Bio-equivalence Study Comparing Permethrin Cream, 5% With Elimite in Patients With Active Scabies.: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Bio-equivalence Study Comparing Permethrin Cream, 5% With Elimite in Patients With Active Scabies. (NCT02978508), a randomized phase 3 study. The primary outcome is Proportion of Patients That Are Identified as Cured..

2. Clinical Question

3. Trial Design

The registry describes a Phase 3, randomized, parallel-group study with an enrollment of 140 and a completed status. The study compared Permethrin Cream, 5% with Elimite in patients with active scabies. It is described as multicenter and double-blind; the masking field is recorded as quadruple. The record does not specify which parties were included in that masking designation.

The planned sequence began with screening lasting up to 5 days, followed by a treatment phase lasting 28±4 days. Eligibility was assessed during screening, and randomization was to occur after eligibility confirmation at baseline, identified as Day 1. The registry describes equal allocation to the test and reference groups, with randomization stratified by site. Treatment was administered in an outpatient setting. Each product was described as topical, with a maximum of two applications during the treatment duration.

The registry describes safety and tolerability assessments at Day 7, efficacy, safety, and tolerability assessments at Day 14, and an end-of-study assessment at Day 28. Participants with positive identification of scabies at Day 14 were to receive a second application of the investigational product. The primary outcome is recorded at Day 28, while a secondary outcome with the same title is recorded at Day 14.

Although enrollment is recorded as 140, the primary outcome counts are 68 and 70 in the two groups. The registry also notes two subjects excluded from the per-protocol analysis, with reasons involving application and visit timing. The relationship between the enrollment figure, the analysis populations, and the posted outcome counts is not fully explained. A detailed participant flow and the handling of missing outcome data are not reported in the registry record.

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: 2 subjects were not included in the per protocol anaylis for the following reasons: 101-036: Subject rinsed off the IP after 6:45 mins of application. As per protocol IP is to be rinsed off after at least 8-14 hours of application. 103003: Subject's visit 3 and 5 was performed out of allowed visit window period.

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 Proportion of Patients That Are Identified as Cured., measured over Day 28.

The primary endpoint is the proportion of patients identified as cured at Day 28. It is a binary outcome: each participant is classified as cured or not cured according to the study’s assessment. The registry gives the outcome unit as participants and records counts rather than a continuous measurement. Its stated purpose is to assess bioequivalence between Permethrin Cream, 5% and Elimite in patients with active scabies.

A cure outcome is directly relevant to the stated comparison because it records whether the condition was identified as resolved at the specified assessment time. Comparing the proportions in the two randomized groups can describe the difference in observed cure frequency. A risk difference expresses that contrast as a difference between proportions; a value near zero indicates similar observed proportions in the analyzed groups. That descriptive similarity is not, by itself, proof of bioequivalence. Such a conclusion requires a prespecified acceptable range for the difference and an analysis showing that uncertainty is contained within that range. The registry record does not report a bioequivalence margin or a formal analysis of whether the confidence interval falls within such a margin.

The posted Day 28 summary records 68 cured participants among 68 in the Permethrin Cream, 5% group and 70 among 70 in the Elimite group. The record does not give further detail about the cure definition, assessment procedure, or how unassessed participants were handled. Those details matter for interpreting a binary endpoint, particularly when the analysis population and missing-data approach are not fully documented.

7. Results Posted in the Registry

• Elimite: 100.0% (70/70) versus 100.0% (68/68) on control; risk difference 0.0 percentage points (95% CI 0.0 to 0.0), risk ratio 1.00 (1.00–1.00); unadjusted two-proportion z-test p = n/a.

8. Secondary Efficacy Endpoints

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

Proportion of Patients That Are Identified as Cured.

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Elimite: 30.0% (21/70) versus 27.9% (19/68) on control; risk difference 2.1 percentage points (95% CI -13.1 to 17.2), risk ratio 1.07 (0.64–1.81); unadjusted two-proportion z-test p = 0.790.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Elimite and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcome is the proportion identified as cured at Day 14. Its counts, 19 of 68 in the Permethrin Cream, 5% group and 21 of 70 in the Elimite group, show numerically similar observed proportions. The estimated risk difference is small, the confidence interval includes zero and values in both directions, and the unadjusted p-value is 0.79. Taken together, these figures do not indicate a clear separation between groups at that assessment, but they also do not demonstrate equivalence.

The Day 14 outcome is earlier than the Day 28 primary outcome and is not a substitute for it. The registry describes a second application for participants with positive identification of scabies at Day 14. Thus, the timing of the secondary assessment sits within a treatment schedule that could include retreatment, and the later endpoint reflects a different point in the study. The record does not provide a detailed account of how this feature was handled in the secondary analysis.

Secondary outcomes generally warrant more cautious interpretation than a prespecified primary outcome, particularly when the number of planned comparisons and any adjustment for multiple testing are unclear. Repeated testing can increase the chance of obtaining an apparently notable result by chance. The registry record does not report a multiplicity adjustment or a detailed testing hierarchy. In this case the posted unadjusted result is not statistically notable, but its unadjusted status still matters when considering it alongside the primary outcome and any other analyses.

The secondary result adds context about the earlier assessment, but it does not resolve the reporting gaps around the primary interval, analysis population, or formal bioequivalence criteria. The broad pattern is one of similar observed counts at the two recorded assessment times, with uncertainty and incomplete reporting limiting stronger conclusions.

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

• Proportion of Patients That Are Identified as Cured.

9. Statistical Interpretation

10. Statistical Methods Explained

What does a risk difference describe?

For a binary outcome such as being identified as cured, a group’s observed proportion is the number of participants with the outcome divided by the number assessed in that group. A risk difference compares those proportions by subtracting the reference-group proportion from the test-group proportion. A value of zero means the observed proportions are the same. A positive or negative value indicates which group has the larger observed proportion according to the subtraction order used. The registry’s primary comparison reports a risk difference of 0.0. At Day 14, the estimated difference is positive but small; the confidence interval includes differences in both directions.

This contrast is descriptive unless the analysis and assumptions support a broader inference. Randomization can support comparisons between groups, but it does not resolve uncertainty about outcome measurement, exclusions, missing observations, or how the analysis set was formed. Those features should be reported so that readers can assess how well the estimate corresponds to the randomized comparison.

How should a confidence interval be read?

In general, a confidence interval is a range of values compatible with the data and the method used to calculate it. It communicates uncertainty around an estimate; it is not a range containing a known true value with certainty. For a risk difference, an interval that crosses zero is compatible with no difference as well as with differences in either direction under the stated method. The Day 14 interval extends from a negative to a positive value, so the posted result is not narrowly confined to one direction.

The primary comparison reports limits equal to its point estimate, giving the interval no width. That is unusual as a description of uncertainty for a comparison based on finite participant counts. The registry does not explain the calculation or report a primary analysis; accordingly, readers cannot determine from the record whether the interval reflects a particular procedure, a reporting issue, or another feature of the analysis. It should not be interpreted as showing that uncertainty is absent.

What does the p-value contribute?

In general, a p-value describes how unusual data at least as extreme as the observed data would be under a specified statistical model and a null hypothesis. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of a difference. The Day 14 unadjusted p-value is 0.79. That value does not indicate a statistically clear difference under a conventional testing framework, but a failure to detect a difference does not demonstrate equivalence.

The primary comparison reports p=1.0 alongside identical observed proportions. Because the registry does not describe the primary analysis method, this should be read as a reported comparison statistic rather than as a complete account of the inferential procedure. The record also does not state whether the primary comparison was intended to be a superiority test, an equivalence test, or another formal decision rule.

Why does an equivalence question need a margin?

In general, an equivalence analysis asks whether the difference between treatments is sufficiently small to fall within a prespecified range judged acceptable for the question. A point estimate near zero alone is not enough: uncertainty must also be considered relative to that range. The registry’s stated objective is to demonstrate bioequivalence, but it does not report the margin, the formal testing approach, or a conclusion based on such a criterion. The posted primary counts therefore describe observed outcomes but cannot alone establish the stated objective.

What can the planning illustrations say?

The Day 14 planning illustrations use the observed effect as a basis for hypothetical sample-size planning. They list participants per arm for 80% power and participants per arm for 90% power when planning for 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. For example, planning for 75% of the observed effect gives 13,476 participants per arm for 80% power and 18,039 participants per arm for 90% power. These are planning illustrations, not observed power and not the trial’s original design justification.

In general, a smaller effect to detect requires more information, all else equal, because it is harder to distinguish a small difference from random variation. These calculations use the listed assumptions: two-sided significance level 0.05, equal allocation, and a normal approximation. They are based on the Day 14 observed effect and should not be treated as a formal sample-size recommendation or as evidence that the trial was adequately powered for its stated bioequivalence objective. The original sample-size justification is not reported in the registry record.

For outcomes expressed as counts, over-dispersion is relevant when observed variability exceeds what a chosen statistical model expects. In general, ignoring over-dispersion can make uncertainty appear smaller than it is. The registry records this endpoint as a binary participant outcome, not a continuous count process, and does not report a dispersion estimate or an analysis model. No claim about over-dispersion in this trial is warranted from the record.

11. Confidence Intervals and Precision

The Day 14 risk difference estimate is 0.021, with a reported confidence interval from -0.131 to 0.172. The limits fall on opposite sides of zero, so the result is compatible with a range of possible differences in either direction under the reported calculation. The interval is wide relative to the small point estimate, indicating that the estimate does not pin down the direction or size of a difference precisely. The unadjusted p-value is 0.79, which likewise does not provide clear evidence of a difference under a conventional significance test.

The primary result is reported differently: the risk difference is 0.0 and both confidence limits are 0.0. That interval conveys no uncertainty, which is difficult to interpret for a comparison based on the posted participant counts. The registry record does not report the primary analysis method or explain this interval. The primary population note also identifies per-protocol exclusions without fully clarifying how the note relates to the listed analysis counts. This limits confidence in interpreting the displayed precision as a meaningful measure of sampling uncertainty.

In general, an interval’s width depends on both the data and the method used to calculate it. A narrow interval can support a more precise estimate only when the calculation is appropriate and the analyzed population is clearly defined. Here, the Day 14 interval communicates substantial uncertainty about the risk difference, while the primary interval’s zero width is unexplained. Neither result can establish bioequivalence without a prespecified margin and an appropriate interval-based decision rule. The registry record does not report those elements, so precision for the stated bioequivalence objective cannot be fully assessed.

12. Multiplicity, Missing Data and Analysis Populations

The registry lists a Day 28 primary outcome and a Day 14 secondary outcome, both titled as the proportion of patients identified as cured. It does not report a detailed statistical analysis plan, the planned testing hierarchy, or whether any adjustment for multiple comparisons was intended. The secondary comparison is explicitly described with an unadjusted p-value. Without a stated plan, it is not possible to determine how the study controlled the chance of false-positive findings across outcomes or analyses.

Missing-data handling is also not reported in the registry record. The posted counts identify 68 and 70 participants in the primary outcome groups, but the record does not explain whether these are all randomized participants, participants with observed outcomes, or a defined analysis set. The primary population description mentions two subjects not included in the per-protocol analysis, citing application duration for one and visit timing for another. It does not fully explain whether either subject contributed to the posted outcome counts, how the exclusions were applied, or whether any other exclusions occurred.

The distinction between an intention-to-treat population and a per-protocol population can be important in a randomized comparison. In general, an intention-to-treat analysis retains participants according to their randomized groups, while a per-protocol analysis applies specified criteria for adherence or protocol eligibility. Equivalence questions often require careful attention to analysis populations, but the registry record does not report which primary analysis population was used or provide a complete account of any supporting analyses.

The record lists no reported analyses, despite presenting outcome summaries and comparisons. It does not report a missing-data method, sensitivity analyses, or a protocol-defined approach to handling participants without an assessed outcome. These omissions make it difficult to judge whether the reported counts and comparisons are robust to exclusions or missing observations. The original analysis plan and sample-size justification are not reported in the registry record.

13. 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 summary records zero serious adverse events in each group and zero deaths in each group. These are counts for the safety populations recorded as 70 at risk in each arm. The registry’s serious-event terms list is empty, consistent with no serious events being recorded in the summary.

Zero recorded serious events means that none were reported in these safety summaries; it does not establish that the risk of serious harm is absent. A study of this size and duration may not characterize uncommon or later events, and the registry record does not provide additional detail about surveillance procedures or event adjudication. The safety figures should therefore be read as a description of events recorded during this study, not as a broad safety guarantee.

The summary also records other adverse events in 8 participants in the Permethrin Cream, 5% group and 5 participants in the Elimite group. These are separate from the serious adverse event counts. The record does not provide event terms in the serious-event list and does not provide enough detail to interpret the nature, severity, or relationship of the other events to treatment. These counts are descriptive and should not be treated as a formal comparative safety analysis.

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

The posted primary result describes identical observed cure proportions at Day 28: 68 of 68 participants in the Permethrin Cream, 5% group and 70 of 70 in the Elimite group were recorded as cured. This is a direct description of the registry’s posted counts. It does not establish that the underlying probabilities of cure are exactly the same, nor does it establish that any difference is small enough to meet a formal bioequivalence standard.

Bioequivalence is not demonstrated merely by obtaining the same observed counts or by failing to detect a difference. In general, a formal equivalence assessment needs an acceptable difference range specified in advance and an analysis that accounts for uncertainty relative to that range. The registry record states a bioequivalence objective but does not report the margin or the formal decision procedure. Its primary confidence interval also has no width, and the method behind it is not explained. Those limitations prevent a complete assessment of whether the stated objective was met.

The Day 14 secondary result shows similar observed proportions, but its confidence interval includes zero and differences in either direction. The unadjusted p-value does not offer evidence of a clear difference, but this is not affirmative evidence of equivalence. It is an earlier assessment and is distinct from the primary Day 28 outcome.

The results do not describe every aspect of treatment experience or long-term outcomes. The registry record does not report full details of endpoint definition, missing-data handling, analysis populations, or the complete statistical plan. Safety summaries record no serious adverse events or deaths in either group, while other adverse events are listed as counts; these limited summaries do not establish the absence of risk.

In short, the record documents similar observed cure counts at the stated assessments. The extent to which those counts support a formal bioequivalence conclusion remains uncertain because essential criteria and analysis details are not reported.

15. Why This Trial Matters Statistically

This trial illustrates a distinction central to clinical statistics: observed similarity is not the same as demonstrated equivalence. Equal observed cure proportions can be a useful descriptive result, but an equivalence question asks whether the plausible differences are contained within a prespecified acceptable range. Without that margin and a clearly reported analysis, the numerical similarity alone cannot answer the formal question.

It also illustrates why confidence intervals need to be interpreted in context. The Day 14 interval spans differences in both directions and communicates uncertainty around a small estimated difference. The primary interval is reported with zero width, but the registry does not explain how it was obtained. A confidence interval is only as informative as its calculation and the population to which it applies; an unexplained interval should not be taken literally as certainty.

Analysis-population reporting is especially important when the record describes protocol-related exclusions. The registry mentions two subjects excluded from a per-protocol analysis, while the connection between those exclusions and the posted primary counts is unclear. Transparent reporting of randomized, analyzed, and excluded participants would make it easier to assess the role of adherence and missing outcomes.

Finally, the Day 14 planning illustrations show how strongly planning requirements can depend on the effect chosen for detection. They are based on an observed secondary effect and stated assumptions, rather than the trial’s original design justification. They are not observed power and cannot establish whether the study was adequately planned for its bioequivalence objective. Together, these features make the record a useful example of why effect estimates, uncertainty, design criteria, and analysis transparency must be considered together.

16. Limitations

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

Several limitations specific to this record constrain interpretation. The primary outcome comparison reports a confidence interval with identical lower and upper limits, but the calculation method is not described. The record lists no reported analyses despite presenting outcome counts and comparison statistics. This makes it difficult to establish what inferential procedure generated the primary result.

The primary outcome population note states that two subjects were not included in the per-protocol analysis and gives protocol-related reasons. However, it does not clearly reconcile those exclusions with the posted primary counts or state whether the primary summary uses a per-protocol population. A complete participant flow, group-specific analyzed populations, and reasons for all exclusions are not reported in the registry record.

The stated objective is bioequivalence, but the registry does not report the acceptable margin, the formal testing method, or a conclusion based on that criterion. The definition and ascertainment process for being identified as cured are also not described in detail. The record does not explain how missing or unassessed outcomes were handled, or whether sensitivity analyses were conducted.

The Day 14 result is reported with an unadjusted p-value, while the broader multiplicity approach is not reported. The study description says that participants with positive identification of scabies at Day 14 were to receive a second application, but the record does not detail how this treatment feature was handled in later outcome analyses. The original sample-size justification and statistical analysis plan are not reported in the registry record.

These limitations do not change the posted counts, but they narrow what those counts can establish. They leave unresolved the precision, analysis population, and formal evidential basis for the study’s stated objective.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: Bio-equivalence Study Comparing Permethrin Cream, 5% With Elimite in Patients With Active Scabies. — NCT02978508.
• Registry record last updated 2020-09-02; status last verified 2020-08.
• Results first posted 2020-09-02.
• 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.

20. Record Summary

The registry describes a completed Phase 3 randomized, parallel-group study comparing Permethrin Cream, 5% with Elimite in patients with active scabies. It records enrollment of 140 and describes a multicenter, double-blind study with masking listed as quadruple. The treatment phase was planned for 28±4 days, with assessments at Day 7, Day 14, and Day 28.

The primary outcome was the proportion identified as cured at Day 28. The posted counts were 68 of 68 for Permethrin Cream, 5% and 70 of 70 for Elimite. The registry reports a risk difference of 0.0 and a confidence interval with limits of 0.0 and 0.0, without explaining the interval method. The Day 14 secondary counts were 19 of 68 and 21 of 70; the reported interval spans zero and the unadjusted p-value is 0.79.

The record states a bioequivalence objective but does not report a margin or formal bioequivalence analysis. It also does not fully clarify analysis populations, missing-data handling, or the relationship of the per-protocol exclusions to the posted counts. No serious adverse events or deaths were recorded in either safety group; other adverse event counts were 8 and 5.