Evaluation of Initiation Time on the Efficacy of Gabapentin in Treating Neuropathic Pain in SCI: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of Initiation Time on the Efficacy of Gabapentin in Treating Neuropathic Pain in SCI (NCT04256603), a non-randomized phase 4 study. The primary outcome is Neuropathic Pain.

2. Clinical Question

The key comparison is not simply gabapentin versus no gabapentin. It also concerns whether initiation before admission differs from initiation during admission. Because the registry classifies the allocation as non-randomized, these groups may differ in ways beyond treatment timing. A contrast in observed pain scores would therefore describe an association between group membership and the recorded outcome; it would not, on its own, isolate a causal effect of starting gabapentin at a particular time.

3. Trial Design

The registry identifies this as a Phase 4, parallel, non-randomized study with no masking. MetroHealth Medical Center is listed as the sponsor. The study status is completed. Its start date is 2019-08-01, and its primary completion date is 2020-03-30. The registry reports enrollment of 27.

Three groups are described: gabapentin before admission, gabapentin during admission, and no gabapentin. The primary-outcome population description reports 21 subjects in the gabapentin group and 6 in the no-gabapentin group. The record does not give separate outcome-population counts for the early and late gabapentin groups. It also does not report how people entered each group, whether treatment decisions were made before enrollment, or what factors determined initiation timing.

Non-randomized allocation is important when interpreting a treatment comparison. In a randomized study, the allocation process is intended to reduce systematic differences between groups. Here, assignment was not randomized, so the registry does not support assuming that groups were comparable at the outset. For example, differences in injury characteristics, clinical circumstances, or other care could be related both to treatment timing and to pain. These are general concerns about non-randomized comparisons; the registry record does not report whether any such factors were measured or adjusted for.

The study objective focuses on whether timing of gabapentin initiation influences neuropathic pain after acute spinal cord injury. The endpoint is assessed at discharge and the stated timeframe is through completion of the study, up to 4 weeks after injury. The record does not report masking, and it lists masking as none. It does not describe procedures for assigning the pain score or whether the person recording or analyzing it knew the treatment group.

The registry record does not report a protocol-level statistical plan, a sample-size justification, or details of interim analyses. Those items should not be inferred from the design description. The study's non-randomized structure and the absence of a reported group outcome comparison limit what can be concluded from the registry information.

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: 21 subjects were enrolled in the group treated with gabapentin, vs 6 in then no gabapentin

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 Neuropathic Pain, measured over Through completion of the study, up to 4 weeks after injury..

The primary endpoint is neuropathic pain measured using the Neuropathic Pain Scale. The record describes an average of pain during the previous 7 days, based on self-identified nerve or neuropathic pain levels, assessed at discharge. It reports five measurements at that time and describes a total score ranging from 0 to 50. The pain-level scale is described as 0-10, with 0 representing no pain and 10 representing worst pain. The unit is listed as units on a scale, and the outcome is summarized as a mean with standard deviation.

A continuous score can capture differences in reported pain intensity across its range rather than reducing every observation to a yes-or-no pain classification. The registry's stated aim includes prevalence as well as intensity, but the described primary endpoint is a score. The record does not describe a separate primary prevalence measure or give a threshold for classifying a participant as having neuropathic pain.

Using an average of recent pain reports is one way to characterize pain over a defined recall period rather than at a single moment. In general, a mean summarizes the center of observed scores, while the standard deviation describes their spread. Neither statistic is reported for the groups in the registry record. As a result, readers cannot use the registry description alone to assess the observed mean pain levels, variability, or difference between treatment groups.

The endpoint is assessed at discharge, with the timeframe stated as through completion of the study, up to 4 weeks after injury. The registry record does not report whether every participant had a score at that time or how missing measurements were handled.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods determine how observations are summarized and how comparisons are interpreted. The registry identifies the primary outcome as continuous and reports that it is to be summarized as a mean and standard deviation. It does not report the actual group summaries or an analysis result. Accordingly, general explanations of these methods can clarify what the measures would mean without implying that a particular result was observed.

What does a mean describe?

General: A mean is a measure of the center of a set of numerical observations. For this study, it would summarize pain scores for a group at the specified assessment. The mean can be useful for comparing average scores, but it does not show the distribution of individual scores or whether the average represents every participant's experience. The group mean and standard deviation are not reported in the registry record.

What does the standard deviation describe?

General: A standard deviation describes how spread out observations are around their mean. A larger standard deviation indicates greater variability among recorded scores; a smaller one indicates observations are more clustered around the mean. It is not the same as a confidence interval or the standard error of a mean. The registry lists standard deviation as the measure of dispersion but does not report group values.

What would a group contrast show?

General: A comparison of group means would describe the average difference between the groups included in the analysis. The interpretation depends on which groups are compared, how outcome data are handled, and whether the analysis accounts for relevant differences between participants. Here, the registry describes gabapentin before admission, gabapentin during admission, and no gabapentin, but it does not report a group contrast or explain which comparisons were included in the primary analysis.

The non-randomized allocation is central to interpreting any contrast. General: Randomization is one way to reduce systematic differences in prognostic characteristics between treatment groups. In a non-randomized study, group membership may be related to factors that also affect the outcome. Statistical adjustment can sometimes address measured factors, but it cannot automatically eliminate confounding, particularly when important factors are unmeasured or poorly recorded. The registry record does not report an adjustment model, covariates, or a method for controlling confounding. No adjusted result should be inferred.

How should uncertainty be read?

General: A confidence interval expresses uncertainty around an estimate under the assumptions of the analysis. It can help readers judge both the range of effect sizes compatible with the data and the estimate's precision. A point estimate alone does not show how uncertain the result is. The registry record does not report a confidence interval or a standard error for the primary outcome.

General: A hypothesis test evaluates data relative to a null hypothesis and a specified model. A p-value is not a measure of the probability that a treatment works, nor does it indicate the practical importance of a difference. Interpretation should consider the estimated effect and its uncertainty, not only whether a p-value crosses a decision threshold. The registry record does not report a primary-outcome test statistic or p-value, and it does not report the statistical plan that would define the test.

What does the planning illustration mean?

The sample-size assumptions describe a planning illustration based on the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustration considers an effect to detect expressed as a stated fraction of the observed effect. These are planning assumptions, not evidence that the study was designed with those assumptions, and the registry does not report a sample-size justification as part of its own design. A planning sample size is not observed power and does not establish the probability that this study detected an effect. The record does not report a power calculation in the protocol or an independently justified target effect.

General: Sample-size calculations depend on assumptions about the outcome variability, the effect to detect, the allocation, the test, and the desired power. If assumptions do not match the study conditions, a planning estimate may not describe the actual precision of the resulting data. In a non-randomized study, sample-size arithmetic also does not correct bias or confounding. The planning assumptions should therefore be read as illustrations and not as a substitute for reported outcome estimates, uncertainty intervals, or a transparent analysis plan.

The registry does not report whether the primary analysis used all enrolled participants, only participants with measured outcomes, or another analysis population. It also does not report the handling of missing pain scores, repeated measurements, or possible differences in follow-up. These details matter because analysis choices can affect the estimate and its uncertainty. Without a reported statistical analysis, readers cannot reconstruct the methods used for the primary comparison from the registry description alone.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Gabapentin Group", "No Gabapentin Group")
n   <- c(21, 6)
m   <- c(13.3, 15.6)
sp  <- c(18.8, 18)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Gabapentin Group  21  13.300  18.800  4.742  21.858
CARM  No Gabapentin Group  6  15.600  18.000  -3.290  34.490

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure and one analysis. It does not report whether additional exploratory comparisons or outcomes were examined outside the record's listed measures. A multiplicity plan—how inference is handled when several outcomes, groups, time points, or contrasts are tested—is not reported in the registry record. If multiple comparisons were made, the interpretation of nominal significance levels would depend on how those comparisons were selected and addressed. No such procedure should be assumed.

Missing data are also important for a pain outcome measured at discharge. The registry record does not report the number of participants with a recorded primary outcome, the reasons for any missing scores, or the method used to handle missingness. It does not state whether analyses used complete cases, imputation, or another approach. These omissions prevent assessment of whether the available outcome data represent all enrolled participants or whether missingness could affect a group comparison.

The record does not define an analysis population, such as an intention-to-treat population or a per-protocol population. Because allocation was non-randomized, the meaning of those analysis populations would depend on the actual assignment and follow-up procedures, which are not reported. The registry also does not report whether participants who changed treatment or started gabapentin at a different time remained in their original group for analysis.

These are reporting gaps, not evidence that missing data or multiplicity problems occurred. They mean that the registry record does not allow readers to determine how these issues were handled. A complete interpretation would require the analysis population, outcome availability, missing-data methods, and the planned or applied approach to multiple comparisons; these are not reported in the registry record.

12. 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 lists serious adverse event counts of 0 in the gabapentin group and 0 in the no-gabapentin group. It also lists deaths as 0 in both groups. For other adverse events, the record lists 0 in the gabapentin group and 0 in the no-gabapentin group. The groups at risk are reported as 21 for gabapentin and 6 for no gabapentin. The registry lists no top serious adverse-event terms.

These figures describe events recorded in the registry; they do not establish that treatment caused or prevented an event. A zero count means that no event was recorded for that category in the listed group in this record. It does not prove that the risk is absent, and it does not show how completely events were monitored or reported. The record does not describe the collection procedures, observation time for safety outcomes, or definitions used for event categories.

The group sizes differ, and the allocation was non-randomized. General: Counts alone are not directly comparable as measures of risk when group sizes or follow-up differ. A safety comparison also requires attention to event definitions, observation time, completeness of follow-up, and uncertainty. The registry record does not report a comparative safety analysis or uncertainty interval. The zero counts should therefore be read as descriptive registry entries, not as evidence that the groups had equal safety or that adverse events could not occur.

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

The central statistical result needed to answer the study question is a reported comparison of pain outcomes across the gabapentin timing groups and the no-gabapentin group, together with enough information to assess uncertainty. The registry record describes the outcome but does not report group means, standard deviations, a contrast, a confidence interval, or a p-value. Consequently, the posted registry information does not show whether average pain scores differed between groups or how precise any estimated difference was.

The registry's objective refers to whether the timing of gabapentin initiation influences the prevalence and intensity of neuropathic pain. The described primary endpoint measures a pain score, not a separate prevalence outcome. This distinction matters: a mean score can describe average reported intensity, but it does not by itself give the number of participants meeting a definition of neuropathic pain. The registry record does not report a separate prevalence result or case definition.

Even a reported association would need cautious interpretation because treatment allocation was non-randomized. General: An observed difference between groups can reflect treatment, differences in the participants or their circumstances, or a combination of these. Statistical adjustment may address measured differences, but the registry record does not report whether adjustment was performed or which factors were considered. The description therefore does not justify a causal claim about starting gabapentin before versus during admission.

The completed status indicates that the study is marked as completed in the registry. It does not supply the missing outcome estimates. Similarly, the listed adverse-event counts are descriptive and do not resolve the efficacy question. The registry record does not support a conclusion that gabapentin works, does not work, or has a particular effect on pain or safety. It supports a narrower statement: the study was designed to examine timing and neuropathic pain after spinal cord injury, but the primary results needed to quantify that relationship are not reported in the registry record.

14. Why This Trial Matters Statistically

This study raises a clinically focused statistical question: whether the timing of gabapentin initiation is associated with neuropathic pain after spinal cord injury. Distinguishing timing from treatment status is important. The registry describes gabapentin before admission, gabapentin during admission, and a no-gabapentin group, so a useful analysis would need to make clear which comparison addresses which part of the question.

The non-randomized design makes the interpretation especially dependent on transparent reporting. General: When treatment timing is not randomized, decisions about when treatment begins may be associated with participant characteristics or clinical circumstances. Those same features may relate to pain outcomes. Reporting group characteristics and any adjustment strategy is therefore important for judging how much of an observed contrast might reflect confounding. The registry record does not report such details.

The endpoint also illustrates why the match between a research objective and its measurement matters. The objective refers to prevalence and intensity, while the described primary measure is an average pain score over the previous 7 days. A score can address reported intensity, but prevalence requires a definition of who counts as having the condition and a reported count or proportion. No separate prevalence measure is described in the registry record.

Finally, statistical conclusions require estimates and uncertainty, not only a completed study status or a defined endpoint. The registry record does not report the group outcome values or the comparison's precision. That absence limits what readers can learn about the study's central question. It also demonstrates why outcome reporting, analysis details, and clear definitions of the target comparison are essential to interpreting clinical research, particularly when allocation is non-randomized.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The main limitation of the registry information is that it does not report the primary outcome results. There are no group means or standard deviations, no estimated contrast, and no reported confidence interval or p-value. Readers therefore cannot evaluate the size, direction, or precision of the primary outcome comparison from the registry record.

The design is non-randomized and unmasked. The registry does not report how participants entered the treatment groups, what factors influenced initiation timing, or whether the analysis adjusted for differences between groups. These details are particularly relevant because group membership may be related to factors that also influence pain. No causal conclusion can be drawn from the design description alone.

The record's outcome population description reports 21 subjects in the gabapentin group and 6 in the no-gabapentin group, but it does not report the separate outcome counts for the early and late gabapentin arms. It also does not report baseline characteristics or the number of participants with a completed pain assessment. The registry record does not describe missing-data handling, treatment changes, or the analysis population.

The primary objective mentions prevalence and intensity, but the described endpoint is a continuous pain score. No separate prevalence definition or result is reported. The record also does not describe dosing, detailed follow-up procedures, outcome-assessment procedures, or an analysis plan. These are limitations of the available registry record; they do not establish that the study failed to collect or analyze such information. They do mean that the registry entry alone is insufficient to assess those aspects of the study.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Evaluation of Initiation Time on the Efficacy of Gabapentin in Treating Neuropathic Pain in SCI — NCT04256603.
• Registry record last updated 2021-11-15; status last verified 2021-11.
• Results first posted 2021-11-15.
• 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.

19. Record Summary

The registry record describes a completed Phase 4, parallel, non-randomized, unmasked study sponsored by MetroHealth Medical Center. The study examines gabapentin initiation timing for neuropathic pain after spinal cord injury. Its arms are gabapentin before admission, gabapentin during admission, and no gabapentin. Enrollment is reported as 27.

The primary outcome is a mean pain score on the Neuropathic Pain Scale, based on pain during the previous 7 days and assessed at discharge. The record describes a pain-level scale of 0-10 and a total score range of 0 to 50, with the stated timeframe through completion of the study, up to 4 weeks after injury. The outcome group description reports 21 subjects in the gabapentin group and 6 in the no-gabapentin group.

The registry record does not report the primary outcome results, analysis details, missing-data methods, or adjustment for non-randomized allocation. Serious adverse events, other adverse events, and deaths are listed as 0 in each reported group. These safety counts are descriptive and do not establish comparative risk.