Pramipexole Conversion to Ropinirole Controlled Release (CR): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pramipexole Conversion to Ropinirole Controlled Release (CR) (NCT00275275), a non-randomized phase 3 study. The primary outcome is Adverse Effects Experienced.

2. Clinical Question

In practical statistical terms, the study raises a question about how to describe outcomes after a medication switch, not whether one treatment is superior to another in a randomized trial. The record indicates that participants were converted from pramipexole to ropinirole controlled release, and that several conversion factors were under investigation. It does not give enough information to determine how participants entered each ratio group, whether the ratios were assigned by a defined rule, or whether all participants followed the same conversion process.

The endpoint is described as a count of adverse effects, but the posted record does not clarify whether the count is per participant, per event type, or accumulated across participants. That distinction matters: a count of events is not interchangeable with a count of participants who experienced at least one event. The available adverse-event figures are presented under preference-based group labels, not as a breakdown by the conversion ratios. The record therefore supports a limited description of the study’s purpose and posted safety figures, but not a direct estimate of which conversion factor had better outcomes.

3. Trial Design

The registry identifies this as a Phase 3, completed study with an open-label, non-randomized, single-group design. Enrollment was 61. The study began in 2006-01, and primary completion was recorded as 2008-05. The condition was Parkinson disease. The listed drugs were Requip PR and Mirapex, corresponding to ropinirole controlled release and pramipexole in the study description.

The central design feature was conversion from pramipexole to ropinirole controlled release. The arm descriptions list conversion factors of 1:3, 1:4, and 1:5. For the 1:3 group, the record explains that the ropinirole dose was three times the pramipexole dose. For the other factors, the record gives the ratio but does not provide comparable dosing details, assignment procedures, or a schedule for dose changes. The record describes the study as investigating a conversion factor to assist with switching between the drugs.

Because allocation was non-randomized and masking was absent, participants and study personnel were not blinded to the conversion. The registry’s design fields call this a single-group study, while the arm descriptions refer to different conversion ratios. The posted adverse-event groups have different labels, “Preferred Requip PR” and “Preferred Mirapex,” which do not match those ratio labels. The record does not explain this relationship. These descriptions should not be treated as evidence of randomized or otherwise comparable groups.

The listed primary outcome was the number of adverse effects experienced, with a Week 4 timeframe. The secondary outcome was Number of Dose Adjustments. The registry reports two outcome measures and zero analyses. It does not report the statistical plan, how the ratios were compared, how participants were assigned or classified, or how missing outcome data were handled. The enrollment total and the group counts in the posted adverse-event figures do not have an explained relationship in the record. Accordingly, this design description is best read as a summary of the registry fields, not as a complete protocol account.

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

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 Adverse Effects Experienced, measured over Week 4.

The primary endpoint is titled “Adverse Effects Experienced.” Its unit is number of events, and its timeframe is Week 4. The description says it concerns the number of adverse effects experienced by participants in the different conversion-ratio groups. This is an outcome focused on tolerability after a medication conversion, rather than a measure of Parkinson’s disease symptoms or functioning.

Counting adverse effects can provide a way to summarize unwanted events observed during a specified period. In general, however, event counts need careful interpretation. One participant may experience more than one event, and the same event count can arise from different distributions across participants. A count of events is therefore not necessarily a count of participants affected. The record does not specify whether repeated events of the same type were counted separately, how events were defined or collected, or whether the displayed counts are totals, averages, or another summary.

The registry describes the endpoint as a comparison across conversion-ratio groups, but the posted adverse-event figures are presented under the labels “Preferred Requip PR” and “Preferred Mirapex.” A result by conversion ratio is not reported in the registry record. The endpoint’s measure and timing are stated, but the result and the detailed operational definition needed to reproduce it are not. The Number of Dose Adjustments outcome is listed as secondary; its result is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a non-randomized, open-label, single-group study. That design context is central to interpreting any comparison. The study examines conversion from pramipexole to ropinirole controlled release, and its arm descriptions refer to conversion factors of 1:3, 1:4, and 1:5. The record does not describe random assignment to those factors. It is therefore not appropriate to interpret differences across the described groups as if they came from a randomized trial.

What does a non-randomized design imply?

General statistical explanation: randomization is one way to make comparison groups similar, on average, with respect to factors that can affect outcomes. Without randomization, groups may differ before treatment or conversion, and those differences can influence observed outcomes. A statistical adjustment can sometimes account for measured differences, but it cannot automatically address factors that were not measured or not included in the analysis. The registry does not report an adjustment strategy, covariates, or a comparative model. It also does not report how participants were assigned to or categorized within each conversion factor.

The open-label designation means masking was absent. General statistical explanation: knowledge of the treatment or conversion can affect how participants report experiences and how study personnel collect or classify outcomes. This is particularly relevant to subjective adverse-effect reporting. The record does not describe specific steps used to limit such influences.

How should an event count be read?

The primary outcome is a number of adverse effects experienced, measured at Week 4. General statistical explanation: event-count data are non-negative counts, and statistical methods for counts may need to account for variation in the event totals. For example, over-dispersion occurs when the variability in counts is greater than a simple count model expects. If over-dispersion is present, a model that assumes less variability can give uncertainty estimates that are too narrow. Whether over-dispersion was assessed or whether a count model was used is not reported in the registry record.

The outcome description does not say whether the event count is an aggregate total, a count per participant, or another summary. It also does not state how recurring events were handled, whether an event had to meet a particular definition, or how events were attributed to the conversion. These details affect both the meaning of the endpoint and the suitability of statistical methods. The record lists a Week 4 timeframe but does not provide further information about the observation window or collection procedures.

What can the posted comparisons establish?

The adverse-event information is displayed as two groups titled “Preferred Requip PR” and “Preferred Mirapex.” It gives the numbers at risk and the numbers with serious or other adverse events. The record does not explain how preference was determined or how these groups relate to the 1:3, 1:4, and 1:5 conversion factors. As a result, these figures cannot be treated as a direct comparison of those factors. Nor does the registry identify these two groups as a randomized intervention and control group.

General statistical explanation: a comparative estimate usually needs a clearly defined contrast, a consistent outcome definition, and an uncertainty estimate. A confidence interval can show the precision of an estimate, while a hypothesis test can assess compatibility with a specified null hypothesis under its assumptions. The registry record reports zero analyses and does not give a test, model, confidence interval, or adjusted estimate. No such inferential result should be inferred from the displayed counts alone.

What do the planning illustrations mean?

General statistical explanation: sample-size planning asks how many participants would be needed under specified assumptions to detect a chosen effect with a chosen statistical procedure. The planning illustrations accompanying this page are based on the observed effect and stated assumptions, rather than on the trial’s original design. They are not observed power, do not establish that the study was adequately powered, and should not be read as evidence about the trial’s actual enrollment rationale. A planning result depends on the assumed effect, significance level, allocation, and model. The registry does not report its own sample-size justification.

More generally, observed power is not a substitute for an estimate and its uncertainty. When results are imprecise or not reported, a retrospective planning calculation cannot supply the missing analysis. In this record, the registry does not report a result for the primary endpoint by conversion ratio, so the planning illustrations cannot resolve the underlying clinical comparison.

Which methods are not documented?

The statistical analysis plan, analysis populations, missing-data methods, handling of protocol deviations, and methods for the Number of Dose Adjustments outcome are not reported in the registry record. The record also does not describe any interim analyses or a multiplicity adjustment. These absences do not prove that such procedures were not used; they mean that the registry account does not document them. Interpretation should remain anchored to the posted descriptive information and avoid assuming an analysis method that is not recorded.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists the primary outcome as Adverse Effects Experienced and the secondary outcome as Number of Dose Adjustments. It reports two outcome measures and zero analyses. The statistical plan, any hierarchy among outcomes, and any adjustment for multiple outcomes or comparisons are not reported in the registry record. Thus, the record does not show whether the conversion factors were tested separately, whether there were multiple time points or subgroups, or how any multiplicity was handled.

General statistical explanation: examining several outcomes or comparisons can increase the chance of finding an apparently notable result by chance. A prespecified testing plan or an adjustment can help control that risk. Since no formal analyses are reported, there is no documented testing procedure to evaluate. This is not evidence that an adjustment was or was not performed outside the posted record.

The registry does not report an analysis population, the number contributing to the primary endpoint, or how missing outcomes were handled. Although enrollment was 61, the adverse-event figures list 33 and 27 participants at risk in the two displayed groups. The record does not explain the difference in these counts or identify the populations used for the primary endpoint. It also does not state whether participants with incomplete follow-up were excluded, retained, or handled through an imputation method.

These gaps limit interpretation of both completeness and comparability. The available figures can be described as posted, but they cannot establish that all enrolled participants contributed to each outcome or that missingness was unrelated to outcome. The absence of documented analysis details should be treated as uncertainty about what the registry record supports, rather than as proof of a particular analysis practice.

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 0% reporting threshold.

Most frequent non-serious adverse event terms

The posted serious-adverse-event fields show zero serious events in the Preferred Requip PR group, with 33 participants at risk, and zero in the Preferred Mirapex group, with 27 at risk. The fields for other adverse events list 9 affected participants in the Preferred Requip PR group and 8 in the Preferred Mirapex group. These are the registry’s displayed counts and group labels.

These values do not establish that the groups are like-for-like comparators. The study is listed as non-randomized and single-group, and the record does not explain how the preference labels relate to the conversion ratios. The zero serious-event figures describe what is posted for the displayed groups; they do not establish the absence of all possible harms, or rule out events that were not captured or reported. Deaths are not reported in the registry record.

General statistical explanation: when event counts are small or absent, estimates of risk can still be uncertain. A zero count is not equivalent to proof that the underlying event risk is zero. The registry does not provide confidence intervals or a formal comparative safety analysis. The figures should therefore be read descriptively, without inferring a treatment effect or a difference between conversion strategies.

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

This record documents a completed, open-label conversion study in people with Parkinson’s disease. It describes conversion from pramipexole to ropinirole controlled release and lists conversion factors of 1:3, 1:4, and 1:5. The stated purpose was to investigate an appropriate conversion ratio and side effects related to the drug. The primary endpoint was the number of adverse effects experienced at Week 4.

The posted adverse-event figures show zero serious adverse events in each displayed group and list other adverse events for participants under the labels “Preferred Requip PR” and “Preferred Mirapex.” These figures are descriptive. The record does not explain whether these groups correspond to the conversion-ratio groups, and it does not report a formal analysis of the primary endpoint by ratio. It also does not provide a comparative estimate or uncertainty interval.

The record does not establish that one conversion factor is better or worse than another. The non-randomized design, unclear relationship between the group labels, and absence of a reported analysis prevent a direct causal interpretation. The posted safety counts also cannot be used to conclude that one approach is safer than another. They summarize events in the displayed groups, not a randomized head-to-head comparison.

General statistical explanation: a study’s result is most informative when the outcome definition, analysis population, group assignment, and uncertainty are clear. Here, key details about event counting, allocation, missing data, and analysis are not reported in the registry record. The absence of a result for the primary endpoint by conversion factor means that the central comparison cannot be evaluated from the posted information.

Accordingly, the appropriate conclusion is narrow: the registry describes a conversion study and posts limited safety counts, but it does not supply the comparative endpoint results needed to assess the different conversion ratios. This is a statement about what the record reports, not a conclusion about clinical benefit or harm.

13. Why This Trial Matters Statistically

This trial is statistically notable because its central question concerns conversion between medications, while its registry design is described as non-randomized and single-group. The arm descriptions name several conversion ratios, but the posted safety groups use preference labels instead. Without a clear link between these group structures, readers cannot tell from the record how the adverse-event figures map to the conversion factors being investigated.

The example also shows why an endpoint’s unit matters. The primary outcome is described as a number of adverse-effect events. The safety summary separately reports participants with serious and other adverse events. Event counts and counts of affected participants answer different questions, and the registry does not clarify how the primary count was constructed. That distinction affects interpretation and the choice of statistical method.

General statistical explanation: a comparative design, transparent outcome definitions, and reported uncertainty help distinguish a real pattern from variation that could arise by chance or group differences. Non-randomized comparisons can be useful, but they require sufficient information about group formation and analysis to assess potential bias. Here, the registry reports no analyses and does not document an adjustment strategy or analysis population. The displayed counts should therefore remain descriptive.

The record also illustrates the limits of sample-size planning illustrations. Such calculations can show how planning assumptions relate to a hypothetical target, but they cannot recreate the original design justification or turn unreported endpoint results into evidence. The trial’s own sample-size rationale is not reported in the registry record.

For biostatisticians and clinical researchers, the key lesson is not about the success of a conversion strategy. It is about the need for clear alignment among the design description, group labels, endpoint definition, and analysis. When those elements are not documented together, even simple counts can be difficult to interpret as a comparison.

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.

Several limitations arise from the registry information specific to this study. First, the design is identified as non-randomized, with no masking. The record does not describe assignment to the conversion factors or explain how participants were classified. As a result, the groups cannot be assumed to be comparable, and the posted counts do not support a causal comparison.

Second, the registry describes the study as a single-group study but lists conversion-ratio arm descriptions. The adverse-event results use different labels, “Preferred Requip PR” and “Preferred Mirapex.” The relationship between these descriptions is not reported. This makes it unclear whether the posted safety figures correspond to the conversion-factor groups at all.

Third, the primary endpoint is a count of adverse effects at Week 4, but the event-counting rules and the distinction between events and participants are not explained. No result by conversion ratio is reported. The secondary Number of Dose Adjustments outcome is listed, but its result is not reported in the registry record.

Fourth, the registry reports enrollment of 61, while the displayed safety groups list 33 and 27 participants at risk. The record does not explain how those counts relate to enrollment or to the primary analysis population. Missing-data handling, analysis populations, protocol deviations, and outcome collection procedures are not reported.

Finally, the record reports zero analyses and provides no statistical model, comparison estimate, confidence interval, or hypothesis test. It does not report the sample-size justification, any interim analyses, or a multiplicity plan. These omissions limit what can be concluded from the posted results; they do not establish what procedures may have been used but were not documented.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Pramipexole Conversion to Ropinirole Controlled Release (CR) — NCT00275275.
• Registry record last updated 2012-08-24; status last verified 2012-07.
• Results first posted 2012-08-24.
• 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

NCT00275275 is a completed Phase 3, open-label, non-randomized, single-group conversion study in Parkinson’s disease. It enrolled 61 participants and examined conversion from pramipexole (Mirapex) to ropinirole controlled release (Requip PR). The record lists conversion factors of 1:3, 1:4, and 1:5. The primary outcome was the number of adverse effects experienced at Week 4; Number of Dose Adjustments was listed as a secondary outcome.

The registry posts safety figures under the labels “Preferred Requip PR” and “Preferred Mirapex,” including zero serious adverse events in each group and counts of other adverse events. The record does not explain how these groups relate to the conversion factors. It reports zero analyses and does not provide a primary endpoint result by ratio, a formal comparison, or uncertainty estimates. Further details about allocation, outcome definitions, missing data, analysis populations, and statistical methods are not reported in the registry record.