Evaluation of Effectiveness of Risperdal® Consta® Compared to Abilify® Over a Two-year Period in Patients With Schizophrenia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of Effectiveness of Risperdal® Consta® Compared to Abilify® Over a Two-year Period in Patients With Schizophrenia (NCT00299702), a randomized phase 4 study. The primary outcome is Time to Relapse.

2. Clinical Question

This is a comparative effectiveness question about the duration until a defined relapse event, not simply whether participants experienced any relapse during the study. Time-to-event outcomes use both the timing of an event and information about how long participants were followed without an event. Interpretation therefore depends on the endpoint definition, the analysis population, and how follow-up and censoring were handled. Those details are not all reported in the registry record.

3. Trial Design

This was a Phase 4, randomized, parallel-group study comparing Risperdal Consta with Abilify in adults with schizophrenia. The official title describes a prospective, multicenter study with blinded raters, open-label treatment, and an active control. The registry lists masking as none. These descriptions are not interchangeable: the title characterizes the study as blinded-rater, while the registry masking field records no masking. The registry record does not give further detail about which assessments or personnel were blinded.

The study was intended to examine long-term efficacy and effectiveness over a two-year treatment period. The recorded start was 2006-02, and primary completion was 2009-01. The status is completed. Enrollment was 355. The primary outcome analysis lists 177 participants in the Risperdal Consta arm and 172 in the Abilify arm; the registry defines the analysis population more narrowly than enrollment, requiring study-drug administration and a follow-up efficacy measurement.

The active-controlled design compares two named treatments rather than comparing a treatment with no treatment. Random allocation is intended to make treatment groups comparable, on average, with respect to factors that could affect outcomes. It does not guarantee that every measured or unmeasured characteristic is balanced in the realized groups, nor does it remove the need to consider the analysis population and missing follow-up.

The study is described as open-label, but the registry’s masking field is none and its official title specifies blinded raters. The record does not explain the procedures used to maintain any rater blinding or how treatment knowledge might have affected other aspects of care or outcome assessment. Arm descriptions are blank in the record. Further details about dosing, treatment changes, adherence, and follow-up procedures are not reported in the registry record.

The posted primary outcome is time to relapse. The registry also records two outcome measures and two analyses overall, but no secondary outcomes are posted. The method reported for the primary comparison is the log-rank test. Details of the full statistical analysis plan, including any prespecified covariate adjustment or handling of departures from the intended treatment, 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.

Before assignment: A Screening Visit (maximum of 14 days) prior to the Treatment Phase. Baseline included psychiatric exam, lab, ECG, and schizophrenia symptom rating scale. Subjects were permitted to remain on previous psychotropic medications (i.e., antipsychotic, antidepressant, mood stabilizer, anxiolytics) up to the first 4 weeks of the Treatment Phase.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: explanatory ITT analysis data set (eITT) contains all subjects who had at least one administration of study drug as well as at least one follow-up efficacy measurement; includes assessments while the subject is on study drug.

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 Time to Relapse, measured over Day 1 to relapse.

The primary endpoint is time to relapse, measured in days from the date of the first dose to the date of relapse. The registry says relapse was determined by the Relapse Monitoring Board. This definition makes the endpoint a time-to-event measure: it concerns when relapse occurred, rather than only whether a participant relapsed at some point.

The registry reports the median time to relapse for each arm, with a 95% confidence interval. The median is the time by which half of the analyzed group is estimated to have experienced the event, under the time-to-event analysis. A confidence interval conveys uncertainty around that estimated median. It is not an interval containing the event times of individual participants, and it does not by itself establish whether the treatment groups differ.

Time-to-event endpoints are useful when participants may have different lengths of follow-up or when some participants do not experience the event during observed follow-up. Such participants can contribute information up to the point their follow-up ends, provided the analysis appropriately accounts for censoring. The registry record does not describe the censoring rules, the number of events, or the follow-up distribution, so those features cannot be assessed from the posted result.

The stated timeframe is “Day 1 to relapse,” while the endpoint description defines the start as the date of first dose. These descriptions identify the intended period of measurement, but the record does not give additional operational detail about how event dates or censoring dates were assigned.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary comparison is a time-to-event analysis. In general, time-to-event methods are used when the outcome is the time until a defined event, such as relapse. Unlike an analysis that classifies every participant only as having or not having an event, these methods retain information about when events occurred. They can also account for participants whose event was not observed before their follow-up ended, through censoring. Censoring means that the event time is not known beyond the participant’s last observed follow-up; it is not the same as observing that the event never occurred.

What the median represents

The registry reports median time to relapse by arm. In general, a median time-to-event estimate is the point at which the estimated event-free experience has reached its midpoint. It summarizes the distribution without describing every event time. It can be informative when the event-time distribution is not well represented by a mean, but it does not show the full shape of that distribution. The record does not report a survival curve or other detailed distributional summaries in the registry record for this analysis.

The posted median for Risperdal Consta is 131.0 days, with a 95% confidence interval of 100.0 to 197.0 days. For Abilify, the median is 113.0 days, with a 95% confidence interval of 99.0 to 169.0 days. A confidence interval expresses uncertainty in an estimate under the analysis method. Its width is affected by the information available to estimate the endpoint, including the event and censoring pattern. It does not mean that most participants’ individual times fell inside the interval.

What the log-rank test does

The registry reports a log-rank test for the two-group comparison, with p = 0.684. In general, the log-rank test compares the observed timing of events between groups across the follow-up period. It is not simply a comparison of the two medians, and its result can reflect differences in event timing beyond the median point. The test’s interpretation depends on the data and assumptions used in the analysis. The registry record does not report enough detail to assess those assumptions or reproduce the test.

A p-value describes how unusual results at least as discrepant as those observed would be under a specified null hypothesis and test model. It does not give the probability that a treatment is effective, the probability that the null hypothesis is true, or the size of a treatment effect. The reported p-value should therefore be read alongside the median estimates and their confidence intervals, not as a standalone measure of clinical importance. The registry does not provide a hazard ratio and confidence interval that would quantify the relative event rate and its uncertainty.

Why censoring and follow-up matter

Time-to-event analyses can use partial follow-up from participants who have not had a recorded relapse by their last observation. This is valuable when follow-up duration varies, but it relies on appropriate censoring information and assumptions. For example, the analysis needs a defensible account of when a participant’s event status stops being observed. The registry gives the endpoint’s broad start and event definition but does not report the censoring rules, loss-to-follow-up details, event count, or follow-up distribution. The posted summaries alone therefore do not show how much information was available at later times.

The endpoint is defined from first dose to relapse as determined by the Relapse Monitoring Board. That adjudication process identifies who determined relapse, but the registry does not describe the criteria applied, the board’s procedures, or whether the board was blinded to treatment. Those details can matter when an endpoint involves clinical judgment. They are not reported in the registry record.

Analysis population and treatment assignment

The registry calls the primary analysis population an explanatory ITT analysis data set. It includes all subjects with at least one administration of study drug and at least one follow-up efficacy measurement, and includes assessments while the subject is on study drug. This definition is important for interpretation: the posted result applies to that group as defined in the record. It is not enough to infer from the label alone that every randomized participant was included in the primary analysis. The record does not state how data after treatment discontinuation were handled or how participants missing a qualifying assessment were treated.

Randomization assigns participants to treatment groups by chance and, in general, aims to support a fair comparison by reducing systematic baseline differences. The registry states that allocation was randomized and the model was parallel. It does not report the sequence-generation or concealment procedures, or whether the analysis adjusted for baseline characteristics. Those methods are not reported in the registry record.

Planning illustrations and limits of recalculation

Planning sample-size illustrations use the observed effect as a basis for hypothetical planning scenarios. They are not observed power and do not show the probability that this completed trial detected a true effect. The stated assumptions for the illustrations are a two-sided significance level of 0.05, equal allocation, a normal approximation, and an effect to detect expressed as a fraction of the observed effect. For time-to-event outcomes, the illustration is based on the total number of events. These assumptions describe planning calculations, not the trial’s original design rationale.

The registry record does not state the trial’s own sample-size justification or whether the planning assumptions used in the illustrations match the protocol. No claim about the original target, interim analyses, or stopping rules can be made from the posted information. For the two-arm median-time endpoint, values needed for a separate recalculation are missing or not estimable in the registry record. The reported log-rank result is therefore the available inferential comparison; a new relative-effect estimate should not be inferred from the arm medians alone.

10. Analyses Reported by the Sponsor

The registry’s reported between-group analysis is a log-rank test with p = 0.684. The registry also reports arm-specific medians and confidence intervals, but it does not report a hazard ratio or a confidence interval for that relative effect. A hazard ratio would be a different summary from the median and would describe a relative event rate under its analysis assumptions. It cannot be recovered from the medians alone.

No recalculated relative-effect estimate is available for this median-time comparison because the required values are missing or not estimable in the registry record. The sponsor’s reported log-rank analysis is therefore the inferential result to use when describing the posted comparison. There is no discrepancy flagged between a recalculation and the sponsor’s analysis.

The log-rank p-value should not be treated as a measure of effect size or as evidence of equivalence. The registry’s posted medians describe each arm separately, while the log-rank test compares event timing across the groups. Without a reported hazard ratio, its confidence interval, event counts, and fuller follow-up information, the relative magnitude and precision of the treatment contrast remain incompletely characterized.

11. Multiplicity, Missing Data and Analysis Populations

The registry records two outcome measures and two analyses, but no secondary outcomes are posted. The primary outcome is time to relapse, and the registry reports one log-rank p-value for the comparison. The statistical analysis plan is not reported in the registry record, so it is not possible to establish whether this was the sole prespecified primary test, how outcome hierarchy was defined, or whether any other comparisons were planned.

Multiplicity arises when several hypotheses or outcomes are tested. In general, conducting multiple tests can increase the chance of at least one apparently unusual result even when none of the underlying effects is present. Analysis plans may address this through prespecified ordering, adjustment, or other procedures. The registry does not report a multiplicity strategy, so no adjustment should be assumed and no statement can be made about whether one was used outside the information in the record.

The analysis population is defined as participants with at least one study-drug administration and at least one follow-up efficacy measurement. Assessments while participants were on study drug were included. The registry does not report how many randomized participants lacked a qualifying measurement, reasons for missing outcome data, or how their data were handled. It also does not describe whether participants who stopped treatment remained under efficacy follow-up or how follow-up ended for participants without relapse.

These omissions matter for a time-to-event endpoint because the amount and pattern of follow-up affect the information available to estimate event timing. In general, censoring methods rely on assumptions about the relationship between loss of observation and the chance of the event. The registry record does not provide enough detail to assess those assumptions. It also does not report the number of relapse events or the number censored in each arm.

The primary analysis population should therefore be read according to its stated definition rather than assumed to include every randomized participant. The record does not report sensitivity analyses for missing data, alternative analysis populations, interim analyses, or the full prespecified statistical plan.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: schizophrenia (6.8%), psychotic disorder (6.7%), suicidal ideation (1.1%), aggression (1.1%), depression suicidal (1.1%).

The registry lists serious adverse events for 31 of 179 participants at risk in the Risperdal Consta safety group and 35 of 176 participants at risk in the Abilify safety group. These are posted counts and denominators for the safety groups; they are not the primary efficacy analysis population sizes. The record does not explain the safety analysis definitions or provide additional detail about the observation period for these figures.

The most frequent serious-event terms listed are schizophrenia at 6.8%, psychotic disorder at 6.7%, suicidal ideation at 1.1%, aggression at 1.1%, depression suicidal at 1.1%, and anaemia at 0.6%. The registry record does not identify the denominator or calculation details for these term percentages, so they should be read as listed rather than converted into participant counts. The event terms do not by themselves establish whether an event was caused by treatment.

Deaths are not reported in the registry record. The serious-event counts are descriptive and do not establish a comparative safety effect. Differences in counts alone do not account for event timing, exposure, severity patterns, or other factors that could affect interpretation. The posted safety information is limited to these figures and terms.

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

The registry results show estimated median times to relapse of 131.0 days for Risperdal Consta and 113.0 days for Abilify in the stated explanatory ITT analysis data set. The reported log-rank p-value is 0.684. These results describe the observed registry analysis; they do not establish that the treatments have the same effect or that either treatment is superior.

A failure to detect a statistically significant difference is not evidence that the groups are equivalent. Equivalence or non-inferiority requires an appropriate design, prespecified margins, and analyses suited to those questions. Such margins and plans are not reported in the registry record. The p-value also does not quantify how large a clinically important difference might be, and no hazard ratio with a confidence interval is reported.

The medians are group summaries. They do not describe every participant’s course, the proportion who relapsed by a chosen time, or the shape of the event-time distributions. The registry does not report event counts, censoring counts, or detailed follow-up information needed to characterize those aspects. The confidence intervals indicate uncertainty around the median estimates but do not resolve the missing information about the comparative effect.

The endpoint depends on relapse as determined by the Relapse Monitoring Board and on the stated analysis population. The registry does not describe the relapse criteria in detail, the adjudication procedures, or all aspects of missing follow-up and censoring. The results should be interpreted within those limits and should not be generalized beyond the population and study conditions represented in the record.

The serious adverse event figures are also descriptive. They report affected counts in the two safety groups and a list of serious-event terms with percentages, but they do not establish causation or a comparative safety effect. Death counts are not reported in the registry record.

Overall, the posted information supports a description of the analyzed groups’ median relapse times and the sponsor-reported log-rank test. It does not support a claim of equivalence, a precise relative treatment effect, or conclusions about aspects of the protocol and analysis that the record does not describe.

14. Why This Trial Matters Statistically

This trial illustrates why the choice of endpoint matters. Time to relapse retains information about when an event occurred, while an analysis that only counts whether relapse ever occurred would discard timing. The registry’s median estimates summarize the event-time distribution at a useful point, and the log-rank test compares event timing across the groups. Neither summary alone gives a complete account of the treatment contrast.

It also illustrates the distinction between an arm-specific estimate and a comparative estimate. The two medians and their confidence intervals describe each group, whereas the log-rank p-value addresses the between-group comparison. A hazard ratio and confidence interval, which would provide another comparative summary, are not reported. This limits the ability to describe the magnitude and precision of a relative effect.

The analysis population is another important statistical feature. The registry defines the explanatory ITT set by study-drug exposure and availability of a follow-up efficacy measurement. That definition is necessary context for understanding who contributed to the primary result. The enrollment count and the outcome analysis group sizes serve different purposes and should not be treated as interchangeable.

Finally, registry results can leave important questions unanswered even when an outcome and a test result are posted. Here, the record does not report the event counts, censoring details, complete missing-data handling, or the full statistical plan. Recognizing these gaps helps separate what the estimates show from what cannot be concluded. That distinction is central to responsible interpretation of clinical trial statistics.

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 registry provides a limited account of the primary time-to-relapse analysis. It reports arm-specific medians, confidence intervals, and a log-rank p-value, but no hazard ratio or confidence interval for the relative effect. It does not report the number of relapse events, censoring counts, or a detailed account of follow-up. These omissions constrain assessment of the information supporting the comparison.

The endpoint description identifies the first dose as the starting point and the Relapse Monitoring Board as the body determining relapse. The record does not provide the detailed relapse criteria, adjudication procedures, or the board’s masking status. The official title describes blinded raters, while the registry masking field says none; the record does not explain how those descriptions relate in practice.

The eITT analysis population requires at least one study-drug administration and at least one follow-up efficacy measurement. The registry does not report the number or characteristics of participants excluded by this definition, how missing measurements were handled, or whether follow-up continued after treatment discontinuation. It also does not provide sensitivity analyses that could indicate how robust the result is to alternative missing-data assumptions or analysis populations.

The statistical analysis plan, sample-size justification, interim analyses, and stopping rules are not reported in the registry record. No secondary outcomes are posted, even though the record counts two outcome measures and two analyses. Multiplicity procedures and any covariate adjustments are not described.

Safety reporting is also limited. Serious adverse event counts and selected terms are listed, but the denominator details for the term percentages, event-level information, and death counts are not reported. The registry record does not establish causal attribution for these events. These limitations mean the posted information should be read as a concise registry result rather than a complete account of the trial’s methods and findings.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Evaluation of Effectiveness of Risperdal® Consta® Compared to Abilify® Over a Two-year Period in Patients With Schizophrenia — NCT00299702.
• Registry record last updated 2011-12-30; status last verified 2011-12.
• Results first posted 2010-03-16.
• 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

NCT00299702 is a completed, randomized, Phase 4, parallel-group study comparing Risperdal Consta with Abilify in adults with schizophrenia. The official title describes an open-label study with blinded raters and an active control; the registry lists masking as none. Enrollment was 355. The recorded start was 2006-02 and primary completion was 2009-01.

The primary outcome was time from first dose to relapse, determined by the Relapse Monitoring Board. In the defined explanatory ITT analysis data set, the median was 131.0 days for Risperdal Consta and 113.0 days for Abilify. The reported log-rank p-value was 0.684. No hazard ratio is reported in the registry record.

The registry lists serious adverse events for 31 of 179 participants at risk in the Risperdal Consta group and 35 of 176 in the Abilify group. Death counts are not reported. Details of the full statistical plan, event counts, censoring, and missing-data handling are not reported in the registry record.