Canadian Assessment of Patient Outcomes and Effectiveness of Etanercept (Enbrel) in Psoriasis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Canadian Assessment of Patient Outcomes and Effectiveness of Etanercept (Enbrel) in Psoriasis (NCT00332332), a non-randomized phase 4 study. The primary outcome is Participants With a Status of Mild or Better on Physician Global Assessment at Month 12.

2. Clinical Question

The study was intended to evaluate use of etanercept in psoriasis for up to 1 year. The primary question is descriptive: it concerns the number meeting a specified assessment threshold during treatment, not a randomized comparison of treatment strategies. The registry lists additional outcomes concerning change from baseline in patient global assessment, affected body surface area, and dermatology life quality of life score. Their results are not reported in the registry record.

3. Trial Design

This was a completed Phase 4, non-randomized, open-label, single-group study sponsored by Amgen. The registry lists an enrollment of 246 and describes a treatment period of 12 months. The study started in 2006-03 and reached primary completion in 2009-07. These record dates describe study conduct, not the timing of a particular participant’s treatment or assessment.

All participants in the described group received etanercept. The registry describes 50 mg twice weekly by subcutaneous administration for 3 months, followed by 50 mg twice a week for 9 months. Because the study is single group and non-randomized, it does not supply a concurrent untreated or alternative-treatment control for the primary question. Changes over time within the group can be described, but they do not by themselves separate treatment effects from other explanations for change.

The primary endpoint was assessed at Month 12 and counted participants rated mild or better on the Physician Global Assessment. The record defines a Full Analysis Set for this endpoint, including participants who received at least one dose and had a baseline and at least one post-baseline endpoint measurement. Missing post-baseline values were imputed using last observation carried forward. The number included in this endpoint analysis and the number with an observed Month 12 measurement are not reported in the registry record.

The registry lists three secondary outcomes focused on percent change from baseline at Month 12. It records four outcome measures and one analysis, but the detailed results and a fuller account of the analysis plan are not reported in the registry record. The enrollment figure is not the same as the number analyzed for every outcome; the record does not provide enough information to reconcile enrollment with the primary endpoint population.

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: Full Analysis Set, composed of enrolled participants who received at least one dose of study medication and who had a baseline and at least one post-baseline measurement of the endpoint of interest. Missing post-baseline values were imputed using last observation carried forward.

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 Participants With a Status of Mild or Better on Physician Global Assessment at Month 12, measured over Month 12.

The primary endpoint is the number of participants whose Physician Global Assessment (PGA) status was mild or better at Month 12. The qualifying scores are 0, 1 or 2 on a scale from 0 to 5, with 0 defined as the best outcome. The endpoint is a count of participants meeting a threshold, rather than a continuous measure of change or a comparison between treatment groups.

A threshold-based assessment can make a clinical status easier to interpret than a scale score alone: it identifies how many participants meet a prespecified category at the assessment time. However, a count does not show how far each participant’s score changed from baseline, and it does not describe outcomes among participants who did not meet the threshold. The registry record does not report the endpoint count, the denominator assessed at Month 12, or a confidence interval, so the precision of the observed result cannot be evaluated from the record.

The record lists patient global assessment, body surface area affected by psoriasis, and Dermatology Life Quality Index total score as secondary outcomes, each framed as percent change from baseline to Month 12. Those outcomes may describe other aspects of disease status and quality of life, but their numerical results are not reported in the registry record. The primary endpoint’s stated analysis population also uses last observation carried forward for missing post-baseline values. That method affects which value represents a participant with a missing later measurement; the record does not report how many values were imputed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record describes a single-group study with a binary primary endpoint expressed as a count: participants either meet the defined PGA threshold at Month 12 or do not. The statistical interpretation of such an endpoint depends on both the number meeting the criterion and the number included in the analysis. The record supplies neither the endpoint count nor its analysis denominator. The enrolled total cannot substitute for those missing outcome details.

What does a threshold-based count describe?

A threshold converts a scale into a category. Here, scores 0, 1 or 2 qualify as mild or better, while the scale ranges from 0 to 5 and defines 0 as best. This makes the outcome a count of participants meeting that category at a specified time. It does not retain all distinctions among scores within the qualifying category, nor does it describe the size of change from baseline. A separate analysis of change or of the full scale could address different questions, but results for such analyses are not reported in the registry record.

Why does the study structure matter?

Random allocation is a way to create groups for a comparative treatment question. This study is recorded as non-randomized and single group, with no separate comparator. Therefore, a within-group outcome is descriptive rather than a randomized treatment contrast. General statistical principle: without a suitable comparison, changes observed over time cannot isolate the effect of treatment from other possible influences. The registry record explicitly cautions that the arms are not a like-for-like control comparison; it does not report a randomized comparison.

The study is also open label. In general, when participants and assessors know the treatment, reported or assessed outcomes can be influenced by that knowledge. The degree to which this affected the PGA assessment in this study is not reported in the registry record. This is a design consideration, not evidence that the recorded assessments were biased.

What does a confidence interval add?

In general, a confidence interval communicates the uncertainty associated with an estimated quantity under the statistical model and assumptions used. For a participant count or proportion, it would help readers judge how precisely the underlying outcome is estimated. The registry record does not report a confidence interval or the primary endpoint estimate, so neither the estimate nor its precision can be assessed. No new estimate can be derived from the endpoint definition alone.

A p-value, in general, evaluates compatibility between data and a stated statistical null hypothesis under specified assumptions. It is not a measure of clinical importance and does not replace an effect estimate with uncertainty. The primary endpoint’s p-value, null hypothesis, and inferential test are not reported in the registry record. The single-group design also means that no randomized between-group test is described.

How should the analysis population be read?

The Full Analysis Set is defined as enrolled participants who received at least one dose and had baseline and at least one post-baseline measurement of the endpoint. This definition excludes some enrolled participants by design if they did not meet those conditions. The record does not state how many participants qualified, how many had a Month 12 measurement, or why any participants lacked measurements. The enrollment figure of 246 and the safety risk set of 230 refer to different reported quantities; the record does not explain the relationship between them.

Missing post-baseline endpoint values were imputed using last observation carried forward. In general, this method substitutes a participant’s last available observation for a missing later observation. It can produce an analysis dataset, but it relies on an assumption that carrying the earlier value forward is an appropriate representation of the later outcome. That assumption may not fit every participant’s course. The registry record does not report the number of imputed values, the timing of the last observations, or analyses using alternative missing-data assumptions.

What do the planning assumptions mean?

The record describes sample-size planning illustrations based on the 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 illustrations, not the trial’s own design justification or observed power. They do not turn the study into a two-arm trial: the registry design is single group and non-randomized. The record does not report the trial’s sample-size justification, and numerical planning outputs are not reported in the registry record.

In general, planning calculations ask how much information a hypothetical design might require to detect a specified effect under stated assumptions. Their outputs depend on those assumptions and should not be interpreted as the probability that a completed study found a true effect. No sample-size illustration can fill in the missing primary endpoint result or supply a randomized comparison that the design did not include.

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("Etanercept")
n      <- c(226)
events <- c(166)
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  Etanercept  226  166  73.5  67.2  79.1  67.3  78.8  67.3  78.8

11. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures and one analysis. It names a primary endpoint and three secondary outcomes: percent change from baseline to Month 12 in patient global assessment, body surface area affected by psoriasis, and Dermatology Life Quality Index total score. The numerical results for the secondary outcomes are not reported in the registry record.

When a study evaluates multiple outcomes, multiplicity can arise because several statistical questions are considered. In general, testing multiple hypotheses without an appropriate strategy can increase the chance of at least one apparently notable result by chance. The registry record does not report a multiplicity adjustment, a hierarchy for testing outcomes, or details sufficient to determine how the listed outcomes were handled statistically. The record’s count of one analysis does not explain the analysis procedures or establish how multiplicity was addressed.

For the primary endpoint, the record defines a Full Analysis Set of enrolled participants who received at least one dose and had a baseline and at least one post-baseline endpoint measurement. It states that missing post-baseline values were imputed using last observation carried forward. The number in this analysis set, the number with missing Month 12 data, the quantity imputed, and the reasons for missing data are not reported in the registry record.

In general, missing-data methods make assumptions about outcomes that were not observed. Last observation carried forward uses an earlier measurement in place of a later missing value; whether that represents the later status is an assumption, not an observed fact. The registry record does not report sensitivity analyses or alternative handling of missing observations. It also does not give enough detail to assess whether missingness differed by participant characteristics or outcome status.

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: atrial flutter (0.4%), cardiac failure congestive (0.4%), intestinal obstruction (0.4%), death (0.4%), cellulitis (0.4%).

The registry lists 12 participants affected in the serious adverse event category among 230 at risk. It lists 59 affected in the other adverse event category among 230 at risk. These are reported safety figures for the etanercept group; there is no separate randomized control group in this single-group study for a comparative safety assessment.

The serious-event term list includes Atrial flutter, Cardiac failure congestive, Intestinal obstruction, Death, Cellulitis, and Sepsis, each listed at 0.4%. These entries are registry-listed terms and should not be treated as a complete account of all event details, timing, or clinical circumstances. The deaths field is not reported in the registry record, even though Death appears in the serious-event term list. The record does not reconcile those entries, so a death count should not be inferred from the term listing.

In general, an adverse event recorded during a study is not necessarily caused by the treatment. The registry figures alone do not establish causality, comparative risk, or the pattern of an individual participant’s events. The record does not report further details needed to interpret event timing, duration, severity beyond the serious-event classification, or the investigators’ assessment of relatedness.

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

The study record describes an open-label, single-group evaluation of etanercept in psoriasis and defines a Month 12 PGA threshold as its primary endpoint. It also specifies a Full Analysis Set and an approach to missing post-baseline values. These details establish what the primary outcome was intended to measure and how the registry says the analysis population and missing observations were handled.

The record does not report the primary endpoint count, its denominator, or a measure of uncertainty. It therefore cannot show how many participants met the mild-or-better threshold or how precisely that result was estimated. The secondary outcome results are also not reported in the registry record. No numerical conclusion about the observed clinical outcomes can be drawn from the endpoint definitions alone.

Even if a within-group change were available, the design would not provide a randomized comparator. General statistical interpretation: an outcome observed during treatment is not, by itself, evidence of what would have occurred without treatment or under another treatment. The single-group, non-randomized design limits causal interpretation, and the open-label design is relevant when considering assessment outcomes. The registry record does not quantify the influence of these limitations.

The safety listings provide counts for serious and other adverse events among participants at risk, plus a short list of serious-event terms. They do not establish that events were caused by etanercept or allow comparison with an alternative. The Death term and unreported deaths field are not reconciled in the registry record.

Accordingly, the record supports a description of the study design, endpoint definition, analysis-set criteria, imputation method, and listed safety figures. It does not provide the outcome results needed to assess the primary endpoint’s observed magnitude or precision, and it does not support a controlled treatment-effect comparison.

14. Why This Trial Matters Statistically

This study is statistically informative as an example of why a clearly named endpoint and a reported result are both necessary. The registry defines a clinically interpretable category on the PGA scale and specifies the Month 12 assessment. But without the count meeting that category and its denominator, readers cannot evaluate even the basic descriptive outcome, much less its uncertainty.

The design also illustrates the distinction between observing outcomes during treatment and estimating a comparative treatment effect. A single-group, non-randomized study can document outcomes among participants who received treatment, but it lacks a concurrent randomized comparator. That limitation shapes what the data can answer, regardless of how the endpoint is defined.

The analysis population and missing-data rule matter as well. The Full Analysis Set requires treatment exposure and endpoint measurements, and missing post-baseline values were handled by carrying the last observation forward. Those choices influence which participants and values contribute to the endpoint. The record does not report the set size, amount of missingness, or sensitivity analyses, leaving important aspects of the result’s robustness unassessable.

Finally, the safety listings reinforce the need to distinguish descriptive event reporting from causal or comparative claims. Counts and listed terms provide some information about events recorded in the study, but they do not establish attribution or relative risk. Because the primary outcome results are absent, this record is more useful for understanding planned measurement and design constraints than for evaluating the magnitude or precision of the clinical outcomes.

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 most direct limitation of the registry record is that it does not report the primary endpoint result. The number meeting the mild-or-better PGA threshold, the Month 12 denominator, and uncertainty estimates are not reported. Results for the listed secondary outcomes are also not reported, so the clinical outcome findings cannot be assessed from this record.

The study was non-randomized, open label, and single group. There is no concurrent randomized comparator in the registry description, limiting comparative interpretation. The record cautions that the arms are not a like-for-like control comparison. Participant eligibility details beyond the analysis-set definition, the recruitment setting, and further information about outcome assessment are not reported in the registry record.

The primary endpoint analysis population is defined by treatment exposure and availability of baseline and at least one post-baseline measure. Its size and its relationship to the enrollment of 246 are not reported. The safety figures list 230 at risk, but the record does not explain the relationship between this number and the endpoint population. Missing-data frequency, reasons for missingness, and sensitivity analyses are not reported. Last observation carried forward may not represent a participant’s later outcome, and the record does not show how dependent the result is on that assumption.

The registry does not report the detailed statistical plan, sample-size justification, multiplicity strategy, or inferential analysis for the primary endpoint. Its planning assumptions describe illustrations rather than the trial’s own design justification. Safety information is limited to the listed affected counts and serious-event terms; details of timing, relatedness, and the discrepancy between the Death term and unreported deaths field are not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Canadian Assessment of Patient Outcomes and Effectiveness of Etanercept (Enbrel) in Psoriasis — NCT00332332.
• Registry record last updated 2014-07-25; status last verified 2014-07.
• Results first posted 2011-06-14.
• 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 NCT00332332 as a completed Phase 4, open-label, non-randomized, single-group study of etanercept in psoriasis, sponsored by Amgen. Enrollment was 246. The study started in 2006-03 and reached primary completion in 2009-07. The stated treatment period was 12 months.

The primary endpoint counted participants with a PGA status of mild or better at Month 12. The Full Analysis Set required treatment exposure and baseline and post-baseline endpoint measurements; missing post-baseline values were imputed using last observation carried forward. The primary endpoint result and secondary outcome results are not reported in the registry record.

The safety listing reports 12 affected among 230 at risk for serious adverse events and 59 affected among 230 at risk for other adverse events. The registry lists serious-event terms at 0.4% each, including Death, while the deaths field is not reported. The study has no randomized comparator, so the record does not support a controlled treatment-effect comparison.