A Study to Determine the Effect of Methotrexate (MTX) Dose on Clinical Outcome and Ultrasonographic Signs in Subjects With Moderately to Severely Active Rheumatoid Arthritis (RA) Treated With Adalimumab (MUSICA): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study to Determine the Effect of Methotrexate (MTX) Dose on Clinical Outcome and Ultrasonographic Signs in Subjects With Moderately to Severely Active Rheumatoid Arthritis (RA) Treated With Adalimumab (MUSICA) (NCT01185288), a randomized phase 4 study. The primary outcome is Disease Activity Score for 28 Joints Based on C-reactive Protein (DAS28[CRP]) at Week 24.

2. Clinical Question

3. Trial Design

MUSICA was a Phase 4, randomized, double-blind, parallel-arm study. Its official title describes it as multicenter. The registry record reports an enrollment of 309 and a completed status. The study began in 2010-09, and primary completion was recorded as 2013-01.

The treatment groups received open-label adalimumab combined with blinded methotrexate at either 7.5 mg or 20 mg orally once weekly. Adalimumab was given at 40 mg subcutaneously every other week in both groups. Because adalimumab was part of both regimens, the central randomized comparison is the methotrexate dose accompanying adalimumab.

The study summary describes efficacy evaluation among participants with rheumatoid arthritis who had an inadequate response to high-dose methotrexate. It also describes evaluation of pharmacokinetics and safety. The registry lists rheumatoid arthritis as the condition and identifies adalimumab and methotrexate as the interventions.

The primary outcome was DAS28(CRP) at Week 24, analyzed as a continuous score. The listed primary analysis population included randomized participants who received at least one dose of study medication, with missing responses handled by last observation carried forward. Secondary outcomes included ultrasound improvement, ACR50 and ACR70 response, a threshold for change in HAQ-DI, and change in the MOS Sleep Problem Index 9. The registry record does not report further design details such as the randomization procedure or a sample-size justification.

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: All participants who were randomized and received at least one dose of study medication (intent to treat). Missing responses were imputed using last observation carried forward (LOCF).

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.

6. Primary Endpoint

The registry lists the primary outcome as Disease Activity Score for 28 Joints Based on C-reactive Protein (DAS28[CRP]) at Week 24, measured over Week 24.

The primary endpoint was the Disease Activity Score for 28 Joints based on C-reactive protein, or DAS28(CRP), at Week 24. The measure combines 28 tender joint counts, 28 swollen joint counts, C-reactive protein, and the participant’s global assessment of disease activity. It is a continuous score ranging from 0 to 10.

The registry describes a score of at least 5.1 as indicating high disease activity and a score < 2.6 as indicating clinical remission. These reference points help describe the scale, but the reported primary result is the group-level Week 24 score rather than the proportion of participants who crossed either threshold.

Using a composite score allows several aspects of disease activity to contribute to one outcome. For this trial, the registry reports least-squares means and 95% confidence intervals for each treatment group. The means were estimated using an analysis of covariance model that included baseline DAS28(CRP), treatment group, and prior methotrexate dose group. The endpoint therefore addresses the Week 24 score after accounting for the listed model terms; it is not itself a measure of change from baseline.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a least-squares mean represent?

In general, a least-squares mean is a model-based estimate of a group mean after accounting for the variables included in the model. It is often used when treatment groups are compared while adjusting for baseline measurements or other specified covariates. It is not necessarily the same as a simple arithmetic average of the observed scores. In this trial, the registry identifies baseline DAS28(CRP), treatment group, and prior methotrexate dose group as effects in the two-way ANCOVA model. The reported values are therefore adjusted estimates for the Week 24 DAS28(CRP) outcome.

Adjustment can improve the relevance of a comparison when baseline outcome values or other included factors are associated with the endpoint. However, adjustment does not itself establish a treatment difference. The registry reports arm-specific adjusted means and confidence intervals, but not a primary adjusted contrast. A direct contrast and its uncertainty would answer the comparative question more explicitly than separate arm-level estimates.

How should the confidence intervals be read?

In general, a confidence interval represents the range of values compatible with the data and the specified statistical procedure, under the procedure’s assumptions. A narrower interval indicates greater precision for the quantity being estimated; a wider interval indicates more uncertainty. The registry gives 95% confidence intervals for the two least-squares means. Those intervals concern the means in the separate arms, not a confidence interval for the difference between arms.

It is important not to treat a visual comparison of arm-level intervals as a substitute for the analysis of a treatment contrast. The uncertainty of a contrast depends on the joint comparison, including the covariance structure used by the model. The registry record does not report the primary contrast estimate or its interval, so the arm-specific intervals should be read as precision summaries for the arm means rather than as a complete test of the randomized comparison.

What does ANCOVA contribute?

In general, analysis of covariance (ANCOVA) estimates an outcome while including baseline or other covariates in the model. For a continuous endpoint, it can account for baseline outcome differences and can produce adjusted group estimates. Here, the listed model includes the baseline DAS28(CRP) value, treatment group, and prior methotrexate dose group. The registry does not report model diagnostics, assumptions checks, or further specification such as interaction terms. Those details are not reported in the registry record.

ANCOVA’s model-based estimates rely on assumptions about the relationship between the outcome and included covariates, as well as the residual behavior of the model. General statistical practice is to examine whether those assumptions are reasonable and whether the model is adequately specified. The registry record does not report such diagnostic information, so the posted analysis cannot be assessed on those details alone.

What is the effect of last observation carried forward?

In general, last observation carried forward (LOCF) fills a missing endpoint value using that participant’s last recorded value. The primary analysis description says missing responses were imputed using LOCF. This makes the analysis more complete in the presence of missing endpoint measurements, but it imposes an assumption: the last observed value is used as a stand-in for the missing Week 24 value. That assumption may not reflect the participant’s unobserved course after the last measurement.

LOCF does not remove uncertainty due to missing data. Its implications depend on when and why values were missing and on how outcomes may have changed after the last observation. The registry record does not report the amount or pattern of missing primary responses, reasons for missingness, or sensitivity analyses using alternative missing-data methods. Those details are not reported in the registry record.

How do the secondary comparisons differ?

The posted binary secondary comparisons are recalculated, unadjusted comparisons based on the reported summary statistics. In general, a risk difference expresses the difference between two proportions, while a confidence interval describes uncertainty around that difference. A p-value summarizes how compatible the observed data are with a specified null hypothesis under the test’s assumptions; it does not measure clinical importance or the probability that a treatment effect is true. The secondary comparison results should not be confused with sponsor-reported analyses: the registry record lists no reported analyses for these outcomes.

For the binary outcomes, planning illustrations are based on the observed effect and use a two-sided significance level of 0.05, equal allocation between the arms, and a normal approximation. They show participants per arm for 80% or 90% power when planning for 100%, 75%, or 50% of the observed effect. These are planning illustrations, not evidence of observed power and not the trial’s reported sample-size justification. The registry record does not report the trial’s own sample-size assumptions or justification.

In general, over-dispersion means that observed variability is greater than a model’s assumed variability. It can make standard errors too small if the model does not account for the extra variability. It is a general consideration for analyses of count or clustered data; the primary endpoint is continuous, and the registry does not report an over-dispersion analysis. No specific over-dispersion finding should be inferred from this record.

10. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when several outcomes, time points, subgroups, or statistical tests are considered. In general, examining more than one hypothesis without accounting for the full set can increase the chance of a nominally notable finding occurring by chance. This trial lists a primary endpoint and several secondary outcomes, but a multiplicity procedure, testing hierarchy, or other method for controlling the interpretation of multiple outcomes is not reported in the registry record.

The three posted binary secondary comparisons have unadjusted recalculated statistics, while the registry lists no reported analyses for them. The unadjusted results are useful for describing the posted group summaries, but they do not establish that any outcome met a sponsor-defined statistical criterion. The registry record does not report whether the secondary outcomes were intended to be confirmatory, how they were ordered, or whether any adjustment was used in the study’s own analysis.

For the primary endpoint, the registry identifies the intent-to-treat population as randomized participants who received at least one dose of study medication. Missing primary responses were imputed using LOCF. The amount and timing of missing data, the reasons for missingness, and sensitivity analyses are not reported in the registry record. Those omissions limit assessment of how robust the primary result is to the handling of missing observations.

The registry record does not report interim analyses, a detailed statistical analysis plan, or the trial’s sample-size justification. Planning illustrations based on observed secondary effects are not a substitute for the trial’s original design calculations. They do not show observed power and do not establish the planned approach to multiplicity, missing data, 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: anaemia (0.6%), acute myocardial infarction (0.6%), colitis ischaemic (0.6%), bile duct cancer (0.6%), transient ischaemic attack (0.6%).

The registry reports serious adverse event counts in both treatment groups: 6 among 154 participants in the low-dose methotrexate group and 11 among 155 participants in the high-dose methotrexate group. It also reports other adverse event counts of 57 among 154 participants and 48 among 155 participants, respectively. These are counts alongside the stated group sizes; they are not, by themselves, a complete account of event timing, severity, duration, or attribution to study treatment.

The listed serious adverse event terms each have a reported frequency of 0.6%: anaemia, acute myocardial infarction, colitis ischaemic, bile duct cancer, transient ischaemic attack, and Raynaud's phenomenon. The registry record does not provide enough detail in these figures to assess the clinical course of each event or whether events were judged related to treatment. Death counts are not reported in the registry record.

In general, adverse event counts are safety descriptions, not randomized efficacy comparisons. Differences in counts should be interpreted with attention to event definitions, follow-up, exposure, and uncertainty. Those details are not reported in the registry record, so the figures should not be used alone to make a treatment-safety conclusion.

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

The primary result describes adjusted average DAS28(CRP) scores at Week 24 among randomized participants who received at least one dose of study medication, with missing responses handled by LOCF. The point estimate is lower for the high-dose methotrexate combination than for the low-dose combination. The registry reports an interval for each mean, but does not report a primary between-group estimate, confidence interval, or p-value.

That distinction matters. A group’s estimated mean is not the same as a direct estimate of how much the groups differ, and the interval around an individual mean is not the interval for a treatment contrast. The registry result therefore provides a descriptive comparison of adjusted arm means but does not supply all the information needed for a direct inferential assessment of the primary randomized contrast.

The secondary results provide additional descriptions of ultrasound and response outcomes, but their comparative statistics are unadjusted recalculations, not analyses reported in the registry. The registry also does not report a multiplicity approach, and results for some listed secondary outcomes are not reported in the registry record. These limitations mean that secondary findings should be read as context, not as a collection of independent confirmations.

These results do not establish that either regimen is clinically preferable, nor do they show what would happen outside the studied population and treatment setting. Both groups received adalimumab, so the study does not compare adalimumab with no adalimumab. The record also does not report sufficient information to make a broad safety judgment. The results should be understood within the trial’s population, Week 24 endpoint, analysis method, and reporting limitations.

13. Why This Trial Matters Statistically

This trial is statistically informative because it compares two doses of methotrexate while keeping the adalimumab regimen the same in both randomized groups. That design focuses the central contrast on the methotrexate dose accompanying adalimumab. The blinded methotrexate assignment and double-blind designation are relevant design features when interpreting the reported outcomes.

The primary endpoint also illustrates the distinction between a model-adjusted mean and a treatment-effect contrast. ANCOVA produced least-squares means that account for baseline DAS28(CRP) and prior methotrexate dose group, but the registry reports no primary between-group estimate. Readers therefore need to distinguish the arm-specific estimates from the comparative quantity that directly addresses the randomized question.

The record also shows why secondary results require careful interpretation. Several secondary outcomes are listed, while the comparative results available for three are recalculated and unadjusted. With no reported multiplicity strategy and no sponsor-reported analyses for those comparisons, their role is descriptive. Planning illustrations based on observed effects can support future study planning, but they do not represent the trial’s design justification or its observed power.

Finally, the primary analysis uses LOCF, and the registry does not report missingness patterns or sensitivity analyses. That makes the handling of missing observations an important part of interpreting the result. The combination of model adjustment, imputation, secondary comparisons, and incomplete reporting demonstrates why statistical conclusions should reflect both the numerical estimates and the methods and information available in the registry record.

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 primary outcome is reported as separate least-squares means with 95% confidence intervals, but the registry record does not report a primary treatment contrast, its interval, or a p-value. This restricts direct assessment of the randomized comparison using the primary endpoint. The means are adjusted for the listed model terms, but model diagnostics and additional specification details are not reported in the registry record.

Missing primary responses were imputed using LOCF. The amount, timing, and reasons for missing data, as well as sensitivity analyses with alternative assumptions, are not reported in the registry record. The impact of the imputation approach on the estimates therefore cannot be assessed from the posted information.

The reported secondary comparisons are unadjusted recalculations, and no sponsor-reported analyses are listed for them. A multiplicity approach is not reported. In addition, the registry lists secondary outcomes for which posted results are not reported in the registry record. These gaps constrain the strength and breadth of conclusions that can be drawn from secondary outcomes.

The record does not report the trial’s sample-size justification, interim analyses, or a full statistical analysis plan. It also does not report further details needed to evaluate safety comparisons, such as event attribution and exposure context. Although the registry describes a randomized, double-blind, parallel-arm study, additional operational details are not reported in the registry record. These limitations concern what can be evaluated from the record and do not, by themselves, establish that the study methods were inadequate.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study to Determine the Effect of Methotrexate (MTX) Dose on Clinical Outcome and Ultrasonographic Signs in Subjects With Moderately to Severely Active Rheumatoid Arthritis (RA) Treated With Adalimumab (MUSICA) — NCT01185288.
• Registry record last updated 2014-03-18; status last verified 2014-01.
• Results first posted 2014-03-18.
• 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

MUSICA was a completed Phase 4 randomized, double-blind, parallel-arm study of adalimumab combined with low-dose or high-dose methotrexate in participants with rheumatoid arthritis and an inadequate response to high-dose methotrexate. Enrollment was 309. The primary outcome was the Week 24 DAS28(CRP) score, analyzed with a two-way ANCOVA model and LOCF for missing responses.

The reported least-squares mean was 4.11 (95% CI 3.88 to 4.34) with low-dose methotrexate and 3.75 (95% CI 3.52 to 3.97) with high-dose methotrexate. A primary between-group estimate is not reported in the registry record. Three secondary outcomes have unadjusted recalculated comparisons, while results for other listed secondary outcomes and a multiplicity strategy are not reported in the registry record. Safety counts are reported, but deaths are not reported in the registry record.