Observational Study of Tildrakizumab in Patients With Moderate to Severe Plaque Psoriasis in Routine Clinical Practice: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Observational Study of Tildrakizumab in Patients With Moderate to Severe Plaque Psoriasis in Routine Clinical Practice (NCT04203693), a registered phase not stated study. The primary outcome is Cohort 1: Absolute Psoriasis Area and Severity Index (PASI) Score at Week 48.

2. Clinical Question

3. Trial Design

This was an observational, non-interventional study of tildrakizumab in routine clinical practice for participants with moderate to severe plaque psoriasis. Its stated aims included assessing effectiveness, safety, and real-life prescribing and utilization patterns. The registry record lists Almirall, S.A. as sponsor and gives an enrollment of 331. The study started on 2019-10-30, reached primary completion on 2024-05-02, and is listed as completed.

The record separates participants into two cohorts. Cohort 1 consists of participants treated with tildrakizumab who had participated in prior tildrakizumab studies. Cohort 2 consists of participants newly prescribed tildrakizumab, with the prescription occurring independently of study enrollment. This distinction matters: prior study participation and new prescribing identify different treatment histories, not randomized study arms. The registry record does not state how participants were allocated, and it does not describe a like-for-like control comparison.

The primary outcome is Cohort 1's absolute PASI score at week 48, summarized as a mean with standard deviation. Other registered outcomes include dermatology-related quality of life measures at cohort-specific follow-up times, itch and pain visual analogue scale scores, and participant and physician satisfaction measures. The record lists 55 outcome measures but no analyses. Numerical results for the primary endpoint and the secondary outcomes are not reported in the registry record.

The safety listing distinguishes four cohort-and-dose groups: Cohort 1 at 100 mg and 200 mg, and Cohort 2 at 100 mg and 200 mg. Since treatment was observed in routine practice rather than assigned through randomization, differences in patient characteristics, prescribing, follow-up, or other care could contribute to differences between groups. The registry record does not report a statistical analysis plan, a sample-size justification, or details of interim analyses.

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: A total of 331 participants were enrolled in two cohorts. Cohort 1 included participants who completed tildrakizumab clinical trials (reSURFACE and non-reSURFACE Studies) and Cohort 2 included newly tildrakizumab prescribed participants.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: FAS population included all those participants in safety population that had at least some effectiveness data. Here, "Overall Number of Participants Analyzed" signifies participants who were evaluable for this outcome measure.

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: Safety population included all participants for whom it was known that they had at least one tildrakizumab dose during the study duration.

6. Primary Endpoint

The registry lists the primary outcome as Cohort 1: Absolute Psoriasis Area and Severity Index (PASI) Score at Week 48, measured over At Week 48.

The primary endpoint is the absolute Psoriasis Area and Severity Index score at week 48 for Cohort 1. PASI is a continuous measure of psoriasis extent and severity. It assesses four body regions: head, arms, trunk, and legs. For each region, the affected area is graded, and three clinical signs—erythema, induration, and desquamation—are assessed. Regional severity and area are combined using weights for the body regions to form an overall score. The scale ranges from 0, indicating no psoriasis on the body, to 72, indicating the most severe case; higher scores indicate more severe outcomes.

An absolute score describes the measured level at a specified time, rather than the change from an earlier measurement. A week 48 score can therefore describe participants' disease status at that follow-up point, but without baseline values or a reported change analysis it does not by itself quantify how much participants changed over time. In an observational study, the score also does not isolate the effect of treatment from the course of disease or other influences.

A mean and standard deviation are appropriate descriptive summaries for a continuous measure: the mean conveys the group's average score, while the standard deviation conveys how dispersed individual scores are around that average. The registry record identifies these summary measures but does not report their values or the number of participants analyzed for this endpoint. Thus, the endpoint's definition is available, but its numerical distribution at week 48 is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record describes a continuous primary endpoint summarized by a mean and standard deviation. A mean is the arithmetic average of measured scores in the analyzed group. The standard deviation describes spread around that average: a larger standard deviation indicates that individual scores tend to be more dispersed. These summaries answer different questions. The mean describes the central level, while the standard deviation describes variability among participants.

What does an absolute endpoint describe?

An absolute endpoint is the value measured at a specified follow-up time. In this study, the primary measure is the PASI score at week 48 for Cohort 1. It is distinct from a change-from-baseline endpoint, which compares a follow-up measure with an earlier value. Absolute and change measures can provide related but non-identical descriptions. The registry record names the absolute score as primary; it does not report a numerical week 48 score or a numerical change for this endpoint.

PASI combines assessments of affected area and clinical severity across body regions. This makes it a structured summary rather than a direct count of affected skin or a single sign. Its range and direction are specified in the record: scores run from 0 to 72, and higher scores indicate more severe outcomes. Interpreting a group mean requires the score definition, follow-up time, and analyzed population to be clear. The record supplies the definition but does not give the endpoint mean, standard deviation, or analyzed count.

How should precision be assessed?

A confidence interval is a general statistical way to express uncertainty around an estimate. It gives a range of values compatible with the data under the method's assumptions; a narrower interval indicates greater precision, while a wider interval indicates less precision. A confidence interval is not the range containing all individual participants' scores, and it does not remove bias from study design. No confidence interval for the primary endpoint is reported in the registry record.

Precision depends in part on the amount of information available, including how many participants have evaluable measurements and how variable those measurements are. The total enrollment of 331 does not establish the analyzed sample size for week 48. The record defines the endpoint population as participants in the safety population with at least some effectiveness data and says the analyzed number represents those evaluable for the endpoint. The actual evaluable number is not reported in the registry record.

What can an observational comparison establish?

In a randomized study, assignment can help balance measured and unmeasured characteristics across treatment groups on average. This study is described as observational and non-interventional; treatment was not assigned by the study. Cohort membership also reflects different treatment histories: prior tildrakizumab study participation in Cohort 1 and a newly occurring prescription in Cohort 2. Any difference in outcomes across these groups could reflect those histories, participant characteristics, clinical decisions, follow-up, or other factors, as well as treatment exposure. Without an appropriate design and analysis, a group contrast should not be read as a causal treatment effect.

Adjustment methods can sometimes account for measured differences between groups, but they cannot guarantee that all confounding is removed. The registry record reports zero analyses, so it does not identify an adjusted model or an unadjusted comparison. A statistical model, covariates, and assumptions are not reported in the registry record. No analysis method should be inferred from the endpoint's mean-and-standard-deviation summary specification.

What do the planning assumptions mean?

The registry record includes 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. The target effect is described as a stated fraction of the observed effect. These are planning assumptions, not evidence that the study was designed with those choices or that it enrolled the calculated numbers. The record does not report a sample-size justification for the observational study. Any sample-size figures in a planning illustration are hypothetical participants per arm for a specified power target, not observed power and not the number of participants who contributed outcome data.

Planning from an observed effect also depends on how that effect was estimated and on assumptions about future variability and design. It should not be confused with the precision of the observed estimate, nor does a planning calculation establish that an analysis was conducted. The registry record lists no analyses and does not report a primary endpoint estimate from which readers could assess the observed effect directly.

Why can over-dispersion matter?

As a general statistical concept, over-dispersion occurs when the variability in data is greater than a model assumes. If a model understates variability, standard errors can be too small and confidence intervals too narrow, giving a misleading impression of precision. Appropriate methods depend on the data type and model. The primary endpoint is continuous and specified as a mean with standard deviation; the registry record does not report a model or identify over-dispersion as an issue in the analyses.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Cohort 1: Tildrakizumab 100 mg", "Cohort 1: Tildrakizumab 200 mg")
n   <- c(55, 4)
m   <- c(1.13, 1.63)
sp  <- c(2.06, 1.45)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Cohort 1: Tildrakizumab 100 mg  55  1.130  2.060  0.573  1.687
CARM  Cohort 1: Tildrakizumab 200 mg  4  1.630  1.450  -0.677  3.937

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists 55 outcome measures spanning PASI, dermatology-related quality of life, itch, pain, and satisfaction. The follow-up times differ between cohorts for several outcomes. When many outcomes or time points are examined, the chance of at least one apparently notable finding can increase if each is tested separately. Multiplicity methods can address that issue, for example by adjusting the threshold for interpretation or by defining a hierarchy of outcomes. The registry record does not report whether any multiplicity adjustment, outcome hierarchy, or prespecified testing strategy was used.

The record lists zero analyses. It therefore does not report statistical tests, confidence intervals, model specifications, or an analysis plan for the outcomes. It also does not report whether the analyses were prespecified or conducted after data collection. These omissions limit assessment of how findings across the outcome set would be interpreted together.

Missing data are another important consideration in follow-up studies. If some participants lack measurements, the analyzed group may differ from the enrolled group. Statistical approaches can address missingness under particular assumptions, but those assumptions need to be described and considered alongside the amount and reasons for missing data. The registry record does not report missing-measure counts, reasons for missingness, imputation methods, sensitivity analyses, or follow-up completeness for the primary endpoint.

The primary endpoint population is described as the safety population with at least some effectiveness data; the number analyzed is those evaluable for the outcome. This definition does not reveal how many participants were evaluable at week 48 or whether all eligible participants had complete measurements. The numerical analyzed count and the handling of missing endpoint values are not reported in the registry record.

Nor does the registry record report a detailed analysis-population definition beyond that description, such as any additional exclusions or rules for handling deviations. These details matter for understanding which participants contribute to an estimate and whether the analysis population matches the study question.

12. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: cholangitis (33.3%), multiple sclerosis (33.3%), nervous system disorder (1.4%), syncope (1.4%), myocardial infarction (1.4%).

The safety listing separates serious adverse events, other adverse events, and deaths by cohort and dose group. For Cohort 1 at 100 mg, 73 participants were at risk for each adverse-event category, 5 were listed as affected by serious adverse events, 0 by other adverse events, and 1 death was reported. For Cohort 1 at 200 mg, 4 were at risk, 0 were listed with serious adverse events, 2 with other adverse events, and 0 deaths were reported.

For Cohort 2 at 100 mg, 251 participants were at risk, 12 were listed with serious adverse events, 21 with other adverse events, and 2 deaths were reported. For Cohort 2 at 200 mg, 3 were at risk, 2 were listed with serious adverse events, 2 with other adverse events, and 0 deaths were reported. These counts should be read with their group denominators in mind, particularly where the at-risk group is small. The registry record does not provide a randomized safety comparison, and the groups should not be treated as equivalent control arms.

The record lists serious-event terms with percentages: cholangitis and multiple sclerosis at 33.3% each; nervous system disorder, syncope, myocardial infarction, and death at 1.4% each. The basis for these percentages and further event-level details are not reported in the registry record. The figures describe reported events in the registry listing; they do not establish that tildrakizumab caused an event or provide a comparative estimate of risk.

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

The study's registry entry is useful for understanding its setting, cohorts, outcome definitions, and intended scope. It describes routine-practice observation of tildrakizumab in participants with moderate to severe plaque psoriasis, with one cohort drawn from participants who had taken part in prior tildrakizumab studies and another from newly prescribed participants. It also defines a week 48 PASI endpoint for Cohort 1 and lists additional outcomes related to quality of life, symptoms, and satisfaction.

However, the registry record does not report the numerical primary outcome. The week 48 mean PASI score, standard deviation, and number analyzed are not reported in the registry record. Numerical results for the listed secondary outcomes and inferential analyses are also not reported. Therefore, the posted record does not establish the size or precision of an observed change or outcome level.

Even if outcome estimates were available, the observational design would constrain causal interpretation. Participants were not randomly assigned by the study, and the cohorts have different treatment histories. Differences between their outcomes could reflect factors other than treatment. A follow-up score in a treated cohort is also not, by itself, a comparison against what would have happened without treatment.

The primary endpoint is an absolute measure at one follow-up time, not a treatment-effect estimate. It indicates how PASI is defined and what a reported group average would describe, but cannot alone distinguish treatment-associated change from other influences. The record does not report a baseline-to-follow-up analysis for the primary endpoint.

The safety counts describe events recorded within the listed groups. They are not a randomized comparison and should not be interpreted as proof of causation. Overall, the registry record documents a completed observational study and its outcome framework, but the absence of numerical effectiveness results and analyses prevents assessment of endpoint magnitude, statistical precision, or comparative treatment effects.

14. Why This Trial Matters Statistically

Routine clinical practice can differ from the conditions of a controlled experiment. Observational studies can describe how a treatment is prescribed and used, and can collect outcomes in settings that reflect clinical care. This study's stated interest in effectiveness, safety, prescribing, and utilization patterns makes its design relevant to questions about how tildrakizumab was used in practice among participants with moderate to severe plaque psoriasis.

Its two-cohort structure is statistically important. Participants previously involved in tildrakizumab studies and those newly prescribed the treatment have distinct treatment histories. This can make their outcomes informative as separate descriptions, but it does not make one cohort a valid control for the other. Recognizing the distinction prevents an observational contrast from being mistaken for a randomized comparison.

The endpoint definition also matters. PASI combines affected area and clinical severity across body regions, and the registry record makes clear that higher scores indicate more severe outcomes. Specifying the score, follow-up time, summary measure, and analysis population is necessary for interpreting a numerical result. Here, those definitions are recorded, but the endpoint's actual mean, standard deviation, and analyzed count are not reported.

The gap between enrollment and outcome-specific analysis is another general issue in longitudinal research. The registry record reports 331 enrolled participants but does not report the number evaluable for the primary endpoint. Readers therefore cannot determine the precision of the planned summary or judge how much follow-up information contributed to it. The record lists many outcomes and no analyses, which also leaves multiplicity and analysis choices unresolved.

Statistically, the study matters as an example of why design, outcome reporting, and analysis transparency must be considered together. The registry entry gives a useful framework for the questions the study intended to address, while its missing numerical outcome results prevent conclusions about the magnitude or precision of the primary endpoint.

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 study-specific limitation for interpretation is that the registry record does not report numerical results for the primary endpoint. Although it names the week 48 absolute PASI score for Cohort 1 and specifies mean and standard deviation summaries, it does not provide those values or the number analyzed. The listed 331 participants are the enrollment count, not a reported week 48 analysis count.

The observational design does not assign treatment, and the record does not describe a randomized comparator. Cohort 1 and Cohort 2 are defined by different treatment histories, so they cannot be assumed to be exchangeable. The registry record does not report an adjusted comparative analysis that could address measured differences, nor does it provide details of participant characteristics for evaluating possible confounding.

Outcome follow-up times are not identical across the cohorts for several secondary outcomes. The record lists different weeks for the quality-of-life measures and for itch, pain, and satisfaction outcomes. Without numerical results, analyzed counts, and missing-data information, it is not possible to assess the completeness or comparability of those measurements.

The record lists 55 outcome measures but zero analyses. It does not report a statistical analysis plan, multiplicity approach, missing-data strategy, or sample-size justification. The planning assumptions described in the record do not establish the study's original design rationale or the precision of any actual estimate.

Finally, safety counts are presented across groups of different sizes, including small 200 mg groups. The listing does not establish causality or provide a randomized risk comparison. Event details and the basis for the displayed serious-event percentages are not reported in the registry record. These limitations mean the registry entry is more informative about design and measurement than about effectiveness or comparative safety results.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Observational Study of Tildrakizumab in Patients With Moderate to Severe Plaque Psoriasis in Routine Clinical Practice — NCT04203693.
• Registry record last updated 2026-03-02; status last verified 2026-02.
• Results first posted 2026-03-02.
• 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

This completed observational, non-interventional study examined tildrakizumab use in routine clinical practice among participants with moderate to severe plaque psoriasis. The registry record lists enrollment of 331 participants and identifies two cohorts: participants with prior tildrakizumab study participation and participants newly prescribed tildrakizumab independently of study enrollment.

The primary endpoint is Cohort 1's absolute PASI score at week 48, summarized as a mean and standard deviation. The record lists 55 outcome measures and zero analyses. It does not report numerical primary or secondary outcome results, the primary endpoint analyzed count, missing-data handling, or a statistical analysis plan. Safety counts are listed by cohort and dose group, but do not constitute a randomized comparison. The registry record supports description of the study framework, not an estimate of treatment effect.