Evaluation of the 755nm Alexandrite Laser for the Treatment of Scars: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of the 755nm Alexandrite Laser for the Treatment of Scars (NCT01811030), a na na study. The primary outcome is Photographic Evaluation of Scar Clearance.

2. Clinical Question

3. Trial Design

The registry record describes a completed, single-group device study of the 755nm Alexandrite Laser in people with scars. Enrollment is listed as 33. The record lists Cynosure, Inc. as sponsor, gives a start of 2012-06 and primary completion of 2014-05, and marks the study status as completed. Its phase is recorded as NA.

Allocation is recorded as NA, and the masking entry is NONE. No control arm is described. This matters for interpretation: outcomes in a single group can describe what was recorded among participants who received the intervention, but without a comparator they cannot establish how the same outcomes would have developed without it. Changes over time also cannot by themselves separate an intervention effect from other influences.

The registry lists the 755nm Alexandrite Laser as the intervention and describes it as a device. It does not report treatment settings, the treatment schedule, or a detailed protocol in the registry record for this analysis. Those details should not be inferred from the device name or the study aim.

The primary outcome was photographic evaluation of scar clearance at 1 Month Post Last Treatment. The record describes use of the ECCA Grading scale and 2D and 3D photography. Although the study lists two outcome measures, the primary endpoint result is not reported in the registry record, and there are no analyses listed. The record also notes loss to follow up, withdrawals, and a participant who cancelled multiple appointments and could not come in; the endpoint denominator and handling of missing observations are not reported.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Analysis population for the primary outcome, as defined in the registry: 7 subjects were lost to follow up. 3 subjects withdrew. 1 subject cancelled multiple appointments and could not come in.

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 Photographic Evaluation of Scar Clearance, measured over 1 Month Post Last Treatment.

The primary endpoint is titled Photographic Evaluation of Scar Clearance. It is a continuous measure reported as a score on a scale, with the mean and standard deviation specified as the summary format. The assessment was scheduled for 1 Month Post Last Treatment. The description says photographs were evaluated using the échelle d'évaluation clinique des cicatrices d'acné (ECCA) Grading scale with 2D and 3D photography.

The scale ranges from 0 to 4. A score of 0 represents 0% improvement or worse; 1 represents 1-25% improvement; 2 represents 26-50% improvement; 3 represents 51-74% improvement; and 4 represents >75% improvement. These categories provide an ordered description of photographic improvement, while the registry labels the endpoint summary as a mean. A mean can describe the average score, but does not show how scores are distributed across participants or categories.

Photographic assessment offers a structured way to rate visible scar change. However, the record does not report further details about image assessment procedures, who rated the photographs, or how ratings were reconciled. Most importantly, the primary endpoint’s observed mean and standard deviation are not reported in the registry record. The scale definition therefore explains what the measure was intended to capture, but cannot establish the amount of improvement observed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean and standard deviation describe?

For a continuous outcome, the mean is an average across the observations included in the analysis. The standard deviation describes how much those observations vary around the average. They answer different questions: the mean locates the group’s average score, while the standard deviation describes the spread of individual scores. Neither one alone shows every participant’s result or the shape of the score distribution.

In this study, the registry describes the primary endpoint as a mean score on a scale and specifies the standard deviation as its dispersion measure. The ECCA Grading scale has defined categories from 0 through 4. Reporting a mean can be convenient, but a mean of category-based ratings may not communicate how many observations fell in each category. A distribution of scores or category counts can add context. Those outcome values are not reported in the registry record, so this explanation is general rather than a description of observed results.

What would a confidence interval add?

A confidence interval is a statistical range expressing uncertainty around an estimate, under the assumptions of the analysis. A narrower interval indicates greater precision than a wider interval, while the interval’s location indicates which values are compatible with the data and method. It is not a guarantee that the true value lies within the interval, and it does not correct biases caused by study design or missing data.

No confidence interval for the primary endpoint is reported in the registry record. Without an estimate and its uncertainty, readers cannot judge how precisely the average score was estimated. A standard deviation is not a substitute for a confidence interval: the former describes variability across observations, whereas the latter describes uncertainty in an estimate.

Why does the single-group design matter?

A single-group study can record outcomes among people receiving an intervention, but it does not provide a concurrent control group for comparison. Without that comparison, an observed outcome or change cannot be attributed solely to the intervention. This is a design limitation, not a statement that the intervention has or lacks an effect. In this record, no primary score result is reported either, so there is no observed efficacy estimate to interpret.

Allocation is listed as NA, and masking as NONE. The record therefore does not describe random allocation or masking. The implications of these entries depend on the procedures and outcome-assessment details, which are not reported in the registry record. In general, masking can reduce the influence of expectations on assessments, especially when outcomes require judgment. The registry describes photographic grading, but does not report who performed ratings or whether assessors were masked.

What are planning sample sizes?

Sample-size illustrations based on an observed effect are planning calculations, not results from the study. They describe, under stated assumptions, how a future two-arm design might be planned to detect a chosen fraction of an effect. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Because the study is single group and the primary effect estimate is not reported in the registry record, such illustrations should not be read as the study’s design rationale or as evidence about its power. The sample-size justification and any original design calculations are not reported in the registry record.

Power is a property of a design under specified assumptions about the effect, variability, allocation, and analysis. It is not the probability that a particular finding is true. A retrospective calculation based on an observed effect, when available, is especially unsuitable as a measure of what the completed study was likely to detect. Planning figures are not observed power and cannot replace the missing endpoint estimate or its uncertainty.

Why can over-dispersion matter?

Over-dispersion is a general issue for outcomes whose variability is greater than a statistical model assumes. If a model understates variability, its uncertainty estimates can be too small and statistical evidence can appear more precise than it is. The endpoint described in this study is a continuous scale score summarized by a mean and standard deviation. The registry entries do not report a fitted model, an over-dispersion assessment, or model-based analyses. This concept therefore explains a general statistical concern and does not imply that over-dispersion occurred in this study.

What can the posted analyses establish?

The registry record lists two outcome measures and zero analyses. The primary outcome definition and adverse-event entries describe what was planned or recorded, but they do not supply an inferential analysis of the primary endpoint. The statistical analysis plan, adjustment methods, and any interim analyses are not reported in the registry record. Without those details and the endpoint results, it is not possible to evaluate the prespecified analysis, estimate uncertainty, or assess whether any reported conclusion follows from an analysis plan.

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("755nm Alexandrite Laser")
n   <- c(22)
m   <- c(1.82)
sp  <- c(0.73)
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  755nm Alexandrite Laser  22  1.820  0.730  1.496  2.144

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists two outcome measures, but the details available for this analysis describe the primary photographic scar-clearance endpoint only. The other outcome’s name, definition, timing, and result are not reported in the registry record. The number of listed outcome measures alone does not show whether multiple statistical tests were performed.

Multiplicity arises when several outcomes, time points, subgroups, or comparisons are tested. Repeated testing can increase the chance of finding an apparently notable result by chance. Common approaches include identifying a primary outcome in advance, adjusting inference for multiple tests, or clearly distinguishing confirmatory from exploratory analyses. The statistical plan and any multiplicity approach are not reported in the registry record. The record lists zero analyses, so no multiplicity-adjusted or unadjusted primary analysis is available to assess.

Missing observations are relevant because the record notes 7 subjects lost to follow up, 3 withdrawals, and 1 subject who cancelled multiple appointments and could not come in. These entries do not establish how many participants had a primary score available; the endpoint denominator is not reported. The record does not explain whether missingness was handled by excluding incomplete observations, using an imputation method, or applying another approach. No missing-data assumptions are reported.

The analysis population is also not reported in the registry record. It is therefore unclear which participants were included in any endpoint summary, and no analysis set should be assumed. With no endpoint values, analysis population, or missing-data method reported, the direction or extent of any missing-data influence cannot be evaluated.

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.

Most frequent non-serious adverse event terms

The serious adverse-event entries list 33 at risk and 0 affected for the 755nm Alexandrite Laser group. The deaths entry is 0. The record also lists 33 at risk and 17 under other adverse events. These are the registry’s reported counts; they do not establish whether the entries refer to unique participants or to event counts, and that distinction is not reported in the registry record.

No serious adverse-event terms are listed in the registry record for this analysis. A zero count in a registry entry means no events were recorded in that category in the posted results; it does not prove that an event is impossible or that every event was captured. The record does not describe the nature, severity, timing, or relatedness of the other adverse events listed. It also does not report further details about how adverse events were collected or monitored.

These figures describe the single intervention group. With no comparator group, they do not provide a comparative estimate of event risk. They should be read as the safety entries reported in the registry record, alongside the study’s design and the absence of further event detail, rather than as a complete characterization of safety.

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

The record establishes that a completed, single-group study evaluated a 755nm Alexandrite Laser for scars and specified photographic scar clearance as its primary endpoint. It also defines the ECCA Grading scale and the assessment time, 1 Month Post Last Treatment. These details explain the study question and how the primary measure was intended to be interpreted.

The record does not report the primary endpoint result. No observed mean, standard deviation, confidence interval, or analysis is available in the registry record for this analysis. Consequently, the posted information does not show how participants’ scar scores changed, how variable the scores were, or how precisely an average was estimated. The scale’s categories cannot be used as a substitute for the missing observations.

The single-group design also means there is no concurrent control comparison. This prevents a like-for-like estimate of what would have happened without the intervention. The study structure therefore cannot support a causal comparison, regardless of whether an outcome might otherwise be observed.

The adverse-event entries report 0 serious adverse events, 0 deaths, and 17 other adverse events, with 33 at risk in the listed group. These entries do not provide detailed descriptions of the other events, and they are not a comparison with another group. The record also reports follow-up losses, withdrawals, and a cancelled-appointment situation, without specifying the endpoint analysis population or missing-data handling.

In short, the record describes a study aim, design, endpoint, and selected safety counts, but not the primary outcome results needed to estimate scar clearance. It neither establishes nor rules out an effect. It also does not support a comparative safety conclusion. The distinction is between knowing how an outcome was defined and knowing what the observed data showed; the former is reported, while the latter is not.

14. Why This Trial Matters Statistically

This study illustrates an important distinction in clinical-trial interpretation: a clearly defined endpoint is not the same as a reported endpoint result. The registry describes a photographic scale, its scoring categories, the summary measure, and the assessment time. Those details make the intended measurement understandable, but without the observed mean, standard deviation, or analysis, they do not reveal the outcome among participants.

Its single-group structure is also statistically important. An intervention group can be described, but without a control group there is no direct estimate of the outcome that would have occurred under a different treatment or no intervention. This limits causal interpretation and makes the design different from a randomized comparison. The record lists allocation as NA and masking as NONE, reinforcing the need to interpret the study as a single-group evaluation rather than a controlled comparison.

The record further highlights why follow-up and analysis populations matter. It reports subjects lost to follow up, withdrawals, and a participant who could not attend after cancelling multiple appointments. Yet it does not report the endpoint denominator or how missing observations were handled. Without those details, readers cannot assess how much the available observations represent the enrolled group.

Finally, safety counts should be read in context. The registry lists serious adverse events, deaths, and other adverse events, but does not give further detail on the other events or provide a comparator. These entries are useful as a record of posted counts, not a complete comparative safety assessment. Together, the design and reporting features show why statistical interpretation depends not only on an endpoint definition, but also on observed results, uncertainty, analysis methods, and follow-up information.

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 central limitation is that the primary endpoint result is not reported in the registry record. The record defines photographic scar clearance as a mean score with standard deviation, but provides neither value. No endpoint estimate, uncertainty interval, or analysis is available to interpret.

The single-group design has no comparator, so it cannot provide a like-for-like control comparison. Allocation is recorded as NA and masking as NONE. The record does not provide further design details that would clarify procedures for outcome assessment or reduce concerns about assessment influence.

Follow-up information raises additional uncertainty. The record notes 7 subjects lost to follow up, 3 withdrawals, and 1 subject who cancelled multiple appointments and could not come in. It does not report the number with an observed primary endpoint, the analysis population, or the method used to handle missing data. The relationship among these follow-up entries is not specified, so they should not be combined into a single total.

The registry lists two outcome measures, but the other measure’s definition and results are not reported in the registry record for this analysis. It lists zero analyses, and the statistical analysis plan, any multiplicity procedures, and interim analyses are not reported in the registry record. The photographic rating procedures, including who assessed images, are also not described beyond the use of 2D and 3D photography and the ECCA scale.

Safety interpretation is limited by the absence of further descriptions for the 17 entries under other adverse events and by the lack of a comparator. These limitations mean the available entries describe the study record but do not yield a full assessment of outcome magnitude, precision, or comparative safety.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Evaluation of the 755nm Alexandrite Laser for the Treatment of Scars — NCT01811030.
• Registry record last updated 2021-01-14; status last verified 2020-12.
• Results first posted 2020-12-19.
• 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 record describes a completed, single-group device study of the 755nm Alexandrite Laser for scars, sponsored by Cynosure, Inc. Enrollment is listed as 33. The study began in 2012-06 and had primary completion in 2014-05. Allocation is recorded as NA and masking as NONE.

The primary endpoint was photographic evaluation of scar clearance using the ECCA Grading scale at 1 Month Post Last Treatment. The registry lists two outcome measures and zero analyses. The primary endpoint result, analysis population, and missing-data approach are not reported in the registry record. Follow-up notes include 7 subjects lost to follow up, 3 withdrawals, and 1 subject who cancelled multiple appointments and could not come in.

For the intervention group, the record lists 0 serious adverse events, 0 deaths, and 17 under other adverse events, with 33 at risk. The study has no comparator, and the available information does not support a comparative estimate of efficacy or safety.