This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Safety and Efficacy Study of NatrOVA Creme Rinse - 1% and NIX Creme Rinse in Subjects 6 Months or Older With Head Lice (NCT00545168), a randomized phase 3 study. The primary outcome is Efficacy of NatrOVA Creme Rinse - 1% Relative to NIX Creme Rinse in Subjects Infested With Head Lice.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00545168 |
| Phase | Phase 3 |
| Condition | Pediculus Capitis Infestation |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 480 |
| Arms in the primary outcome | n/a |
| Lead sponsor | ParaPRO LLC |
| Results posted | Yes |
2. Clinical Question
Population
People 6 months of age or older with head lice were eligible. The primary efficacy analysis focused on the youngest enrolled member of each household who had at least three live lice at study entry. The registry record calls these participants the primary subjects.
Intervention
NatrOVA Creme Rinse (spinosad) 1% was studied in two regimens: one with no nit combing required and one requiring a nit-combing regimen.
Comparator
The comparator was NIX Creme Rinse (permethrin 1%), applied according to its over-the-counter instructions for use.
Primary question
The primary question concerned the proportion of primary subjects who were free of live lice, adults or nymphs, 14 days after their last treatment. The registry record does not report the numerical results needed to quantify the comparison between regimens.
The study was a phase 3 comparative safety and efficacy trial conducted under actual-use conditions. Its three arms distinguish two NatrOVA use regimens from the NIX comparator. The primary endpoint is described for primary subjects in enrolled households, rather than for every enrolled person. That population definition matters when interpreting any reported efficacy percentage: it identifies whose outcome would contribute to the primary analysis.
The registry record describes the primary efficacy analysis as using Intent to Treat data from those primary subjects. A subject counted as lice free at the designated assessment was considered a success. The assessment was 14 days after the final product treatment; because participants could treat once or twice, the corresponding assessment could be Day 14 or Day 21. The registry record does not give arm-specific success counts, percentages, or an estimated difference. It therefore does not permit a numerical answer about the relative endpoint results.
3. Trial Design
This was a phase 3, randomized, double-masked, parallel-group comparative study. The registry record lists an enrollment of 480 and describes NatrOVA Creme Rinse - 1% versus NIX Creme Rinse in people 6 months of age or older with head lice. The listed study status is completed. The registry record gives a start of 2007-09 and primary completion of 2008-03.
There were three described treatment arms. Arm A used NatrOVA Creme Rinse (spinosad) 1% with no nit combing required. Arm B used the same product with a nit-combing regimen required. Arm C used NIX Creme Rinse (permethrin 1%) according to its over-the-counter instructions for use. For the safety results, the two NatrOVA arms are combined as A/B, while NIX is listed separately. This grouping means the posted safety counts do not distinguish the two NatrOVA regimens.
Randomization is a design feature intended to support fair comparisons by assigning participants to treatment groups by chance. Double masking indicates that the registry record describes the study as double-masked, but it does not report which participants, evaluators, or study personnel were masked or how masking was maintained. The parallel model means the record describes separate groups receiving their assigned regimens rather than a crossover sequence.
The primary subjects were defined as the youngest enrolled members of households who had at least three live lice at study entry. The primary endpoint was assessed 14 days after the final treatment. The registry record does not report how many people were allocated to each efficacy arm, whether assignment was stratified, how allocation was concealed, or the detailed study procedures beyond the arm descriptions and endpoint timing. The enrollment figure should not be treated as the number included in the primary efficacy analysis because the record does not provide the analysis counts.
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: After admission to the study, subjects could have withdrawn at any time for any reason such as they no longer met the eligibility criteria, personal reasons, etc.
Overall Study
| Stage | A - NatrOVA 1% - no Nit Combing | B - NatrOVA 1% - Nit Combing Required | C - NIX |
|---|---|---|---|
| STARTED | 203 | 63 | 214 |
| COMPLETED | 187 | 58 | 193 |
| NOT COMPLETED | 16 | 5 | 21 |
Reasons for not completing this period:
| Reason | A - NatrOVA 1% - no Nit Combing | B - NatrOVA 1% - Nit Combing Required | C - NIX |
|---|---|---|---|
| Lost to Follow-up | 5 | 5 | 5 |
| Withdrawal by Subject | 9 | 0 | 13 |
| Protocol Violation | 1 | 0 | 1 |
| Visit for Day 21 was not done in error | 1 | 0 | 2 |
Analysis population for the primary outcome, as defined in the registry: Primary efficacy analysis was conducted using the Intent to Treat data obtained from primary subjects (i.e., youngest enrolled members of each household who had at least three live lice at the time of entry into the study). Subjects who were lice free 14 days post-treatment were considered successes and all other subjects were considered failures.
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.
| Characteristic | Unit | A - NatrOVA 1% - no Nit Combing | B - NatrOVA 1% - Nit Combing Required | C - NIX | Total |
|---|---|---|---|---|---|
| Participants analysed | 203 | 63 | 214 | 480 | |
| Age, Categorical: <=18 years | Participants | 147 | 46 | 147 | 340 |
| Age, Categorical: Between 18 and 65 years | Participants | 56 | 17 | 64 | 137 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 3 | 3 |
| Age Continuous | years | 15 (SD 14) | 14 (SD 13) | 16 (SD 15) | 16 (SD 14) |
| Sex: Female, Male: Female | Participants | 166 | 48 | 185 | 399 |
| Sex: Female, Male: Male | Participants | 37 | 15 | 29 | 81 |
| Region of Enrollment: United States | participants | 203 | 63 | 214 | 480 |
6. Primary Endpoint
The registry lists the primary outcome as Efficacy of NatrOVA Creme Rinse - 1% Relative to NIX Creme Rinse in Subjects Infested With Head Lice, measured over Assessment were made 14 days following the final product treatment.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | participants |
| Endpoint classification | Binary Endpoint |
The primary efficacy endpoint was the proportion of primary subjects in enrolled households who were lice free at the assessment 14 days after their last treatment. Lice free was defined as having no live lice, including adults or nymphs, based on assessment by a trained evaluator. Participants who met that definition were counted as successes.
This is a binary endpoint at the participant level: each assessed primary subject is classified as either a success or not a success under the stated definition. A proportion makes the outcome interpretable as the share of the analyzed participants meeting the lice-free criterion. Such endpoints are commonly used when the clinical question is whether a prespecified state is present at a defined follow-up time. That is a general statistical explanation, not a report of additional trial procedures.
The timing is tied to the last treatment rather than being identical calendar days for every participant. The registry record specifies Day 14 for subjects who treated once and Day 21 for subjects who treated twice, with both assessments occurring 14 days after the final treatment. This distinction should be retained when describing the endpoint: it is not a single fixed day from study entry for all participants.
The record states that the analysis used Intent to Treat data from primary subjects, defined as the youngest enrolled household member with at least three live lice at entry. However, the numerical success counts, proportions, and comparative estimates are not reported in the registry record. The endpoint definition can therefore be described, but its observed efficacy results cannot be reconstructed from the record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record gives a clear definition of the primary efficacy outcome and its analysis population, but it does not provide numerical efficacy findings. It reports no arm-specific numbers of primary subjects who were lice free, no corresponding proportions, and no comparative effect estimate. No confidence interval or p value for the primary endpoint is reported in the registry record. Consequently, the relative efficacy result cannot be quantified from these posted data.
The record identifies a randomized, double-masked comparison with two NatrOVA regimens and a NIX comparator. That design describes how the comparison was organized, not what the outcome was. Without the endpoint counts and an analysis, the record does not establish the direction, size, or precision of any difference between the regimens. In particular, the completed status and enrollment figure do not substitute for outcome results.
The safety counts are reported separately from efficacy. In the combined A/B NatrOVA group, 0 participants were listed with a serious adverse event among 258 at risk; in the NIX group, 1 participant was listed among 211 at risk. For other adverse events, the record lists 2 participants among 258 in A/B and 16 among 211 in C. These are descriptive counts in the posted safety record. They do not supply the missing primary efficacy comparison, and the NatrOVA safety figures combine the two NatrOVA regimens.
For a binary endpoint, a proportion describes how often a defined outcome occurred in the analysis population. A comparative estimate would then describe the contrast between groups, while a confidence interval would communicate the range of values compatible with the data under the analysis assumptions. These are general statistical concepts; the corresponding efficacy estimates and intervals are not reported in the registry record.
The registry record lists 480 enrolled participants, but the number enrolled is not the same as the number contributing to a particular endpoint analysis. The primary efficacy population was defined more narrowly, and its size is not reported. The safety counts have their own at-risk denominators. These populations and denominators should not be conflated when reading the record.
The posted information supports a description of the design, endpoint, eligibility definition for primary subjects, and selected safety counts. It does not support a conclusion about the magnitude or statistical precision of the primary efficacy comparison. Any planning illustration based on an observed effect should be understood as a planning calculation, not as observed power or as the study’s original design justification.
9. Statistical Methods Explained
The primary endpoint is binary because each primary subject is classified as lice free or not lice free at the specified assessment. For a binary outcome, the basic descriptive result is the number of participants meeting the definition and the number assessed. Dividing those quantities gives a proportion. This is a general explanation of the usual summary, not a claim that a particular calculation or test appears in the registry record. The posted record does not give the efficacy counts or proportions.
What does a confidence interval communicate?
In general, a confidence interval expresses the statistical uncertainty around an estimate under a specified method and its assumptions. A narrow interval indicates greater precision than a wide interval, while an interval that includes values representing no difference may leave the direction or size of a contrast uncertain. A confidence interval is not a guarantee that the true effect lies within its limits. No primary efficacy confidence interval is reported in the registry record, so precision for that comparison cannot be assessed from these results.
How does randomization relate to comparison?
In general, random assignment helps create groups that are comparable on average with respect to factors known and unknown at the time of assignment. This supports interpretation of between-group differences, provided the trial is carried out and analyzed appropriately. The registry record describes the study as randomized, but it does not report the allocation procedure, concealment details, or a numerical primary outcome analysis. The design label alone cannot establish that every possible source of bias was prevented.
Why does the analysis population matter?
The registry record says the primary efficacy analysis used Intent to Treat data from primary subjects. It defines a primary subject as the youngest enrolled member of each household who had at least three live lice at entry. This makes the analysis population different from a general count of everyone enrolled. In general, an Intent to Treat approach aims to analyze participants according to their assigned group, preserving the advantages of randomization. The registry record does not give detailed rules for participants with missing assessments, treatment deviations, or other circumstances that could affect inclusion.
The household-based definition also deserves attention. The primary subject is selected from each enrolled household, and the record does not report how many households contributed or whether any households contributed more than one primary subject. General statistical methods account for clustered observations when multiple outcomes from the same household may be related. Whether such an adjustment was needed or used is not reported in the registry record; it should not be assumed from the endpoint description alone.
What does the study design say about treatment groups?
The trial is described as parallel, randomized, and double-masked. The arm descriptions identify two NatrOVA regimens, one with no nit combing required and one with nit combing required, and a NIX regimen. These design details identify the intended comparisons but do not reveal the statistical model, test, or adjustment used for the primary endpoint. Those analysis details are not reported in the registry record.
The listed primary endpoint has a timing rule tied to the final treatment: assessment was 14 days after that treatment, with Day 14 for subjects treated once and Day 21 for those treated twice. A well-defined assessment window is important because binary outcomes can depend on when they are measured. The registry record does not provide further information about assessment windows, deviations, or the handling of measurements outside the intended timing.
What can planning calculations tell a reader?
In general, sample-size planning asks how many participants may be needed to detect a chosen effect under stated assumptions about the significance level, allocation, and statistical method. The registry record describes a planning illustration based on the observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. Such planning illustrations are not observed power, do not show that the trial was originally designed around those assumptions, and do not replace the trial’s efficacy analysis. The registry record does not report the trial’s own sample-size justification.
For a binary outcome, the assumptions behind a planning calculation can matter: the expected event proportion, the target effect, allocation, and analysis method all influence the required sample size. This is general statistical context. The registry record does not report a detailed original calculation or a numerical efficacy estimate from which to assess whether its enrollment was adequate for the primary comparison.
The record indicates that the primary outcome has several categories or time points and was not reduced to one comparison in the analysis listing. It also lists zero analysis entries. These registry entries reinforce that no complete inferential result for the primary efficacy endpoint is posted in the registry record. Statistical significance, effect magnitude, and precision therefore remain undetermined in the posted efficacy information.
10. Multiplicity, Missing Data and Analysis Populations
The registry record does not report a multiplicity-adjustment plan for the efficacy comparisons. The study has two NatrOVA regimens and a NIX comparator, creating more than one possible comparison of interest. When multiple hypotheses are tested, the chance of at least one false-positive finding can rise if each is assessed separately without an adjustment. This is a general statistical concern, not a claim that a particular testing procedure was or was not used.
The analysis listing indicates that the primary outcome has several categories or time points and was not reduced to one comparison. The registry record also lists zero analysis entries. It does not state which comparisons were prespecified, how testing across regimens or time points was handled, or whether a hierarchy of hypotheses was used. Accordingly, the record does not permit assessment of multiplicity control.
The primary population is described as Intent to Treat primary subjects: the youngest enrolled member of each household with at least three live lice at entry. How participants with missing outcome assessments were handled is not reported in the registry record. The record does not say whether missing outcomes were treated as failures, imputed, excluded, or addressed in sensitivity analyses. These choices can affect a binary endpoint and its interpretation, so the lack of detail limits appraisal.
The record also does not report a per-protocol or other efficacy population, or how deviations from assigned treatment were handled. The stated safety counts have their own at-risk denominators and should not be assumed to use the primary efficacy population. Overall, the population definition is partly specified, but missing-data procedures, analysis populations beyond the stated primary efficacy population, and multiplicity methods are not reported in the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| A/B - NatrOVA 1% - With/Without Nit Combing | 0 | 258 | 0.0% |
| C - NIX | 1 | 211 | 0.5% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 1% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| A/B - NatrOVA 1% - With/Without Nit Combing | 2 of 258 |
| C - NIX | 16 of 211 |
Most frequent serious adverse event terms
| Event term | Organ system | A/B - NatrOVA 1% - With/Without Nit Combing | C - NIX |
|---|---|---|---|
| Gastrointestinal Viral | Gastrointestinal disorders | 0 of 258 | 1 of 211 |
Most frequent non-serious adverse event terms
| Event term | Organ system | A/B - NatrOVA 1% - With/Without Nit Combing | C - NIX |
|---|---|---|---|
| Application site erythema | General disorders | 2 of 258 | 14 of 211 |
| Diarrhea | Gastrointestinal disorders | 0 of 258 | 2 of 211 |
Serious events with the highest arm-level rate: gastrointestinal viral (0.5%).
The posted serious adverse event figures are 0 participants with an event among 258 at risk in the combined A/B NatrOVA group and 1 participant among 211 at risk in the NIX group. The A/B group combines NatrOVA with and without nit combing, so the record does not show separate serious-event counts for those regimens. These figures describe the participants listed with serious events; they do not by themselves establish a comparative safety effect.
For other adverse events, the record lists 2 participants among 258 at risk in A/B and 16 among 211 at risk in C. These counts are also descriptive. The registry record does not provide further information about event severity categories, timing, causal attribution, or statistical comparison. The listed top serious term is Gastrointestinal Viral, 0.5%; the record does not clearly connect that term to a particular group in the information presented.
Deaths are not reported in the registry record. The safety counts should be read separately from the efficacy endpoint: they do not indicate how many participants were lice free and cannot fill in the missing efficacy results. A small number of observed serious events also does not, by itself, establish the absence of risk. Interpretation depends on the event definitions, follow-up, completeness of reporting, and the size of the safety population, details not fully reported in the registry record.
12. What the Result Does, and Does Not, Mean
The registry record establishes what the trial set out to compare: NatrOVA Creme Rinse - 1% in two nit-combing regimens and NIX Creme Rinse in people aged 6 months or older with head lice. It also specifies a primary efficacy outcome based on being free of live lice 14 days after the last treatment. These details make the intended question and endpoint understandable.
What the record does not establish is the observed primary efficacy result. It does not report the arm-specific number of primary subjects who were lice free, the corresponding proportions, a comparative estimate, or a confidence interval. Without those results, it is not possible to describe the direction, magnitude, or precision of an efficacy difference using the registry record. The completed status and enrollment total do not supply that information.
The safety record does contain event counts: one serious event is listed in the NIX group and none in the combined NatrOVA group; other-event counts are also listed. These are descriptive observations, not a complete account of comparative safety. The NatrOVA safety group combines two regimens, and the information does not include a reported statistical comparison. Deaths are not reported in the registry record.
General statistical interpretation distinguishes an observed estimate from its uncertainty. An estimate describes the data; an interval or other inferential result indicates how much uncertainty remains under the method used. Neither can be assessed for the primary efficacy outcome because the corresponding results are not reported. Planning calculations based on an observed effect, when present, are illustrations for future study design rather than evidence of observed power or a substitute for treatment-group results.
Therefore, the defensible reading is limited: the study design, treatment arms, endpoint definition, analysis population description, and selected safety counts are available, while the numerical primary efficacy comparison and several analytical details are not reported in the registry record. No conclusion about treatment benefit or lack of benefit follows from the missing efficacy results.
13. Why This Trial Matters Statistically
This trial is statistically notable for separating two use regimens of the same NatrOVA product. One arm did not require nit combing, while the other required a nit-combing regimen; both were compared in a study that also included NIX. Keeping these arms distinct is relevant to the intended comparisons, whereas the posted safety counts combine them. Readers should recognize that the efficacy question and the safety grouping are not presented at the same level of detail.
The endpoint is also tied to the final treatment rather than a uniform day from entry. The assessment occurred 14 days after the last treatment, corresponding to Day 14 for participants treated once and Day 21 for those treated twice. This timing rule is central to interpreting what “lice free” means in the trial. It also shows why endpoint definitions need to include both the outcome criterion and its assessment schedule.
The primary efficacy population is defined around households: the youngest enrolled member with at least three live lice at study entry. That definition clarifies who contributes to the primary question, but the record does not provide the number of primary subjects or the outcome counts. This distinction illustrates why a total enrollment figure cannot stand in for an endpoint-specific analysis population.
Finally, this record demonstrates the difference between a detailed trial description and a posted numerical result. Randomization, masking, treatment arms, and endpoint definitions describe design; they do not reveal efficacy without outcome data and an analysis. The absence of a reported primary estimate limits statistical interpretation even though some design and safety information is available.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The main limitation for statistical interpretation is that the registry record does not report numerical results for the primary efficacy endpoint. There are no arm-specific success counts or proportions, comparative estimates, confidence intervals, or p values reported. The efficacy effect and its precision therefore cannot be evaluated from the posted information.
The record lists enrollment of 480 but does not give the number of primary subjects included in the efficacy analysis or the arm-specific efficacy denominators. The primary analysis population is described as the youngest enrolled household member with at least three live lice at entry, but the number of participants meeting that definition is not reported. The sample size for the primary analysis cannot be inferred from total enrollment.
Analysis details are limited. The statistical test or model, covariate adjustment, treatment of multiple comparisons, and approach to missing efficacy assessments are not reported in the registry record. The record does not provide details of allocation concealment or identify who was masked. It also does not explain how the endpoint’s several categories or time points relate to specific planned comparisons.
Safety reporting is limited to the listed counts and at-risk denominators. The A/B NatrOVA group combines two regimens, preventing a separate reading of those safety counts. The record does not report deaths, and it does not provide further details about event timing, attribution, or a formal comparison. These limitations constrain interpretation of both efficacy and safety and should be kept separate from the stated trial design.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Safety and Efficacy Study of NatrOVA Creme Rinse - 1% and NIX Creme Rinse in Subjects 6 Months or Older With Head Lice — NCT00545168.
- Registry record last updated 2012-10-11; status last verified 2012-09.
- Results first posted 2012-10-11.
- 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.
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18. Record Summary
The registry record describes a completed phase 3 randomized, double-masked, parallel comparative study with enrollment of 480. It compared NatrOVA Creme Rinse (spinosad) 1% in two regimens—without required nit combing and with a nit-combing regimen—with NIX Creme Rinse (permethrin 1%).
The primary efficacy outcome was the proportion of primary subjects who were free of live lice 14 days after their final treatment. Primary subjects were defined as the youngest enrolled household members with at least three live lice at entry. Numerical efficacy results and analysis details are not reported in the registry record.
Safety counts are listed for combined NatrOVA arms and for NIX. The record does not report deaths. Its posted information supports a description of the design and outcome definitions, but not a numerical conclusion about the primary efficacy comparison.