Effect of Sclerotherapy on Fistulas and Sinus Tracts in Hidradenitis Suppurativa: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effect of Sclerotherapy on Fistulas and Sinus Tracts in Hidradenitis Suppurativa (NCT02805595), a na phase 2 study. The primary outcome is HS Physician Local Improvement Assessment - PAIN.

2. Clinical Question

3. Trial Design

This completed Phase 2 trial was registered as a single-center clinical trial evaluating sclerotherapy for fistulas and sinus tracts in adults with hidradenitis suppurativa. The intervention was 23.4% hypertonic saline injection. The record describes a single group and no randomized allocation; it also specifies no masking. It does not describe a parallel control arm, placebo, or other concurrent comparator. The registration lists enrollment of 21 participants.

The intervention description allows up to 0.4cc per treatment. If necessary, treatments could occur every two weeks, with no more than three treatments. The registry record does not report the actual treatment schedule received by participants, whether every participant received an injection, or the reasons for any variation in treatment exposure.

The primary outcome timeframe is baseline and Visit 4 (week 8). The registry record says 16 subjects completed the study and had percent score data for this comparison. It does not report a participant-flow account explaining the difference between total enrollment and the number with these data. The listed primary measure is HS Physician Local Improvement Assessment - PAIN. The wider physician assessment included overall clinical state in the treated area, pain, fluid leakage, erythema, tenderness, swelling, hardness, hotness, and odor. Characteristics were rated as improved, no change, or worsened, while the assessment scale is described as ranging from extremely worse to very much improved.

The registry lists eight secondary outcomes, including pain and stinging ratings, fistula length, quality of life, and patient assessments of local symptoms. It also reports 20 outcome measures overall. The specific timing and results for those secondary outcomes are not included in the registry record summarized by the posted information. The record gives a start date of 2016-08 and a primary completion date of 2022-11. Further details of the protocol, recruitment, and conduct 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

Analysis population for the primary outcome, as defined in the registry: 16 subjects completed the study and had percent score data for Baseline and Visit 4 comparison

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: Demographic data was measured for all pariticipants, outcome measures were measured for only 17 completed subjects who had data for all visits. Physician assessment were only reported for 16sujbects

6. Primary Endpoint

The registry lists the primary outcome as HS Physician Local Improvement Assessment - PAIN, measured over Baseline and Visit 4 (week 8).

The primary endpoint is titled HS Physician Local Improvement Assessment - PAIN. It concerns pain in the treated area, as assessed by a physician at baseline and Visit 4 (week 8). The assessment describes multiple clinical characteristics, with physicians classifying them as improved, no change, or worsened. Its broader scale is described as ranging from extremely worse to very much improved. The registry record identifies participants as the unit and describes the measure as a count of participants, while its outcome description refers to percent change in clinical efficacy.

Physician ratings provide a structured way to record clinical impressions rather than relying only on an unstructured narrative. A before-and-after measure can describe how participants’ assessed status changed over the stated period. However, the meaning of a change depends on the scoring and analysis rules, including how categories were summarized and how missing observations were handled. Those details are not reported in the registry record.

The primary endpoint could be used to describe the distribution of physician-rated pain changes among participants with measurements at both time points. It does not, by itself, separate treatment-related change from changes that might occur over time for other reasons. The posted information does not include category counts, a percent change estimate, or an uncertainty interval, so the size and precision of the primary outcome cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The design determines what kinds of conclusions the data can support. This trial is described as single-group, with no randomized allocation and no masking. Its primary comparison is between baseline and Visit 4 (week 8), rather than between separately assigned treatment and control groups. In general, a before-and-after comparison describes change within the measured group. It cannot isolate the intervention effect from all other influences as well as a randomized concurrent comparison can. That is a design limitation, not a statistical correction that can be resolved simply by choosing a different test.

What does the primary assessment measure?

The primary outcome is physician-assessed pain associated with the treated area. The assessment also includes other clinical characteristics of fistula severity. The record describes ratings of improved, no change, or worsened and a scale spanning extremely worse to very much improved. It calls the primary measure a count of participants and describes percent change in clinical efficacy, but it does not state how the category ratings were converted into the reported score or percentage. That scoring and summarization method is not reported in the registry record.

These details matter because different summaries answer different questions. A count in each category describes how many participants fell into each response group. A percentage change could instead summarize a change in a score, but its interpretation depends on the scale and formula. Those summaries should not be assumed to be interchangeable. The actual primary result and its calculation are not reported in the registry record.

How should a before-and-after comparison be understood?

For a paired comparison, the same participant contributes a baseline and a later measurement. In general, an analysis should preserve that pairing, because observations from one person are related rather than independent. The registry identifies the intended baseline and Visit 4 comparison but does not report the statistical method used, whether all participants had paired measurements, or how incomplete pairs were handled.

For categorical ratings such as improved, unchanged, or worsened, an analysis might describe the category distribution or assess paired changes. The appropriate method depends on the exact outcome definition, the number of categories, the analysis objective, and the available observations. The registry record does not state which approach, if any, was used. It would therefore be inappropriate to attribute a particular statistical test or model to this study.

What do uncertainty measures add?

In general, a point estimate gives a single summary of the observed data, while a confidence interval communicates uncertainty around that estimate under the chosen statistical method. A p-value, when used, measures how incompatible the data are with a specified null model under its assumptions; it does not measure the probability that a treatment works. Neither a p-value nor a confidence interval can substitute for a clear effect estimate and outcome definition. No primary outcome estimate, p-value, or confidence interval is reported in the registry record.

The data structure also affects uncertainty. If the analysis concerns paired participant-level changes, the variation in those within-person changes matters. If it instead summarizes categories, the counts in each category matter. The registry record does not provide the distribution of changes or category counts, so the precision of any primary estimate cannot be reconstructed from the information reported.

Why does the one-group design matter?

A control group can help distinguish changes associated with the intervention from changes that would have occurred without it. In this trial, the stated comparison is against baseline within a single group. General influences on before-and-after measurements can include natural fluctuation in symptoms, regression to the mean, concurrent care, participant expectations, and changes in how an assessment is performed. The registry does not report whether these issues were measured or addressed. The possibility of such influences should temper causal interpretations of any within-group change.

Masking is also relevant because physician ratings involve judgment. With no masking specified, the registry does not indicate that assessors were unaware of treatment exposure. This does not show that ratings were biased; it means that the record does not describe a measure designed to prevent assessor knowledge from influencing ratings.

How should planning illustrations be read?

Any sample-size estimates associated with the posted statistical material are planning illustrations based on an observed effect, not the trial’s original design justification and not observed power. The stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. These assumptions describe a hypothetical two-arm planning exercise. They do not match this trial’s single-group design, and they should not be mistaken for its actual enrollment plan or an analysis of the study’s power after completion.

In general, a planning calculation estimates the number of participants needed under specified assumptions to detect a chosen effect with a chosen probability. It is sensitive to the assumed effect size, variability, significance threshold, allocation, and statistical model. A calculation using the observed effect can be especially dependent on the uncertainty of that observed estimate. It cannot repair the lack of a concurrent comparison or establish that the trial had adequate power for its registered endpoint. The registry record does not report the trial’s own sample-size justification or statistical analysis plan.

Over-dispersion is a general concern when count data vary more than a statistical model expects. If present, a model that assumes less variability can understate uncertainty and produce intervals that are too narrow. Whether over-dispersion is relevant depends on the outcome and model. The registry record does not report a count model or provide information to assess over-dispersion, so it should not be assumed to have been present or addressed.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 20 outcome measures. The named secondary outcomes include stinging, pain, fistula length, Dermatology Life Quality Index, and patient local-improvement assessments of pain, fluid from the fistula, erythema, and tenderness. The primary measure is a physician local-improvement assessment of pain. Considering many outcomes can increase the chance of seeing an apparently notable result by chance if each is tested separately. In general, prespecified outcome hierarchy, adjustment procedures, or a focus on effect estimates and uncertainty can help readers interpret multiple comparisons. The statistical plan for multiplicity is not reported in the registry record.

The record describes 16 subjects as having percent score data for the baseline and Visit 4 primary comparison, compared with enrollment of 21. It does not give a participant flow account, the reasons for unavailable data, the amount of missingness for each outcome, or the method used to handle missing observations. It also does not report whether the primary analysis included all enrolled participants, only completers, or another analysis population. Those analysis-population details are not reported in the registry record.

Missing data can affect both the estimate and its precision, especially if availability of measurements is related to participants’ outcomes. This is a general statistical concern, not evidence that missingness followed any particular pattern in this study. Without reasons for missing data and a stated handling method, the direction or size of any resulting bias cannot be assessed.

The registry record does not report interim analyses, a prespecified statistical analysis plan, or a sample-size justification. It also does not provide the primary outcome counts or estimates needed to assess how the stated primary comparison was analyzed. These omissions limit the ability to evaluate whether reported analyses followed a prespecified approach.

11. 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.

The safety figures report zero serious adverse events among 17 participants at risk in the Hypertonic Saline group. The record also reports zero other adverse events among 17 at risk and zero deaths. No serious adverse event terms are listed. These figures describe what was recorded in the registry for the stated group and denominator.

A zero count does not establish that an event cannot occur or that the intervention is free of risk. It indicates that no events of the listed types were recorded in this group during the period and under the definitions used for reporting. The registry record does not provide further detail on the duration of safety follow-up, event ascertainment procedures, or whether all enrolled participants contributed to the safety denominator.

The safety denominator of 17 differs from the enrollment of 21 and from the 16 subjects with primary comparison data. The record does not explain these denominator differences, so they should not be treated as evidence of a particular reason for exclusion or incomplete follow-up. The posted safety counts are descriptive and do not provide a controlled comparison of adverse-event risk.

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

The registry record documents a completed, single-group Phase 2 study of 23.4% hypertonic saline injections for fistulas or sinus tracts in adults with hidradenitis suppurativa. It specifies a primary physician-assessed pain comparison from baseline to Visit 4 (week 8), and reports that 16 subjects completed the study and had percent score data for that comparison. These details describe the study question and available primary comparison data, but they do not report the outcome itself.

The primary result cannot be interpreted because the record does not give the number of participants rated improved, unchanged, or worsened, a percent change, or a statistical estimate. Nor does it report uncertainty around a primary effect. The direction, magnitude, and precision of the assessed change therefore cannot be determined from the information recorded.

Even if a before-and-after change were available, the single-group design would support a description of change over time, not a definitive attribution of that change to the injections. Without a concurrent control group, alternative explanations for change cannot be separated as reliably. This is a general limitation of uncontrolled before-and-after designs and does not establish that any particular alternative explanation occurred in this trial.

The record lists several secondary outcomes and 20 outcome measures overall, but the analysis plan for multiple outcomes and details of missing-data handling are not reported. Enrollment was 21, while 16 subjects had the stated primary comparison data and 17 participants were at risk in the safety listing. The record does not explain the different denominators. Zero serious adverse events, zero other adverse events, and zero deaths are reported for the stated safety group; those counts should be read as recorded observations, not as proof that risk is absent.

In short, the registry information describes an intervention, design, assessment schedule, and denominators, but it does not supply the primary efficacy result needed to judge the observed clinical change. It supports no conclusion that the intervention works or does not work.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of how design and reporting determine what can be learned from a clinical study. A single-group baseline-to-follow-up assessment can document changes in physician ratings over time. Without a concurrent comparison group, however, the analysis cannot cleanly distinguish changes associated with treatment from changes associated with other influences. The design therefore constrains causal interpretation before any statistical test is considered.

The primary measure is based on physician assessment of pain, with categories ranging from improvement to worsening. Clear reporting of the scoring rule, category counts, estimate, and uncertainty would make the outcome easier to interpret. The registry record identifies the outcome and its timing but does not include the result or enough detail to reconstruct the analysis. This illustrates why an endpoint description alone is not a substitute for outcome data and an analysis method.

The differing reported denominators also matter. Enrollment is 21, 16 subjects are described as having primary comparison data, and 17 participants are listed as at risk for safety reporting. Those values refer to different stated groups or purposes, and the record does not explain the differences. Transparent participant flow and analysis-population definitions would help readers understand which observations contribute to each result and whether missing data could affect interpretation.

Finally, the listing of 20 outcome measures raises a general need for clear prespecification and multiplicity reporting. A complete statistical analysis plan can identify the primary comparison, explain how secondary outcomes are treated, and define missing-data procedures before results are known. Those details are not reported in the registry record. The main statistical lesson is that conclusions depend on design, outcome definition, analysis transparency, and complete reporting—not just on whether a measure was named as primary.

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.

Several trial-specific limitations constrain interpretation. First, the study is single-group, with no randomized allocation or concurrent control group described. Its primary comparison is baseline versus Visit 4 (week 8), so a change over time cannot by itself establish that the intervention caused the change. The registry also specifies no masking, and does not describe whether physician assessors were blinded to treatment exposure.

Second, the primary outcome result is not reported in the registry record. Although the record identifies physician-assessed pain and says that 16 subjects had percent score data, it does not provide category counts, a percent change result, or an uncertainty estimate. The scoring and analysis details behind the description of percent change are also not reported.

Third, the reported denominators differ: enrollment was 21, 16 subjects had primary comparison data, and 17 participants were at risk in the safety listing. Participant flow, reasons for unavailable data, and outcome-specific missingness are not reported. The record does not state which analysis population was used or how missing observations were handled.

Fourth, 20 outcome measures are listed, but the multiplicity strategy, analysis plan, and trial-specific sample-size justification are not reported in the registry record. The intervention schedule allows treatment every two weeks if necessary and a maximum of three treatments, but actual exposure by participant is not described. Further eligibility, baseline characteristics, co-interventions, and the duration and methods of safety follow-up are also not reported. These gaps limit assessment of the results, reproducibility, and the applicability of the study findings.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Effect of Sclerotherapy on Fistulas and Sinus Tracts in Hidradenitis Suppurativa — NCT02805595.
• Registry record last updated 2025-03-28; status last verified 2025-03.
• Results first posted 2025-03-28.
• 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

NCT02805595 is a completed Phase 2, single-center, single-group trial of 23.4% hypertonic saline injections for fistulas or sinus tracts in adults with hidradenitis suppurativa. The registry lists enrollment of 21, a start date of 2016-08, and a primary completion date of 2022-11. Treatment could involve up to 0.4cc per session, every two weeks if necessary, with a maximum of three treatments.

The primary outcome is physician-assessed pain at baseline and Visit 4 (week 8). The record states that 16 subjects completed the study and had percent score data for this comparison, but does not report the primary outcome result or statistical analysis. It lists 20 outcome measures and describes zero serious adverse events, zero other adverse events, and zero deaths among 17 participants at risk. Details of missing-data handling, multiplicity, the analysis plan, and reasons for differing denominators are not reported in the registry record.