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 Evaluation of Humira Retention Rate in Psoriasis Patients in Daily Practice and Assessment of Work Productivity and Quality of Life (NCT01169987), a registered phase not stated study. The primary outcome is Adalimumab Treatment Retention Status.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01169987 |
| Phase | Phase not stated |
| Condition | Psoriasis |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 191 |
| Arms in the primary outcome | n/a |
| Lead sponsor | AbbVie (prior sponsor, Abbott) |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned participants with chronic plaque psoriasis who began adalimumab treatment in daily clinical practice. The registry reports enrollment of 191 participants. Its stated intention-to-treat population includes enrolled participants who received at least one dose and had any follow-up data; the number meeting that definition is not reported in the registry record.
Intervention
Participants initiated adalimumab (Humira). Treatment was prescribed in the usual manner, in accordance with the marketing authorization and Belgian reimbursement criteria. The study observed how treatment continued, was interrupted, restarted or permanently stopped; it did not assign a treatment regimen as part of a randomized comparison.
Comparator
No separate control group or alternative treatment arm is described. The retention categories distinguish participants by their observed treatment course, rather than comparing randomized groups. Any comparisons by retention status among secondary outcomes are therefore comparisons within the observed cohort, not like-for-like randomized treatment contrasts.
Primary question
At the Month 24 or Early Termination visit, what percentage of participants fell into each adalimumab treatment-status category: continuous, early intermittent, late intermittent, permanently discontinued or other? The study also planned to describe psoriasis severity, quality of life and work productivity, including outcomes by retention status. Numerical primary and secondary outcome results are not reported in the registry record.
The central question is descriptive: how treatment was retained or stopped during routine care, and how clinical and patient-reported measures were recorded over follow-up. The registry summary specifies a follow-up period of 2 years and notes that reasons for interruption, permanent discontinuation and restarting were to be documented. It does not report those reasons or numerical findings. The observational design can describe what happened in this cohort, but without a randomized comparator it cannot isolate the effect of adalimumab from other explanations for observed changes or treatment decisions.
3. Trial Design
The registry identifies this as an observational study in psoriasis. It describes participants with chronic plaque psoriasis starting adalimumab in daily practice, with treatment prescribed in the usual manner under the marketing authorization and Belgian reimbursement criteria. The stated enrollment is 191. The registry lists AbbVie (prior sponsor, Abbott) as the sponsor. The recorded study start is 2010-05, primary completion is 2015-03, and status is COMPLETED.
The follow-up plan was to document whether adalimumab treatment continued, was interrupted, or was permanently discontinued during a period of 2 years. The summary also says that reasons for interruption, permanent discontinuation and restarting would be noted. The primary outcome is assessed at Month 24 or an Early Termination visit. The registry record does not report the actual duration of follow-up for each participant, the number completing follow-up, or the number who ended participation early.
There is one described participant group: people treated with adalimumab. Allocation is not stated, and no randomized comparison is described. The retention categories are defined by treatment history and status at study termination, so they are observational classifications rather than assigned arms. A participant classified as continuous had no treatment interruption, remained on treatment at termination and completed the study. Early and late intermittent status both require a treatment interruption of at least 70 consecutive days and being on treatment at termination; they differ according to whether treatment continued every other week for fewer than 112 days (16 weeks) or at least 112 days (16 weeks) after initiation. Permanent discontinuation means treatment was stopped permanently after at least one dose; other covers those outside the listed categories.
The registry lists outcomes concerning psoriasis severity, quality of life and work productivity in addition to retention. The actual observation schedules for those measures, rules for handling missed visits, and any analysis plan are not reported in the registry record. Because treatment was not randomized, comparisons across retention groups may reflect differences in participants or their clinical course as well as differences in time on treatment.
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 | Participants Treated With Adalimumab |
|---|---|
| STARTED | 191 |
| COMPLETED | 160 |
| NOT COMPLETED | 31 |
Reasons for not completing this period:
| Reason | Participants Treated With Adalimumab |
|---|---|
| Withdrawal by Subject | 3 |
| Lost to Follow-up | 24 |
| Other | 4 |
Analysis population for the primary outcome, as defined in the registry: Intention to Treat (ITT) set: all participants enrolled in the study who received at least 1 dose of adalimumab, and for whom any follow-up data were available.
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.
| Characteristic | Unit | Participants Treated With Adalimumab |
|---|---|---|
| Participants analysed | 191 | |
| Age, Continuous | years | 44.9 (SD 12.1) |
| Sex: Female, Male: Female | Participants | 58 |
| Sex: Female, Male: Male | Participants | 133 |
6. Primary Endpoint
The registry lists the primary outcome as Adalimumab Treatment Retention Status, measured over Month 24/ Early Termination visit.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | percentage of participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the percentage of participants in each adalimumab treatment-status category at Month 24 or the Early Termination visit. The categories are continuous, early intermittent, late intermittent, permanently discontinued and other. The registry defines them using treatment initiation, interruption history, whether treatment was ongoing at study termination, and—in the intermittent categories—the timing and duration of treatment interruption. “Other” covers participants who do not meet the definitions of the other categories.
Retention is useful as a descriptive measure in a daily-practice study because it captures whether a treatment course was continued, interrupted, resumed or ended during the observation period. It can provide context about treatment persistence and the range of treatment experiences in the enrolled cohort. The endpoint is not a direct measure of psoriasis control, quality of life or work productivity; those were addressed through separate secondary outcomes.
For a percentage endpoint, the numerator is the number of participants assigned to a category and the denominator is the defined analysis population. The registry defines its intention-to-treat set as enrolled participants who received at least one dose of adalimumab and had any follow-up data. The number in that set and the category counts or percentages are not reported in the registry record, so the observed retention distribution cannot be interpreted from the endpoint definition alone.
As a general statistical point, a percentage describes the frequency of an outcome in the population being analyzed; its precision depends in part on the amount of information available. A confidence interval, if reported, would help show the uncertainty around an estimated percentage. No numerical estimate or confidence interval for this primary endpoint is reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes the intended outcomes and their definitions, but it does not report numerical primary or secondary results. It is therefore not possible to state what percentage of participants were continuous, intermittent, permanently discontinued or classified as other. Nor can the degree of uncertainty around those percentages be assessed from the record. Enrollment of 191 is reported, but the registry-defined intention-to-treat population is narrower: it includes enrolled participants who received at least one dose and had any follow-up data. The size of that population is not reported.
This distinction matters because enrollment is not automatically the denominator for an outcome analysis. Participants may not have received a dose or may not have had follow-up data, and the record does not state how many met the analysis-population definition. The actual category counts, percentages, confidence intervals and any reasons for missing follow-up are also not reported. Without those details, readers cannot assess the retention distribution, the precision of estimates, or whether missing observations might affect interpretation.
The outcome definition indicates that treatment history, interruption duration and treatment status at termination contribute to classification. A participant in an intermittent category must have had a qualifying interruption and be on treatment at study termination. Permanent discontinuation is defined separately, and “other” captures participants outside the other categories. Those definitions make clear what the categories were intended to represent, but they do not reveal how many participants fell into each one or why treatment was interrupted, resumed or stopped.
The secondary outcomes include psoriasis severity measures (PASI, affected body surface area and physician’s global assessment), dermatology-related quality of life (DLQI), and work productivity and activity impairment (WPAI). The registry names outcomes concerning mean scores, categories and percentage changes, including summaries by treatment-retention status. It does not report the numerical results, assessment-specific denominators or uncertainty estimates for these measures. Accordingly, there is no basis in the registry record to describe the size or direction of any observed changes or differences among retention groups.
Even if results were available, comparisons between retention categories would be observational. Participants were not assigned to those categories at random; the categories arise from their subsequent treatment histories. Differences in outcomes could therefore reflect baseline characteristics, disease course, other clinical decisions, or factors related to stopping and restarting treatment. The registry record does not report adjusted analyses or enough information to determine how such differences were handled.
The most supportable reading is thus about study scope rather than treatment effects: the study was designed to describe treatment retention and related clinical, quality-of-life and work-productivity measures in daily practice. Its posted record does not provide the numerical findings needed to quantify those outcomes or judge their precision.
9. Statistical Methods Explained
The statistical methods that can be described from the registry record are limited to the outcome definitions and stated analysis population. A detailed statistical analysis plan is not reported in the registry record. The study is described as observational, and no randomized allocation or control group is listed. The following concepts explain how the planned measures are generally interpreted; they should not be taken as a claim that a particular unreported method was used.
What does a percentage endpoint represent?
The primary measure is a percentage of participants in each treatment-retention category. In general, a percentage expresses the count meeting a category definition relative to the analysis denominator. Here, the registry defines the intention-to-treat set as participants enrolled who received at least one dose and had any follow-up data. The number in this set, the category counts and the percentages are not reported in the registry record. The enrollment figure alone should not be substituted for the analysis denominator without evidence that all enrolled participants met the stated definition.
The categories encode different treatment histories. Continuous status requires no interruption, treatment ongoing at study termination and study completion. Early and late intermittent status require an interruption of at least 70 consecutive days, subsequent treatment at termination and study completion; their distinction depends on the duration of every-other-week treatment after initiation. Permanent discontinuation is defined by having received at least one dose and then stopping permanently. “Other” is a residual category for people outside the preceding definitions. These rules describe classification, not a statistical comparison between assigned groups.
How should precision be understood?
In general, an estimate is more informative when accompanied by a measure of uncertainty. A confidence interval represents a range of values compatible with the data and the method used to calculate it; it is not a guarantee that the true value lies in that range. For a percentage, the interval's width depends on the number of observations and the frequency of the outcome, among other considerations. The registry record does not report confidence intervals for the primary endpoint, and no interval can be inferred from the endpoint definition or enrollment alone.
For continuous measures such as mean PASI, BSA, DLQI or WPAI values, a mean describes the average among the observations included in that analysis. Its interpretation depends on the scale, assessment time, population and handling of missing data. The registry lists mean outcomes and categorical summaries but does not report their numerical values, distributions, variability measures or analysis denominators. The record also does not state whether any continuous outcomes were transformed, adjusted or analyzed using a repeated-measures model.
What does over-dispersion mean in general?
For count outcomes, over-dispersion occurs when variability exceeds what a simple statistical model assumes. In general, ignoring over-dispersion can make standard errors too small and uncertainty appear narrower than it is. This study's stated primary endpoint is a percentage, not a count rate, and the registry does not describe a count model or report a dispersion parameter. There is therefore no basis for saying that an over-dispersion adjustment was used or was needed for the posted primary outcome.
What can comparisons by retention status establish?
In general, a comparison between groups is most straightforward when group membership is assigned independently of participants' characteristics and outcomes. In this study, retention status is determined by treatment behavior during follow-up. Factors associated with disease severity, tolerability, access, personal circumstances or clinical decisions could be related both to retention and to later outcomes. These are possible sources of confounding in observational comparisons, not findings established by this registry record. The registry does not report a covariate-adjustment strategy, matching, weighting or another method for addressing confounding.
The secondary outcomes are described as being reported for all participants and by treatment-retention status. A difference between such groups would be descriptive unless supported by a suitable analysis and assumptions. Further, retention classification depends in part on events occurring during follow-up, so group definitions and outcome timing matter when interpreting comparisons. The registry record does not provide enough detail to establish the timing of each secondary assessment relative to classification, or whether analyses accounted for that timing.
What is not specified about the analysis?
The number of analyses is recorded as zero in the registry information, while outcome measures are listed. This does not supply numerical findings or a statistical analysis plan. The record does not report hypothesis tests, model forms, covariates, confidence-interval methods, handling of repeated measurements, interim analyses, or a sample-size justification. Those details should not be inferred from the outcome names.
In general, a sample-size calculation is a planning exercise based on assumptions about an effect, variability, significance level and desired power. It is not evidence that an effect was observed, and a planning illustration is not observed power. The registry record does not report the trial's own sample-size justification. Any sample-size planning assumptions shown with the posted results should therefore be understood as illustrations, not as a description of the study's original design or evidence about its findings.
10. Multiplicity, Missing Data and Analysis Populations
The study lists a primary retention outcome and multiple secondary measures covering psoriasis severity, quality of life and work productivity. The registry record does not report a multiplicity strategy, such as a hierarchy of tests, adjustment of significance levels, or a distinction between confirmatory and exploratory analyses. It also does not report numerical test results. Consequently, the record does not establish whether any findings were adjusted for the number of outcomes or comparisons.
Multiplicity is a general statistical concern when many hypotheses are tested: the chance of at least one apparently notable result can rise as more tests are considered. Adjustment methods can address that issue, but may also affect precision or power. This general point does not indicate that any particular result from this study is false or reliable; without posted results and an analysis plan, the implications cannot be assessed.
Missing-data procedures are not reported in the registry record. The stated intention-to-treat set includes enrolled participants who received at least one dose and had any follow-up data, but the record does not provide the number meeting that definition, outcome-specific denominators, reasons for missing observations, or the method used to handle missing values. It also does not say whether participants with incomplete follow-up were included in particular assessments or how early termination affected the secondary outcomes.
The registry names an intention-to-treat population, but that label alone does not describe every analysis population used. The number and definition of any additional populations are not reported in the registry record. Without denominators and missing-data methods, readers cannot determine whether outcome estimates represent all enrolled participants, only those with observed measurements, or another subset. This limits interpretation of both the level of precision and the possibility of bias from incomplete follow-up.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Participants Treated With Adalimumab | 19 | 191 | 9.9% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Participants Treated With Adalimumab | 67 of 191 |
Most frequent serious adverse event terms
| Event term | Organ system | Participants Treated With Adalimumab |
|---|---|---|
| Psoriasis | Skin and subcutaneous tissue disorders | 4 of 191 |
| Arthralgia | Musculoskeletal and connective tissue disorders | 3 of 191 |
| Vomiting | Gastrointestinal disorders | 2 of 191 |
| General physical health deterioration | General disorders | 2 of 191 |
| Hypersensitivity | Immune system disorders | 2 of 191 |
| Weight increased | Investigations | 2 of 191 |
| Depression | Psychiatric disorders | 2 of 191 |
| Rash | Skin and subcutaneous tissue disorders | 2 of 191 |
| Thrombocytopenia | Blood and lymphatic system disorders | 1 of 191 |
| Aortic valve incompetence | Cardiac disorders | 1 of 191 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Participants Treated With Adalimumab |
|---|---|---|
| Drug ineffective | General disorders | 36 of 191 |
| Psoriasis | Skin and subcutaneous tissue disorders | 23 of 191 |
| Guttate psoriasis | Skin and subcutaneous tissue disorders | 3 of 191 |
| Injection site pain | General disorders | 2 of 191 |
| Foetal exposure during pregnancy | Injury, poisoning and procedural complications | 2 of 191 |
| Inappropriate schedule of drug administration | Injury, poisoning and procedural complications | 2 of 191 |
| Dermatitis | Skin and subcutaneous tissue disorders | 2 of 191 |
| Pruritus | Skin and subcutaneous tissue disorders | 2 of 191 |
Serious events with the highest arm-level rate: psoriasis (2.1%), arthralgia (1.6%), vomiting (1.0%), general physical health deterioration (1.0%), hypersensitivity (1.0%).
The safety summary lists 191 participants at risk, 19 with a serious adverse event, and 67 with another adverse event. These are the posted counts; the registry record does not provide further details about event timing, recurrence, severity grading beyond the serious classification, or attribution to treatment. It reports no death count, so deaths are not reported in the registry record.
The serious-event terms with posted percentages are psoriasis at 2.1%, arthralgia at 1.6%, vomiting at 1.0%, general physical health deterioration at 1.0%, hypersensitivity at 1.0%, and weight increased at 1.0%. These percentages describe listed terms in the safety summary; the record does not provide additional term-specific counts or explain whether one participant could contribute to more than one term. They should not be added together or interpreted as a single overall risk estimate.
In general, adverse-event counts collected in an observational cohort describe events recorded among participants, not proof that treatment caused them. Without a comparison group and further information on event ascertainment and attribution, the figures cannot establish whether an event occurred more or less often because of adalimumab. The safety information is a descriptive record, not a causal estimate.
12. What the Result Does, and Does Not, Mean
The study's planned contribution is a description of adalimumab treatment retention in daily practice among people with chronic plaque psoriasis, alongside measures of disease severity, quality of life and work productivity. The registry supplies definitions for the retention categories and identifies the outcomes the study intended to assess. It does not report numerical primary or secondary results. As a result, no conclusion about the observed retention distribution, changes in clinical measures, or differences by retention status can be drawn from the registry record.
The record can still clarify what the study set out to measure. Treatment retention was not defined simply as whether a participant remained on therapy at a single visit: the categories also distinguish interruption history and, for intermittent treatment, timing after initiation. The secondary measures span clinical assessments and participant-reported impacts. This breadth can help frame questions about real-world treatment experience, but listing an outcome is not the same as reporting its result.
The observational design also sets limits on interpretation. Treatment status was observed rather than assigned, and the registry describes no randomized comparator. If outcome differences between retention categories were reported, those differences would not by themselves show that retention caused better or worse outcomes. Treatment decisions and clinical course may be related to the measurements being compared. The registry record does not report methods that would resolve those issues.
The enrollment figure of 191 does not establish the denominator for every endpoint. The stated intention-to-treat set requires at least one dose and some follow-up data, and endpoint-specific counts are not reported. The registry also does not provide confidence intervals or missing-data methods, which prevents assessment of the precision and potential sensitivity of results even if a point estimate were available.
The safety summary records serious and other adverse-event counts and selected serious-event terms. Those figures describe recorded events in the treated group; they do not establish causation or provide a controlled estimate of comparative risk. Overall, the record is informative about study scope, outcome definitions and the descriptive safety summary, but it does not support a numerical evaluation of retention, efficacy, quality of life, work productivity or comparative safety.
13. Why This Trial Matters Statistically
Real-world treatment use can differ from a tightly assigned treatment schedule. A retention study can therefore address a practical descriptive question: whether treatment is continued, interrupted, restarted or permanently discontinued during routine care. This study's definitions make those patterns explicit, distinguishing uninterrupted treatment from interruption followed by treatment resumption and from permanent discontinuation. Such definitions are important because “retention” can otherwise refer to different experiences.
The study also planned to relate treatment-retention status to measures beyond a clinical severity assessment. PASI, affected body surface area and physician’s global assessment describe disease-related outcomes, while DLQI and WPAI address quality of life and work or activity impairment. Considering these types of measures together can broaden the questions asked about treatment experience. The registry record, however, does not report their numerical findings, so their contribution in this study cannot be quantified.
Statistically, the design highlights the difference between describing observed groups and estimating a treatment effect. Retention groups form after treatment begins and reflect subsequent behavior and clinical circumstances. That makes them useful for describing treatment patterns, but potentially confounded when comparing outcomes. The absence of a randomized comparator means that any such comparison would need cautious interpretation and clear reporting of the analysis methods.
The record also illustrates why endpoint definitions, analysis populations and denominators matter. The primary outcome is expressed as a percentage, but the registry-defined analysis set excludes participants without a dose or any follow-up data. The record does not report how many participants met that definition or how missing outcomes were handled. Without those details and numerical estimates, readers cannot assess precision or judge how representative the reported outcomes would be.
Thus, the study is statistically relevant as an example of a real-world retention question paired with clinical and patient-centered outcomes. Its registry record explains the intended measurements and their classification rules, while leaving the quantitative findings and analysis details unreported.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The main limitation for interpreting this registry record is that numerical primary and secondary results are not reported. The planned retention categories are defined, but their counts and percentages are unavailable. Numerical values for PASI, BSA, PGA, DLQI and WPAI outcomes are likewise not reported, so direction, magnitude and precision cannot be assessed.
The record reports enrollment of 191 but not the number in the stated intention-to-treat set or the denominator for each outcome. It does not report the number completing follow-up, the amount of missing data, reasons for missingness, or methods used to handle missing observations. These omissions make it impossible to evaluate how incomplete follow-up may have affected the intended summaries.
As an observational study without a described randomized comparator, it is vulnerable to confounding in comparisons by treatment-retention status. The registry does not report whether analyses adjusted for participant characteristics or other potential sources of confounding. The timing of secondary assessments relative to treatment classification is also not specified in the record, limiting interpretation of any proposed subgroup comparisons.
Additional statistical details are not reported in the registry record: the analysis plan, confidence-interval methods, hypothesis-testing procedures, multiplicity handling, interim analyses and the study's sample-size justification. The record therefore does not support evaluation of those design or analysis choices.
The safety summary is limited to posted counts and selected serious-event terms with percentages. It does not provide a comparison group, event timing, attribution details or a reported death count. The figures can be read descriptively but cannot establish treatment causation or comparative safety. These limitations concern what can be concluded from the registry record; they do not establish that unreported analyses or information do not exist elsewhere.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Evaluation of Humira Retention Rate in Psoriasis Patients in Daily Practice and Assessment of Work Productivity and Quality of Life — NCT01169987.
- Registry record last updated 2016-07-13; status last verified 2016-06.
- Results first posted 2016-06-14.
- 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.
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18. Record Summary
This completed observational study concerned adalimumab treatment retention among participants with chronic plaque psoriasis in daily practice. The registry reports enrollment of 191 and defines the primary outcome as the percentage in each treatment-status category at Month 24 or an Early Termination visit. The planned secondary outcomes cover psoriasis severity, quality of life and work productivity.
The registry defines the intention-to-treat set as enrolled participants who received at least one dose and had any follow-up data. It does not report the size of that analysis set, numerical primary or secondary outcome findings, confidence intervals, missing-data methods or a detailed analysis plan. The safety summary records 19 participants with a serious adverse event and 67 with another adverse event among 191 at risk; deaths are not reported in the registry record.
The record supports a description of the study question, outcome definitions and posted safety counts. It does not provide the quantitative results needed to assess retention patterns, outcome changes, precision or causal effects.