A Study of Re-Treatment With MabThera (Rituximab) in Patients With Rheumatoid Arthritis Who Have Had an Inadequate Response to a Single Anti-TNF Inhibitor.: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of Re-Treatment With MabThera (Rituximab) in Patients With Rheumatoid Arthritis Who Have Had an Inadequate Response to a Single Anti-TNF Inhibitor. (NCT00502840), a na phase 3 study. The primary outcome is Change From Baseline in DAS28 Score at Week 24.

2. Clinical Question

3. Trial Design

This phase 3 study is described as an open-label extension study evaluating the safety of rituximab re-treatment and its effect on treatment response in participants with rheumatoid arthritis. Participants had taken part in ML19070 and completed the week 24 visit. The eligibility description specifies DAS28 >2.6 after week 24. The study is classified as a single-group design, with no masking and allocation listed as not applicable.

The registry reports enrollment of 193. Its brief description says eligible participants received 2 infusions of 1g MabThera on Day 1 and day 15, with up to 3 repeated courses allowed for participants in the extension. The anticipated time on study treatment was 1-2 years. These are features of the registry description; the record does not provide participant-level treatment histories or the number who received each permitted course.

The study started on 2007-07-23, had primary completion on 2011-09-20, and is marked completed. Its stated target sample size was 100-500 individuals. A separate sample-size justification is not reported in the registry record. The single-group, open-label design is important when reading the response outcome: the record does not describe a concurrent control group that could distinguish change during follow-up from other influences on disease activity.

The primary measure was change from baseline in DAS28 score at Week 24. Listed secondary outcomes include DAS28 by treatment course and follow-up visit, EULAR response categories, HAQ-DI, FACIT-F, and SF-36 scores. The registry identifies 25 outcome measures, but numerical results for the primary endpoint are not reported in the registry record.

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: Intent-to-Treat (ITT) Population: all participants who signed the informed consent form, received at least 1 dose of study medication, and where the DAS28 was measured at least once under study medication.

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 Population: all participants who received at least 1 dose of the trial medication and had at least 1 safety follow-up, whether withdrawn prematurely or not. A safety follow-up was assumed if the participant had at least 1 documented study visit after baseline or if at least 1 adverse event had been documented with start date after baseline.

6. Primary Endpoint

The registry lists the primary outcome as Change From Baseline in DAS28 Score at Week 24, measured over Week 24.

The primary endpoint is change from baseline in DAS28 score at Week 24. DAS28 combines the swollen joint count and tender joint count, based on 28 joints, with erythrocyte sedimentation rate and the participant’s global assessment of disease activity. The registry describes transformed scores ranging from 0 to 10, with higher scores indicating greater disease activity.

A change score expresses how far the Week 24 measurement differs from the baseline measurement. It can therefore describe the direction and magnitude of within-participant change over follow-up. A group mean summarizes those individual changes, while a standard deviation describes their spread. These statistics answer different questions: the mean estimates the average change, and the standard deviation indicates how variable individual changes were around that average.

The registry defines a clinically meaningful improvement as an improvement of 1.2 units. This threshold gives clinical context to a change estimate, but it does not replace reporting the estimate and its uncertainty. The numerical primary endpoint result, its standard deviation, and any confidence interval or test result are not reported in the registry record. It is therefore not possible to assess from this record how the observed group change compares with the stated threshold.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary endpoint as a mean change in a continuous measure, DAS28, from baseline to Week 24. The stated dispersion measure is the standard deviation. The record defines the primary analysis population as participants who signed informed consent, received at least 1 dose of study medication, and had DAS28 measured at least once under study medication. The numerical results of that analysis are not reported in the registry record.

What does a mean change describe?

In general, a mean change is the average of participants’ changes between two measurements. It preserves the direction of change, unlike a measure that reports only the size of differences. For DAS28, lower scores indicate less disease activity than higher scores according to the registry’s description. A negative change would therefore indicate a reduction in score, while a positive change would indicate an increase; the actual mean change is not reported in the registry record.

The standard deviation describes the spread of individual change values around the group mean. It is not the uncertainty of the mean itself. In general, a confidence interval for a mean change would help show the range of values compatible with the data and the statistical model, while a standard deviation describes participant-to-participant variability. Neither the standard deviation nor a confidence interval for the primary change is reported in the registry record.

How should a confidence interval be read?

In general, a confidence interval conveys uncertainty around an estimate. A narrower interval indicates greater precision under the analysis assumptions, while a wider interval indicates less precision. Its interpretation depends on the study design, the population analyzed, and the statistical method. No confidence interval for the primary DAS28 endpoint is reported in the registry record, so the precision of the endpoint estimate cannot be evaluated.

What can a single-group change estimate establish?

A within-group estimate can describe the change observed among participants during the study. It does not by itself show what would have happened to those same participants over the same period without re-treatment. In general, a concurrent comparison group helps account for changes that might occur over time independently of the study intervention. This record describes a single-group, open-label study, so it does not provide a randomized comparison of re-treatment with another treatment or with no re-treatment.

The trial’s open-label status is also relevant because DAS28 includes a participant-rated global assessment. General measurement considerations include the possibility that expectations or awareness of treatment can influence subjective assessments. This does not establish that such influence occurred in this study; it identifies a design feature to consider when interpreting a participant-reported component.

What do the planning assumptions mean?

The registry describes sample-size calculations as planning illustrations based on the observed effect, not as the trial’s original design. The stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. For time-to-event outcomes, the illustration is described as giving the total number of events; for other outcomes, it gives participants per arm. These assumptions describe hypothetical planning calculations and do not describe the design of this single-group study.

A planning calculation is not observed power. In general, a sample-size calculation asks how much information a future design might require under specified assumptions. Observed power, calculated after a study using its observed effect, does not replace an estimate and confidence interval and can be misleading as a summary of results. The registry does not report the trial’s own sample-size justification. Numerical planning illustrations are not reported in the registry record.

Why can extra variation matter?

In general, over-dispersion means that outcome variation is greater than a model assumes. When a model underestimates variation, its uncertainty estimates can be too small and its intervals or tests can be misleading. Whether over-dispersion is relevant depends on the outcome and analysis model. The registry record does not report a model for the primary endpoint or information allowing an assessment of over-dispersion.

The record lists 25 outcome measures and 0 analyses. It identifies several secondary outcomes, but does not report numerical findings or a detailed statistical plan. The outcome descriptions alone do not establish which models, covariates, repeated-measures methods, or decision rules were used. Those analysis details 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("Rituximab Plus MTX")
n   <- c(173)
m   <- c(-2.12)
sp  <- c(1.41)
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  Rituximab Plus MTX  173  -2.120  1.410  -2.332  -1.908

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 25 outcome measures, including the primary change in DAS28 and secondary measures of disease activity, EULAR response, physical function, fatigue, and health status. Assessing multiple outcomes can raise a multiplicity issue: in general, the chance of at least one apparently notable result may increase when many hypotheses are tested. Statistical approaches can address multiplicity, but the appropriate choice depends on the questions and analysis plan. A multiplicity procedure or hierarchy for interpreting outcomes is not reported in the registry record.

The record identifies the primary analysis population using consent, treatment exposure, and availability of at least one DAS28 measurement under study medication. It does not report how many participants contributed to the Week 24 analysis, how missing Week 24 measurements were handled, or whether all listed outcomes used the same population. The missing-data method and sensitivity analyses are not reported in the registry record.

These omissions limit interpretation because missing measurements can affect both the estimated change and its precision, depending on why data are missing and how the analysis handles them. In general, an analysis that uses only available observations relies on assumptions about those observations; other methods make different assumptions. Without the analysis method and outcome-level denominators, the robustness of the endpoint findings cannot be judged. The registry record also does not report a detailed statistical analysis plan or interim-analysis procedures.

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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: rheumatoid arthritis (2.6%), pneumonia (1.0%), respiratory tract infection (1.0%), arthritis (1.0%), intervertebral disc protrusion (1.0%).

For the Rituximab Plus MTX group, the registry reports 193 participants at risk for serious adverse events and 47 affected. For other adverse events, it reports 193 at risk and 105 affected. These are descriptive counts for the study group, not comparisons with a separate control group. The record does not provide a comparative estimate of risk.

The listed serious adverse event terms include rheumatoid arthritis at 2.6%, pneumonia at 1.0%, respiratory tract infection at 1.0%, arthritis at 1.0%, intervertebral disc protrusion at 1.0%, and osteoarthritis at 1.0%. These percentages describe the terms as recorded; they should not be read as evidence that each term occurred in a separate participant or as a ranking of comparative risk. The registry record does not provide further detail about event timing, duration, severity beyond the serious classification, or attribution to treatment.

In general, adverse-event counts describe events observed and recorded during a study, while comparative safety conclusions require an appropriate comparison and attention to follow-up and exposure. The single-group design and the information support a descriptive reading only. The registry lists no death count for this group.

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

The registry record describes a study of repeated rituximab courses in participants with rheumatoid arthritis who had taken part in ML19070 and met the stated extension eligibility criteria. It identifies change from baseline in DAS28 at Week 24 as the primary endpoint and defines a clinically meaningful improvement as 1.2 units. It also reports descriptive adverse-event counts and lists secondary outcome measures.

What the record does not report is the numerical primary endpoint result. Without a mean change and its variability or uncertainty, the size and precision of the observed change cannot be assessed. The stated threshold provides a reference for interpreting a result, but it cannot establish whether the threshold was met in the absence of the result. The record also does not provide numerical results for the secondary measures listed in the registry record for this analysis.

The design limits what can be concluded from any within-group change. A change over time is not the same as a treatment effect relative to an alternative. Because this is an open-label, single-group extension study, the record does not establish how participants’ outcomes would have differed under a concurrent comparator. It also does not allow the effects of treatment to be separated from other influences on change over follow-up.

The adverse-event counts describe events in the study group, but are not comparative safety estimates. The record does not report a control-group event rate or provide further detail needed to compare risks. The findings should therefore be read as registry descriptions of the study’s measured outcomes and recorded events, not as a basis for medical advice or a treatment recommendation.

14. Why This Trial Matters Statistically

This study raises several important statistical interpretation issues in a familiar clinical setting: repeated treatment, a continuous disease-activity measure, multiple secondary outcomes, and safety reporting. The primary endpoint uses a mean change in DAS28, while its stated standard deviation would describe variation among participant changes. Keeping these two quantities distinct is essential: the average describes the group’s change, and the spread describes how uneven that change may be across participants.

The stated clinically meaningful improvement of 1.2 units illustrates why statistical and clinical interpretation are related but not interchangeable. A numerical estimate and its uncertainty are needed to assess the observed change in context. The registry record gives the threshold but does not report the primary estimate or its precision.

The design also illustrates why within-group change and comparative treatment effects are different questions. An extension cohort can document what was observed among participants receiving repeated courses, but a single-group design does not provide a randomized comparison against another strategy. Open-label assessment adds a further consideration because the DAS28 measure includes a participant global assessment.

Finally, a long list of outcomes makes transparent reporting of the analysis plan and missing-data handling important. The registry names 25 outcome measures but does not report the primary result or detailed methods for multiplicity and missing data. These gaps limit the ability to assess precision, robustness, and the relationship between the planned outcomes and the reported findings.

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 main limitation for interpreting efficacy is that the registry record does not report the numerical primary endpoint result. It therefore does not provide the Week 24 mean change in DAS28, its standard deviation, a confidence interval, or a test result. The clinical threshold is stated, but the missing estimate prevents comparison with that threshold.

The study is open-label and single-group, with no concurrent control described. This prevents a direct randomized comparison and limits attribution of change to re-treatment. DAS28 also includes a participant-rated global assessment, which is a measurement component to consider in an unmasked study. The registry does not report details of outcome assessment procedures beyond the endpoint description.

The record lists multiple secondary outcomes, but does not describe a multiplicity strategy, a detailed statistical analysis plan, or interim analyses. It defines the primary analysis population but does not report the population contributing to the Week 24 result or a missing-data method. These details are not reported in the registry record, limiting assessment of possible selection, missingness, or analytic sensitivity.

For safety, the record reports affected-participant counts and selected serious adverse event terms, but no comparative group. It does not report event timing, treatment attribution, or other details that would support a comparative safety interpretation. The registry’s planning assumptions are illustrations rather than a reported original sample-size justification, and their numerical outputs are not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Study of Re-Treatment With MabThera (Rituximab) in Patients With Rheumatoid Arthritis Who Have Had an Inadequate Response to a Single Anti-TNF Inhibitor. — NCT00502840.
• Registry record last updated 2017-08-18; status last verified 2017-07.
• Results first posted 2014-09-10.
• 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 identifies NCT00502840 as a completed phase 3, open-label, single-group extension study of rituximab re-treatment in rheumatoid arthritis. Participants had participated in ML19070, completed the week 24 visit, and were eligible under the stated DAS28 criterion. Enrollment is listed as 193.

The primary outcome was change from baseline in DAS28 at Week 24. The registry defines a clinically meaningful improvement as 1.2 units, but the numerical primary outcome result is not reported in the registry record. The record lists 25 outcome measures and reports serious and other adverse-event counts for the Rituximab Plus MTX group. Its single-group design does not provide a concurrent randomized comparison.