Comparative Study of Two Topical Anesthetics Prior to Fractional Nonablative Laser Treatment of the Face: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparative Study of Two Topical Anesthetics Prior to Fractional Nonablative Laser Treatment of the Face (NCT04523961), a randomized phase 2, phase 3 study. The primary outcome is Self-reported Pain After Laser Treatment.

2. Clinical Question

The study addresses a comparison between two topical anesthetic regimens in the setting of facial laser treatment. The question is about the pain scores recorded after treatment, rather than a general comparison of anesthetic use or a comparison of laser procedures. The posted primary outcome is a mean score, with lower values indicating lower reported pain and higher values indicating greater reported pain.

The split-face arrangement means the treatment conditions were assigned to halves of the face within participants, as described in the arm details. That arrangement makes the within-participant comparison important to understanding the analysis. The registry’s design classification also says “parallel”; the record does not explain how that classification relates to its split-face description or how the analysis accounted for the within-participant assignment.

3. Trial Design

The registry record describes a prospective, randomized, double-blinded study and lists both Phase 2 and Phase 3. Mayo Clinic is the sponsor. The study is marked completed, with an enrollment of 22. Its start date is 2021-01-08, and its primary completion date is 2025-02-19.

The protocol title identifies a split-face comparison. In the arm descriptions, a randomly assigned half of each participant’s face received one topical regimen and the other half received the other regimen. The lidocaine 23%/tetracaine 7% ointment was used without occlusion, while lidocaine 2.5%/prilocaine 2.5% cream was used with occlusion. Each application was described as lasting 60 minutes. The registry’s overall model field says parallel, but the record does not clarify the relation between that label and the split-face procedure.

The registry reports 22 observations for each treatment arm for the primary outcome. Because the intervention descriptions assign treatments to facial halves, those arm summaries should not automatically be read as two separate groups of participants. The record does not state whether the posted statistical analysis used a paired method, adjusted for the within-participant structure, or treated the arm results as independent.

The primary outcome was self-reported pain after laser treatment, approximately 60 minutes. The record also lists itching and burning after treatment as secondary outcomes. It does not report detailed eligibility criteria, baseline participant characteristics, the original sample-size justification, the planned analysis populations, or a full statistical analysis plan.

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 Self-reported Pain After Laser Treatment, measured over After laser treatment, approximately 60 minutes.

The primary endpoint is participants’ self-reported pain after laser treatment, assessed approximately 60 minutes after the procedure. Participants rated pain using a visual analog scale (VAS) from 0 to 10. A score of 0 means no pain, and a score of 10 means the worst pain. The posted summary uses the mean and standard deviation for each treatment arm.

A pain rating is a direct report of the experience the study set out to compare. The scale also preserves more gradation than a simple yes-or-no response: participants can report different levels of pain within the stated range. The mean gives a summary of the group’s reported scores, while the standard deviation describes the spread of scores around that mean. Neither statistic shows how every participant rated pain, and a group mean does not imply that all participants had a similar experience.

Interpretation depends on the direction of the scale: lower scores represent lower reported pain, and higher scores represent greater reported pain. The primary endpoint is a short-term, post-treatment rating, not a measure of pain at other times or of other effects of the regimens. The record does not explain whether the VAS was recorded separately for each side of the face, how the rating was elicited in relation to the two treated sides, or how any within-participant pairing was incorporated in the primary analysis.

7. Results Posted in the Registry

• 7.5 g Lidocaine 2.5%/ Prilocaine 2.5% Cream: mean 5.00 versus 4.50 on control; difference 0.50 (95% CI -0.65 to 1.65), standardized effect d = 0.26; z-test p = 0.395.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Number of Participants Who Self-reported Itching After Laser Treatment

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • 7.5 g Lidocaine 2.5%/ Prilocaine 2.5% Cream: 9.1% (2/22) versus 9.1% (2/22) on control; risk difference 0.0 percentage points (95% CI -17.0 to 17.0), risk ratio 1.00 (0.15–6.48); unadjusted two-proportion z-test p = 1.000.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between 7.5 g Lidocaine 2.5%/ Prilocaine 2.5% Cream and the control. The interval gives the range of effects that remain compatible with the data.

Number of Participants Who Self-reported Burning After Laser Treatment

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • 7.5 g Lidocaine 2.5%/ Prilocaine 2.5% Cream: 31.8% (7/22) versus 40.9% (9/22) on control; risk difference -9.1 percentage points (95% CI -37.4 to 19.2), risk ratio 0.78 (0.35–1.72); unadjusted two-proportion z-test p = 0.531.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between 7.5 g Lidocaine 2.5%/ Prilocaine 2.5% Cream and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes give a mixed descriptive picture: the itching counts are the same across the two treatment conditions, while burning was reported less often with the cream regimen than with the ointment regimen. The uncertainty around the secondary comparisons is broad, and the posted analyses do not establish a clear difference for either symptom. These outcomes do not provide a consistent additional signal that resolves the uncertain primary pain comparison.

Itching and burning are related to the treatment experience, but they are distinct outcomes from the VAS pain score. Their results should not be combined mentally into a single overall measure of tolerability, because the record does not report a combined endpoint or an analysis that integrates them with pain. Nor do the secondary results change the direction or precision of the primary mean-score comparison.

The registry reports more than one outcome and does not report a plan for adjusting secondary tests for multiplicity. When multiple outcomes are examined, unadjusted p-values do not account for the opportunity to observe a small p-value among several comparisons. That does not make the secondary observations useless; it means they are better viewed as exploratory descriptions than as independent confirmatory evidence.

The sample counts are limited, particularly for binary symptom outcomes, so estimates can be imprecise when events are uncommon. The record does not report participant-level paired symptom data or explain how the analysis dealt with the split-face design for these participant-level counts. Taken together, the secondary outcomes add context about reported symptoms but do not materially settle the interpretation of the primary endpoint.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Number of Participants Who Self-reported Itching After Laser Treatment
• Number of Participants Who Self-reported Burning After Laser Treatment

9. Statistical Interpretation

10. Statistical Methods Explained

What does the mean difference represent?

The primary outcome is continuous: it is a score on a 0-to-10 visual analog scale rather than a count of events. The mean difference compares the average scores between the two regimens. The recalculated contrast is defined as the cream regimen’s mean minus the ointment regimen’s mean. A positive value therefore points toward a higher average pain score with the cream, because higher scores indicate greater pain. The observed contrast is 0.5 points.

A mean difference describes the size and direction of an estimated contrast in the scale’s original units. It is not itself a probability, and it does not say how many participants had higher or lower scores. The registry does not report a threshold for what would constitute an important difference on this VAS, so the clinical importance of the observed contrast cannot be determined from the record alone.

What does the standard deviation describe?

The standard deviation summarizes variation in individual scores around an arm’s mean. The posted standard deviations are 1.9 for the ointment and 2.0 for the cream. A larger spread means scores are more dispersed around the mean; it does not describe uncertainty in the mean difference by itself. Standard deviations also do not reveal the distribution’s shape or the scores of individual participants.

General statistical context: the standard error describes the estimated sampling variability of a statistic, while a standard deviation describes variation among observations. In a split-face study, the relationship between the two sides’ scores within a participant can affect the precision of a treatment contrast. The registry record does not post the paired covariance or enough individual-level information to reproduce a paired estimate from the arm summaries.

How should the p-values be read?

The sponsor reports a two-sided t-test with p = 0.102. A separate, unadjusted recalculation from the posted summary statistics gives p = 0.395. A p-value measures how unusual data at least as incompatible with a specified null hypothesis would be under the assumptions of the test. It is not the probability that the null hypothesis is true, nor does it measure the size or importance of a treatment difference.

These two p-values differ. The registry record does not give the details needed to reconcile them, including whether the sponsor’s analysis incorporated the split-face pairing or other analysis choices. The recalculated result is therefore best understood as a simple calculation from the posted arm summaries, not as a replacement for the analysis conducted by the sponsor. The difference between the p-values is a reason to keep the methods distinction visible, not a basis for choosing whichever result appears more favorable.

General statistical context: a two-sided test considers departures in either direction. It does not prespecify that only a higher score or only a lower score matters. The record identifies the sponsor’s test as two-sided, but does not report the full set of assumptions or diagnostics for that test.

Why does the study structure matter?

The arm descriptions say that each participant’s face was divided into two randomly assigned treatment areas. This is a within-participant design description. Scores from two sides of one participant may be related because they come from the same person and treatment visit. A paired analysis can use that relationship; an analysis that treats observations as independent does not use it in the same way.

The record also labels the model as parallel. It does not explain this label alongside the split-face treatment descriptions. Nor does it say whether the sponsor’s t-test was paired, whether the primary analysis was based on side-specific VAS ratings, or how the posted arm sample sizes relate to the randomized facial halves. These missing details limit independent assessment of whether the test matches the design. The recalculation remains an unadjusted comparison based only on the posted summaries.

What do the secondary tests add?

Itching and burning are recorded as participant counts, rather than continuous scores. The sponsor reports Wilcoxon (Mann-Whitney) analyses for these outcomes, while the summary-based calculations include unadjusted comparisons of the reported counts. The registry record does not describe the rationale for the reported test or how it handled the split-face structure for outcomes recorded at the participant level.

General statistical context: binary outcomes can be summarized as counts or proportions, and a risk difference describes a difference between proportions. Sparse counts can make estimated differences imprecise. If several outcomes are tested, the chance of obtaining at least one apparently unusual result can increase unless the analysis plan addresses multiplicity. The registry record does not report a multiplicity adjustment, so secondary p-values should be treated cautiously.

The analysis plan, missing-data methods, and population definitions are not reported in the registry record. These details matter because the treatment effect estimate and its uncertainty depend not only on the endpoint and test name, but also on how incomplete observations, paired measurements, and analysis sets are handled.

11. Confidence Intervals and Precision

The recalculated mean difference in pain score is 0.5 points, with an uncertainty interval whose lower limit is -0.653 and upper limit is 1.653 when rounded to no more than three decimal places. The interval crosses zero. It therefore includes no mean difference as well as differences in either direction. Its span indicates that the posted summaries do not tightly pin down the contrast.

A confidence interval expresses a range of values compatible with the data under the calculation’s assumptions. In general, a wider interval indicates less precision, while a narrower interval indicates greater precision. The interval does not assign a probability to the true effect being inside its particular limits. The registry record does not identify the confidence level for the interval shown by the recalculation, so no confidence percentage is assigned.

The interval is based on the unadjusted summary-statistic recalculation. It does not incorporate unreported paired information from the split-face design. The sponsor’s analysis has a reported p-value but no reported effect estimate or confidence interval in the registry record. This means the sponsor’s test result cannot be used to assess the sponsor’s estimate’s precision from the posted record alone.

The secondary outcome summaries also have limited precision. The itching risk-difference interval spans zero. For burning, the recalculated risk difference is -0.091, with an interval extending from -0.374 to 0.192. These estimates are consistent with uncertainty in either direction, rather than a precisely established difference. The sparse counts and the missing detail about analysis methods further limit what can be inferred from these comparisons.

Precision is separate from whether a result crosses a significance threshold. A non-significant result can reflect a small effect, imprecision, or both. Here, the primary interval allows a range of possible contrasts and does not establish that the regimens have the same effect.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size illustrations are expressed as participants per arm, not as total events. They are planning illustrations based on the observed effect, rather than the trial’s original design calculation. The registry record does not report the original sample-size assumptions or justification.

The stated assumptions for these illustrations are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each planning row uses a specified fraction of the observed effect: 100%, 75%, or 50%. The columns for 80% and 90% power describe the number of participants per arm that the calculation estimates would be needed to have those respective chances of detecting the specified effect, under the listed assumptions and statistical model.

For the primary continuous outcome, planning for 100% of the observed effect gives 239 participants per arm for 80% power and 320 participants per arm for 90% power. Planning for 75% of the observed effect gives 425 participants per arm for 80% power and 569 participants per arm for 90% power. Planning for 50% of the observed effect gives 956 participants per arm for 80% power and 1,280 participants per arm for 90% power. The burning outcome has a separate illustration; no corresponding planning illustration is posted for itching.

Smaller effects require more participants to detect under the same assumptions, which is why the participant counts increase as the target fraction of the observed effect decreases. These estimates are planning aids based on observed effects in this study; they do not describe the study’s actual design or its ability to detect an effect after completion. This is not observed power.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 0.500; pooled standard deviation σ = 1.951.
2. n = 2 × (1.96 + 0.842)² × 1.951² / 0.500² = 238.9, rounded up to 239 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 0.5                      # observed difference in means
sigma <- 1.95064092031312                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(4523961)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 239 (80% power), 320 (90% power)
 75% of observed effect: n per arm = 425 (80% power), 569 (90% power)
 50% of observed effect: n per arm = 956 (80% power), 1,280 (90% power)
power.t.test: 239.9 
Simulated power at n = 239 per arm: 0.798 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

The sponsor reports a two-sided t-test with p = 0.102 for the primary comparison. The unadjusted recalculation from posted arm-level summary statistics gives a mean difference of 0.5 and p = 0.395. The sponsor’s registry analysis does not include a reported effect estimate or confidence interval, so the registry record does not allow a direct comparison of the sponsor’s estimated difference and its precision with the recalculated estimate.

The difference between the p-values may reflect differences in the analysis details or information used, but the registry record does not report enough detail to identify the reason. In particular, it does not state how the sponsor’s analysis handled the split-face assignment or whether it used paired observations. The recalculation cannot recover those details from means and standard deviations alone.

Both p-values are above 0.05, and neither establishes a clear difference. The recalculation is useful as a transparent, unadjusted check on the posted summaries, but it is not a substitute for the sponsor’s test. The registry record does not mark a discrepancy between the reported and recalculated analyses. Readers should distinguish the sponsor’s reported test from the simple summary-based recalculation rather than treating them as interchangeable results.

15. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary pain outcome and secondary itching and burning outcomes. It reports analyses for all three, but does not state whether a multiplicity procedure was planned or used. When multiple outcomes are tested, interpreting each unadjusted result as though it were the only test can overstate the strength of evidence. The secondary findings therefore warrant less weight than a prespecified primary analysis, especially when the analysis plan and hierarchy of hypotheses are not reported.

The registry record does not report how missing outcome values were handled, whether any participants or observations were excluded from an analysis, or how the analysis populations were defined. It also does not state whether the results followed an intention-to-treat approach, a per-protocol approach, or another population definition. No assumption about missingness or exclusions can be made from the posted summaries.

The design description raises another unresolved analysis issue. Arm details describe random assignment to halves of each participant’s face, whereas the model field says parallel. The registry does not report whether the statistical analysis accounted for pairing between facial sides, nor does it provide the within-participant correlation or paired differences. Those details would help assess whether the analysis reflects the randomization structure and how precisely the treatment contrast was estimated.

The original sample-size justification, any interim analyses, and a detailed statistical analysis plan are not reported in the registry record. Their absence does not establish that such procedures were or were not used. It limits the ability to assess whether the posted analyses match prespecified decisions or whether the study was designed around a particular clinically important difference. These omissions make the posted descriptive results interpretable, but leave important questions about analysis choices unresolved.

16. 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.

For each treatment group, the registry reports 22 participants at risk for serious adverse events and zero with a serious adverse event. It also reports zero deaths in each group. For other adverse events, the registry reports 22 participants at risk and zero affected in each treatment group.

These are the adverse-event figures posted in the registry record. They describe what was recorded for the stated groups and reporting categories; they do not establish that no unrecorded events occurred or that the regimens have no risks. The record does not provide event terms for serious adverse events because none are listed, nor does it give further detail about surveillance, severity definitions, or the period covered by the adverse-event reporting.

The itching and burning outcomes are separately posted symptom endpoints and should not be confused with the adverse-event counts. A symptom count in an outcome analysis does not change the adverse-event figures or establish how the registry categorized each symptom for safety reporting.

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

The results show that the mean self-reported pain score was 4.5 for lidocaine 23%/tetracaine 7% ointment and 5.0 for lidocaine 2.5%/prilocaine 2.5% cream. The summary-based mean difference is 0.5 points in the direction of a higher mean score with the cream regimen. The recalculated uncertainty interval crosses zero, and the sponsor-reported and recalculated p-values do not establish a statistically clear difference.

That finding does not demonstrate equivalence. A failure to establish a difference is not the same as showing that two treatments have identical effects or that any difference is small enough to be unimportant. The registry record does not report an equivalence or noninferiority margin, and the uncertainty interval allows differences in both directions. The results also do not provide a basis to declare one regimen superior.

The study concerns a particular setting: topical anesthesia before 1927 nm fractional thulium fiber laser treatment of the face for photodamage. It does not establish results for other procedures, populations, application conditions, or time points. Its primary measure is a short-term self-reported pain rating after treatment, not a broader measure of clinical outcome or long-term experience.

The record’s description of a split-face design is relevant to how the estimates should be interpreted. The posted arm summaries and the absence of paired-analysis details limit independent assessment of the treatment contrast and its precision. The results are best read as an uncertain comparison in this study, not as medical advice or a general conclusion about which topical anesthetic to use.

18. Why This Trial Matters Statistically

This trial illustrates why the design and the analysis need to be read together. The arm descriptions assign the two regimens to different halves of the face within participants, while the registry also labels the model as parallel. A within-participant design can carry information about how treatment responses compare within the same person, but that information depends on the analysis retaining and appropriately handling the pairing. The registry record does not explain whether this occurred.

It also illustrates the distinction between a test result and an estimate. The sponsor reports a p-value, while the posted arm means and standard deviations permit a simple unadjusted mean-difference calculation. The recalculation supplies an effect estimate and an uncertainty interval, but it cannot reproduce a paired analysis without the corresponding paired information. Statistical interpretation benefits from keeping those sources of information separate.

The observed difference is not enough on its own to establish a meaningful clinical contrast. The interval crosses zero, and the registry record does not state what difference on the VAS would matter to patients or clinicians. The sample-size illustrations show how planning requirements change with the effect targeted, but they are not evidence that the completed study had a particular probability of detecting an effect.

Finally, the outcome structure matters. Pain is the primary continuous endpoint, whereas itching and burning are secondary counts. Several unadjusted outcomes require more caution than a single prespecified primary comparison. Together, these features make the study useful for teaching how to separate descriptive results, uncertainty, design structure, and confirmatory claims.

19. 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 gives limited detail about eligibility criteria and participant characteristics, so it is not possible to assess how closely the enrolled participants represent other groups undergoing facial laser treatment. The enrollment listed is 22, and the posted summaries do not provide participant-level data or a detailed account of the distribution of pain scores.

The split-face treatment assignment makes the within-participant structure important, but the record does not say whether the primary test used paired data. The model field says parallel, while the arm descriptions say each participant’s face was divided between treatments. Without an explanation of this relationship, the exact analysis structure cannot be independently assessed. The recalculated contrast is unadjusted and based on arm summaries, so it does not recover information about paired responses.

The sponsor reports a test but no effect estimate or confidence interval for the primary outcome in the registry record. The summary-based recalculation gives an estimate, but its p-value differs from the sponsor’s reported p-value. The registry does not provide sufficient analysis details to explain that difference. The original sample-size justification, missing-data approach, analysis populations, interim analyses, and multiplicity plan are also not reported.

The primary outcome is a single post-treatment pain rating, approximately 60 minutes after treatment. The record does not explain whether each facial side was rated separately or how the rating was linked to the treatment area. It also does not report a threshold for a clinically important VAS difference. The itching and burning outcomes are secondary, and their unadjusted results should not be treated as definitive evidence. The adverse-event summary provides counts but little detail about collection and classification.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Comparative Study of Two Topical Anesthetics Prior to Fractional Nonablative Laser Treatment of the Face — NCT04523961.
• Registry record last updated 2026-02-20; status last verified 2026-02.
• Results first posted 2026-02-20.
• 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.

23. Record Summary

NCT04523961 is a completed randomized, double-blinded study sponsored by Mayo Clinic. The registry lists Phase 2 and Phase 3, enrollment of 22, and a prospective split-face comparison before 1927 nm fractional thulium fiber laser treatment of facial photodamage.

The primary endpoint was self-reported VAS pain after treatment, approximately 60 minutes, comparing lidocaine 23%/tetracaine 7% ointment without occlusion with lidocaine 2.5%/prilocaine 2.5% cream with occlusion. The posted mean scores were 4.5 and 5.0, respectively. The recalculated mean difference was 0.5, with an uncertainty interval crossing zero; the sponsor reported p = 0.102, while the unadjusted recalculation gave p = 0.395.

Itching and burning were secondary outcomes. No serious adverse events or deaths were reported in either treatment group. Important analysis details, including the handling of the split-face pairing and missing data, are not reported in the registry record.