Post-Marketing Use Of CT-P13 (Infliximab) For Standard Of Care Treatment Of Rheumatoid Diseases Who Are Naïve To Biologics Or Switched From Remicade: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Post-Marketing Use Of CT-P13 (Infliximab) For Standard Of Care Treatment Of Rheumatoid Diseases Who Are Naïve To Biologics Or Switched From Remicade (NCT02605642), a registered phase not stated study. The primary outcome is Treatment Persistence With CT-P13 in Participants With Rheumatoid Arthritis (RA), Ankylosing Spondylitis (AS) or Psoriatic Arthritis (PsA).

2. Clinical Question

The clinical question is descriptive: it concerns persistence in routine use among people with different prior biologic-treatment histories. The record also lists changes in disease activity, function and quality-of-life measures as secondary outcomes. Those outcomes are not the primary persistence measure, and their presence in the record does not itself establish what changes occurred. The registry reports enrollment of 351 participants, but the primary outcome is defined for the safety population rather than simply by the enrollment figure. Results for the primary outcome and the listed secondary measures are not reported in the registry record.

3. Trial Design

PERSIST is described as a prospective observational cohort study of CT-P13 use among people with rheumatoid diseases. The conditions named in the record are rheumatoid arthritis, ankylosing spondylitis and psoriatic arthritis. The study enrolled 351 participants, and its status is completed. The recorded start date is 2015-09-10 and the primary completion date is 2018-12-31.

The cohort included two treatment-history groups: people who were biologic-naive and people who switched from stable Remicade to CT-P13. The registry does not state how participants were allocated to these groups; the groups therefore should not be treated as randomized arms or as equivalent groups differing only in treatment. The record identifies CT-P13 as biosimilar infliximab and does not describe a concurrently assigned control treatment.

The main objective was to evaluate real-life persistence in the disease groups and treatment-history groups. Other objectives were to characterize patient populations and drug-use patterns and to assess safety for up to 2 years. The primary outcome timeframe is described as an observation period of 2 years. The record defines the primary-outcome population as participants who received at least one dose of CT-P13 during that observation period.

The secondary outcomes include changes from baseline in DAS28 for rheumatoid arthritis and psoriatic arthritis; BASDAI, ASDAS and BASFI for ankylosing spondylitis; HAQ-DI; and EQ-5D-3L measures. These are listed at months 6, 12, 18 and 24. The registry record does not report the detailed visit procedures, the extent of follow-up actually achieved, or the results for these outcomes. It also does not report a detailed statistical analysis plan, how treatment-history groups were formed in practice, or whether any adjustments were planned to address differences between them.

Because this is an observational cohort, the findings are intended to describe the recorded experience of participants receiving CT-P13 in the study setting. They do not arise from random assignment. Comparisons between the biologic-naive and switched groups may reflect differences in prior treatment history or other characteristics; the registry record does not provide enough information to determine how such differences were handled analytically.

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: The safety population was defined as all participants who received at least one dose of CT-P13 during the study observation period.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: Safety analysis set included all participants who received at least 1 dose of CT-P13 during the study observation period.

6. Primary Endpoint

The registry lists the primary outcome as Treatment Persistence With CT-P13 in Participants With Rheumatoid Arthritis (RA), Ankylosing Spondylitis (AS) or Psoriatic Arthritis (PsA), measured over During the observation period of 2 years.

The primary endpoint is treatment persistence with CT-P13, expressed in days. It measures elapsed time from an index date until drug discontinuation. The record defines discontinuation as either switching to another non-infliximab BDMARD or a drug-free interval of 16 weeks from CT-P13. The endpoint is specified as a mean with standard deviation over the observation period of 2 years.

The index date differs according to treatment history. For participants who switched from Remicade, it is the date Remicade was originally commenced. For participants who initiated CT-P13 as their first biologic, it is the date CT-P13 was initiated. This distinction matters for interpretation: the duration is anchored to different treatment events in the two groups, not uniformly to the start of CT-P13.

Persistence is used to describe how long treatment continues before a defined discontinuation event. It can summarize continued use in routine care, but it is not the same as a measure of disease improvement, a direct measure of safety, or proof that one treatment strategy is better than another. The endpoint also depends on the operational discontinuation definition and the observation process. The registry record does not report the mean persistence, its standard deviation, or details about how incomplete follow-up was handled. Accordingly, the endpoint definition is available, but its numerical result and precision are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical information in the registry record is limited. It identifies the primary outcome as a continuous measure summarized by a mean and standard deviation, and it defines how persistence and discontinuation are classified. It does not report the primary estimate, a confidence interval, a test result, or a detailed analysis plan. The explanations below describe general statistical concepts and distinguish them from methods confirmed in the record.

What does a mean and standard deviation describe?

General explanation: a mean is an average of the measured values. For persistence, the measured value is duration in days from the group-specific index date until the defined discontinuation event. A standard deviation describes how widely individual durations vary around the mean. A mean alone cannot show whether most participants had similar durations or whether durations were widely spread. The registry specifies these summary statistics but does not report their values.

A mean duration is not automatically equivalent to a survival estimate. In time-to-event analysis, some participants may not experience the event during observed follow-up, or their later status may be unknown. Such observations are often treated as censored rather than as completed event times. General explanation: methods for time-to-event data can use information from censored observations without treating them as if the event occurred at the end of recorded follow-up. The registry record does not say whether the primary analysis used a time-to-event method, how censoring was treated, or whether the reported mean was calculated only from observed durations. That detail is not reported in the registry record.

How does the event definition affect the endpoint?

The endpoint counts treatment as discontinued after a switch to another non-infliximab BDMARD or after a drug-free interval of 16 weeks from CT-P13. General explanation: an endpoint definition determines which events count and when they are considered to have occurred. Different operational definitions can produce different persistence summaries. The record does not report whether alternative definitions or sensitivity analyses were considered.

The time origin is not the same for the two treatment-history groups. For participants switching from Remicade, the index date is when Remicade was originally commenced; for participants starting CT-P13 as their first biologic, it is when CT-P13 was initiated. Consequently, the endpoint duration for switchers may include time before they began CT-P13. This is part of the registry’s definition and should be kept in mind when interpreting any group-specific persistence figures. The record does not report a harmonized alternative time origin.

Why does observational allocation matter?

General explanation: random allocation can balance measured and unmeasured characteristics across treatment groups on average. In an observational cohort, treatment history and treatment choice are not assigned at random, so groups may differ before the outcome is measured. A simple comparison of group averages can therefore combine differences in treatment experience with differences in who entered each group. The registry says allocation was not stated and notes that the groups are not a like-for-like control comparison. It does not report adjusted estimates, covariates, matching, weighting, or another method to account for group differences.

Even a statistical adjustment, if one had been used, would need to be interpreted in light of the information measured and the analysis assumptions. The registry does not provide sufficient detail to assess such methods, and no adjusted result is reported. No causal interpretation can be established from the registry record alone.

What can a confidence interval tell a reader?

General explanation: a confidence interval conveys the statistical uncertainty around an estimate under a specified model and sampling process. A narrower interval indicates greater precision under those assumptions; a wider interval indicates less precision. It does not correct systematic bias, confounding, inconsistent measurement or incomplete follow-up. The registry record does not report a confidence interval for the primary outcome, so its statistical precision cannot be evaluated from the posted results.

How should planning illustrations be understood?

The accompanying planning illustrations are based on the observed effect, use a two-sided significance level of 0.05, assume equal allocation between two arms and use a normal approximation. The stated effect to detect is a fraction of the observed effect. For time-to-event outcomes, the illustration concerns the total number of events using the Schoenfeld approach; other illustrations concern participants per arm. These are planning assumptions, not descriptions of the study’s actual allocation or an estimate of observed power. The registry record does not report a sample-size justification for the original study design. A planning calculation based on an observed effect also does not establish that the study had a particular probability of detecting an effect.

General explanation: over-dispersion occurs when outcome variability is greater than assumed by a statistical model. If a model underestimates variability, its uncertainty estimates can be too small. This concept is relevant in some kinds of data, but the registry record does not report an over-dispersion assessment or a model for the primary persistence outcome. It should not be inferred that a particular model or correction was used.

In short, the registry record supports explanation of the endpoint and the broad observational design, but not reconstruction of an unreported analysis. The mean, standard deviation, uncertainty interval, handling of incomplete follow-up and detailed statistical procedures are not reported in the registry record.

10. Confidence Intervals for Each Arm

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

R code and output

arm <- c("Biologic Disease Modifying Anti-Rheumatic Drugs (B", "Participants Who Switched From Remicade to CT-P13")
n   <- c(221, 107)
m   <- c(404.1, 542.3)
sp  <- c(291.33, 268.55)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Biologic Disease Modifying Anti-Rheumatic Drugs (B  221  404.100  291.330  365.478  442.722
CARM  Participants Who Switched From Remicade to CT-P13  107  542.300  268.550  490.828  593.772

11. Multiplicity, Missing Data and Analysis Populations

The registry lists several secondary outcome families: disease activity measures for rheumatoid arthritis, psoriatic arthritis and ankylosing spondylitis; a functional measure; and quality-of-life measures. The listed changes from baseline are scheduled at months 6, 12, 18 and 24. Testing several outcomes and time points can raise a multiplicity issue: when many statistical tests are conducted, the chance of at least one apparently unusual result can increase. General explanation: prespecified approaches such as a hierarchy of tests or an adjustment for multiple comparisons can help define how results should be interpreted. The registry record does not report a multiplicity strategy, a testing hierarchy, or which secondary outcomes were formally analyzed.

The record describes the primary outcome population as participants who received at least one dose of CT-P13 during the study observation period. It does not report the number included in the primary analysis, the number with usable outcome data, or whether the analysis followed another population definition. The enrollment figure of 351 should not be assumed to be the analysis denominator for each endpoint.

Missing-data handling is not reported in the registry record. In particular, the record does not explain how missing visits, incomplete follow-up, or participants without a recorded discontinuation event were handled. General explanation: missingness can affect an estimate if the reasons for missing observations are related to treatment duration or outcomes. A statistical method may rely on assumptions about those reasons, and the assumptions matter to interpretation.

The registry record also does not report interim analyses, a detailed statistical analysis plan, or a method for controlling multiplicity. It is therefore not possible to assess whether analyses were prespecified, how missing data affected the reported outcomes, or how uncertainty across the listed measures was managed. The posted record should be read as incomplete on these analysis details, rather than as evidence that a particular method was or was not used.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: anaemia (0.9%), coronary artery stenosis (0.9%), erysipelas (0.9%), herpes zoster (0.9%), lower respiratory tract infection (0.9%).

The registry reports adverse-event figures separately for the biologic disease-modifying anti-rheumatic drug-naive group and the group that switched from Remicade to CT-P13. In the biologic-naive group, 221 participants are listed at risk for serious adverse events and 19 are listed as affected; 221 are listed at risk for other adverse events and 88 as affected. In the switch group, 107 are listed at risk for serious adverse events and 10 as affected; 107 are listed at risk for other adverse events and 24 as affected. The record lists 0 deaths in each group.

These are descriptive registry counts, not a randomized comparison. The groups differ by prior treatment history, and the record does not state allocation or report an adjusted comparison. The figures alone do not establish that CT-P13 caused an event, nor do they show whether group differences reflect treatment, participant characteristics or other factors. The registry’s listed terms for serious events include Anaemia, Coronary artery stenosis, Erysipelas, Herpes zoster, Lower respiratory tract infection and Pilonidal cyst, each reported as 0.9%. The record does not provide enough context to attribute those terms to a particular group.

General explanation: adverse-event counts describe events or affected participants according to the registry’s reporting convention; interpretation depends on definitions, ascertainment and follow-up. The record’s counts should not be taken as a complete causal assessment or as proof that no unlisted event occurred.

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

The registry record is useful for understanding the study question: it describes persistence with CT-P13 in an observational cohort that included people who were biologic-naive and people who switched from stable Remicade. It also defines the discontinuation event and identifies the clinical measures intended as secondary outcomes. The record reports enrollment of 351 participants and adverse-event counts for the two treatment-history groups.

However, the central numerical result for persistence is not reported in the registry record. No mean duration, standard deviation, confidence interval or primary analysis result is available. The listed secondary outcome measures likewise do not come with numerical change results in the registry record. Therefore, the record does not establish the observed degree of persistence, the precision of that estimate, or the direction and size of changes in disease activity, function or quality of life.

Nor does the observational design support a randomized treatment comparison. The treatment-history groups are not a like-for-like control comparison, and allocation is not stated. Any differences between them could reflect prior treatment and other group characteristics as well as treatment experience. The record does not report an analysis that would support a causal interpretation.

The adverse-event counts describe what is recorded for the stated groups, but they do not by themselves establish causality or comparative risk. The registry record does not provide the analysis details needed to judge event ascertainment, adjustment or follow-up completeness. The reported 0 deaths in each group is a descriptive entry, not a conclusion about all possible safety outcomes.

General explanation: an observational result can help characterize treatment use in the study population, but interpretation depends on how participants were selected, measured and followed. A clear endpoint definition does not substitute for a reported estimate, and an estimate alone would not remove limitations from nonrandomized group formation. In this case, the primary result and important analysis details are not reported in the registry record. Conclusions should therefore remain limited to the study’s design, endpoint definitions and posted descriptive safety information.

14. Why This Trial Matters Statistically

This study is statistically notable because its primary question concerns persistence in routine treatment rather than a laboratory measure or a randomized comparison of assigned therapies. Persistence can summarize how long a treatment remains in use under a defined discontinuation rule. That kind of outcome is relevant to understanding real-life treatment patterns, but its meaning depends closely on the event definition, time origin and follow-up process.

The registry makes an important distinction between biologic-naive participants and those switching from stable Remicade. Those groups represent different treatment histories, and the record does not describe them as randomized or equivalent. Treating them as if they were interchangeable control groups would obscure the design. The distinction in index dates is also consequential: persistence begins from CT-P13 initiation for biologic-naive participants, but from the original Remicade start for switchers. Readers need this detail to understand what each duration would represent.

The study also illustrates why an endpoint definition and a result are different kinds of information. The registry states how persistence is measured and gives the planned summary as a mean with standard deviation, but it does not report those values. It therefore allows a reader to understand the intended measurement without allowing assessment of the observed magnitude or precision. This is a substantive reporting limitation, not something that can be repaired by interpreting the endpoint description as a result.

Finally, the registry’s safety counts offer descriptive information but not a controlled safety comparison. The treatment-history groups and the absence of stated allocation limit causal interpretation. General statistical lesson: a detailed measure can be useful while still leaving uncertainty about bias, missingness and comparability. For this record, those issues reinforce the need to distinguish what was planned and defined from what was numerically reported.

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.

Several limitations are specific to the information reported for this study. First, the primary persistence result is not reported in the registry record, despite the endpoint being defined as a mean number of days with a standard deviation. The registry also does not report a confidence interval or other measure of precision. This prevents assessment of the observed duration or its uncertainty.

Second, the cohort is observational, allocation is not stated, and the two groups are separated by treatment history rather than randomized assignment. The record does not report a like-for-like control comparison or an adjusted analysis. Differences between the biologic-naive and switch groups therefore cannot be attributed to treatment without further evidence and analysis.

Third, the index date differs across groups. Switchers are measured from the date Remicade was originally commenced, whereas biologic-naive participants are measured from CT-P13 initiation. This distinction means that the durations have different origins and complicates direct group interpretation. The record does not report an alternative analysis using a common time origin.

Fourth, the registry does not report details about actual follow-up, incomplete observations, censoring, reasons for discontinuation, or missing-data handling. It also does not report the detailed statistical plan, covariate adjustment, sensitivity analyses or multiplicity procedures. These omissions limit assessment of bias and analytic robustness. The listed secondary outcomes have no numerical results reported in the registry record, so their direction and precision cannot be evaluated.

Finally, the adverse-event figures are descriptive and do not establish causality. The record does not explain all event-ascertainment details or provide a randomized safety comparison. The planning illustrations use stated assumptions and are not evidence of observed power or of the original study’s design justification. These limitations should remain visible when interpreting the record’s endpoint definitions and safety counts.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Post-Marketing Use Of CT-P13 (Infliximab) For Standard Of Care Treatment Of Rheumatoid Diseases Who Are Naïve To Biologics Or Switched From Remicade — NCT02605642.
• Registry record last updated 2020-01-13; status last verified 2019-12.
• Results first posted 2020-01-13.
• 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

PERSIST is a completed prospective observational cohort study of CT-P13 use in rheumatoid arthritis, ankylosing spondylitis and psoriatic arthritis. It enrolled 351 participants, including people who were biologic-naive and people who switched from stable Remicade. The primary outcome was persistence in days during an observation period of 2 years, with discontinuation defined by switching to another non-infliximab BDMARD or a drug-free interval of 16 weeks from CT-P13.

The registry record specifies a mean and standard deviation as the primary summary but does not report their values or a primary analysis result. Secondary measures include disease activity, function and quality of life; their numerical results are not reported in the registry record. Descriptive adverse-event counts and listed serious-event terms are available, but the nonrandomized treatment-history groups do not support a like-for-like causal comparison. Missing-data methods, detailed analysis procedures and multiplicity handling are not reported in the registry record.