Study to Evaluate the Efficacy of Infliximab Induction Therapy for Patients With Palmoplantar Psoriasis (PPP)(Study P04555)(COMPLETED): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study to Evaluate the Efficacy of Infliximab Induction Therapy for Patients With Palmoplantar Psoriasis (PPP)(Study P04555)(COMPLETED) (NCT00686686), a non-randomized phase 3 study. The primary outcome is Number of Participants Who Achieve at Least 75% Improvement in Palmoplantar Psoriasis Activity Severity Index (PPPASI) After 3 Infusions..

2. Clinical Question

The study title and official title describe an evaluation of infliximab induction therapy for palmoplantar psoriasis, including pustular palmoplantar psoriasis. The registry classifies the study as Phase 3 and records its status as completed. Those labels describe the registered study; they do not supply the missing primary outcome result or establish what the treatment caused.

The intended regimen began with infusions at Weeks 0, 2, and 6. The record says participants who achieved at least 75% PPPASI improvement at Week 8 and then had deterioration of PPPASI score of 50% from Week 8 until Week 12 were to receive an additional infusion at Week 12. The registry does not report how many participants met those conditions or received that infusion. Thus, the central question can be described from the protocol summary, but the posted record does not provide the outcome data needed to answer it.

3. Trial Design

This was a Phase 3, open-label, non-randomized, single-group study. All participants were assigned to the infliximab intervention described in the registry; no randomized allocation or masking is recorded. The study status is completed. Enrollment is reported as 23, while the primary endpoint description says the per-protocol population included 17 subjects who completed the trial. The registry does not explain the difference between those population counts.

Infliximab was given intravenously at 5 mg/kg over a 2-hour period at Weeks 0, 2, and 6. The record describes a conditional Week 12 infusion: participants meeting the Week 8 response criterion and the subsequent deterioration criterion were to receive it. The primary endpoint was assessed at Week 8, after the three induction infusions, with change evaluated from baseline. Later outcomes listed in the record concern response, physician global assessment, response to a fourth infusion, and dermatology-related quality of life.

The registry gives a study start of 2007-12 and a primary completion of 2009-02. It does not report a planned sample-size justification, a detailed statistical analysis plan, interim analyses, or the rules used to handle missing outcome observations. The record also does not describe a control group against which changes could be contrasted. In a single-group open-label design, observed changes can be described within the treated group, but the design alone cannot separate treatment effects from other explanations for change over time.

Although the study is marked completed, the record contains no analysis entries and does not report the primary endpoint count. Completion status is not the same as availability of results. Accordingly, the design and scheduled assessments are identifiable, but the primary outcome findings and their statistical uncertainty are not.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Per Protocol population included the 17 subjects who completed the trial.

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 Number of Participants Who Achieve at Least 75% Improvement in Palmoplantar Psoriasis Activity Severity Index (PPPASI) After 3 Infusions., measured over Baseline and Week 8.

The primary endpoint counts participants who achieved at least 75% improvement in PPPASI after three infusions. The assessment compares the baseline PPPASI score with the score at Week 8. PPPASI summarizes disease signs and extent in a target palm and/or sole: extent, scales, erythema, erosions or fissures, induration, and pustules. The registry describes extent as scored from 0 to 6 and the other signs from 0 to 4, with a total score range of 0 to 26. A lower score represents improvement.

A threshold endpoint turns a continuous score change into a responder classification: each participant either meets the specified improvement threshold or does not. This can make the clinical meaning of a response criterion easier to communicate, while discarding information about how far individual scores changed and how close nonresponders came to the threshold. The threshold should therefore be interpreted as the study’s chosen definition of response, not as a complete description of every participant’s course.

The registry specifies the endpoint and identifies its per-protocol population as the 17 subjects who completed the trial, but does not report the number who reached the threshold. Without that result, the observed response frequency and its precision cannot be assessed from the registry record. The endpoint is useful for framing the primary question, but its definition by itself is not evidence about the outcome.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a binary primary endpoint: whether a participant meets the specified PPPASI improvement threshold by Week 8. A binary endpoint records a category rather than the full range of score changes. General: a response proportion is commonly estimated by dividing the number meeting the response definition by the number analyzed. A confidence interval can express the uncertainty around that estimate, with wider intervals generally indicating less precision. The registry record does not report the response count, an estimate, or a confidence interval, so none can be interpreted for this endpoint.

What does a confidence interval add?

General: a confidence interval gives a range of values compatible with the data under a statistical procedure and its assumptions. It is not a guarantee that the true value lies in the interval, and it does not correct weaknesses in the study design. In a single-group study, an interval around a response proportion would describe uncertainty about the observed group response, not the causal contrast with an untreated or alternative-treatment group. No interval is reported for the primary endpoint in the registry record.

What is the role of the per-protocol population?

The primary endpoint description states that the per-protocol population included the 17 subjects who completed the trial. General: a per-protocol analysis usually focuses on participants who meet specified study-completion or adherence conditions. The exact definition of those conditions, beyond completion, is not reported in the registry record. Results from a selected analysis population can differ from results based on everyone enrolled, particularly if inclusion depends on events related to outcomes. The record does not give the primary response count in this population, the reasons for exclusion from it, or an analysis of all enrolled participants.

Missing outcome data can affect both the denominator and the interpretation of a response estimate. General: statistical approaches may use explicit assumptions about participants with missing measurements, or may report sensitivity analyses under alternative assumptions. The registry does not report how missing data were defined or handled, and it does not describe sensitivity analyses. It is therefore not possible to assess how missing observations could influence the primary result.

Why does the single-group design matter?

General: random assignment to a comparator can help balance measured and unmeasured factors between groups, allowing a more direct estimate of a treatment contrast. This trial is registered as non-randomized and single-group, with no comparator arm recorded. Baseline-to-follow-up change in such a study can reflect multiple influences, including the course of the condition and other changes over time. Without a concurrent control group, those influences cannot be separated from the intervention by a randomized comparison. This is a design limitation, not a calculation problem.

The study is open-label and has no masking recorded. General: knowledge of treatment assignment can affect behavior, reporting, follow-up, or assessment, especially for outcomes involving judgment or self-report. The registry does not describe measures used to address these possibilities. That absence does not prove that bias occurred; it means the record does not provide enough detail to evaluate safeguards.

What can be said about multiplicity and analysis planning?

The record lists a primary outcome and secondary outcomes, but a statistical plan for controlling the chance of false-positive findings across multiple tests is not reported in the registry record. General: when several outcomes or comparisons are tested, multiplicity procedures can help manage the risk of interpreting a chance finding as persuasive evidence. Without a stated analysis plan and reported tests, the approach to multiplicity cannot be assessed. The registry records 0 analysis entries; that does not establish what analyses may have been conducted outside the registry.

The record’s sample-size assumptions describe planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They are explicitly planning illustrations, not the trial’s own design. The registry does not report a sample-size justification for this single-group study. No illustration values or observed effect are reported in the record used for this analysis, so no sample-size result can be interpreted. Such planning quantities, when available, would be hypothetical design calculations rather than observed power.

General: over-dispersion matters when outcome variability exceeds what a statistical model assumes; if ignored, standard errors and intervals can be misleading. The primary endpoint is a participant count, but the registry does not report a fitted model, a variance estimate, or an analysis method. It is therefore not possible to say whether over-dispersion was relevant to the sponsor’s analysis. More broadly, the statistical procedure, adjustment strategy, confidence level for reported estimates, and handling of protocol deviations are not reported in the registry record.

The key distinction is between an outcome definition, an analysis plan, and an observed result. The registry defines the primary response threshold and names the assessment time. It does not supply the response count or document an analysis method for that endpoint. Statistical interpretation must therefore stop at the design and measurement description rather than infer an effect from the endpoint definition or completion status.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Infliximab 5 mg/kg")
n      <- c(17)
events <- c(4)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Infliximab 5 mg/kg  17  4  23.5  6.8  49.9  9.6  47.3  9.7  47.6

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary endpoint and secondary outcomes covering moderate response, clear-to-minimal PGA score at Weeks 12 and 18, response to a fourth infusion, and DLQI. The record does not report a multiplicity strategy, such as a prespecified hierarchy or adjustment across outcomes. General: when several outcomes are examined, the chance of at least one apparently notable result can increase unless the analysis accounts for that multiplicity. Without a documented plan and reported results, the handling of multiple outcomes cannot be evaluated.

The primary endpoint description identifies a per-protocol population of 17 subjects who completed the trial, while enrollment is recorded as 23. The reasons for this population difference and the disposition of participants are not reported in the registry record. The record does not state whether the primary analysis included only participants with complete Week 8 data, how missing measurements were handled, or whether any sensitivity analyses were performed. These omissions prevent assessment of how the analysis population and missing observations might affect the estimated response.

The registry records 0 analysis entries. That means the registry record does not document statistical analysis entries for these outcomes; it does not establish that no analyses were performed. No statistical analysis plan, interim analysis information, or sample-size justification is reported in the registry record. The stated per-protocol population is the only explicit analysis-population detail for the primary endpoint. There is not enough information to determine whether analysis choices were prespecified or how deviations from any plan were addressed.

12. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: postular psoriasis (8.7%), hepatic enzyme increased (4.3%), liver function test abnormal (4.3%), psoriasis (4.3%).

The registry reports 23 participants at risk for the serious adverse event summary and 4 participants affected. For other adverse events, it reports 23 at risk and 8 affected. These are counts recorded for the infliximab group; the registry does not provide a comparator group for judging relative safety. A count describes how many participants were recorded with an event, but it does not describe event duration, severity beyond the serious classification, timing, or causal attribution.

The listed serious adverse event terms are Postular psoriasis at 8.7%, hepatic enzyme increased at 4.3%, liver function test abnormal at 4.3%, and psoriasis at 4.3%. These are registry-listed terms and percentages. The record does not explain whether participants could contribute to more than one term, so the entries should not be added or treated as mutually exclusive categories. Deaths are not reported in the registry record; the missing death value should not be read as evidence that no deaths occurred.

General: adverse event counts do not by themselves establish that an intervention caused an event. Interpretation usually depends on clinical review, timing, background risk, and comparison data. Those details are not reported, so the safety figures should be read as descriptive registry reports rather than causal estimates.

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

The registry record describes a completed study of intravenous infliximab induction therapy in palmoplantar psoriasis, including its pustular form. It specifies the infusion schedule, the Week 8 PPPASI threshold, and the population stated for the primary endpoint. It also records selected adverse event counts and terms. These details clarify what the study set out to assess and what safety information was registered.

The record does not report the primary endpoint count or an estimate of response. It therefore does not show how many participants achieved at least 75% PPPASI improvement, how uncertain that result was, or how responses were distributed across participants. The record also does not report outcome findings for the secondary endpoints. A completed status cannot substitute for missing results, and the endpoint definition cannot be treated as evidence that the criterion was met.

Even if the primary response result were available, the study’s single-group, open-label, non-randomized design would limit causal interpretation. A response observed between baseline and follow-up would describe change in the studied group, but without a concurrent randomized comparator it would not establish how much change was attributable to infliximab rather than other influences. The record does not offer a like-for-like control comparison.

The posted safety counts provide descriptive information, not a comparison of risk against another treatment. The serious adverse event terms and percentages do not, on their own, establish causation. The record does not report deaths, and that missing information must remain distinct from a report of zero deaths.

Accordingly, the most defensible reading is narrow: the registry documents the study design, endpoint definitions, analysis population description, and selected safety data, while leaving the primary efficacy result and its precision unavailable. The record does not support a conclusion about whether infliximab did or did not produce a particular level of response.

14. Why This Trial Matters Statistically

This trial is statistically informative as an example of why a clearly defined endpoint and a reported endpoint result are separate requirements for interpretation. The registry gives a specific PPPASI improvement threshold and assessment time, allowing readers to understand the intended response definition. But because the response count and estimate are not reported, the primary statistical question remains unanswered by the registry record.

The study also illustrates the interpretive limits of a single-group design. Within-group change can be described, but it does not provide the same evidence as a randomized treatment contrast. A comparator helps distinguish treatment-associated change from changes that might occur over time for other reasons. This study has no recorded comparator, so even a reported response rate would need to be understood as an observation in the treated group rather than a randomized estimate of comparative effect.

The population information matters as well. Enrollment is 23, while the primary endpoint description identifies a per-protocol population of 17 subjects who completed the trial. The registry does not explain this difference or report how missing data were handled. Readers therefore cannot judge whether the stated analysis population might affect the apparent response frequency.

Finally, the registry distinguishes outcome measures from analyses: it lists several secondary outcomes but records no analysis entries. It does not document the statistical plan, multiplicity handling, or sample-size justification. These gaps demonstrate why trial status, endpoint definitions, and outcome listings alone are not enough to evaluate statistical evidence. Transparent outcome reporting and analysis details are needed to assess both the magnitude of a result and its uncertainty.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The main limitation for interpretation is that the registry record does not report the primary response count or an estimate of its precision. It also does not report results for the listed secondary outcomes. Although the study is marked completed, the available record therefore does not answer its stated efficacy question.

The trial was single-group, non-randomized, and open-label, with no comparator recorded. This prevents a like-for-like treatment comparison and limits causal interpretation of any change from baseline. The record does not describe masking safeguards or other procedures that might reduce bias in outcome assessment.

Enrollment is reported as 23, whereas the primary endpoint description says the per-protocol population included 17 subjects who completed the trial. The reasons for that population difference, participant disposition, and the handling of missing outcome measurements are not reported in the registry record. The record does not provide enough detail to assess whether the analysis population was affected by incomplete follow-up or other exclusions.

The statistical analysis plan, multiplicity approach, interim analyses, and sample-size justification are not reported. The record includes assumptions for planning illustrations based on an observed effect, but does not provide values for interpreting those illustrations; those assumptions are not a substitute for the trial’s own design rationale. Safety information is also limited to the recorded counts and listed terms. The registry does not provide comparative safety data or report deaths. These limitations constrain interpretation of both efficacy and safety.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Study to Evaluate the Efficacy of Infliximab Induction Therapy for Patients With Palmoplantar Psoriasis (PPP)(Study P04555)(COMPLETED) — NCT00686686.
• Registry record last updated 2017-04-11; status last verified 2017-03.
• Results first posted 2011-02-23.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry describes a completed Phase 3, open-label, non-randomized, single-group study of intravenous infliximab for palmoplantar psoriasis, including the pustular form. Enrollment was 23. The regimen was 5 mg/kg over a 2-hour period at Weeks 0, 2, and 6, with a possible Week 12 infusion under specified conditions.

The primary endpoint was the number achieving at least 75% PPPASI improvement from baseline to Week 8. Its stated per-protocol population included 17 subjects who completed the trial. The primary response count and secondary outcome results are not reported in the registry record. The record reports 4 participants affected by serious adverse events and 8 by other adverse events, with 23 at risk in each category; deaths are not reported. No analysis entries or detailed statistical plan are recorded.