Neem Lotion With Combing for Lice: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Neem Lotion With Combing for Lice (NCT02974088), a randomized phase 2 study. The primary outcome is Number of Participants Free From Head Louse Infestation as Assessed by Detection Combing.

2. Clinical Question

The clinical question is therefore narrow: it concerns the outcome recorded after combining the lotion with one of two combs. Random assignment supports a comparison between those approaches, but the registry record does not describe the randomization procedure or how assignments were concealed. It identifies the study as assessor blinded, but does not state which assessors were masked or whether participants and other study personnel knew the assigned comb.

The primary outcome is a count of participants meeting the stated success definition, rather than a measure of the number of lice removed or a time-to-event outcome. The record also lists a secondary comparison of participants free from infestation according to comb type and a safety outcome concerning treatment-related adverse events. Those outcomes address additional aspects of the comparison, but do not change the focus of the primary question. The posted results should be read as findings from this particular study population, outcome definition, and follow-up period; they do not by themselves answer questions outside that scope.

3. Trial Design

The registry describes a completed Phase IIa, randomized, parallel-group study of Nice 'n Clear neem-based lotion with combing for head lice. The official title characterizes it as a proof-of-concept study. Recruitment began in 2006-05, primary completion was in 2006-08, and the registry lists enrollment as 47. The two groups differed by the comb used alongside the lotion: one received a head louse detection and removal comb, and the other a regular grooming comb. Both groups therefore received the neem-based conditioning lotion and combing.

Parallel-group design means participants were assigned to one of the two approaches rather than switching between them as part of the reported comparison. Randomization is recorded, but the allocation method, sequence generation, and concealment details are not reported in the registry record. The study is described as assessor blinded and single masked. The identity of the masked party and the practical masking procedures are not reported in the registry record.

The primary outcome timeframe is 15 days. Recruitment is specified at Day 0, and success required no lice at Day 10 and no lice at Day 14. The stated primary population is all participants who completed the 15 study days. The primary outcome counts 23 participants in the louse-comb group and 22 in the grooming-comb group. The secondary outcome record uses 24 as the grooming-comb denominator for its efficacy comparison, while the safety record also lists 24 participants at risk in that group. These different figures should be kept distinct; the reason for the denominator difference is not reported in the registry record.

The registry lists three outcome measures, two secondary outcomes, and no reported analyses. It does not describe a sample-size justification, interim analyses, or a detailed statistical analysis plan. The design information establishes the broad comparison and outcome timing, but does not establish how missing observations or deviations from assigned treatment were handled.

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.

Before assignment: None defined

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All participants who completed the 15 study days

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 Free From Head Louse Infestation as Assessed by Detection Combing, measured over 15 days.

The primary endpoint is the number of participants free from head louse infestation as assessed by detection combing. Its success definition is conjunctive: participants had to have no lice at Day 10 and no lice at Day 14. Recruitment is specified at Day 0, and the outcome timeframe is 15 days. The population for this endpoint is described as all participants who completed the 15 study days.

This endpoint turns the clinical observation into a binary participant-level outcome: a person either met the stated success definition or did not. A count of participants meeting the definition can be compared across the randomized groups. In general, a binary endpoint can be straightforward to interpret when the outcome and assessment procedure are clearly defined, but it discards information about differences among participants who do not meet the definition. It also depends on when and how assessment is performed. In this study the record names detection combing and specifies assessment days, but details such as the assessment procedure and assessor training are not reported in the registry record.

The endpoint is relevant to the stated comparison because the trial asks whether the number free from infestation differs when the same lotion is paired with different combs. It is not a measure of the lotion’s effect in isolation: both groups received lotion. Nor does the endpoint alone describe safety, the course of infestation between assessment times, or outcomes after the stated study period. Its meaning should remain tied to the registry’s specific two-assessment success definition and completed-study-days population.

7. Results Posted in the Registry

• Neem-based Lotion Plus Grooming Comb: 100.0% (22/22) versus 100.0% (23/23) 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.

Difference in Number of Participants Free From Head Louse Infestation According to Comb Type Used

• 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:
  • Neem-based Lotion Plus Grooming Comb: 91.7% (22/24) versus 100.0% (23/23) on control; risk difference -8.3 percentage points (95% CI -19.4 to 2.7), risk ratio 0.92 (0.81–1.03); unadjusted two-proportion z-test p = 0.157.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Neem-based Lotion Plus Grooming Comb and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes add context but do not replace the primary question. The registry lists a secondary comparison of participants free from infestation according to comb type and a safety outcome concerning treatment-related adverse events. The posted efficacy comparison is numerically in the direction of fewer participants meeting the success definition in the grooming-comb group, but its interval includes no difference. This broad pattern is compatible with uncertainty rather than a clear separation between the combing approaches.

The secondary efficacy record uses 24 as the grooming-comb denominator, whereas the primary outcome record uses 22 for that group. The louse-comb denominator is 23 in both records. The reason for this discrepancy is not reported in the registry record. It makes it especially important not to merge the primary and secondary results or to assume that they use precisely the same analysis population.

In general, secondary outcomes can be useful for exploring aspects of a trial that are not the main question, but they are often less conclusive. Their interpretation may be affected by multiple comparisons: when many outcomes are examined, some apparently notable results can arise by chance. The record does not report a multiplicity adjustment or a prespecified hierarchy for the secondary outcomes. The efficacy comparison’s p-value is explicitly unadjusted, so it should be read as exploratory and not as a standalone confirmation.

The secondary safety outcome addresses a different domain from the infestation endpoint. Safety counts cannot establish the comparative efficacy question, just as efficacy counts cannot by themselves establish safety. Taken together, the secondary information does not overturn the primary descriptive finding. It supplies additional observations, but the denominator difference, uncertainty, and lack of reported analysis details warrant restraint in assigning those observations strong evidential weight.

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

• Difference in Number of Participants Free From Head Louse Infestation According to Comb Type Used
• Number of Participants With Treatment-related Adverse Events as Assessed by CTCAE v4.0

9. Statistical Interpretation

10. Statistical Methods Explained

The registry identifies a randomized, parallel-group design and reports participant counts meeting a binary endpoint. The statistical summaries can be understood by separating the observed group outcomes, the between-group contrast, and the uncertainty attached to that contrast. The record does not report the sponsor’s analysis methods, so explanations of statistical concepts below are general unless explicitly tied to the posted result.

What does a binary outcome count?

The primary endpoint classifies each participant according to whether the stated success criteria were met. A group count is the number meeting the criteria, while the group size is the number included in that outcome record. In general, these two quantities together describe the observed proportion of participants with the outcome. The registry’s primary record lists 23 of 23 in the louse-comb group and 22 of 22 in the grooming-comb group. These are the posted outcome counts and denominators; they do not show how participants with missing or incomplete assessments were handled.

A binary endpoint is easy to connect to a yes-or-no clinical state, but it does not preserve every detail of a participant’s experience. For example, it does not quantify the amount of infestation among those who fail the success definition. The endpoint’s interpretation also depends on the wording of success. Here it required no lice at both Day 10 and Day 14, as assessed by detection combing. A different definition or assessment schedule could yield a different outcome classification.

What does the risk difference represent?

In general, a risk difference subtracts one group’s outcome proportion from the other group’s outcome proportion. It expresses the contrast on the original proportion scale. A value of zero means equal observed proportions; a negative or positive value indicates the direction of the numerical difference according to the ordering used in the comparison. The primary posted comparison gives a risk difference of 0.0. The secondary comparison has a negative point estimate, but its interval reaches across zero.

A risk difference is distinct from a ratio measure. Differences are expressed in proportion units and can be read as absolute contrasts, whereas ratios describe relative contrasts. Neither measure alone establishes clinical importance; that requires context about the endpoint and what magnitude would matter. The registry record does not state a threshold for a clinically important difference.

What does a confidence interval add?

In general, a confidence interval is a range produced by a statistical procedure to represent uncertainty around an estimate. A narrow interval indicates greater statistical precision under the method’s assumptions; a wider interval indicates less precision. An interval that includes zero for a risk difference is compatible with no difference under the interval procedure, but it can also include nonzero differences. It does not prove that the groups are identical.

The primary record reports limits equal to its point estimate, resulting in a zero-width interval. The registry does not report how that interval was calculated. It should not be interpreted as showing that sampling uncertainty is absent. In contrast, the secondary interval spans values on both sides of zero, so it reflects uncertainty that includes no difference as well as possible differences in either direction. The numeric limits are not repeated; the key interpretive point is that the secondary interval does not exclude zero.

How should the p-value be read?

In general, a p-value describes how surprising data at least as discrepant as those observed would be under a specified null model and test procedure. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of an effect. The secondary comparison has an unadjusted p-value of 0.157. Because the record labels it unadjusted and lists no sponsor-reported analyses, it should be treated as a secondary, unadjusted result rather than a definitive test of the primary question. No primary p-value is reported in the registry record.

A p-value is meaningful only in relation to the outcome, model, and analysis choices that generated it. Those details are not reported for the sponsor’s analysis. The risk difference and interval can therefore communicate direction and uncertainty more directly than the p-value alone, while still requiring caution about the record’s incomplete methods information.

What can randomization and masking contribute?

In general, random assignment can reduce systematic differences between groups at the time of assignment, supporting a fair comparison when assignment and follow-up are appropriately implemented. Randomization does not guarantee that groups are identical in every characteristic, especially in a small study. The registry confirms randomization but does not describe its sequence-generation or concealment procedures.

Assessor blinding can reduce the possibility that knowledge of group assignment influences outcome assessment. The registry identifies the study as assessor blinded but does not specify which assessors were masked or how masking was maintained. Detection combing is the stated assessment approach, yet the record does not provide operational details that would permit evaluation of consistency across groups.

What do the planning illustrations mean?

In general, sample-size calculations are planning tools that estimate the number of participants needed under chosen assumptions about the effect, significance level, allocation, and statistical model. A planning illustration based on an observed effect is not evidence that the completed trial had adequate power, and it is not “observed power.” The record describes planning illustrations as using a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect defined as a stated fraction of the observed effect. These are described as planning assumptions, not as the trial’s own design justification. The record does not report the study’s sample-size justification.

In general, over-dispersion matters when outcomes vary more than a statistical model expects: standard errors may then be too small and intervals too narrow if the extra variability is ignored. The primary endpoint is binary rather than a count of repeated events, and the registry does not report an over-dispersion model. No claim about such a model can be made from the record.

11. Confidence Intervals and Precision

Precision concerns how much uncertainty surrounds an estimated contrast, not whether the observed point estimate is numerically equal to zero. The primary outcome has identical recorded success proportions in the two groups, and the posted risk difference is 0.0. Its reported interval limits are both 0.0. Because those limits coincide, the interval gives no visible range of uncertainty. The registry does not report the method used to produce them, so they should not be treated as a complete account of uncertainty or as proof of exact equivalence.

The group counts are limited: the primary outcome record contains 23 participants in one group and 22 in the other. When a binary outcome is observed in every participant in the outcome record, the observed proportions are at the boundary of the possible range. In general, boundary estimates can make standard uncertainty summaries sensitive to the method used. This is a general statistical caution, not a claim about the sponsor’s undisclosed method. The registry does not report enough detail to determine how the primary interval was calculated.

The secondary efficacy comparison has an interval that includes zero and extends to both negative and positive values. In general, that pattern means the data are compatible with no difference under the interval method, while also allowing nonzero contrasts. It is not a demonstration of equivalence. The secondary denominator also differs from the primary record, and the reason for the difference is not reported in the registry record. These issues limit direct comparison of the two summaries.

Precision should therefore be judged from the observed counts together with the interval and analysis details, rather than from the point estimate alone. The primary point estimate is an exact tie in the recorded groups, but the zero-width reported interval should not be mistaken for extraordinary precision. The secondary interval communicates uncertainty more visibly, but it does not settle the direction or size of a population-level contrast.

12. Multiplicity, Missing Data and Analysis Populations

The registry lists two secondary outcomes alongside the primary outcome, but it does not report a statistical analysis plan specifying which tests were confirmatory, how outcomes were prioritized, or whether any adjustment for multiple testing was planned. The secondary efficacy comparison is labeled unadjusted. The reported analyses list is empty. Therefore, the record does not establish that the secondary tests were adjusted for the number of outcomes examined or that their analysis was prespecified.

In general, testing multiple outcomes increases the chance of obtaining at least one seemingly unusual result even when there is no underlying effect. Adjustment methods can control particular error rates, but they depend on the analysis plan and the family of tests being considered. Without those details, an unadjusted secondary p-value should be treated cautiously and should not be elevated to the same evidential status as a prespecified primary analysis. The registry does not report whether a multiplicity strategy was used outside the posted record.

The primary population is defined as participants who completed the 15 study days. This is not enough to determine whether the analysis followed an intention-to-treat principle, a per-protocol principle, or another rule. The registry does not report how many participants were randomized but did not complete follow-up, how missing outcome assessments were handled, or whether any imputation was used. The reason the secondary grooming-comb denominator is 24 while the primary denominator is 22 is also not reported in the registry record.

These omissions matter because the analysis population and missing-data approach can influence a binary outcome comparison. In general, excluding participants without completed assessments can change the composition of the groups if completion is related to outcome or treatment assignment. That is a general consideration, not evidence that such a bias occurred in this study. The available record does not permit an assessment of the missingness mechanism or the impact of alternative analysis populations.

The record also does not report interim analyses, a sample-size justification, or the sponsor’s detailed statistical methods. Planning illustrations are described as planning calculations rather than as the original design justification. Taken together, the missing analysis details limit reproducibility and make it difficult to judge whether reported analyses followed a prespecified plan.

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 safety record lists zero serious adverse events in the louse-comb group, with 23 participants at risk, and zero in the grooming-comb group, with 24 participants at risk. It also lists zero deaths in both groups. These counts describe what was recorded during the study; they do not establish that serious events cannot occur or precisely quantify the risk beyond the observed participants and follow-up.

In general, observing no serious events in a study does not demonstrate that the underlying risk is zero. A study with limited group counts may not be able to characterize uncommon harms precisely. The registry does not report detailed event definitions beyond the serious-event category, the follow-up period for safety assessments, or the method used to determine attribution. It lists one other adverse event in each group, but the posted serious-event counts remain zero. The registry’s secondary outcome refers to treatment-related adverse events assessed by CTCAE v4.0; the record does not provide further narrative detail about the events or their relationship to treatment.

The safety figures should be read as counts in the recorded at-risk groups, not as proof of comparative safety or a guarantee that no serious harm is possible. The difference between the safety denominators and the primary outcome denominator for the grooming-comb group is another reason to keep outcome-specific populations separate.

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

The primary result says that all participants included in each primary outcome group met the registry’s stated success definition: no lice at Day 10 and no lice at Day 14. The posted point estimate for the difference is 0.0. This is a concise description of the observed result within the recorded primary population. It is not a statement that the two combs have identical effects in the broader population.

The trial compared two comb types while both groups used the same neem-based lotion. It therefore does not estimate the effect of lotion compared with no lotion, and it cannot separate an effect of the lotion from the effect of receiving a lotion-and-combing approach. The outcome also applies only to the detection-combing assessment and specified follow-up. It does not describe outcomes beyond the 15 study days or outcomes measured in another way.

The primary interval is reported with coincident limits at the point estimate, but the registry does not explain the method. That should not be interpreted as certainty. The secondary efficacy comparison has an interval spanning zero, so it does not establish a clear difference between combing approaches. The secondary result also uses a different grooming-comb denominator, whose reason is not reported. The absence of sponsor-reported analyses and details about missing data further constrains interpretation.

In general, randomized comparisons can inform whether groups differed under the conditions studied, but inference depends on design implementation, outcome ascertainment, analysis choices, and precision. The registry confirms randomization and assessor blinding, but leaves important procedural details unreported. Consequently, the posted data support a limited account of observed outcomes, not a broad conclusion about effectiveness, equivalence, or safety. No medical advice follows from these statistical summaries.

15. Why This Trial Matters Statistically

This trial is statistically informative as an example of why point estimates, uncertainty, and data definitions need to be considered together. The primary comparison is a perfect tie in the recorded success proportions, yet the interval reported for that comparison has no width. A point estimate can describe what happened in the observed groups, but its precision depends on an appropriate uncertainty calculation. When the method is not reported and the interval appears to omit uncertainty, the estimate should be read descriptively rather than as proof of exact equivalence.

The record also illustrates the importance of denominator consistency. The grooming-comb group has one denominator in the primary efficacy outcome and a different one in the secondary efficacy and safety records. Each outcome should be interpreted using its own stated denominator; silently substituting one for another would change the meaning of the comparison. Because the reason for the difference is not reported in the registry record, readers cannot determine whether it reflects eligibility, completion, outcome availability, or another factor.

Finally, the study’s stated question is a component comparison: lotion plus a louse comb versus the same lotion plus a grooming comb. Keeping the contrast clear prevents attributing the result to the lotion alone. The combination of a narrow outcome definition, limited recorded group counts, secondary results with uncertainty, and incomplete analysis details makes this a useful case for distinguishing observed data from stronger claims that the record cannot support.

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 are specific to the information recorded for this study. The primary outcome is restricted to participants who completed the 15 study days, but the registry does not report how many participants were randomized but did not complete follow-up or how incomplete assessments were handled. It also does not state whether the analysis included all randomized participants or only those with a completed outcome.

The primary efficacy record lists 22 participants in the grooming-comb group, while the secondary efficacy record lists 24 in that group. The safety record lists 24 at risk. The reason for these differences is not reported in the registry record, so the outcomes cannot be assumed to share the same analysis population. The primary comparison’s reported interval has coincident limits, and the registry does not report the method that generated it. This makes the interval difficult to use as a measure of precision.

The registry identifies assessor blinding but does not identify who was masked or explain how masking was maintained. It also does not report the randomization sequence or allocation concealment procedures. Details of detection-combing conduct and consistency between assessors are not reported in the registry record. These omissions limit evaluation of potential influences on outcome assessment.

The outcome definition requires no lice at two specified assessments, but the registry does not provide details about outcomes between those assessments or after the stated timeframe. It reports no sponsor analyses and no detailed analysis plan, multiplicity strategy, missing-data procedure, or sample-size justification. The secondary efficacy result is unadjusted, and the record does not report whether other analyses were considered. These limitations do not negate the posted counts; they constrain how confidently the counts can be generalized or interpreted as evidence about underlying effects.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: Neem Lotion With Combing for Lice — NCT02974088.
• Registry record last updated 2024-03-19; status last verified 2024-03.
• Results first posted 2019-03-14.
• 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

NCT02974088 is a completed Phase IIa randomized, assessor-blinded, parallel-group study of neem-based lotion with either a head louse detection and removal comb or a regular grooming comb. The registry lists enrollment as 47 and gives recruitment at Day 0, primary completion in 2006-08, and a primary outcome timeframe of 15 days.

The primary endpoint counted participants free from infestation by detection combing, with success defined as no lice at Day 10 and no lice at Day 14. The primary outcome record lists 23 of 23 in the louse-comb group and 22 of 22 in the grooming-comb group, with a posted risk difference of 0.0. The secondary efficacy record uses 24 as the grooming-comb denominator; the reason is not reported in the registry record. The safety record lists zero serious adverse events and zero deaths in both groups.

The registry lists two secondary outcomes and no reported analyses. It does not report the sponsor’s detailed analysis methods, missing-data procedures, or sample-size justification. The findings are best understood as recorded outcomes for this study’s specific comparison and endpoint definition.