Characterization of Transient Alterations of Cutaneous Sensory Nerve Function by Cryolipolysis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Characterization of Transient Alterations of Cutaneous Sensory Nerve Function by Cryolipolysis (NCT01673113), a randomized na study. The primary outcome is Vibration Detection Threshold (VDT).

2. Clinical Question

The study’s stated purpose was to characterize reversible changes in cutaneous sensory function after cryolipolysis using multiple sensory testing methods. The registry record identifies mechanical detection threshold as a secondary outcome, but gives no secondary outcome results in the information available. The primary comparison is therefore an early post-treatment measurement on the treated flank versus the same subject’s untreated flank. The record does not establish whether the reported group summaries account for the paired nature of that comparison.

3. Trial Design

NCT01673113 is listed as a completed, randomized, parallel-model study sponsored by Massachusetts General Hospital. Its phase is listed as NA. The record gives a start date of 2012-12 and a primary completion date of 2014-08. Enrollment was 11. The intervention was the Zeltiq CoolSculpting device, and the condition listed was adiposity.

The design description indicates that one flank was treated and the opposite flank remained untreated as an internal control for each subject. Subjects were randomized to have either the left or right flank treated. Thus, the treatment and control observations come from the same participants, rather than from two separately enrolled groups. The registry model is nevertheless recorded as parallel. The record does not explain this model designation or give further details of the randomization procedure, including how the left-versus-right assignment was generated or concealed.

Masking is listed as none. The record does not report whether those conducting sensory tests or analyzing the measurements were aware of treatment assignment. The protocol description says sensory testing was performed before and after the procedure, while the primary endpoint is specified for within 48-72 hours after treatment. It describes a computerized vibrometer and repeated measurements for the primary outcome, with values averaged over repeats.

The registry record does not report a sample-size justification, the intended statistical analysis plan, or a formal primary comparison. No analyses are listed. It also does not provide participant flow details, the number completing each assessment, or a description of any departures from the planned procedures. These omissions limit assessment of how closely the analyzed data follow the stated design.

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.

Before assignment: 11 subjects were randomized to have either left or right flank treated. The untreated flank served as the internal control for each subject.

Overall Study

Analysis population for the primary outcome, as defined in the registry: 11 subjects were randomized to have right or left flank treated with cryolipolysis. The untreated flank served as the internal control.

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.

Population: BMI of \<30 kg/m\^2

6. Primary Endpoint

The registry lists the primary outcome as Vibration Detection Threshold (VDT), measured over within 48-72 hours after treatment.

The primary endpoint is Vibration Detection Threshold (VDT), reported in (um/sec) as a mean with a 95% Confidence Interval. It measures the vibration magnitude at which a subject first detects vibration. According to the registry description, a computerized vibrometer with a 1cm2 contact probe was placed perpendicularly on the skin. The device gradually increased vibration magnitude until the subject pressed a stop button to indicate first perception. The test was repeated 8 times, and the values were averaged.

A sensory detection threshold is used to quantify the level of stimulus needed for a person to perceive a sensation. Comparing the treated flank with the untreated flank can help characterize local sensory function following treatment while accounting for differences between people, because both observations are from the same subject. This is a general explanation of the measure and design; the registry record does not specify a clinically important threshold or explain how a change in VDT should be interpreted clinically.

The endpoint was assessed within 48-72 hours after treatment. The registry record reports a treatment mean of 26.3 (um/sec), with a 95% Confidence Interval of 20.9 to 31.7, and a control mean of 19.0 (um/sec), with a 95% Confidence Interval of 13.6 to 24.4. These are separate group summaries. The registry record does not report the paired difference, its confidence interval, or a test of the treatment-control contrast.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: Vibration Detection Threshold measured in (um/sec). A continuous outcome can take values along a scale, rather than being a count of events or a yes/no status. The record summarizes this measure using a mean and 95% Confidence Interval. A mean is a measure of the center of observed values. A confidence interval communicates statistical uncertainty about an estimated quantity, given the analysis and its assumptions. It is not a range that guarantees where individual participant measurements fall.

The registry describes repeated measurement with a computerized vibrometer. A probe was placed on the skin, vibration magnitude increased gradually, and the subject indicated when vibration was first felt. The procedure was repeated 8 times, and the values were averaged. Averaging repeated measurements can yield a single summary for an assessment, but the record does not describe how repeat-level variability was handled beyond that averaging step.

The trial’s control was the untreated flank of each subject. This creates a within-subject or paired comparison: treatment and control measurements are linked because they come from the same person. A paired analysis focuses on the difference between the two measurements within each subject. It can account for the fact that a person’s measurements on both flanks may be more alike than measurements from different people. This is a general statistical explanation, not a claim about an analysis performed in this trial.

The posted results give separate means and confidence intervals for treatment and control, but no paired difference, paired confidence interval, or paired test. The record also does not say whether the reported confidence intervals were calculated with a paired method, or give enough detail to establish the methods used. The trial is labeled randomized and parallel in the registry, while its arm descriptions specify an untreated flank as an internal control. The record does not reconcile these descriptions. Accordingly, the summaries should not be treated as a reported test of the within-subject effect.

In general, the choice of statistical model should reflect the way observations were collected. Treating linked measurements as independent can misrepresent uncertainty because it ignores their relationship. Conversely, a paired analysis requires information about the within-subject differences or their variability. Those details are not reported in the registry record. No new contrast or uncertainty estimate can be recovered from the posted arm summaries alone without making assumptions about the relationship between measurements.

The record reports a mean of 26.3 (um/sec) for treatment and 19.0 (um/sec) for control. The respective 95% Confidence Intervals are 20.9 to 31.7 and 13.6 to 24.4. These intervals characterize uncertainty for the separately reported means, under the methods used to calculate them. They do not answer the inferential question of whether the paired measurements differ, nor do they show the size or precision of a paired difference. A direct contrast estimate and its uncertainty would be needed to describe that comparison statistically.

The primary assessment time is within 48-72 hours after treatment. Timing matters because sensory measurements may depend on when they are taken; results at one time point cannot, by themselves, describe a trajectory. The record’s stated goal concerns reversible sensory alteration, but no series of later measurements or corresponding results are reported in the posted outcomes. The listed primary assessment therefore supports interpretation only at the stated early time window.

The study also lists Mechanical Detection Threshold as a secondary outcome. The record identifies this outcome but does not report its numerical results or analysis. The number of outcome measures is 2, while the number of analyses listed is 0. The registry record does not provide an analysis plan describing tests, model adjustments, confidence-interval methods, or handling of repeated measurements.

Multiplicity is the general issue that arises when several outcomes or hypotheses are examined: the chance of at least one apparently notable result can increase when many tests are conducted. Whether and how to address multiplicity depends on the prespecified analysis plan and the intended interpretation of the outcomes. The record does not report a multiplicity procedure or enough analysis detail to assess one. Since no analysis results are listed, there are no reported p-values to interpret or compare.

Over-dispersion is a concern for count data when variability exceeds what a simple count model expects; it is not the relevant framework for this continuous threshold measure. More generally, the spread and dependence of observations matter for choosing a model and estimating uncertainty. The registry gives confidence intervals for arm means but not standard deviations or paired variability. The sample-size assumptions describe an illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. Actual sample-size illustration values are not reported in the registry record. Such planning illustrations are not observed power and do not establish the study’s original design justification, which is not reported.

There is no sponsor analysis listed and no recalculated comparative result to interpret. The posted arm summaries are not a substitute for a reported statistical analysis. Any conclusion about comparative statistical evidence would require the paired analysis details and results, which are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists Vibration Detection Threshold as the primary outcome and Mechanical Detection Threshold as a secondary outcome. It reports two outcome measures, but no analyses are listed. No multiplicity strategy, hierarchy of hypotheses, or distinction between confirmatory and exploratory analyses is reported in the registry record. In general, multiplicity matters when several outcomes or comparisons are tested because interpreting each test separately can overstate the strength of evidence. Without a stated analysis plan and reported tests, the effect of multiplicity cannot be assessed for this study.

The record gives no missing-data method, imputation approach, or sensitivity analysis. It does not report how many subjects completed the post-treatment assessment, whether all repeated measurements were available, or how missing observations were handled. The enrollment was 11, but enrollment alone does not establish the number included in each analysis. Arm summaries each list n 11.0; the record does not explain whether that count reflects all enrolled subjects or how any incomplete measurements would have been treated.

The record does not define an intention-to-treat, per-protocol, or other analysis population. It also does not describe exclusions from analysis or protocol deviations. Since each subject contributed a treated flank and an untreated flank, it would be important to know whether both observations were available for each included subject and how incomplete pairs were managed. That information is not reported in the registry record.

These omissions do not establish that data were missing or that multiplicity affected the results. They mean the posted information is insufficient to evaluate those aspects of the analysis. No statistical analysis results are listed, so the registry does not show how missingness or multiple outcomes were handled in any inferential procedure.

11. 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 registry reports 11 subjects at risk for serious adverse events in the cryolipolysis group and 0 subjects affected. For other adverse events, it likewise reports 11 at risk and 0 affected. No serious adverse-event terms are listed. Deaths are not reported in the registry record.

These figures describe the events recorded for this study and its listed reporting groups. A report of zero affected subjects means no events are recorded in the posted figures; it does not establish that an event is impossible or that there is no risk. The study enrolled 11 subjects, so the safety observations come from a small group. The registry record does not provide additional details on event definitions, collection procedures, duration of safety follow-up, or whether any events were considered related to the device.

The control was an untreated flank rather than a separate group of participants. The adverse-event summary is presented for the cryolipolysis group and does not give a separate adverse-event count for treated and untreated sides. These data should therefore be read as the registry’s reported safety counts, not as a quantified comparison between treatment and control. They do not support broader safety conclusions beyond the recorded study information.

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

The posted results show separate Vibration Detection Threshold means for the treated and untreated flanks, measured within 48-72 hours after treatment. The treatment mean is 26.3 (um/sec), with a 95% Confidence Interval of 20.9 to 31.7. The control mean is 19.0 (um/sec), with a 95% Confidence Interval of 13.6 to 24.4. These summaries describe the recorded values at the stated time point.

They do not report the paired difference between flanks, its uncertainty, or a statistical test. The separate mean estimates cannot be used by themselves to establish the magnitude or precision of the within-subject contrast. Nor do these results show whether an individual subject’s threshold changed from baseline. Although the study’s rationale discusses reversible sensory changes, the posted primary result alone does not establish reversibility or the course of sensation over time.

The registry record also does not report results for the listed secondary outcome, Mechanical Detection Threshold. It does not state a clinically important difference for VDT, so the numerical summaries cannot be classified as clinically important or unimportant using a threshold specified in the record. The record contains no analysis results from which to draw a formal inference about the comparison.

These findings are specific to the recorded endpoint, its assessment window, and the 11 enrolled subjects. The trial does not provide a basis for broad conclusions about other populations, other treatment conditions, or longer-term outcomes. The statistical information describes measurements and their reported uncertainty; it is not medical advice and does not establish whether the device should or should not be used.

13. Why This Trial Matters Statistically

This trial is statistically notable because treatment and control measurements were collected from opposite flanks of the same subjects. Such a design can make within-person comparison useful when measurements from the two sites are related. To interpret that comparison, however, the analysis needs to respect the pairing and report an estimate of the within-subject contrast with its uncertainty. The registry record provides separate arm means and confidence intervals, but no paired comparison.

The distinction between arm summaries and a comparative estimate is important. The treated mean is 26.3 (um/sec), and the control mean is 19.0 (um/sec), but the registry does not report a difference estimate or test. Separate confidence intervals answer questions about the means, not directly about the paired effect. Their presence does not resolve how precisely the treatment-control contrast is estimated.

The record also illustrates why design descriptions and analysis reporting need to align. It identifies the study as parallel while describing an untreated flank as an internal control for each subject. The registry does not clarify this distinction. Clear reporting of the assignment structure, paired observations, analysis population, and statistical model would help readers understand how the summaries relate to the study question.

Finally, the study’s stated interest in transient or reversible sensory alteration concerns changes over time, while the reported primary endpoint is a measurement within 48-72 hours after treatment. A single stated assessment window cannot characterize persistence or recovery on its own. The registry’s limited outcome reporting makes the study’s statistical contribution primarily descriptive: it records threshold summaries, but does not provide the comparative or longitudinal analyses needed to address the broader aims fully.

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 main limitation in interpreting the primary result is that the registry reports treatment and control means with separate confidence intervals, but no estimate or test for the within-subject comparison. Because each untreated flank served as the control for that subject, the relationship between paired measurements affects the uncertainty of a contrast. The record does not report paired variability or enough analytical detail to evaluate that uncertainty.

The enrolled sample was 11 subjects. This limits the amount of participant-level information represented in the summaries and makes the precision of estimates important to consider. The reported confidence intervals describe the means, but the record does not give individual values, standard deviations, or paired differences. The record also does not report participant characteristics beyond the listed condition, so applicability to other groups cannot be assessed from these details.

The primary endpoint is measured within 48-72 hours after treatment. The record does not provide later primary-outcome results that would show whether a change persists or resolves, despite the study’s stated interest in reversible sensory alteration. Baseline test procedures are mentioned, but baseline measurements and change-from-baseline estimates are not reported in the registry record.

Other limitations include the absence of reported results for the secondary Mechanical Detection Threshold outcome, no listed analyses, and no report of a multiplicity approach, missing-data handling, or analysis population. Masking is listed as none, and the record does not say whether outcome assessors or analysts were masked. It also does not explain the registry’s parallel-model label alongside the within-subject control description. These gaps constrain interpretation of the design and the posted results without establishing that any particular bias or missingness occurred.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Characterization of Transient Alterations of Cutaneous Sensory Nerve Function by Cryolipolysis — NCT01673113.
• Registry record last updated 2019-10-01; status last verified 2019-09.
• Results first posted 2017-04-10.
• 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.

18. Record Summary

NCT01673113, titled Characterization of Transient Alterations of Cutaneous Sensory Nerve Function by Cryolipolysis, is listed as completed and sponsored by Massachusetts General Hospital. The registry gives a start date of 2012-12, a primary completion date of 2014-08, and enrollment of 11. The study is described as randomized, with no masking reported and a parallel model.

One flank received a single Zeltiq CoolSculpting treatment, while the untreated flank served as an internal control. The primary endpoint was Vibration Detection Threshold within 48-72 hours after treatment. The registry reports a treatment mean of 26.3 (um/sec), with a 95% Confidence Interval of 20.9 to 31.7, and a control mean of 19.0 (um/sec), with a 95% Confidence Interval of 13.6 to 24.4. It does not report a paired comparison or statistical test. Mechanical Detection Threshold is listed as a secondary outcome, but its results are not reported in the registry record. No analyses are listed.