Mechanical Intervention on the Scalp Microbiome: Setting the Stage for the Future Management of Cicatricial Alopecias: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Mechanical Intervention on the Scalp Microbiome: Setting the Stage for the Future Management of Cicatricial Alopecias (NCT06357169), a na na study. The primary outcome is Scalp Microbiome Composition.

2. Clinical Question

In practical terms, the study aims to assess whether standardized mechanical cleansing is associated with a change in the scalp microbiome and to characterize the microbiome of healthy scalp. These are related but distinct aims: observing microbiome composition after care is not, by itself, the same as establishing a treatment effect against a control. The record describes a single-group design and does not report a comparator, baseline outcome values, or the results of any microbiome analyses.

The registry's primary-outcome description refers to variation in microbiome composition between treatment groups, while the design is listed as single group and the described arm is healthy-experimental. How the intended group comparison was to be implemented is not reported in the registry record. Accordingly, the clinical question can be described as an intended assessment of scalp microbiome composition following mechanical cleansing, but a controlled comparison cannot be inferred from the recorded design.

3. Trial Design

The registry identifies this as a single-group study of the Venus Glow device, with allocation listed as NA and masking listed as none. It records an enrollment of 23 and a status of terminated. The listed start date is 2023-01-13, and the primary completion date is 2023-06-30. These registry entries describe the study record; they do not establish how many participants completed follow-up or contributed to each outcome analysis.

The described arm, Healthy-experimental, consists of healthy participants who have not been diagnosed with scalp or hair disease. They were to be followed over 2 weeks to assess the scalp microbiome and evaluate the device's effect on scalp microbial burden. The intervention is named Venus Glow and classified as a device. The study summary describes mechanical cleansing with the device and water. The registry lists lichen planopilaris of the scalp and alopecia areata among the conditions, but the relationship of those conditions to the described healthy group is not reported in the registry record.

No randomized allocation or masking is described. With a single-group model, the record does not identify a concurrent control arm for estimating how microbiome outcomes might differ without the intervention. The primary-outcome description mentions variation between treatment groups, which does not align clearly with the single-group design and listed arm. The intended comparison structure is not reported in the registry record.

The record lists four outcome measures, including scalp health outcomes and the primary microbiome outcome. It does not report analysis results. The study's stated focus includes both the effect of standardized care and characterization of the healthy scalp microbiome, but the record does not provide enough detail to establish the analysis populations, actual follow-up, or the protocol for handling outcome measurements.

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

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 Scalp Microbiome Composition, measured over Day 14.

The primary endpoint is titled Scalp Microbiome Composition and is described as a mean of a continuous measure, with genera as its unit and standard deviation as its dispersion measure. It is assessed at Day 14 using the relative abundance of genera derived from DNA extraction of scalp swabs collected from the right and left mid-frontal scalp. The endpoint therefore concerns the composition of the microbial community, expressed through the relative representation of genera, rather than a clinical diagnosis or a direct measure of hair growth.

Microbiome composition can be used to characterize a biological community and to examine whether its measured profile varies following an intervention. The study summary also states an aim of characterizing the normal, healthy scalp microbiome as a reference for comparison with scalp affected by hair and scalp disease. Such characterization may be useful for framing later research, but the registry does not report the measured baseline profile or Day 14 findings.

The registry describes Kruskal-Wallis testing to assess variation in microbiome composition between treatment groups. That description is difficult to reconcile with the listed single-group model and the one described arm. The record does not explain whether distinct groups or repeated observations were intended for this analysis. It also does not report results for the primary endpoint, so no conclusion about the direction, size, or precision of any observed change can be drawn from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the listed design imply?

The registry lists a single-group model, no masking, and allocation as NA. In general, a single-group design measures participants under one study condition rather than comparing randomized groups. It may describe outcomes over time, but interpretation of change depends on clear measurement timing, baseline data, and information about who contributes observations. Those details and the primary outcome results are not reported in the registry record. The described arm is Healthy-experimental, and the intervention is mechanical cleansing with the Venus Glow device and water.

The primary-outcome description refers to assessing variation between treatment groups with a Kruskal-Wallis test. In general, Kruskal-Wallis is a rank-based method for comparing distributions across independent groups. It is often considered when a continuous outcome may not meet assumptions used by some parametric comparisons. Its use requires a meaningful grouping structure and independent observations. Here, the single-group model and the one described arm leave the intended groups unclear. The registry record does not say whether there were additional groups, how repeated scalp samples were handled, or whether the stated test was used in an analysis.

How should a mean and standard deviation be read?

The outcome is classified as a mean of a continuous measure, with standard deviation as its dispersion measure. In general, a mean describes a central value, while a standard deviation describes how measurements vary around that mean. These summaries can be helpful for continuous data, but microbiome relative-abundance measures may have distributions that are skewed, sparse, or constrained by their relative nature. Whether these features arose in this study cannot be determined without the data. No endpoint means or standard deviations are reported in the registry record.

What does the endpoint represent?

The recorded measure is relative abundance of genera derived from scalp swab DNA extraction at the right and left mid-frontal scalp, assessed at Day 14. In general, relative abundance describes a component's share of the measured community rather than an absolute count of organisms. A change in one component's share may be related to changes in other components, so it should not automatically be read as a change in the absolute amount of that organism. The registry does not describe any absolute microbial burden result or report the relative-abundance values.

The right and left sampling locations could yield related observations from the same participant. In general, measurements from one participant are not automatically independent of each other. An analysis may need to account for such dependence, or define a participant-level summary, depending on the study question. The registry record identifies both sides but does not report how they were combined, whether they were analyzed separately, or how within-participant correlation was handled.

How should significance and uncertainty be understood?

In general, a statistical test evaluates how compatible observed data are with a specified null model, given the assumptions of the test. A p-value does not quantify the size or practical importance of a finding, and it does not establish that an intervention caused an observed difference. A confidence interval, in general, conveys uncertainty around an estimated quantity by identifying a range of values compatible with the data and method. The registry record reports no p-value, confidence interval, test statistic, or effect estimate for the primary outcome, so none can be interpreted for this study.

The primary outcome description names the Kruskal-Wallis test, but there is no reported analysis to show whether this test was conducted or what comparison it addressed. It would be inappropriate to infer a result from the method description alone. The registry also does not report whether any statistical method was used to adjust for possible covariates or repeated sampling.

How should planning calculations be viewed?

The planning assumptions accompanying the record describe an illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They describe detecting a stated fraction of the observed effect. The assumptions explicitly characterize the calculation as a planning illustration, not the study's own design. This matters because a planning calculation is conditional on its assumptions and is not an analysis of observed treatment effects. It is also not observed power. No resulting participant counts for the illustration are reported in the registry record.

Those assumptions describe equal allocation between two arms, whereas the registry lists a single-group model and one described arm. They therefore should not be read as evidence that this study had two arms or used that allocation. The registry record does not report a protocol sample-size justification, a target based on a prespecified effect, or a statistical analysis plan. The planning assumptions do not resolve the mismatch between the endpoint's reference to treatment groups and the recorded design.

Why can over-dispersion matter?

In general, over-dispersion means that observed variability is greater than a model expects. If a method assumes less variability than the data actually contain, uncertainty can be understated and tests may be poorly calibrated. This is a general statistical issue rather than a reported feature of this study. No distributional diagnostics or model-based results are reported in the registry record. Given the absence of outcome data and analysis results, it is not possible to determine whether over-dispersion or another distributional feature affected the study analysis.

Overall, the registry contains descriptive information about the endpoint and a named test, but not enough information to assess the analysis itself. The result, analysis population, missing-data handling, and relationship between the described sampling sites and the statistical unit are not reported in the registry record.

10. Confidence Intervals for Each Arm

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

R code and output

arm <- c("Healthy-experimental")
n   <- c(21)
m   <- c(10)
sp  <- c(0.005)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Healthy-experimental  21  10.000  0.005  9.998  10.002

11. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures, including Scalp Microbiome Composition and secondary outcomes named Scalp Health, Post-treatment 1 Right-sided Scalp Health, and Post-treatment 2 Right-sided Scalp Health. It does not report how these outcomes were prioritized beyond identifying the microbiome measure as primary, or whether any adjustment for multiple statistical tests was planned or performed. When several outcomes or comparisons are examined, general statistical practice recognizes that the chance of at least one apparently unusual result can increase. Whether that issue arose in this study cannot be assessed because no analyses are reported.

The record does not report a missing-data plan, the number of participants with observed primary endpoint measurements, or how incomplete follow-up was handled. It also does not report whether both scalp sides had usable samples for each participant. These gaps matter because the primary measure involves sampling on both sides and is scheduled at Day 14, while the arm description refers to a 2-week follow-up.

The registry lists an enrollment of 23 and reports 21 participants at risk in the adverse-event group. The relationship between these counts is not reported in the registry record. The counts do not establish how many people were included in an efficacy analysis, if any, and should not be used to infer the number with missing outcomes.

The analysis population is not reported in the registry record. There is no description of whether an analysis was intended to include all enrolled participants, only those who received the device, only those with completed follow-up, or another defined group. With no outcome analyses reported, it is also unclear whether the named primary outcome was assessed on all available samples or a subset.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

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

The registry's adverse-event summary reports 21 participants at risk in the Healthy-experimental group. It records 0 participants affected by serious adverse events, 0 affected by other adverse events, and 0 deaths. No top serious adverse-event terms are listed. These figures describe the entries in the registry safety summary and should not be extended to participants outside that reported group.

In general, a count of zero reported events means that no events of that category appear in the recorded summary; it does not establish that an event is impossible or that the intervention is risk-free. The registry does not report the method or period used for safety collection, whether all participants had complete safety follow-up, or whether events were assessed for relatedness to the device. The enrollment figure is 23, while the safety summary lists 21 at risk. The reason for that difference is not reported in the registry record.

The record is marked terminated, but does not state why the study ended or whether termination affected safety follow-up. The safety counts should therefore be read narrowly as registry-reported counts, not as a comprehensive characterization of risk or a comparison with another group. No comparator safety results are described.

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

The record establishes that a study was registered to examine standardized mechanical scalp cleansing and scalp microbiome composition, with a healthy experimental group followed over 2 weeks. It also gives the intended primary sampling approach and names a statistical test. These details clarify the research question and the planned measurement, but they do not provide evidence about the observed microbiome profile or any change following the intervention.

No primary outcome results or analyses are reported in the registry record. As a result, there is no numerical estimate to describe, no measure of statistical uncertainty, and no basis in the posted results for judging the direction or magnitude of a difference. The record's stated objective is not a result. Likewise, the study's termination status does not indicate what the outcome would have been or why the study ended.

The single-group design is also important to interpretation. In general, without a comparator, changes measured over time cannot readily be separated from changes that might occur for other reasons. The record does not describe baseline microbiome results or give the analysis details needed to evaluate change. In addition, the endpoint's reference to variation between treatment groups does not align clearly with the recorded single-group model; the intended comparison is not reported in the registry record.

The study's aim to characterize healthy scalp microbiome composition may be distinct from testing an intervention effect. The registry record does not report the observations needed to assess either aim. It therefore cannot establish a reference profile from the posted results, and it cannot establish an intervention effect. These are limits of what can be concluded from the registry record, not claims about data that may exist outside it.

The safety summary records no serious adverse events, other adverse events, or deaths in the group listed as at risk, but this does not substitute for outcome results or a controlled safety comparison. Overall, the registry supports a description of the study question, design entries, and limited safety counts. It does not support a conclusion about microbiome effects or clinical benefit.

14. Why This Trial Matters Statistically

This study is statistically notable because it combines a microbiome endpoint, measurements from two scalp sides, and a design recorded as single group. Each feature affects what an analysis can answer. Relative abundance describes the composition of a community, while measurements from two sites in one participant may be related. A sound interpretation depends on defining the unit of analysis and accounting for the structure of the observations. The registry describes the sampling sites but does not report how their measurements were analyzed.

The registry also illustrates why a clearly stated comparison is essential. The primary-outcome description refers to variation between treatment groups, but only a single-group model and one described arm are recorded. Without a clear definition of the groups or a control condition, readers cannot tell what contrast the stated test was intended to estimate. This is particularly important because a measured difference over time in one group is not equivalent to a controlled treatment effect.

The distinction between a research objective and a reported result is equally important. The objective names an intervention and a biological outcome, but the registry contains no reported analyses. Statistical interpretation requires estimates and their uncertainty, together with details about the analysis population and missing observations. In their absence, readers should treat the record as a description of the research question rather than evidence of an observed effect.

Finally, the study's stated interest in a healthy scalp microbiome points to a descriptive aim alongside the intervention question. A descriptive reference and an intervention comparison answer different questions and may require distinct summaries. The record does not report results for either aim. The mismatch between the recorded design and the comparison language reinforces the value of transparent, consistent descriptions of study structure, endpoints, and analysis plans.

15. Limitations

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

Several trial-specific limitations affect interpretation. The registry marks the study as terminated but does not report why it ended, whether follow-up was completed, or whether results were analyzed outside the registry. No primary outcome results are reported, so the intended microbiome assessment cannot be evaluated for magnitude, direction, or precision.

The design is listed as single group, with allocation NA and masking none. The record describes only a Healthy-experimental arm, yet the primary endpoint description refers to variation between treatment groups. The intended comparison structure is not reported in the registry record. The conditions list includes lichen planopilaris of the scalp and alopecia areata, while the arm description specifies participants without scalp or hair disease; how these entries relate is not explained.

The registry records enrollment of 23, while 21 participants are listed at risk in the safety summary. It does not reconcile those counts or state how many participants completed the 2-week follow-up or had primary outcome measurements. The analysis population, missing-data approach, handling of right- and left-sided samples, and treatment of repeated measurements are not reported.

The endpoint is described as relative abundance of genera at Day 14. The record does not report baseline values, absolute microbial counts, sample processing details beyond DNA extraction, or the actual statistical analysis. It names the Kruskal-Wallis test but does not explain how this method was to fit the single-group design. It also does not report whether multiple-outcome considerations were addressed.

Finally, the planning assumptions describe an illustration based on an observed effect and a two-arm allocation, rather than the recorded single-group study design. They do not provide the trial's own sample-size justification. These limitations concern the information in the registry record and do not establish whether additional information exists elsewhere.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Mechanical Intervention on the Scalp Microbiome: Setting the Stage for the Future Management of Cicatricial Alopecias — NCT06357169.
• Registry record last updated 2025-02-12; status last verified 2025-01.
• Results first posted 2025-02-12.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry describes a University of Minnesota study of mechanical scalp cleansing with the Venus Glow device and water, aimed at assessing scalp microbiome composition and characterizing healthy scalp. The study is listed as single group, unmasked, and terminated. Enrollment is recorded as 23. The described Healthy-experimental group was to be followed over 2 weeks.

The primary outcome is relative abundance of genera from scalp swab DNA extraction at the right and left mid-frontal scalp, assessed at Day 14. The record names a Kruskal-Wallis test but reports no analyses or primary outcome results. The relationship between the stated treatment-group comparison and the single-group design is not explained. The registry lists lichen planopilaris of the scalp and alopecia areata as conditions, while the described arm comprises healthy participants.

The safety summary lists 21 participants at risk, with 0 serious adverse events, 0 other adverse events, and 0 deaths. The relationship between the enrollment and safety counts is not reported. The reason for termination, missing-data handling, analysis population, and study-specific sample-size justification are not reported in the registry record.