This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Non-interventional Study of the Effect of Smoking Status of the Patient on the Success of Etanercept Therapy in Psoriasis (NCT02192164), a registered phase not stated study. The primary outcome is Change From Baseline in Psoriasis Assessment and Severity Index (PASI) Score at Week 24.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02192164 |
| Phase | Phase not stated |
| Condition | Plaque Psoriasis |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 126 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
People with plaque psoriasis who received etanercept are the population of interest. The primary endpoint population is described as all treated participants with available post-baseline documentation. The record reports an enrollment of 126, but does not report how many participants contributed to the primary endpoint or how many were smokers or non-smokers.
Intervention
This is not a treatment comparison in which an investigator assigned different therapies. The record describes a non-interventional study and identifies a smoking questionnaire as its behavioral intervention. The study concerns the relationship between participants’ smoking status and the success of etanercept therapy; it does not describe assigning participants to smoke or not smoke.
Comparator
The relevant comparison is between the registry’s Etanercept: Smokers and Etanercept: Non Smokers groups. These are smoking-status groups, not randomized treatment arms or a like-for-like control comparison. Allocation is not stated, and the registry record cautions that the groups are not a like-for-like control comparison.
Primary question
The primary question is how PASI score changed from baseline to Week 24 among treated participants with available post-baseline documentation, and how that change relates to smoking status. PASI measures psoriasis severity using both lesion severity and affected area. The registry record does not report the group-specific changes, their uncertainty, or a statistical comparison, so it does not establish the direction or precision of any association.
3. Trial Design
The record identifies this as a completed, non-interventional pilot observational study concerning smoking status and etanercept therapy in psoriasis. Its stated purpose is to describe the relationship between the smoking status of a person with psoriasis and the success of etanercept therapy. The condition listed is plaque psoriasis. The record reports enrollment of 126, a start date of 2013-11, and primary completion in 2016-05.
The smoking questionnaire is listed as a behavioral intervention. In this context, the questionnaire records information about smoking status; the record does not describe it as a treatment or as an assignment to a smoking condition. The two groups named in the safety record are Etanercept: Non Smokers and Etanercept: Smokers. The registry cautions that this is not a randomized comparison and that the groups are not a like-for-like control comparison. Allocation is not stated.
The primary outcome is change from baseline in PASI score at Week 24, expressed as a mean with standard deviation. The outcome description places baseline at Day 1 and identifies Week 24 as the follow-up point. Other registered outcomes include change from baseline in PASI at Week 12, PASI75 response at Week 12 and 24, and percent change from baseline in PASI at Week 12 and 24. The record lists seven outcome measures and two analyses, but does not report the complete analysis procedures or outcome estimates. It also does not report how the study justified enrollment, how many participants completed follow-up, or how smoking groups were defined beyond their labels.
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
| Stage | Etanercept |
|---|---|
| STARTED | 126 |
| Etanercept Treated Population | 112 |
| COMPLETED | 112 |
| NOT COMPLETED | 14 |
Reasons for not completing this period:
| Reason | Etanercept |
|---|---|
| Other | 8 |
| Withdrawal by Subject | 1 |
| Physician Decision | 4 |
| Did not meet the exclusion criteria | 1 |
Analysis population for the primary outcome, as defined in the registry: All treated participants with available post-baseline documentation.
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: All treated participants with available post-baseline documentation.
| Characteristic | Unit | Etanercept |
|---|---|---|
| Participants analysed | 112 | |
| Age, Continuous | years | 47.37 (SD 15.59) |
| Sex: Female, Male: Female | Participants | 45 |
| Sex: Female, Male: Male | Participants | 67 |
6. Primary Endpoint
The registry lists the primary outcome as Change From Baseline in Psoriasis Assessment and Severity Index (PASI) Score at Week 24, measured over Baseline (Day 1), Week 24.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | units on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is change from baseline in the Psoriasis Assessment and Severity Index (PASI) score at Week 24. It is a continuous outcome, and the registered summary measure is the mean with standard deviation. The endpoint population is all treated participants with available post-baseline documentation. Baseline is identified as Day 1.
PASI combines assessments of the severity of skin lesions and the area affected. The registry describes a score ranging from 0, meaning no disease, to 72, meaning maximal disease; higher scores represent greater psoriasis severity. The body is divided into head and neck, arms, trunk, and legs. For each region, the assessment incorporates the estimated area involved and clinical signs of erythema, induration, and scaling, then weights and combines regional scores.
A change score is used to describe how the measured severity differs between baseline and follow-up. In general, a continuous change endpoint retains information about the magnitude of an individual’s measured score change, rather than reducing the result to a response category. However, the registry record does not report the Week 24 mean change, its standard deviation, the number contributing data, or a comparison between smoking-status groups. The endpoint definition alone therefore explains what was intended to be measured, not what the observed data showed.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registered primary outcome is clearly identified: mean change from baseline in PASI score at Week 24, with standard deviation as the dispersion measure. The registry describes the scoring scale and specifies an endpoint population of treated participants with available post-baseline documentation. These details establish the measurement and intended population, but they are not outcome results.
The registry record does not report the mean change for either smoking-status group, the group-specific standard deviations, the number of participants contributing to the endpoint, or an estimated between-group contrast. It also does not report a confidence interval, a p-value, or a conclusion about the primary outcome. Consequently, the size, direction, and precision of any difference in PASI change cannot be assessed from the reported information. It is not possible to tell whether the smokers’ group had a larger, smaller, or similar mean change than the non-smokers’ group.
Even if group estimates were available, an observed difference in this non-interventional comparison would describe an association between recorded smoking status and PASI change, not an effect caused by smoking status. The registry explicitly says the comparison is not randomized and the groups are not a like-for-like control comparison. Differences between groups could therefore reflect characteristics or circumstances not balanced by assignment; the registry record does not report an adjustment strategy that would address this concern.
The listed secondary outcomes concern PASI change at Week 12, PASI75 responses at Week 12 and 24, and percent change in PASI at Week 12 and 24. Their registration does not establish that their findings were reported. The record also lists seven outcome measures and two analyses without supplying enough detail to determine the analysis population, model, handling of repeated observations, or multiplicity approach.
The record’s safety fields list zero participants at risk and zero affected for serious and other adverse events in each smoking-status group; deaths are recorded as null. These fields should be read as registry entries, not as evidence that all participants were assessed or that no events occurred. The record does not explain what the zero and null entries mean in relation to safety ascertainment.
Overall, the posted record supports a description of the research question, outcome definition, and design limitations. It does not provide the numerical results needed to judge the observed PASI changes or the precision of a smoking-status comparison.
9. Statistical Methods Explained
The registry identifies the primary outcome as a mean change in a continuous PASI score, with standard deviation used to describe dispersion. The summary identifies two analyses, but does not report their methods or results. The following explanations are general statistical context; they should not be mistaken for methods confirmed in the registry record.
What does a mean change describe?
For a continuous measure, a mean change summarizes the average difference between each participant’s follow-up score and baseline score within the analysis population. It can communicate the overall direction and typical magnitude of change, while individual participants may have changes that differ from the average. The standard deviation describes how dispersed participant values are around the mean. It is not the same as the uncertainty in the estimated mean: a confidence interval, when reported, expresses uncertainty about an estimate under the assumptions of the analysis.
The registry’s primary outcome description names the mean and standard deviation but gives no numerical estimates. It does not report a confidence interval or another measure of uncertainty for the primary outcome. Thus, the endpoint’s summary plan can be described, but its precision cannot be evaluated from the registry record.
Why does the comparison design matter?
In a randomized comparison, assignment is intended to make groups comparable on average, apart from the assigned treatment. This study is described as non-interventional, and the registry cautions that its groups are not a like-for-like control comparison. Participants’ smoking status was not described as randomized, and allocation is not stated. A difference between the named groups would therefore be observational. General statistical adjustment can sometimes account for measured differences, but it cannot guarantee that all relevant differences were measured or handled correctly. The registry record does not report whether an adjusted analysis was used, which covariates it might include, or how any model was specified.
The record also does not state whether the primary comparison was a difference between group mean changes, a model-based contrast, or another estimand. An estimand is the precise quantity an analysis seeks to estimate, including the population, outcome, and handling of events or missing measurements. Without the analysis description, the registered endpoint should not be conflated with a fully specified statistical estimand.
How should dispersion and uncertainty be read?
Standard deviation describes variation among observed scores or changes. General statistical interpretation distinguishes that variation from uncertainty about a group mean or a difference between groups. A confidence interval, if available, would give a range of values compatible with the data and stated modeling assumptions; a wider interval generally indicates less precision. No such interval is reported for the primary outcome. The record also does not provide the group sample sizes or observed standard deviations needed to understand the precision of the estimates.
General methods for continuous outcomes may use models that account for baseline values, covariates, or repeated measurements. Whether any such method was used is not reported in the registry record. Nor is the handling of distributions, influential observations, or departures from model assumptions described. For example, if a model’s residual variation differs across groups, a method that assumes equal variation may give misleading uncertainty estimates. This is general methodological context, not a claim about these data.
What do the sample-size illustrations represent?
The record describes planning illustrations based on the observed effect, using a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation. The illustration considers an effect defined as a stated fraction of the observed effect. For non-time-to-event outcomes, the stated convention is participants per arm; time-to-event illustrations use a total number of events. The record does not give numerical illustration values in the information available for this analysis.
Such calculations are planning illustrations, not observed power and not evidence that the study was designed around those assumptions. The registry does not report its own sample-size justification or design assumptions. Since the endpoint estimates are also not reported, the numerical implications of the illustrations cannot be assessed. A planning calculation based on an observed effect cannot establish that a result is reliable or that a future study will reproduce it.
What remains unknown about the analysis?
The registry record does not report a full statistical analysis plan, the test or model used for either listed analysis, whether analyses were adjusted, or the method for calculating standard errors or confidence intervals. It does not report interim analyses. It also does not specify how the seven outcomes relate to the two analyses, which outcome was designated for each analysis, or whether any results were selected for reporting. These omissions limit reproducibility and prevent a detailed assessment of how the primary comparison was conducted.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists seven outcome measures and two analyses. It identifies the Week 24 change from baseline in PASI score as the primary outcome and lists additional PASI outcomes at Week 12 and Week 24. The record does not explain how the outcomes were assigned to the analyses, whether any outcomes were exploratory, or whether the analysis plan specified a hierarchy of hypotheses.
Multiplicity is a general concern when several outcomes, time points, or statistical comparisons are examined. If many tests are conducted, the chance of at least one apparently noteworthy result can increase. Statistical approaches may control or describe this issue, but whether any such approach was used is not reported in the registry record. No p-values or outcome estimates are reported, so the practical impact of multiplicity cannot be evaluated.
The primary endpoint population is described as all treated participants with available post-baseline documentation. That wording indicates that endpoint inclusion depends on having post-baseline documentation, but the record does not report the number with such documentation or the amount and pattern of missing data. It does not state how missing measurements were handled, whether participants with incomplete follow-up were excluded, or whether any sensitivity analyses assessed the impact of missingness. The reasons for missing data are not reported.
The registry record also does not explain how smoking status was classified when questionnaire information was incomplete or whether status could change during follow-up. It does not report the number analyzed in each group or whether all enrolled participants were treated. The treatment of participants who lacked a Week 24 PASI measurement is therefore unclear. Without these details, readers cannot determine whether the analysis population represents all enrolled participants, all treated participants, or only a subset with observed follow-up data.
11. What the Result Does, and Does Not, Mean
The registry record documents a question about the relationship between smoking status and etanercept therapy in psoriasis, an observational study design, and a primary endpoint based on PASI change from baseline to Week 24. It also provides a description of PASI and identifies the intended primary endpoint population. These registry entries clarify what the study set out to describe.
The record does not report the primary outcome values or a statistical comparison between smokers and non-smokers. It therefore does not show whether PASI change differed between the groups, how large any difference might have been, or how precisely it was estimated. It also does not provide a result that can be interpreted as evidence for or against an association. The presence of an outcome definition is not evidence of a particular outcome.
General interpretation of observational comparisons requires caution. Because smoking status was not assigned at random and the registry warns that the groups are not a like-for-like control comparison, an observed association, if reported elsewhere, would not by itself establish that smoking status caused a difference in PASI change. Other differences between groups could be relevant. The registry does not report sufficient analytical details to assess whether such differences were measured or addressed.
The listed secondary outcomes indicate additional registered measurements, not findings. Likewise, safety fields with zero entries and null death entries do not, without information about ascertainment and completeness, establish that no events occurred. The record does not explain these entries.
Accordingly, the appropriate conclusion from the registry record is limited: it identifies the study’s purpose, design, groups, and outcome definitions, while leaving the numerical efficacy and safety findings unavailable. It cannot support a claim that etanercept did or did not work, nor a causal claim about smoking status. Any interpretation of treatment or smoking effects would require complete results and a careful assessment of the study’s non-randomized design and analysis.
12. Why This Trial Matters Statistically
This study is statistically interesting because it asks about an association using a clinically defined continuous outcome while comparing groups formed by smoking status. PASI combines both affected body area and lesion severity, so its change score captures more information than a simple yes-or-no response classification. The registry also lists PASI75 response outcomes, which represent a different type of summary from mean change.
The non-interventional design is central to interpretation. The registry explicitly cautions that the groups are not a like-for-like control comparison, and allocation is not stated. This makes the question different from a randomized treatment comparison: the statistical challenge is not only to summarize observed change, but also to understand how group comparability affects interpretation. The record does not report whether methods were used to address measured differences between groups.
The record’s endpoint definition and population description are useful, but the absence of group results, participant counts for analysis, and uncertainty estimates means that readers cannot evaluate the magnitude or precision of the observed data. A clear outcome definition is necessary for interpretation, but it does not replace reporting estimates and their uncertainty.
The study also illustrates why registration of several outcomes does not settle how results should be interpreted. With seven outcome measures and two analyses listed, readers would need the analysis plan and results to understand which comparisons were conducted and how multiplicity was handled. Those details are not reported in the registry record. The statistical importance lies in the distinction between a documented research question and evidence that can be quantitatively assessed: the record describes the former, but does not provide the results needed for the latter.
13. 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 trial-specific limitation is that the registry record does not report the primary endpoint results. There are no group-specific mean changes, standard deviations, analyzed participant counts, between-group estimate, confidence interval, or p-value. The direction, size, and precision of the comparison therefore remain unknown.
The study is observational, and the registry states that the groups are not a like-for-like control comparison. Allocation is not stated. This limits causal interpretation of any association between smoking status and PASI change. The record does not provide adjustment methods or enough detail to assess whether differences between groups were considered in analysis.
The record reports enrollment of 126 but does not state the number treated, the number in each smoking-status group, or the number with available post-baseline documentation. The primary endpoint population excludes, by description, participants without such documentation, but the extent and handling of missing data are not reported. Smoking-status definitions and any handling of incomplete questionnaire responses are also not described.
Although seven outcome measures and two analyses are listed, the registry does not provide the complete statistical plan, the mapping of outcomes to analyses, or a multiplicity approach. It does not report interim analyses or the study’s sample-size justification. The listed planning illustrations are not a substitute for those design details and are not observed power.
Finally, the safety fields show zero entries for participants at risk and affected in the two groups, with deaths recorded as null, but the record does not explain completeness or interpretation of these fields. These entries cannot resolve the absence of a fuller safety account.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: Non-interventional Study of the Effect of Smoking Status of the Patient on the Success of Etanercept Therapy in Psoriasis — NCT02192164.
- Registry record last updated 2017-06-28; status last verified 2017-04.
- Results first posted 2017-06-28.
- 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.
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17. Record Summary
The completed study concerns the relationship between smoking status and etanercept therapy in plaque psoriasis. The registry reports enrollment of 126, a start date of 2013-11, and primary completion in 2016-05. It describes a non-interventional pilot observational study and lists a smoking questionnaire.
The primary outcome is mean change from baseline in PASI score at Week 24, with standard deviation, among treated participants with available post-baseline documentation. PASI combines lesion severity and affected area. The registry also lists PASI outcomes at Week 12 and Week 24, seven outcome measures, and two analyses.
The registry record does not report the primary outcome estimates, group sizes for analysis, uncertainty measures, or detailed statistical methods. It cautions that the smoking-status groups are not a like-for-like control comparison. The record therefore describes the question and planned measurement, but does not permit quantitative conclusions about the observed relationship.