Silk'n HST Device Usability and Self Selection Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Silk'n HST Device Usability and Self Selection Study (NCT02919007), a na na study. The primary outcome is Usability Assessment.

2. Clinical Question

3. Trial Design

This was a completed, single-group device usability study of Silk'n HST. The registry lists an enrollment of 25 and identifies wrinkles as the condition. The intervention was Silk'n HST treatment, described as use on the periorbital areas according to the user's manual. Its stated measure was the ability to operate the device correctly according to that manual.

The record lists allocation as NA and masking as none. It also identifies the study as single group and states that it was not a randomized comparison. No control or comparator arm is described. Consequently, the design can address whether participants in the study group completed the specified usability tasks, but it does not provide a randomized between-group contrast.

The study start and primary completion are both listed as 2015-12, and the status is completed. The brief summary describes the purpose as testing Silk'n HST device usability. The official title also refers to self-selection and labeling comprehension, but the listed primary outcome is a usability assessment; results for self-selection or labeling comprehension are not reported in the registry record.

The record lists one outcome measure and zero analyses. It does not report a statistical analysis plan, sample-size justification, interim analyses, or a detailed protocol. These omissions mean that design details beyond the listed registry fields cannot be established from the record. The enrollment figure describes the study size, not the number of participants who completed the endpoint or had usable data; those counts 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

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 Usability Assessment, measured over 1 hour.

The primary endpoint is titled Usability Assessment, measured in participants, with a timeframe of 1 hour. Its description defines success as all subjects completing device-related tasks, including applying and operating the device without assistance within up to 1 hour and with minimal attempts to ask for assistance. This is a binary, participant-count outcome: a participant either meets the stated task-completion criterion or does not, though the record does not give individual outcomes or a total meeting the definition.

For a usability study, a task-completion endpoint can describe whether participants can follow the intended instructions and perform specified device tasks. In general, an operational definition is important because it makes clear what counts as successful use. The criterion combines unaided task completion, a time limit, and minimal requests for assistance. However, the record does not define how many requests qualify as minimal, how task completion was assessed, or how ambiguous performance was classified.

The endpoint is not a measure of change in wrinkles or another clinical outcome. It is a measure of device use under the stated task conditions. Although the study title mentions self-selection and labeling comprehension, the registered primary outcome description is focused on device-related tasks. The actual number of participants meeting the success definition is not reported in the registry record, so the endpoint's observed result cannot be characterized from the listed information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry classifies the primary outcome as binary and describes it as a count of participants. In general, a binary outcome places each participant into one of two categories, such as meeting or not meeting a prespecified criterion. A count then records how many participants fall into the category of interest. For this study, the stated success definition concerns all subjects completing the device tasks under the specified conditions. The record does not give the count meeting that definition, so no endpoint proportion or uncertainty estimate can be described.

In general, analysis of a binary outcome depends on clearly defined categories, a stated analysis population, and a consistent approach to participants whose outcome is unavailable or unclear. Those details matter because excluding participants or classifying incomplete assessments differently can change the interpretation of a count. The registry record does not report an analysis population, missing-data method, or rules for incomplete or ambiguous task performance. It also does not report individual participant outcomes.

The design is single group. In general, a single-group study can describe outcomes observed in its participants, but it does not by itself provide a controlled estimate of the difference attributable to an intervention. A randomized comparison would use a control group to help separate the intervention contrast from other explanations for a difference. This study has no listed comparator, and the registry explicitly warns that the arms are not a like-for-like control comparison. No treatment contrast should therefore be inferred.

The registry lists allocation as NA and masking as none. These entries indicate that the record does not describe a randomized allocation or masking. They do not establish whether any particular assessment safeguards were used; such details are not reported in the registry record. In general, masking can reduce the influence of expectations on some assessments, while usability tasks may also depend on how instructions and success criteria are standardized. The record does not give enough procedural detail to assess these considerations.

The record lists one outcome measure and zero analyses. In general, a registry analysis entry may provide estimates, comparisons, and statistical methods, while an outcome measure describes what was intended to be assessed. Here, the outcome definition is available, but no analysis is listed. The statistical plan, including any planned model or uncertainty calculation, is not reported in the registry record. It is therefore not possible to determine whether an analysis was planned but omitted from the record, or whether no formal analysis was conducted.

The sample-size assumptions described for planning illustrations are not the study's own design justification. They describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect stated as a fraction of the observed effect. The guidance distinguishes total events for time-to-event illustrations from participants per arm for other illustrations. In general, such illustrations show how a hypothetical design might be sized under chosen assumptions; they are not observed power and do not establish that a completed study was adequately powered. In this case, the actual study is single group, and an observed endpoint effect is not reported in the registry record. The study's own sample-size justification is not reported in the registry record.

In general, over-dispersion means that observed variation exceeds what a particular statistical model assumes. It can make standard errors too small if the model does not account for that extra variation. This concept is most relevant where outcomes arise from counts with variability beyond a simple model's assumptions. The listed primary endpoint is a participant count from a binary outcome, but no analysis is reported, so there is no fitted model to assess for over-dispersion.

In general, a p-value summarizes how incompatible observed data are with a specified null model, under the assumptions of the test. It does not measure the probability that a hypothesis is true or quantify the practical importance of an outcome. No p-value or hypothesis test is reported for the usability endpoint. Likewise, no confidence interval or adjusted estimate is listed. There is therefore no inferential result to interpret, and no basis for reconstructing an analysis from the endpoint definition alone.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Silk'n HST Treatment")
n      <- c(25)
events <- c(25)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Silk'n HST Treatment  25  25  100.0  86.3  100.0  86.7  100.0  86.8  99.9

11. Multiplicity, Missing Data and Analysis Populations

The record lists one outcome measure, titled Usability Assessment, and zero analyses. The registered primary endpoint is therefore identifiable, but no additional analyzed outcomes or results are listed. The official title refers to self-selection and labeling comprehension as well as device use; results for those topics are not reported in the registry record.

Multiplicity concerns arise when several outcomes, time points, or comparisons are tested, because the chance of at least one apparently notable finding can increase as the number of tests grows. In general, a prespecified analysis plan can explain which outcomes are primary and how multiple tests will be handled. The registry record does not report a multiplicity plan or adjustment. With no listed analyses, there is no reported set of tests from which to assess multiplicity in practice.

Missing-data handling and the analysis population are also not reported in the registry record. The enrollment is 25, but the record does not state how many participants completed the usability assessment, had an evaluable result, withdrew, or were excluded from analysis. It does not explain how incomplete task attempts or missing assessments were classified. These omissions limit assessment of whether the observed outcome, if reported, would represent all enrolled participants or a subset.

In general, missing-data assumptions matter because an analysis that excludes participants with unavailable outcomes may differ from one that treats them as unsuccessful or uses another justified method. No such method can be attributed to this study from the registry information. The absence of these details is distinct from the adverse-event counts, which are listed for 25 participants at risk in each adverse-event category.

12. Safety Results

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

Other (non-serious) adverse events

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

The adverse-event record lists 25 participants at risk for serious adverse events, with 0 affected. It separately lists 25 participants at risk for other adverse events, with 0 affected. These are the posted counts and should be read as registry entries for this study, not as a substitute for a detailed safety report.

The death count is not reported in the registry record. No top serious adverse event terms are listed. The record does not provide descriptions of how adverse events were collected, the duration of safety follow-up, event definitions, or whether any participants had incomplete safety reporting. Those details should not be inferred from the zero counts.

In general, an observed count of zero does not establish that an event is impossible or that risk is absent. The extent to which a zero count informs safety depends on factors such as the number of people assessed, follow-up, and completeness of reporting. The registry entries can be reported as recorded, but they do not establish a broader safety profile or answer the primary usability question.

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

This record documents a completed usability study of Silk'n HST, with 25 enrolled participants and a primary task-completion endpoint. The endpoint definition specifies completing device-related tasks without assistance within up to 1 hour and with minimal attempts to ask for assistance. These details clarify what the study intended to assess.

The record does not report the number of participants who met the task-completion criterion. It therefore does not show whether the study's stated success condition was achieved, nor does it provide an estimate of the frequency of successful completion or its precision. The record also lists zero analyses, so there is no reported statistical analysis to interpret.

The study's single-group design and lack of a comparator mean that it cannot provide a randomized comparison with another approach. In general, a usability result from one study group describes performance in that study's setting and among its participants; it does not by itself establish how performance would compare under another device or condition. The registry does not describe the participant characteristics or detailed testing procedures needed to judge how broadly any result might apply.

The title refers to self-selection and labeling comprehension, but the registered primary endpoint focuses on device tasks, and results for self-selection or labeling comprehension are not reported in the registry record. The listed adverse-event counts are 0 affected among 25 at risk for serious adverse events and 0 affected among 25 at risk for other adverse events. The death count is not reported in the registry record. Those safety entries do not fill the gap in the usability outcome.

In short, the record supports a description of the trial's purpose, design, enrollment, endpoint definition, and posted adverse-event counts. It does not support a conclusion about whether participants could use the device successfully, because that endpoint result is not reported. It also does not support a comparative efficacy claim, a broad safety conclusion, or a conclusion about outcomes not reported in the registry record.

14. Why This Trial Matters Statistically

Usability studies ask a distinct kind of question from trials designed to compare clinical outcomes. This study's primary endpoint is about whether participants could carry out specified device tasks under instructions from the user's manual. That focus makes the endpoint definition central: the time condition, lack of assistance, and minimal requests for help all shape what counts as successful use.

Statistically, clear criteria are useful because they make an outcome more reproducible and interpretable. In general, a binary endpoint is straightforward to summarize as a count, but its meaning still depends on the assessment rules, the participants included, and how missing or incomplete performance is treated. The registry describes the task criterion but does not report those additional analysis details or the observed count.

The study also illustrates why design and result reporting need to be read together. A single-group design can be appropriate for describing device-use performance, but it cannot estimate a randomized contrast with a control group. The record explicitly notes that this is not a randomized comparison. In addition, an endpoint definition without an endpoint result cannot answer whether the study's usability criterion was met.

The record's limited reporting is therefore statistically meaningful in itself: it shows which questions are answerable and which remain unresolved. Enrollment, study status, endpoint framing, and adverse-event counts are available, while the primary outcome result, analysis, and analysis population are not reported in the registry record. Separating these registry entries prevents a stated study aim from being mistaken for a demonstrated result.

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.

The most direct limitation is that the registry does not report the primary usability result. Although the success criterion is described, the number of participants who completed tasks according to that definition is not reported in the registry record. This prevents assessment of the endpoint's observed magnitude or precision.

The study has a single-group design and no listed comparator. The record states that it was not a randomized comparison, so it cannot support a controlled comparison of device use. The registry also does not report a detailed protocol, participant characteristics, or the task-assessment procedures beyond the endpoint description and reference to the user's manual. These omissions limit evaluation of how the assessment was conducted and how applicable the findings might be elsewhere.

The number of participants who completed the endpoint assessment and the analysis population are not reported in the registry record. Missing-data rules, handling of incomplete tasks, and reasons for any unavailable results are also not reported. The statistical analysis plan and the study's own sample-size justification are not reported, and the record lists zero analyses. Consequently, no inferential result can be checked or interpreted.

Although the official title mentions self-selection and labeling comprehension, results for those aspects are not reported in the registry record. Safety details are also limited: the record lists the adverse-event counts but does not report follow-up duration, event-collection procedures, or a death count. These limitations mean the registry information supports a narrow description of the study design and recorded counts, not a complete evaluation of usability or safety.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Silk'n HST Device Usability and Self Selection Study — NCT02919007.
• Registry record last updated 2018-10-31; status last verified 2016-09.
• Results first posted 2018-09-27.
• 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

NCT02919007 is a completed, single-group usability study sponsored by Home Skinovations Ltd. The listed enrollment is 25; the condition is wrinkles, and the intervention is Silk'n HST treatment on the periorbital areas according to the user's manual. The study start and primary completion are both listed as 2015-12.

The primary outcome is a participant-count usability assessment with a timeframe of 1 hour. Success is described as all subjects completing device-related tasks without assistance within up to 1 hour and with minimal attempts to ask for assistance. The record lists one outcome measure and zero analyses. The number meeting the endpoint definition is not reported in the registry record.

The study is not a randomized comparison and has no listed comparator group. The posted safety entries report 0 affected among 25 at risk for serious adverse events and 0 affected among 25 at risk for other adverse events. The death count is not reported in the registry record.