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 Investigation of 9 Consecutive Infusions of Remicade for Psoriatic Arthritis in Austria (Study P04264) (NCT00725296), a registered phase not stated study. The primary outcome is Mean Time Interval Between Infusions During Maintenance Therapy.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00725296 |
| Phase | Phase not stated |
| Condition | Arthritis, Psoriatic |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 178 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Merck Sharp & Dohme LLC |
| Results posted | Yes |
2. Clinical Question
Population
Participants had active and progressive psoriatic arthritis and had responded inadequately to disease-modifying anti-rheumatic drugs. The primary outcome description focuses on Infliximab-naive participants who received induction and maintenance therapy. The registry reports 178 enrolled participants and notes that 152 Infliximab-naive participants were treated; 94 received induction therapy, and 83 received induction therapy and subsequent maintenance therapy. These counts describe different stages of treatment and should not be treated as interchangeable analysis populations.
Intervention
Participants received Remicade (infliximab). The described induction infusions occurred at weeks 0, 2, and 6, with dosage determined by physicians. Up to six maintenance infusions were planned after induction. This was a one-arm observational study, not a randomized comparison.
Comparator
There was no comparator arm described. The registry characterizes the study as one-arm; allocation is not stated. Consequently, the record does not establish a like-for-like control group against which to compare infusion timing or other outcomes.
Primary question
The primary outcome was the mean number of days between successive infliximab infusions during maintenance therapy, following induction. The intervals were defined between infusions 3 and 4 through infusions 8 and 9. The registry specifies a timeframe of up to 24 months, but the numeric mean and standard deviation are not reported in the registry record. The posted record therefore describes the question being measured without giving the primary outcome estimate needed to characterize the observed timing.
3. Trial Design
This was a prospective, open-label, one-arm, multicenter observational study in Austria. Its stated aim was to determine the dose and time interval of Remicade (infliximab) infusions in people with psoriatic arthritis. The registry lists the condition as psoriatic arthritis and the intervention as a biological treatment. Because the study is observational and has one arm, it describes treatment use rather than a randomized contrast between treatment strategies.
The treatment description concerns participants with active and progressive psoriatic arthritis who had responded inadequately to disease-modifying anti-rheumatic drugs. Induction infusions were given at weeks 0, 2, and 6, at a dosage decided by physicians. A maximum of six maintenance infusions was described. The physician-determined dose and observational setting are important: the record does not describe a fixed dose assigned uniformly by randomization.
The registry reports enrollment of 178. It also states that 152 Infliximab-naive participants were treated, that 94 received induction therapy, and that 83 received induction therapy and subsequent maintenance therapy. The primary outcome population is described as Infliximab-naive participants receiving induction and maintenance therapy, but the population description is truncated in the registry record. The relationship between all listed counts and the complete analysis population is therefore not fully detailed.
The study start is recorded as 2004-12, and primary completion as 2010-07. Its status is completed. The registry lists six outcome measures and zero analysis records. The record does not report a randomized allocation procedure, a control group, or a detailed statistical analysis plan. This design can describe infusion intervals in the studied treatment setting, but without a comparator it cannot isolate a treatment effect relative to another regimen.
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 178 participants were enrolled in this study. Of these, 159 participants were Infliximab-naive and 19 participants were already on Remicade (Infliximab). A total of 163 participants received at least one dose: 152 of the 159 naive participants and 11 of the 19 non-naive participants.
Overall Study
| Stage | Infliximab |
|---|---|
| STARTED | 163 |
| COMPLETED | 101 |
| NOT COMPLETED | 62 |
Reasons for not completing this period:
| Reason | Infliximab |
|---|---|
| Adverse Event | 11 |
| Lack of Efficacy | 7 |
| Withdrawal by Subject | 3 |
| Non-Compliance | 2 |
| Lost to Follow-up | 1 |
| Other | 38 |
Analysis population for the primary outcome, as defined in the registry: N= number of Infliximab-naive participants that received induction \& maintenance therapy. Out of 152 Infliximab-naive participants who were treated, 94 participants received induction therapy (Infliximab at weeks 0, 2, and 6), 83 participants received induction therapy and subsequent maintenance therapy (maximum of 6 maintenance infusions).
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 | Infliximab |
|---|---|---|
| Participants analysed | 163 | |
| Age, Continuous | years | 47.96 (SD 13.22) |
| Sex: Female, Male: Female | Participants | 62 |
| Sex: Female, Male: Male | Participants | 101 |
6. Primary Endpoint
The registry lists the primary outcome as Mean Time Interval Between Infusions During Maintenance Therapy, measured over Up to 24 months.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | days |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the mean time interval, in days, between infliximab infusions during maintenance therapy. It covers the successive intervals between infusions 3 and 4, 4 and 5, 5 and 6, 6 and 7, 7 and 8, and 8 and 9, after induction. The stated observation timeframe is up to 24 months.
A mean gives a measure of the average interval across the observations included in an analysis. The standard deviation, which is the stated measure of dispersion, describes how much individual intervals vary around that average. Together, these statistics would describe both the central timing and the spread of observed maintenance intervals. They would not by themselves explain why an interval occurred, establish that a particular schedule caused an outcome, or describe the distribution fully.
Infusion timing is relevant to the study's stated descriptive aim: determining dose and time interval in a real-life regimen. In this observational setting, actual schedules were not assigned through a randomized comparison, and the dose was determined by physicians. The registry record does not report the primary endpoint's mean, standard deviation, or an interval estimate. It therefore does not permit a numerical description of the observed average interval or its variability.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary outcome is clearly defined as a mean interval in days between successive maintenance infusions after induction, with a stated timeframe of up to 24 months. However, the registry record does not report a numerical value for that mean or its standard deviation. Without those results, readers cannot determine the average interval recorded, how variable the intervals were, or how precisely the average was estimated. A defined outcome is not the same as a reported outcome.
The record identifies 178 participants as enrolled. It further describes 152 Infliximab-naive participants as treated, 94 as having received induction therapy, and 83 as having received induction and subsequent maintenance therapy. The primary population description refers to Infliximab-naive participants who received induction and maintenance therapy, but its text is incomplete. The counts indicate that treatment stages and outcome-population membership differ; they do not supply the missing endpoint estimate or explain all participant flow.
There is no control arm described. The study is prospective, open-label, observational, and one-arm, with physician-determined dosage. The results, even if fully reported, would describe infusion timing in this study setting. They would not establish how timing compares with an alternative regimen, nor would they separate the effects of treatment decisions from participant characteristics or clinical circumstances. Allocation is not stated in the registry record.
For a continuous endpoint, a mean is one summary of the observed values, and a standard deviation describes dispersion. A confidence interval, if reported, would communicate uncertainty around an estimated quantity under the analysis assumptions. No confidence interval, standard error, or numeric mean or standard deviation is reported for the primary outcome. Thus, no conclusion about its precision can be drawn from the posted result details.
The registry lists six outcome measures but zero analysis records. This does not establish which statistical tests were or were not conducted outside the registry, and it does not establish that no analyses occurred. It means the registry record does not provide analysis entries from which to assess model choices, hypothesis tests, or adjustment. The record also does not report a sample-size justification, missing-data approach, or interim-analysis plan.
The safety record lists six serious adverse events in the infliximab group among 163 at risk, and zero other adverse events among 163 at risk. The listed serious-event terms include Pain at 1.2%, Diarrhoea at 0.6%, Psoriatic Arthropathy at 0.6%, Demyelinating Polyneuropathy at 0.6%, Pulmonary Embolism at 0.6%, and Drug Eruption at 0.6%. These figures describe registry safety reporting; they do not provide a comparative safety estimate. The deaths field is not reported in the registry record.
Overall, the record supplies useful design and outcome-definition information but lacks the numeric primary endpoint result. Interpretation should therefore remain focused on what was planned and who was described at each treatment stage, rather than on an unreported estimate.
9. Statistical Methods Explained
The primary outcome is a continuous measure: elapsed time in days between maintenance infusions. The registry specifies the mean as the summary parameter and the standard deviation as the measure of dispersion. These are descriptive statistics. They answer different questions: the mean locates the average interval, while the standard deviation describes variation among the values contributing to that mean. Neither is reported numerically for the primary outcome in the registry record.
What does a mean describe?
In general, the arithmetic mean combines observed values into one average. It can be useful when the research question concerns typical average timing, but it can be affected by unusually short or long intervals. The mean alone does not show whether most observations cluster near that value or whether the data include a broad range. The standard deviation adds information about spread, though it also does not show the full shape of the distribution. A median, range, or distributional plot could offer complementary descriptions, but these are not stated as primary summaries in the registry record.
What is the unit of analysis?
The outcome description defines intervals between successive infusion pairs, from the interval between infusions 3 and 4 through the interval between infusions 8 and 9. These are repeated intervals within a participant's course of treatment, rather than separate randomized treatment groups. In general, repeated observations from the same participant may be related to one another. Analyses that treat correlated observations as independent can understate uncertainty; methods for repeated measures can account for within-participant dependence when appropriate. The registry record does not report whether the analysis used each interval separately, summarized intervals within participants first, or applied a repeated-measures method.
The distinction matters because an average across all interval observations can weight participants with more observed intervals differently from an average of participant-level summaries. These are general possibilities, not claims about the analysis used in this study. The registry record does not report the detailed calculation procedure or an analysis population count for the primary endpoint beyond its partially stated population description.
Why does follow-up matter?
The primary timeframe is up to 24 months. In general, participants may contribute different amounts of follow-up or different numbers of observed intervals. A participant who does not reach a later infusion pair cannot contribute that pair's interval. The number of intervals available can therefore vary, and the handling of incomplete sequences can affect which data contribute to a summary. The registry record does not report how incomplete follow-up, discontinued treatment, or missing infusion dates were handled.
A standard deviation is not a measure of precision of the estimated mean. In general, a confidence interval or standard error is used to describe uncertainty in an estimate, while the standard deviation describes variability among observed values. The registry record does not report a confidence interval, standard error, or numeric primary estimate. Consequently, neither the observed spread nor the precision of the average can be assessed from the posted primary result information.
What can an observational design establish?
In general, an observational study records care without assigning participants to treatment groups through randomization. This study is described as prospective, open-label, one-arm, and observational. Its stated focus is the dose and timing of infliximab infusions in a real-life regimen. Dosage was determined by physicians. Such a design can characterize observed practice, but treatment choices and infusion timing may reflect clinical decisions or participant circumstances. Without a comparator and an appropriate design for causal inference, a descriptive pattern should not be read as a causal effect.
The study does not describe a like-for-like control comparison. Allocation is not stated in the registry record. Therefore, there is no registry-described randomized contrast from which to estimate a difference between treatment strategies. This is distinct from whether the outcome is clinically interesting: the design determines what comparisons the data can support.
How should inferential statistics be read?
In general, a hypothesis test evaluates data against a specified statistical model and null hypothesis. A p-value is not an effect size, nor does it measure the probability that a treatment works. Confidence intervals convey a range of values compatible with the data and assumptions, and their width reflects precision. The registry lists zero analysis records and does not report a test, p-value, confidence interval, or model for the primary outcome. There is therefore no basis in the registry record for describing statistical significance or inferential precision.
Over-dispersion is a general concern when observations vary more than a chosen statistical model expects. If intervals are clustered within participants, or if participant-to-participant variation is substantial, a model that assumes less variation than is present can produce uncertainty estimates that are too narrow. This is a general methodological consideration, not a finding about this study. The registry record does not describe a model, an over-dispersion assessment, or a correction for dependence or extra variation.
How should planning illustrations be distinguished from results?
Sample-size calculations are planning illustrations, not observed outcomes or observed power. The stated planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and effects expressed as fractions of an observed effect. Those assumptions describe a hypothetical planning framework. This trial is described as one-arm, so a two-arm equal-allocation calculation is not a direct description of its design. No numeric planning values or primary observed effect are reported in the registry record. Such illustrations should not be interpreted as evidence that the study had a particular power or that it detected an effect.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists six outcome measures but zero analysis records. The record does not report which outcomes were designated primary or secondary beyond the stated primary endpoint description, nor does it describe a prespecified testing hierarchy or adjustment for multiple comparisons. When several outcomes or repeated tests are examined, the chance of at least one apparently unusual result can increase. In general, multiplicity procedures can control error rates, but the choice depends on the research questions and analysis plan. No such procedure is reported in the registry record, so the handling of multiplicity cannot be assessed.
The registry does not report how missing infusion dates, incomplete infusion sequences, treatment discontinuation, or other missing endpoint data were handled. For a sequence of intervals, incomplete observation can mean that some participants contribute fewer intervals than others. In general, excluding incomplete observations, using available intervals, or applying a model that accommodates incomplete follow-up can lead to different summaries and assumptions. These are possible approaches, not descriptions of what this study did.
The primary population is described as Infliximab-naive participants who received induction and maintenance therapy, but the population text is truncated. The record gives counts at several treatment stages: 152 treated, 94 receiving induction, and 83 receiving induction and subsequent maintenance. It does not fully explain the endpoint analysis population or account for every participant between enrollment and analysis. A complete participant-flow description and explicit denominators for the primary analysis are not reported in the registry record.
The registry also does not report a sample-size justification, interim-analysis plan, or detailed statistical plan. The absence of these details in the registry record does not establish what may have been specified elsewhere; it limits assessment of whether analyses followed a prespecified plan.
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 |
|---|---|---|---|
| Infliximab | 6 | 163 | 3.7% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Infliximab | 0 of 163 |
Most frequent serious adverse event terms
| Event term | Organ system | Infliximab |
|---|---|---|
| Pain | General disorders | 2 of 163 |
| Diarrhoea | Gastrointestinal disorders | 1 of 163 |
| Psoriatic Arthropathy | Musculoskeletal and connective tissue disorders | 1 of 163 |
| Demyelinating Polyneuropathy | Nervous system disorders | 1 of 163 |
| Pulmonary Embolism | Respiratory, thoracic and mediastinal disorders | 1 of 163 |
| Drug Eruption | Skin and subcutaneous tissue disorders | 1 of 163 |
Serious events with the highest arm-level rate: pain (1.2%), diarrhoea (0.6%), psoriatic arthropathy (0.6%), demyelinating polyneuropathy (0.6%), pulmonary embolism (0.6%).
The registry safety group is labeled Infliximab. It reports 163 participants at risk for serious adverse events and six serious adverse events. For other adverse events, it reports 163 at risk and zero affected. The record lists Pain at 1.2%, Diarrhoea at 0.6%, Psoriatic Arthropathy at 0.6%, Demyelinating Polyneuropathy at 0.6%, Pulmonary Embolism at 0.6%, and Drug Eruption at 0.6% among the top serious-event terms.
These are descriptive safety figures from a one-arm study. They do not provide a comparison with an untreated group or another regimen, and they do not establish that treatment caused any listed event. The registry record does not describe the method used to attribute events or provide a comparative risk estimate. The deaths field is not reported in the registry record.
Counts and percentages should be read according to their distinct roles: the at-risk count identifies the group covered by the safety reporting, while the event figures describe recorded safety outcomes. The registry record does not give enough detail to determine from these figures alone whether event counts represent unique participants or total event occurrences. They should not be interpreted as a complete account of all possible safety outcomes.
12. What the Result Does, and Does Not, Mean
The record documents a prospective, open-label, one-arm observational study of infliximab infusion timing in psoriatic arthritis. It specifies induction infusions at weeks 0, 2, and 6, with dosage determined by physicians, followed by a maximum of six maintenance infusions. Its primary endpoint is the mean interval in days between successive maintenance infusions after induction, over a timeframe of up to 24 months.
However, the numeric mean and standard deviation for that endpoint are not reported in the registry record. The posted details therefore do not show the average observed interval, the amount of variation around that average, or the precision of an estimate. No numerical conclusion about the primary outcome can be drawn from its definition alone.
The study's design also shapes what its results could mean. As an observational one-arm study, it can describe treatment and infusion patterns in the participants studied. It does not provide a randomized control group for estimating a contrast with another treatment strategy. Physician-determined dosage and the absence of a comparator mean that observed patterns cannot, on their own, distinguish the influence of treatment decisions from other factors related to care or participant circumstances.
The participant counts show that enrollment and treatment progression were not identical: the registry reports 178 enrolled, 152 Infliximab-naive participants treated, 94 receiving induction, and 83 receiving induction and subsequent maintenance. The primary population description is incomplete, so the precise endpoint analysis population and participant flow cannot be reconstructed from the record.
The safety figures are likewise descriptive. Six serious adverse events and zero other adverse events are reported in the infliximab group, with 163 at risk for each category. The listed event terms and percentages do not establish causation or comparative risk. The deaths field is not reported in the registry record. Overall, the record helps define the study question and setting, but the absent primary estimate and limited analysis details constrain interpretation of results.
13. Why This Trial Matters Statistically
This study raises a practical statistical question about how infusion timing is described in an observational, real-life treatment setting. Its primary endpoint is an average number of days between successive maintenance infusions, rather than a comparison of outcomes between randomized groups. That focus makes the distinction between describing treatment patterns and estimating treatment effects especially important.
The endpoint also has a repeated-observation structure: a participant may have several successive infusion intervals. In general, multiple intervals from one person are not necessarily independent. The choice between summarizing within participants and analyzing intervals as repeated observations can affect both the meaning of the average and the uncertainty around it. The registry record does not report which approach was used, so this issue cannot be resolved from the posted analysis details.
Participant progression through induction and maintenance is another statistical consideration. The registry reports different counts for treated participants, induction recipients, and those receiving subsequent maintenance. This illustrates why an outcome definition should be paired with a clearly described analysis population and participant flow. The primary population text is incomplete, and the numeric endpoint summary is not reported.
The one-arm observational design is also central to interpretation. It can describe what infusion schedules were recorded in the study setting, but it does not supply a randomized comparator for causal contrasts. The stated planning assumptions concern a two-arm calculation, while the trial itself is described as one-arm. Keeping planning illustrations separate from observed results and from the actual design prevents inappropriate conclusions about power or comparative effects.
For statistical readers, the record is therefore informative about design and endpoint construction, but incomplete for evaluating the primary estimate, its uncertainty, and its analysis methods. These gaps matter because clear outcome reporting and transparent analysis populations are necessary to judge how robustly a descriptive result represents the observations collected.
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 most direct limitation of the registry record is that it defines the primary endpoint without reporting its mean or standard deviation. No confidence interval or other measure of precision is reported. This prevents quantitative assessment of the primary outcome, including its average level and variability.
The population description is incomplete. It identifies Infliximab-naive participants receiving induction and maintenance therapy, but the text ends before the full description is available. The record lists 178 enrolled, 152 treated, 94 receiving induction, and 83 receiving induction and subsequent maintenance. It does not give a complete account of the transition from enrollment to the endpoint analysis population, or explicitly state the denominator used for the primary outcome.
The outcome involves successive infusion intervals, but the registry does not report how repeated intervals within a participant were handled statistically. It also does not describe how participants with incomplete infusion sequences, missing dates, or different durations of follow-up were treated. These details matter for interpreting an average based on observations collected over a timeframe of up to 24 months.
The study is described as observational, open-label, multicenter, and one-arm. Dosage was determined by physicians, and no comparator arm is described. These features limit comparative interpretation and leave treatment timing embedded in clinical decision-making. Allocation is not stated in the registry record.
The registry lists six outcome measures but zero analysis records. It does not report a detailed statistical plan, a sample-size justification, multiplicity handling, interim analyses, or missing-data methods. Safety information is descriptive and lacks a comparator; the deaths field is not reported in the registry record. Together, these omissions limit assessment of endpoint precision, analytic choices, participant flow, and comparative safety.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Investigation of 9 Consecutive Infusions of Remicade for Psoriatic Arthritis in Austria (Study P04264) — NCT00725296.
- Registry record last updated 2015-11-05; status last verified 2015-10.
- Results first posted 2011-07-29.
- 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
The registry record describes a completed, prospective, open-label, one-arm multicenter observational study in Austria of Remicade (infliximab) for psoriatic arthritis. Enrollment is listed as 178. The study start is recorded as 2004-12 and primary completion as 2010-07.
The treatment description includes physician-determined induction doses at weeks 0, 2, and 6, followed by a maximum of six maintenance infusions. The primary endpoint is the mean number of days between successive maintenance infusions after induction, over up to 24 months. Its numerical mean and standard deviation are not reported in the registry record.
The record reports 152 Infliximab-naive participants treated, 94 receiving induction, and 83 receiving induction and subsequent maintenance. It lists six outcome measures and zero analysis records. Safety reporting lists six serious adverse events and zero other adverse events among 163 at risk in the infliximab group; deaths are not reported in the registry record.