Fibrin Glue in Inguinal Lymphadenectomy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Fibrin Glue in Inguinal Lymphadenectomy (NCT04666051), a randomized na study. The primary outcome is Number of Participants With Seroma Formation.

2. Clinical Question

3. Trial Design

This was a randomized, single-masked, parallel-group trial with an enrollment of 32. The registry lists the phase as NA and the study status as completed. The record identifies Menoufia University as the sponsor. The study dates are listed as 2015-05 for start and 2020-10 for primary completion.

Participants undergoing inguinal lymphadenectomy were allocated to one of two groups, with 16 patients in each. One group received fibrin glue applied to the lymphadenectomy bed before wound closure and drain insertion. The summary specifies 2ml per 100 cm2 of surface area. The control group received drain placement without fibrin glue. The design is parallel: participants were assigned to one group rather than receiving both procedures in sequence.

The registry describes the masking as single but does not identify which people involved in the study were masked. It does not report how the random sequence was generated, whether allocation was concealed, or how masking was maintained. Those details should not be inferred from the labels for randomization and masking alone.

The trial was focused on seroma after inguinal lymphadenectomy. The main outcome was the number of participants with seroma formation, assessed four weeks after the procedure. The registry reports one outcome measure and one analysis, and no secondary outcomes are posted. It does not report the study’s original sample-size justification or the assumptions used when the trial was designed. The planning illustrations associated with the observed results are separate from that original design 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: Serum formation has been looked for

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 Number of Participants With Seroma Formation, measured over 4 weeks postpertively.

The primary endpoint was the number of participants with seroma formation. The registry describes seroma as collection of serous fluid under the wound flaps and specifies assessment four weeks after the procedure. For this outcome, Grade 2 and Grade 3 under CTCAE 4.0 were considered. Grade 2 is described as symptomatic, with simple aspiration indicated; Grade 3 is described as symptomatic, with elective radiologic or operative intervention indicated.

This endpoint turns an observed clinical event into a participant count: each group’s result records how many participants met the stated criteria. It is therefore a binary outcome at the participant level, rather than a measure of the volume of fluid or the duration of drainage. Counting participants makes it possible to compare the frequency of qualifying seroma between the randomized groups.

The definition is important to interpretation. The reported count does not encompass every possible fluid collection; it follows the stated grade criteria. The registry does not give a separate count for Grade 2 and Grade 3, nor does it report a more detailed assessment schedule or adjudication process. The endpoint is useful for describing how many participants experienced the defined event, but it does not by itself describe severity beyond the criteria used, timing between assessments, or other postoperative outcomes.

7. Results Posted in the Registry

• Fibrin Glue: 12.5% (2/16) versus 50.0% (8/16) on control; risk difference -37.5 percentage points (95% CI -66.9 to -8.1), risk ratio 0.25 (0.06–1.00); unadjusted two-proportion z-test p = 0.022.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary at the participant level: each person either met the recorded seroma definition or did not. The posted group counts are 2 events among 16 participants with fibrin glue and 8 among 16 control participants. For a binary outcome, the event proportion in each group is one straightforward way to describe the data. The posted proportions are 0.125 and 0.5, respectively. These figures describe the observed participants and are not adjusted for other variables.

What does the risk difference express?

The risk difference subtracts one group’s event proportion from the other group’s event proportion. In the reported comparison, the fibrin-glue group is contrasted with control, so the difference is -0.375. A negative sign indicates that the observed event proportion was lower in the fibrin-glue group. Unlike a relative measure, the risk difference stays on the absolute probability scale and directly describes the separation between the two observed proportions. It does not, by itself, account for uncertainty or show whether the observed difference would be similar in another study.

How should the p-value be read?

The sponsor’s reported analysis is a chi-squared test and gives p = 0.022. In general, a p-value is calculated under a null model in which there is no difference between groups. It describes how unusual data at least as discrepant as those observed would be under that model and its assumptions. It is not a measure of the probability that the null model is true, and it does not say how large or important a difference is. The registry does not report further details of the sponsor’s test beyond identifying it as chi-squared.

The re-calculated unadjusted comparison also gives p = 0.022. The agreement is reflected in the absence of a flagged discrepancy. The sponsor result remains the reported trial analysis; the re-calculation is a simple comparison based on posted summary counts and should not be confused with a separate adjusted or participant-level analysis.

What does a confidence interval add?

A confidence interval gives a range of values compatible with the data under a specified statistical procedure. For this re-calculation, the interval is for the risk difference. Its limits are both below zero, so the range does not include no difference. The range also conveys the uncertainty around the point estimate: the result is not just a single value, and a range of effect sizes remains compatible with the data. In general, a wider interval signals less precision than a narrower interval. The registry record does not state the method used to construct this re-calculated interval, so it should be interpreted as an unadjusted interval accompanying the posted-count comparison, not as a reported sponsor interval.

General statistical caution applies to tests and intervals based on small group counts. A chi-squared approximation relies on assumptions about the data, and with limited counts, alternative methods can produce different inferential results. The record does not report an alternative test or a sensitivity analysis. The close agreement between the posted and recalculated p-values does not by itself establish that every possible method would yield the same conclusion.

Why does the randomized design matter?

Random allocation is intended, in general, to make treatment groups comparable on average with respect to factors that could influence outcomes. It does not guarantee balance in any single small trial, and the registry does not provide enough baseline detail to evaluate balance in this study. Information about how the allocation sequence was generated and concealed is also not reported. The single-masked designation is recorded, but the registry does not say who was masked. These omissions limit assessment of possible selection and measurement biases.

The analysis concerns the primary endpoint as defined in the registry: participants with qualifying seroma at the stated assessment time. No secondary outcome measures are posted. No adjusted model, subgroup analysis, or analysis population definition is described in the registry record. Consequently, the interpretation should stay with the simple group counts and unadjusted comparison rather than imply a broader model or additional analyses.

Finally, a statistically notable result and an estimate of practical relevance are different concepts. The p-value addresses compatibility with a no-difference model under assumptions; the risk difference gives the observed absolute contrast; and the confidence interval conveys precision. None alone supplies all the information needed to judge generalizability, clinical importance, or the balance of benefits and harms.

10. Confidence Intervals and Precision

The point estimate of the unadjusted risk difference is -0.375, with fibrin glue compared with control. The confidence interval for this estimate has both limits below zero, so it excludes a risk difference of zero. This supports the direction of the observed contrast under the re-calculation, but it does not make the estimate exact or eliminate uncertainty about its size.

A confidence interval is best read as a range of effect values reasonably compatible with the data and the procedure used to calculate the interval. In general, intervals that extend across a broad range offer less precision than narrow intervals. The interval in this comparison extends from a substantially negative estimate toward a value closer to no difference. That span cautions against treating -0.375 as a precise prediction of the difference that would be seen in another group of patients.

Only 16 participants were recorded in each arm, and the event counts were 2 and 8. With group sizes of this scale, a small number of participants can materially affect the estimated proportions and their difference. The confidence interval helps communicate that sampling uncertainty; the p-value alone does not. The reported p-value is 0.022, but it should be read alongside the estimate, interval, outcome definition, and study size.

The interval is a re-calculated unadjusted interval based on posted summary statistics, not a confidence interval reported with the sponsor’s chi-squared analysis. The registry record does not identify its interval-construction method. Its interpretation is therefore limited to the calculation attached to the posted counts. Precision also does not resolve limitations in the design details or establish that the same result applies beyond the studied participants and follow-up.

11. Planning a Similar Trial: Sample Size

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

The planning figures are participants per arm, not total events. They illustrate how many participants each group might require under stated assumptions to detect an effect set at a specified fraction of the observed effect. The calculations use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. They are based on the observed effect and are planning illustrations, not the original trial’s design assumptions.

For planning at 100% of the observed effect, the illustration gives 23 participants per arm for 80% power and 30 participants per arm for 90% power. At 75% of the observed effect, it gives 45 participants per arm for 80% power and 60 participants per arm for 90% power. At 50% of the observed effect, it gives 107 participants per arm for 80% power and 143 participants per arm for 90% power.

In general, power is the probability that a planned study will reject a no-difference hypothesis if a particular effect is present and the planning assumptions hold. The 80% and 90% columns represent different target probabilities for detecting the chosen effect under those assumptions; the 90% target requires more participants than the 80% target for the same effect. The examples also show the general pattern that smaller effects need more participants to detect than larger effects.

These calculations are not observed power. They are hypothetical planning estimates based on the effect observed in this trial, and the original sample-size justification is not reported in the registry record. They should not be read as a retrospective measure of the trial’s success or as a guarantee that a future study of those sizes would reproduce the observed result.

12. How the Sample Size Is Derived

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

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.500; treatment proportion p₁ = 0.125; average p̄ = 0.312.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6555 = 1.2848.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.5995 = 0.5045.
4. n = (1.2848 + 0.5045)² / (-0.3750)² = 22.8, rounded up to 23 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
p0 <- 0.5                          # control proportion
p1 <- 0.125                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^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 (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(4666051)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 23 (80% power), 30 (90% power)
 75% of observed effect: n per arm = 45 (80% power), 60 (90% power)
 50% of observed effect: n per arm = 107 (80% power), 143 (90% power)
power.prop.test: 22.8 
Simulated power at n = 23 per arm: 0.815 (20000 replicates)

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

13. Analyses Reported by the Sponsor

The sponsor’s posted analysis compares the two groups using a chi-squared method and reports p = 0.022. The unadjusted re-calculation from the posted group counts also reports p = 0.022. The record does not flag a discrepancy between the sponsor result and the re-calculation.

The re-calculation adds an absolute effect estimate: the risk difference is -0.375 for fibrin glue compared with control, and its confidence interval lies entirely below zero. These quantities express the direction and estimated size of the contrast, along with uncertainty, whereas the sponsor’s posted result is a p-value from the identified test. The two types of information answer related but different statistical questions.

The recalculated quantities are not a replacement for the sponsor’s analysis. They are simple unadjusted calculations from the posted summary counts; the registry does not report an adjusted analysis or participant-level analysis. The absence of a flagged discrepancy and the matching p-values indicate agreement for the reported test result, but do not establish agreement for analyses that were not posted. The sponsor’s own analysis is therefore the reported trial analysis, while the re-calculation provides a complementary description of the summary data.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and one analysis, with the primary outcome defined as the number of participants with seroma formation. No secondary outcome measures are posted. This limited record does not show whether other outcomes were collected but not entered, or whether the primary endpoint was the only outcome specified in the full protocol.

Multiplicity arises when multiple outcomes, time points, groups, or analyses are tested. When many comparisons are made, the chance of at least one apparently notable result can increase unless the analysis plan addresses that issue. The registry record does not report a multiplicity adjustment or a hierarchy among outcomes. Because it lists only one outcome and one analysis, the scope of any unreported analyses cannot be assessed from this record.

Missing-data information is not reported in the registry record. There is no posted account of whether every randomized participant contributed an outcome, whether any outcome assessments were missing, or how missing values would be handled. The arm counts total 16 participants each, and the outcome counts are reported for those same group sizes, but the record does not explicitly describe an analysis population or explain how those denominators were defined.

The analysis population is also not specified. The registry does not say whether participants were analyzed according to their randomized assignment, whether any exclusions occurred after randomization, or whether a per-protocol or other population was used. Such details matter because excluding participants or changing group assignment can affect the comparability created by randomization.

Interim analyses, stopping rules, prespecified subgroup analyses, and adjustments for baseline characteristics are not reported in the registry record. Their absence from the registry entry should not be taken to mean that they did or did not occur; the available information simply does not document them. These gaps limit a full assessment of the analysis plan and selective reporting, so interpretation should remain focused on the posted primary comparison.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The serious adverse event figures list 0 affected participants among 16 at risk in the fibrin-glue group and 0 among 16 at risk in the control group. The figures for other adverse events list 3 affected participants among 16 at risk in the fibrin-glue group and 9 among 16 at risk in the control group. Deaths are listed as 0 in each group.

These are participant counts, not descriptions of event types or severity beyond the distinction between serious and other events in the registry fields. The record lists no serious adverse event terms. It does not provide details about the nature, timing, duration, or relationship of the other adverse events to the study procedure or intervention. It also does not describe how events were collected or whether multiple events in one participant were counted separately.

With 16 participants in each group, the counts are a limited summary and cannot establish that an event is absent from a broader population. They also do not, by themselves, establish that the difference in other-event counts is caused by the intervention. The safety figures should be read as the adverse-event information posted for this trial, alongside the limits in event detail and study size.

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

The observed primary outcome was less frequent in the fibrin-glue group than in the control group: 2 of 16 participants compared with 8 of 16. The unadjusted risk difference was -0.375, and its confidence interval did not include zero. The sponsor’s chi-squared analysis reported p = 0.022, matching the p-value from the unadjusted re-calculation. Taken together, these figures describe a difference between the groups in this trial on the recorded endpoint.

The result does not establish that the same difference will occur in other groups of patients. The trial enrolled 32 people undergoing lymphadenectomy for various causes, and the registry does not report additional participant characteristics or the specific causes represented. The small group sizes mean the estimated difference is uncertain, even though the interval excludes zero. The posted data do not determine how much of the observed contrast would be expected to persist with a different sample.

The endpoint also has a specific scope. It counts participants with Grade 2 or Grade 3 seroma under CTCAE 4.0 at the recorded assessment time. It is not a measure of every fluid collection, the quantity of fluid, or the full course of recovery. The registry does not break down the outcome by grade or provide additional follow-up results.

The comparison concerns fibrin glue added to a drain, versus a drain without glue. It does not compare fibrin glue with no drainage. Nor do the posted results address outcomes beyond the primary seroma measure and the summarized adverse-event counts. The result should not be treated as proof of a particular mechanism, as evidence about longer-term outcomes, or as a medical recommendation. It is one randomized trial’s statistical comparison, with uncertainty and reporting limits that need to be considered alongside evidence from other sources.

17. Why This Trial Matters Statistically

This trial illustrates why reporting both event counts and an effect estimate matters. The counts, 2 of 16 and 8 of 16, make the observed group outcomes concrete. The risk difference of -0.375 expresses their absolute contrast, while the confidence interval communicates uncertainty around that estimate. A p-value alone would not show the size of the observed difference or how precisely it was estimated.

The design also makes clear that treatment comparisons often concern an addition to standard procedural steps rather than a choice between unrelated alternatives. Here the groups both received a drain, and the intervention group also received fibrin glue. Keeping that comparison explicit prevents the result from being interpreted as a comparison of glue against drainage itself.

At the same time, statistical interpretation depends on the details that a registry entry records. The sample is limited to 32 participants, and details about sequence generation, allocation concealment, masking, missing data, and analysis populations are not reported. Such information helps readers assess how a randomized comparison was implemented and analyzed. Its absence does not erase the posted findings, but it narrows what can be concluded about their reliability and reach.

Finally, planning illustrations based on the observed effect can help readers understand how assumed effect size and power targets influence study size. They are not evidence that a design was adequate or that a future study will reproduce the estimate. Distinguishing a result from a planning calculation, and an estimate from its uncertainty, is central to reading clinical trial statistics responsibly.

18. Limitations

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

The trial enrolled 32 participants, with 16 in each group. This provides a limited amount of information for estimating the frequency of a binary outcome, and the point estimate may be sensitive to a small number of participants. The confidence interval reflects uncertainty around the re-calculated risk difference, but does not remove it.

The registry describes the participants as undergoing lymphadenectomy for various causes but does not provide a breakdown of those causes or further baseline characteristics. The extent to which the results apply to a particular patient population or surgical context therefore cannot be determined from the record alone. Randomization is reported, but the method used to generate the allocation sequence and whether allocation was concealed are not reported.

The record identifies the study as single-masked without saying who was masked or how masking was implemented. It does not report protocol details about outcome assessment, missing data, the analysis population, or adjustments for other variables. No secondary outcomes are posted, and the primary outcome is assessed at the stated four-week time point. The record does not provide later outcome assessments or a breakdown between Grade 2 and Grade 3 events.

The sponsor’s reported result is a chi-squared p-value; the effect estimate and interval are unadjusted re-calculations from the posted counts. The interval method is not specified in the registry. Safety reporting is also limited: the record gives serious-event, other-event, and death counts but no event terms for serious events or detailed descriptions of other events. These limitations leave important aspects of trial conduct, analysis, follow-up, and event characterization unreported.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Fibrin Glue in Inguinal Lymphadenectomy — NCT04666051.
• Registry record last updated 2022-08-30; status last verified 2022-08.
• Results first posted 2022-08-30.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

22. Record Summary

NCT04666051, titled “Fibrin Glue in Inguinal Lymphadenectomy,” is a completed randomized, single-masked, parallel-group study sponsored by Menoufia University. It enrolled 32 patients undergoing inguinal lymphadenectomy for various causes, with 16 assigned to fibrin glue plus drain and 16 to drain alone.

The primary outcome was the number of participants with seroma formation at four weeks, using Grade 2 and Grade 3 criteria under CTCAE 4.0. The posted counts were 2 of 16 in the fibrin-glue group and 8 of 16 in control. The sponsor reported a chi-squared p-value of 0.022; the unadjusted re-calculation also gives p = 0.022 and a risk difference of -0.375. The registry does not report secondary outcomes, detailed analysis-population or missing-data information, or the original sample-size justification.