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 Study of Picosecond and Nanosecond Q-switched Lasers for Tattoo Removal (NCT01973166), a randomized na study. The primary outcome is Tattoo Clearing at 6 Weeks Post-final Laser Treatment for Each Treatment Arm as Assessed by Blinded Reviewers..
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01973166 |
| Phase | NA |
| Condition | Tattoo Removal |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 42 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Cutera Inc. |
| Results posted | Yes |
2. Clinical Question
Population
People receiving laser treatment for unwanted tattoos. The registry lists tattoo removal as the condition and records an enrollment of 42. It does not describe participant eligibility criteria, tattoo characteristics, or the population’s demographic profile.
Intervention
Picosecond Q-switched Nd:YAG laser treatment using 1064 nm and 532 nm wavelengths. The registry describes this as the investigational medical-grade device.
Comparator
Nanosecond Q-switched Nd:YAG laser treatment using 1064 nm and 532 nm wavelengths. The registry describes this as a marketed medical-grade device and the active control.
Primary question
At 6 weeks after the final laser treatment, how did blinded reviewers’ tattoo-clearing scores compare between the picosecond and nanosecond treatment arms? The registry also describes a comparison of treatment discomfort and says the study would compare side effects.
The primary outcome is a physician-rated score on a scale from 0 to 4, with higher scores representing better tattoo clearing. The registry lists mean scores and 95% confidence intervals for each arm. It does not post a statistical analysis of the between-arm contrast, so the arm-level summaries do not by themselves establish whether the treatments differed statistically.
The study is described as randomized, and its official title calls it a split-tattoo study. At the same time, the registry’s model field says parallel. The record does not clarify how tattoos or treatment assignments were paired or whether the statistical comparison accounted for a within-person or within-tattoo relationship. That design detail matters for interpreting a comparison, because observations from the same person or tattoo may not be independent.
3. Trial Design
The registry identifies this as a randomized study of two device interventions for tattoo removal. One arm received picosecond Q-switched Nd:YAG laser treatment, and the other received nanosecond Q-switched Nd:YAG laser treatment. Both descriptions specify wavelengths of 1064 nm and 532 nm. The study status is completed, and the registry lists enrollment of 42.
The official title describes a randomized, split-tattoo study, while the registry’s model field identifies the design as parallel. These descriptions leave the assignment unit and analysis structure unclear. The record does not say whether different portions of the same tattoo received different treatments, whether each participant received both treatments, or how any such pairing was handled in the analysis. The registry’s group-level results list 41 for each arm, but the reason for the difference between those arm figures and the enrollment figure is not reported in the registry record.
Masking is listed as none, but the primary outcome description says clearing was assessed by blinded reviewers. The record does not explain which study personnel were unmasked, how reviewers were blinded, or whether blinding was assessed. Randomization methods, allocation concealment, treatment schedules, number of treatment sessions, and follow-up beyond the primary assessment are not reported in the registry record.
The primary endpoint was assessed 6 weeks after the final laser treatment. The registry also lists a secondary outcome concerning subject discomfort or pain during treatment. Although the record lists two outcome measures, it does not post a result for the pain outcome. Details of the analysis plan, including the intended comparison, handling of the design, and procedures for missing observations, 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
| Stage | All Study Participants |
|---|---|
| STARTED | 42 |
| Treatment With Cutera Investigational Picosecond Q-Switched Nd:YAG Laser | 42 |
| Treatment With Comparator Nanosecond Q-switched Nd:YAG Laser | 42 |
| COMPLETED | 41 |
| NOT COMPLETED | 1 |
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 | Picosecond and Nanosecond Q-Switched Laser Treatment |
|---|---|---|
| Participants analysed | 42 | |
| Age, Continuous | years | 34 (20 to 51) |
| Sex: Female, Male: Female | Participants | 18 |
| Sex: Female, Male: Male | Participants | 24 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 10 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 16 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 16 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 1 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 |
| Race (NIH/OMB): White | Participants | 24 |
| Race (NIH/OMB): More than one race | Participants | 2 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 15 |
6. Primary Endpoint
The registry lists the primary outcome as Tattoo Clearing at 6 Weeks Post-final Laser Treatment for Each Treatment Arm as Assessed by Blinded Reviewers., measured over 6-weeks post-final treatment.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | score on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is tattoo clearing at 6 weeks after the final laser treatment, assessed by blinded reviewers using the Physician’s Global Assessment Scale. The score ranges from 0, meaning no change, to 4, meaning very significant clearing. Scores of 1, 2, and 3 represent mild, moderate, and significant clearing, respectively. Higher scores indicate better tattoo clearing. The scale’s category descriptions define mild clearing as 5–25%, moderate clearing as 26–50%, significant clearing as 51–75%, and very significant clearing as greater than 75%; no change is described as less than 5%.
A clinician-rated scale turns an assessment of tattoo appearance into an ordered outcome that can be summarized across participants or treatment units. Reporting a mean allows a broad comparison of average scores, while the category descriptions help readers understand what the scale’s values represent. However, the score is still a rating on a bounded scale. A mean does not show how many observations fell into each category or whether the ratings were concentrated near a particular score.
The registry reports the endpoint as a mean with a 95% confidence interval for each arm. It does not report the distribution of individual scores, the number in each clearing category, or a formal estimate and confidence interval for the between-arm contrast. The assessment time is tied to the final treatment, but the number and timing of treatments are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary results are mean clearing scores of 2.54 for picosecond treatment, with a 95% confidence interval from 2.13 to 2.94, and 2.17 for nanosecond treatment, with a 95% confidence interval from 1.77 to 2.57. The reported assessment took place 6 weeks after the final treatment. The score ranges from 0 to 4, and higher scores represent better tattoo clearing.
These are arm-specific summaries. They describe the mean score estimated in each arm and the uncertainty around each mean. They are not a direct estimate of the difference between treatments. The record does not post a confidence interval, p-value, or other inferential result for a between-arm comparison. The intervals for the two arm means overlap, but overlap or non-overlap of separate confidence intervals is not a substitute for a confidence interval or test of the contrast itself.
The means fall between the scale’s moderate and significant clearing categories, but that does not mean every tattoo or participant had clearing in those categories. A mean can combine observations with different scores, and the registry does not report the score distribution or category counts. The results therefore do not show the proportion of ratings in any individual clearing category.
The registry lists 41 observations in each arm for the primary outcome. It also lists an enrollment of 42. The record does not explain the difference, identify the analysis population, or describe missing primary outcome data. Because the official title calls the study split-tattoo and the model field says parallel, the relationship between the observations is also unclear. A valid comparison would need to reflect the assignment and analysis structure, but the analysis method is not reported in the registry record.
The registry lists zero serious adverse events and zero deaths in each arm, with 42 at risk in each. It also reports other adverse events affecting 42 in each arm. These counts are descriptive and do not establish comparative safety; the registry record does not give event terms or further detail about severity, timing, or attribution. The available results are therefore limited to the reported endpoint summaries and event counts, without a posted inferential comparison or a complete account of the analysis.
9. Statistical Methods Explained
What does a mean score summarize?
A mean is the arithmetic average of the values included in an analysis. For a rating scale, it compresses the scores into one summary for an arm. That can make group-level results easier to compare, but it hides variation among observations. The same mean can arise from different score distributions, so the mean alone cannot show whether ratings were similar across observations or spread across several scale categories.
Here the outcome is bounded between 0 and 4, with ordered categories describing increasing degrees of clearing. The registry reports a mean for each treatment arm. It does not report the individual scores, category frequencies, or a measure of spread other than confidence intervals around the means. Readers therefore cannot determine from the posted summaries how often particular clearing categories occurred.
What does a confidence interval mean?
A confidence interval describes uncertainty in an estimated quantity under the assumptions of the statistical method used to construct it. For repeated studies analyzed in the same way, intervals constructed at a stated confidence level would cover the underlying quantity at the stated rate in the long run, if the method’s assumptions hold. A 95% confidence interval is not a range that contains 95% of individual scores, and it does not mean there is a 95% probability that the true value lies inside this particular interval.
The registry reports a 95% confidence interval for each arm’s mean. Those intervals concern the arm means, not the difference between the arm means. To assess a treatment contrast, an analysis would generally estimate that contrast directly and report its uncertainty. The registry record does not post such an estimate or its confidence interval. Separate arm intervals can be informative about the precision of each mean, but they do not answer the comparative question on their own.
Why does the design structure matter?
Randomized comparisons rely on the allocation structure and on an analysis that reflects how observations were generated. In a parallel design, groups are compared according to their assigned arms. In a paired or split-unit design, measurements within the same person or tattoo may be related, and analysis may need to account for that relationship. Treating related observations as independent can misrepresent uncertainty. This is a general statistical issue, not a claim about the method used in this study.
The registry’s official title describes a split-tattoo study, while its model field lists a parallel design. It does not explain the unit of randomization, the unit counted in the arm results, or the method used to account for any pairing. Those details are important for interpreting the reported confidence intervals and for determining what comparison they represent. The analysis approach is not reported in the registry record.
What can be inferred from the posted comparison?
The posted results give arm-specific means and intervals, but no formal comparative result. A direct analysis could report an estimated contrast with a confidence interval and, if planned, a test result. Such an analysis should reflect the randomized structure and the scale’s properties. The registry record does not report the model, test, adjustment method, or assumptions used for the primary outcome. There is consequently no basis in the registry record for describing a statistically significant or non-significant difference between the treatments.
Even when a comparative estimate is available, statistical uncertainty and practical importance are different questions. A confidence interval can help show which effect sizes are compatible with the data under the analysis assumptions, while the meaning of those effects depends on clinical context and how the scale is interpreted. The registry does not report a threshold for a clinically important difference. No such threshold should be inferred from the arm means alone.
How should planning illustrations be read?
Sample-size illustrations based on an observed effect are planning exercises, not estimates of the probability that this completed study detected an effect. The registry describes its planning assumptions as a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. These are illustrative assumptions, not a reported account of the trial’s original design calculations. The registry record does not report the original sample-size justification or say that these assumptions governed the trial.
In general, sample-size calculations estimate how many observations would be needed under specified assumptions to reach a chosen power for a target effect. Their outputs depend on the assumed effect, variability, significance level, allocation, and analysis. When the effect used for planning is estimated from the same study’s observed results, the illustration should not be mistaken for an independent confirmation of the result. The record does not report observed power, and a planning illustration cannot replace a comparative estimate with its uncertainty.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists two outcome measures: the primary clearing assessment and a secondary measure concerning discomfort or pain during treatment. It posts the primary arm summaries but does not post results for the secondary outcome. The number of analyses recorded is zero. This does not establish what analyses were performed outside the registry; the analysis details are not reported in the registry record.
When a study assesses multiple outcomes or performs multiple comparisons, the chance of at least one apparently unusual result can increase if each is tested separately without an appropriate plan. Statistical approaches can address multiplicity, but the appropriate approach depends on the questions and analysis plan. The registry does not report a multiplicity strategy, a hierarchy of tests, or which outcomes were included in any confirmatory analysis. It is therefore not possible to determine whether or how multiplicity was handled.
The primary outcome arm results list 41 observations per arm, while enrollment is listed as 42. The record does not explain the difference or say whether observations were unavailable, excluded, or handled by another method. Missing-data methods, analysis populations, and reasons for any missing observations are not reported in the registry record. No conclusion about the effect of missing data can be drawn from the count difference alone.
The registry also leaves the relationship between the split-tattoo description and parallel model unclear. The number and unit of observations analyzed, and whether any dependence was accounted for, are not reported. Those omissions limit interpretation of both precision and the intended comparison.
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 |
|---|---|---|---|
| Picosecond Q-Switched Laser Treatment | 0 | 42 | 0.0% |
| Nanosecond Q-Switched Laser Treatment | 0 | 42 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Picosecond Q-Switched Laser Treatment | 0 of 42 |
| Nanosecond Q-Switched Laser Treatment | 0 of 42 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Picosecond Q-Switched Laser Treatment | 42 of 42 |
| Nanosecond Q-Switched Laser Treatment | 42 of 42 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Picosecond Q-Switched Laser Treatment | Nanosecond Q-Switched Laser Treatment |
|---|---|---|---|
| Edema | Skin and subcutaneous tissue disorders | 42 of 42 | 42 of 42 |
| Erythema | Skin and subcutaneous tissue disorders | 42 of 42 | 42 of 42 |
| Pinpoint Bleeding | Skin and subcutaneous tissue disorders | 32 of 42 | 20 of 42 |
The registry reports serious adverse-event counts separately for each treatment arm. For picosecond treatment, 0 serious adverse events are reported among 42 at risk; for nanosecond treatment, 0 are reported among 42 at risk. Deaths are reported as 0 in each arm. These are the posted counts for the registry’s serious-event category.
The record also reports other adverse events affecting 42 participants in each arm, among 42 at risk in each arm. The registry does not list the specific terms for these other events in the posted summary. It also does not provide enough detail to interpret their nature, severity, duration, relationship to treatment, or timing. The broad count should not be read as a description of one particular symptom or event.
Event counts are descriptive. Zero reported serious events does not establish that serious events cannot occur, and the registry does not provide a comparative statistical analysis of safety. The record does not explain how event categories were defined or whether counts represent people, treatment experiences, or another unit. Given the study’s split-tattoo title and parallel model field, the relationship between the event counts and the treatment assignment structure is not clarified in the registry record.
12. What the Result Does, and Does Not, Mean
The registry’s primary results describe average tattoo-clearing ratings at 6 weeks after the final treatment. The picosecond arm has a reported mean of 2.54, with a 95% confidence interval from 2.13 to 2.94. The nanosecond arm has a reported mean of 2.17, with a 95% confidence interval from 1.77 to 2.57. On the 0-to-4 scale, higher values represent better clearing. The score categories provide context for the rating, but the means do not reveal how observations were distributed across categories.
These results do not establish the size or statistical uncertainty of a between-treatment difference, because the registry does not report a direct contrast. The record also does not report a p-value for the primary comparison or a threshold for clinical importance. The arm means and their separate intervals should not be treated as proof that one treatment is superior, equivalent, or non-inferior to the other.
The completed registry record describes a randomized study but leaves important design and analysis details unclear. Its official title refers to a split-tattoo study, while the model field identifies a parallel design. The record does not explain the assignment unit or how the analysis addressed possible dependence. It also does not account for the difference between the enrollment figure and the primary outcome counts.
The safety summary records no serious adverse events or deaths in either arm and reports other adverse events in both arms. The specific other events and a comparative safety analysis are not reported. Accordingly, the posted counts are not a comprehensive account of the types or comparative rates of harms. Overall, the registry provides descriptive endpoint and event summaries, but not the analysis details needed for a full assessment of comparative effectiveness or safety.
13. Why This Trial Matters Statistically
This trial raises a central issue in clinical-trial interpretation: a randomized label alone does not show what quantity was compared or how uncertainty was calculated. The official title describes a split-tattoo design, whereas the registry model field says parallel. If treatment assignments or observations were paired within a tattoo or participant, that structure could affect the appropriate analysis. The record does not resolve the discrepancy, so readers cannot identify the intended unit of comparison from the posted descriptions alone.
The distinction between arm summaries and a treatment contrast is also important. Means with confidence intervals summarize each arm separately. They do not replace a directly estimated between-arm contrast with uncertainty. Without that comparison, readers cannot assess the precision of the treatment difference from the registry’s inferential results, because no such result is posted.
The endpoint itself is a bounded rating scale with ordered categories. A mean is compact, but may conceal the distribution of ratings and the frequency of each degree of clearing. Category counts or a fuller distribution could help readers understand how the average arose. Those details are not reported in the registry record.
Finally, the enrollment and analysis counts, missing-data handling, secondary outcome results, and analysis populations are not explained. These are not merely reporting details: they affect how confidently readers can connect the reported summaries to the randomized comparison. The record therefore illustrates why statistical interpretation requires attention to the estimand, measurement scale, design structure, and analysis—not only the numerical arm results.
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 registry record leaves the assignment and analysis structure ambiguous. The official title calls the study a split-tattoo study, while the model field says parallel. It does not identify the unit of randomization or explain whether observations within a participant or tattoo were paired. That uncertainty limits interpretation of the arm-level confidence intervals and what a treatment comparison should represent.
The primary outcome counts are 41 in each arm, while enrollment is 42. The registry does not explain this difference, report reasons for missing or excluded observations, or describe the analysis population. It is not possible to determine whether the reported summaries include all randomized participants or how unavailable outcomes were handled.
The record does not post a direct estimate of the difference in mean clearing scores, its confidence interval, or a p-value. It also does not report the distribution of scores or counts in the scale’s clearing categories. The secondary outcome concerning treatment discomfort is listed, but its results are not posted. A multiplicity plan, statistical analysis plan, and method for handling the bounded rating scale are not reported in the registry record.
Masking is listed as none, while the primary outcome is described as assessed by blinded reviewers. The record does not explain how reviewer blinding was implemented or maintained. It also does not report details such as treatment schedules, eligibility criteria, or longer-term outcomes. These limitations concern what can be established from the registry record; they do not establish that the study did not collect or analyze the information elsewhere.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study of Picosecond and Nanosecond Q-switched Lasers for Tattoo Removal — NCT01973166.
- Registry record last updated 2023-02-21; status last verified 2023-01.
- Results first posted 2023-02-21.
- 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 randomized device study comparing picosecond and nanosecond Q-switched Nd:YAG laser treatments for tattoo removal. Enrollment is listed as 42. The primary outcome is the mean Physician’s Global Assessment Scale score for tattoo clearing 6 weeks after the final treatment, assessed by blinded reviewers.
The picosecond arm mean is 2.54, with a 95% confidence interval from 2.13 to 2.94; the nanosecond arm mean is 2.17, with a 95% confidence interval from 1.77 to 2.57. A formal comparative result is not posted. The registry also lists a secondary pain outcome without posted results, and reports zero serious adverse events and zero deaths in both arms.
The record does not clarify the split-tattoo title versus parallel model description, the difference between enrollment and primary outcome counts, or the analysis and missing-data methods. These omissions limit interpretation of the treatment comparison.