A Study of the Efficacy and Safety of Tocilizumab in Adults With Rheumatoid Arthritis.: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of the Efficacy and Safety of Tocilizumab in Adults With Rheumatoid Arthritis. (NCT01988012), a na phase 3 study. The primary outcome is Percentage of Participants With Clinical Disease Activity Index (CDAI) Remission and CDAI Low Disease Activity.

2. Clinical Question

The study focused on adults with rheumatoid arthritis and assessed disease activity after treatment with subcutaneous tocilizumab. The primary outcome was framed around two CDAI categories: remission and low disease activity. The registry record defines remission as a CDAI score at or below 2.8 and low disease activity as a score above 2.8 through 10. These categories describe different ranges of the same disease activity index.

This is a within-group clinical question, not a comparative-effectiveness question. With one treatment group and no control group, the record can describe outcomes among participants receiving tocilizumab, but the design cannot by itself separate treatment-associated changes from other explanations such as the course of disease, other care, or expectations. Combination therapy with methotrexate or other non-biologic disease-modifying anti-rheumatic drugs was permitted, which is relevant when interpreting the treatment context.

The registry record names the primary outcome and its Week 24 timeframe but does not report the remission or low-disease-activity results. It therefore does not establish what proportion of participants reached either category. Safety and other outcomes were also listed, but their presence in the record does not substitute for the missing numerical primary outcome results.

3. Trial Design

This was a Phase 3, multicenter, open-label, single-group study sponsored by Hoffmann-La Roche. The registry record gives enrollment as 100 and lists the study status as completed. The recorded start was 2014-01, and primary completion was 2015-07. No randomized allocation or masking was used; allocation is listed as not applicable and masking as none.

Participants were adults with rheumatoid arthritis. The treatment was subcutaneous tocilizumab, described in the study summary as a single weekly injection. The treatment period was 24 weeks, followed by an 8 week follow-up period without treatment. Methotrexate and other non-biologic disease-modifying anti-rheumatic drugs were permitted as combination therapy. The registry record does not report how many participants used those medicines or their treatment patterns.

The single-group structure is central to interpretation. All participants were assigned to the tocilizumab group, and there was no parallel control group against which to compare outcomes. Open-label means treatment masking was not used. Consequently, the study could describe observed disease activity and safety during treatment and follow-up, but the design does not offer a randomized estimate of the difference between tocilizumab and an alternative.

The primary outcome concerned the percentage of participants with CDAI remission and the percentage with CDAI low disease activity at Week 24. The registry record lists 19 outcome measures, including safety, dose modification or discontinuation due to adverse events, immunogenicity, tocilizumab levels, and change in soluble interleukin-6 receptor levels. It lists no analyses. Detailed protocol procedures, the rationale for the planned enrollment, and the statistical analysis plan 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: The analysis population included those participants from the full analysis set (FAS) for whom evaluable data for this outcome measure were available. The FAS included all enrolled participants who received at least one dose of subcutaneous tocilizumab.

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: The full analysis set (FAS) included all enrolled participants who received at least one dose of subcutaneous tocilizumab.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants With Clinical Disease Activity Index (CDAI) Remission and CDAI Low Disease Activity, measured over Week 24.

The primary outcome uses the Clinical Disease Activity Index, or CDAI, to classify rheumatoid arthritis disease activity at Week 24. CDAI combines the swollen joint count from a 28-joint assessment, the tender joint count from a 28-joint assessment, the participant’s global assessment, and the physician’s global assessment. The two global assessments use a visual analogue scale running from 0, indicating no disease activity, to 10, indicating maximum disease activity. CDAI scores range from 0 to 76, with higher scores indicating greater disease activity.

The registry record reports two threshold-based categories. Remission is defined as CDAI at or below 2.8. Low disease activity is defined as CDAI above 2.8 through 10. Reporting the percentage of participants in each category provides a clinically interpretable description of how many participants met those specified disease-activity thresholds at the assessment time. The categories should be understood as separate outcome descriptions, rather than as a comparison between treatment groups.

A threshold outcome can be easier to interpret than a change in a continuous score, but it also depends on the selected cutoffs and the availability of evaluable assessments. The registry record says the analysis population included full-analysis-set participants with evaluable data for this outcome. It does not report how many participants had evaluable data, the numbers meeting either threshold, or the corresponding percentages. Thus, the endpoint definition is available, while the primary outcome findings are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record describes a binary percentage endpoint: the percentage of participants who met a specified CDAI category at Week 24. For each category, an analysis would classify participants according to whether their CDAI score met the stated threshold and then report the share of the evaluable population in that category. The record defines the full analysis set as enrolled participants who received at least one dose of subcutaneous tocilizumab, while the primary outcome analysis population further required evaluable data. It does not report the actual number included in that outcome analysis or the number meeting either threshold.

What does a percentage represent?

A percentage is a summary of how common an outcome was in the analyzed group. It is not, by itself, an estimate of a treatment effect relative to another option. In a randomized comparison, a difference between groups can be used to estimate a comparative effect, subject to the study design and analysis assumptions. In this single-group study, there is no second group to provide that contrast. If the primary percentages were available, they would describe the observed Week 24 status in the relevant participants, not a causal comparison against a control.

The endpoint uses threshold categories rather than a continuous CDAI change as its primary description. Categorization can make a result easier to communicate in terms of remission or low disease activity. It also means that participants with scores near a threshold fall into different categories despite potentially similar scores. The numerical score and its components can provide detail that a category alone cannot. The registry record defines the score and cutoffs, but numerical results for the primary categories are not reported.

How should precision be judged?

General statistical interpretation considers both an estimate and its uncertainty. A confidence interval is a range calculated by a specified method to show uncertainty around an estimate. A narrow interval indicates greater precision than a wide interval, while the interval’s endpoints indicate which values remain compatible with the data and assumptions. The registry record does not report a primary outcome estimate or confidence interval, so precision cannot be assessed for remission or low disease activity.

A p-value, when reported, addresses how compatible data are with a particular null hypothesis under the assumptions of a statistical test. It is not a measure of the size or clinical importance of an effect. The registry record lists no analyses and gives no primary outcome p-value. There is therefore no reported hypothesis test to interpret for the primary outcome.

Why does the single-group design matter?

Randomized concurrent controls can help distinguish treatment effects from changes that might occur over time or from differences between participants. This trial had no randomized comparison: allocation is listed as not applicable, masking as none, and the model as single group. Consequently, no between-group treatment contrast can be estimated from this design. Open-label assessments may also be more susceptible to expectations or assessment influences than masked assessments, particularly for outcomes that include participant and physician global assessments. The registry record does not describe procedures intended to address those concerns.

The clinical setting also included permitted combination therapy with methotrexate or other non-biologic disease-modifying anti-rheumatic drugs. Without detailed use and analysis information, the contribution of concomitant treatment to observed outcomes cannot be determined from the registry record. This does not invalidate a descriptive account of the group; it limits the interpretation of the group’s outcomes as attributable solely to the study drug.

What do the planning assumptions mean?

General sample-size planning uses assumptions about the outcome, the effect to detect, the significance level, allocation, and statistical method. The registry record describes an illustrative planning approach using a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and effects defined as fractions of an observed effect. It also distinguishes planning results expressed per arm from total event counts for time-to-event settings. Those assumptions describe a planning illustration, not the design of this single-group trial. The record does not report that these assumptions were the trial’s own design basis, and it does not report a sample-size justification. Planning illustrations are not observed power and do not establish the probability that this study detected an effect.

General statistical methods must match the outcome structure and study design. A binary endpoint can be summarized by a proportion and an interval, while comparative methods require an appropriate comparison group. The registry record does not identify the analysis method used for the primary outcome, specify an interval method, or report model adjustment. It would therefore be inappropriate to assign a statistical test or model to the analysis on the basis of the endpoint description alone.

Over-dispersion is a general concern when observed variability exceeds what a model assumes, particularly for certain count outcomes. The primary endpoint is a participant percentage, not a count-rate model, and the registry record does not report an over-dispersion assessment. More generally, assumptions and diagnostics should be reported when they are relevant to the selected method; the analysis details necessary to assess them are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists 19 outcome measures, including the primary CDAI categories and several safety and immunogenicity outcomes, but lists no analyses. It does not report a multiplicity strategy, such as a hierarchy of hypotheses or an adjustment for testing several outcomes. When multiple outcomes or comparisons are tested, the chance of at least one apparently unusual result can increase, depending on the analyses and testing plan. That general issue makes a prespecified statistical plan useful, but the registry record does not provide enough information to determine what approach, if any, was used.

The primary outcome population was the full analysis set with evaluable data for the outcome. The full analysis set included enrolled participants who received at least one dose of subcutaneous tocilizumab. The record does not state the number with evaluable Week 24 data or explain how missing assessments were handled. It does not report whether participants with missing outcome measurements were excluded, imputed, or addressed by another method. The potential influence of missing data on the reported primary result therefore cannot be assessed, and the result itself is not reported in the registry record.

The record also does not report protocol deviations, analysis-population sensitivity analyses, or a detailed distinction between planned and completed analyses. No interim analyses are described. These omissions should not be interpreted as evidence that any particular procedure was or was not performed. They mean that the registry information does not document those procedures. As a result, readers cannot assess how the reported outcome analysis—if completed—would respond to alternative missing-data assumptions or analysis populations.

11. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: colitis (1.0%), chest pain (1.0%), cellulitis (1.0%), adnexal torsion (1.0%), urticaria (1.0%).

The registry record lists 100 participants at risk for the tocilizumab group. It records 6 participants affected in the serious adverse event category and 44 affected in the other adverse event category. These are safety counts from a single treatment group, not comparisons against a control. The record does not provide a control-group count or a comparative estimate.

The serious adverse event terms listed include colitis, chest pain, cellulitis, adnexal torsion, urticaria, and haematoma, each with a reported percentage of 1.0%. These term-level entries should be read as the registry’s listed serious-event terms, not as a full clinical account of every event or its course. A participant may experience more than one event or appear under more than one term; the registry record does not state whether categories overlap. The listed percentages should not be added together or interpreted as a distinct-participant total.

The record does not report deaths for this group. A missing death value means death information is not reported in the registry record; it should not be treated as confirmation that no deaths occurred. The safety counts also do not show when events occurred, how long participants were observed while at risk, or how events were assessed. They provide a registry-level count summary, not a complete estimate of comparative risk or a basis for causal attribution.

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

The registry record establishes that a Phase 3, open-label, single-group study evaluated subcutaneous tocilizumab in adults with rheumatoid arthritis. It specifies a Week 24 primary outcome based on CDAI remission and low disease activity, describes the score and thresholds, and identifies a full-analysis-set population with evaluable outcome data. It also records safety counts and lists other clinical and immunogenicity outcomes.

However, the primary outcome percentages are not reported in the registry record. No numerical result is available for the proportion reaching remission or low disease activity, and there is no reported interval or statistical test for those outcomes. Thus the record does not support a conclusion about the level of CDAI response observed at Week 24 or the precision of such a result.

Even if the primary percentages were available, this design would support a description of outcomes in the treated group, not a randomized comparison with another treatment or no treatment. The study had no control group and was open-label. Combination therapy was permitted, and the registry record does not report how concomitant medicines were used or accounted for. Those features limit attribution of any observed outcome specifically to tocilizumab.

The safety figures indicate that the registry recorded 6 participants affected by serious adverse events and 44 affected by other adverse events among 100 at risk. Those counts do not establish relative safety, identify comparative excess risk, or describe the timing and severity course of all events. The record also does not report a death result for the group.

In general, a study’s design and outcome estimates answer different questions. Design determines what comparisons are possible; estimates describe what was observed; uncertainty measures how precisely those estimates are known. Here, the endpoint and design are documented, but the primary estimates and their uncertainty are not reported in the registry record. The appropriate interpretation is therefore limited to the study structure and recorded safety summaries, without inferring an unreported clinical result.

13. Why This Trial Matters Statistically

This study is statistically informative as an example of why an endpoint definition and a result are distinct pieces of evidence. The registry record gives a detailed CDAI definition, the remission and low-disease-activity thresholds, the assessment time, and the population intended for the primary analysis. Those details clarify what the outcome was designed to measure. Yet the numerical primary outcome results are not reported in the registry record, so readers cannot assess the observed proportions or their precision.

The single-group, open-label structure also shows how design constrains interpretation. A one-arm study can document outcomes and safety events in participants receiving treatment, but it does not create a concurrent counterfactual comparison. A change or status observed during follow-up cannot, from this design alone, be separated from time trends, other care, or other influences. This distinction is important when reading descriptive clinical results: what happened in the group is not automatically the same as what happened because of the intervention.

The permitted use of methotrexate or other non-biologic disease-modifying anti-rheumatic drugs adds context to the treatment setting. The registry record does not report use patterns or analysis of those medicines. Statistical readers should therefore distinguish the broad intervention description from a claim that the study isolated the effect of tocilizumab.

Finally, the record lists many outcomes but no analyses. This emphasizes the importance of documenting which outcomes were analyzed, how missing data were handled, and how multiple outcomes were addressed. Without those details, readers cannot judge the inferential framework or determine whether the analyses matched a prespecified plan. The statistical lesson is not a clinical conclusion: study design, outcome reporting, and transparent analysis information are all necessary to interpret trial evidence.

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 information is the absence of numerical results for the primary CDAI outcome. Although the primary outcome is defined for Week 24, the record does not report the percentage in remission or low disease activity, the number of evaluable participants, or uncertainty estimates. This prevents assessment of the magnitude and precision of the primary findings.

The study was open-label and single-group, with no randomized comparator. As a result, the record cannot support a direct comparative estimate against another therapy or usual care. Because participant and physician global assessments contribute to CDAI, the lack of masking is also relevant to interpretation of the endpoint, although the registry record does not describe assessment procedures or possible safeguards.

The outcome analysis included participants with evaluable data, but the number with missing Week 24 data and the handling of missingness are not reported. The record also does not provide details on protocol deviations, concomitant treatment use, subgroup results, or sensitivity analyses. Combination therapy was permitted, so the independent contribution of tocilizumab cannot be distinguished using the information recorded.

Safety interpretation is limited by the lack of a control group and by the summary format. The record lists affected counts and serious-event terms, but does not describe event timing, duration, recurrence, exposure-adjusted rates, or clinical adjudication. It does not report deaths for the group. These limits mean that the recorded safety information should be treated as descriptive, not comparative.

The record lists 19 outcome measures but no analyses. It does not document the statistical analysis plan, multiplicity handling, interim analyses, or the sample-size justification. Therefore, analysis choices and their assumptions cannot be evaluated from the registry record. These are limitations of the available registry information and do not establish what was or was not done outside the record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study of the Efficacy and Safety of Tocilizumab in Adults With Rheumatoid Arthritis. — NCT01988012.
• Registry record last updated 2017-03-06; status last verified 2017-01.
• Results first posted 2017-03-06.
• 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.

18. Record Summary

NCT01988012 is a completed Phase 3, multicenter, open-label, single-group study sponsored by Hoffmann-La Roche. It enrolled 100 adults with rheumatoid arthritis and evaluated weekly subcutaneous tocilizumab. Treatment was planned for 24 weeks, followed by an 8 week period without treatment. Methotrexate or other non-biologic disease-modifying anti-rheumatic drugs were permitted.

The primary outcome was the percentage of participants with CDAI remission and low disease activity at Week 24. The registry record defines the categories and says the analysis population included full-analysis-set participants with evaluable data. Numerical primary outcome results and analysis details are not reported in the registry record. The record lists 19 outcome measures and no analyses.

For safety, the record lists 6 participants affected by serious adverse events and 44 affected by other adverse events among 100 at risk. Listed serious-event terms each have a reported percentage of 1.0%. The design has no control group, so the safety information is descriptive rather than comparative.