hydrocodone dose in mg/kg up to 36 hours. Self-report pain at rest and when swallowing were secondary outcomes.

The registry record does not report efficacy estimates for these outcomes or the primary analysis method. It lists no serious adverse events or deaths in either arm and records other adverse events in both arms. The available information describes the registered design and outcomes, but does not establish the trial’s clinical result.