This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Long-term Study of Duodopa (Levodopa/Carbidopa) in Advanced Parkinson's: Health Outcomes & Net Economic Impact (NCT00141518), a non-randomized phase 4 study. The primary outcome is Unified Parkinson's Disease Rating Scale (UPDRS) Total Score, and UPDRS Subscores I, II, III, and IV at Baseline and Month 12.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00141518 |
| Phase | Phase 4 |
| Condition | Advanced Idiopathic Parkinson's Disease |
| Allocation | Non-Randomized |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 77 |
| Arms in the primary outcome | n/a |
| Lead sponsor | AbbVie (prior sponsor, Abbott) |
| Results posted | Yes |
2. Clinical Question
Population
Participants had advanced idiopathic Parkinson’s disease. The study description refers to severe motor fluctuations and hyper-/dyskinesia. The registry lists an enrollment of 77. The primary outcome population was defined as participants who had at least one dose of study drug and the required baseline and follow-up assessments. The exact number in that analysis population is not reported in the registry record.
Intervention
The intervention was levodopa-carbidopa intestinal gel, also called Duodopa. The treatment was delivered using a portable ambulatory infusion pump, with a PEG tube and jejunal extension tube listed as devices. The descriptions state that treatment was adjusted for each participant to an optimal clinical response. This was not a randomized assignment to treatment.
Comparator
There was no separate control arm. The registry distinguishes participants who were Duodopa-naïve from those already treated with Duodopa for less than 2 years or for at least 2 years. These are exposure-history groups, not randomized treatment and control groups, and should not be read as a like-for-like comparison.
Primary question
The primary outcome was the mean UPDRS total score and subscores at baseline and Month 12. The registry’s stated overall objective was to collect health-economic information on resource use, Parkinson’s disease-related costs, and health-related quality of life over time in a cohort treated with Duodopa. The numerical UPDRS results, health-economic results, and quality-of-life results are not reported in the registry record, so the direction and size of change cannot be described.
3. Trial Design
This was a Phase 4, non-randomized, unmasked, single-group study. The registry lists an enrollment of 77 and describes the study as a long-term health-economics study of intraduodenal levodopa in routine care for people with advanced idiopathic Parkinson’s disease. The study began in 2006-03, primary completion was in 2011-03, and its status is completed.
Although the study is classified as single-group, the registry presents three groups based on prior Duodopa exposure: Duodopa-naïve participants, non-naïve participants treated for less than 2 years, and non-naïve participants treated for at least 2 years. The descriptions indicate that the gel dose was individually adjusted. These groups therefore reflect treatment history, rather than randomized allocation to different interventions. The registry explicitly cautions that the groups are not a like-for-like control comparison.
The primary outcome covers the UPDRS total score and Parts I, II, III, and IV at baseline and Month 12. The listed timeframe describes baseline as Month -3. Secondary outcomes include stages on the Modified Hoehn and Yahr scale, the Schwab and England scale, and MMSE total and subscale scores, with listed follow-up extending to Month 36. The registry lists 60 outcome measures and 43 analyses, but the numerical results of these analyses are not reported in the registry record.
The study objective emphasizes resource use, Parkinson’s disease-related costs, and health-related quality of life. The registry says about one-third of the cohort were Duodopa-naïve before study start. A detailed protocol, statistical analysis plan, allocation procedure beyond the non-randomized designation, and sample-size justification 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
| Stage | Duodopa Naïve | Duodopa Non-naïve < 2 Years | Duodopa Non-naïve ≥ 2 Years |
|---|---|---|---|
| STARTED | 37 | 22 | 18 |
| Safety Sample | 36 | 22 | 18 |
| Full Analysis Sample | 27 | 22 | 18 |
| COMPLETED | 21 | 16 | 12 |
| NOT COMPLETED | 16 | 6 | 6 |
Reasons for not completing this period:
| Reason | Duodopa Naïve | Duodopa Non-naïve < 2 Years | Duodopa Non-naïve ≥ 2 Years |
|---|---|---|---|
| Withdrew Consent Prior to Treatment | 1 | 0 | 0 |
| Adverse Event | 7 | 5 | 2 |
| Withdrawal by Subject | 2 | 0 | 2 |
| Protocol Violation | 1 | 1 | 2 |
| Lack of Efficacy | 5 | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: Full Analysis Set: Participants who had ≥1 dose of study drug and (for Duodopa naives) data for baseline (BL) and ≥1 post-BL assessment of the primary efficacy measurements UPDRS and EQ-5D or (for Duodopa non-naives) had data for Month 0 visit and ≥1 more assessment of UPDRS and EQ-5D. n=participants with assessments at given time point.
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.
| Characteristic | Unit | Duodopa Naïve | Duodopa Non-naïve < 2 Years | Duodopa Non-naïve ≥ 2 Years | Total |
|---|---|---|---|---|---|
| Participants analysed | 27 | 22 | 18 | 67 | |
| Age, Continuous | years | 64.6 (SD 6.4) | 65.4 (SD 5.2) | 66.6 (SD 8.7) | 65.4 (SD 6.8) |
| Sex: Female, Male: Female | Participants | 11 | 7 | 6 | 24 |
| Sex: Female, Male: Male | Participants | 16 | 15 | 12 | 43 |
6. Primary Endpoint
The registry lists the primary outcome as Unified Parkinson's Disease Rating Scale (UPDRS) Total Score, and UPDRS Subscores I, II, III, and IV at Baseline and Month 12, measured over Baseline (Month -3), Month 12.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | units on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the mean score on the Unified Parkinson’s Disease Rating Scale (UPDRS), reported as a total score and as Parts I, II, III, and IV at baseline and Month 12. The registry describes the UPDRS as an investigator-used rating tool for following the longitudinal course of Parkinson’s disease. Parts I to III assess mentation, behavior and mood; activities of daily living; and motor examination. Part IV assesses complications of therapy. Higher scores are associated with more disability.
A score is a summary of responses to questions, not a direct measurement of every aspect of a person’s health. Considering the total and the component parts can distinguish overall score patterns from patterns in particular domains. In general, repeated measurements can describe how scores vary over time in a cohort, but a before-and-after pattern alone does not establish that treatment caused any change.
The registry specifies a mean and standard deviation for this continuous outcome. It does not report the actual means, standard deviations, changes, confidence intervals, or tests for the primary outcome. The result’s direction and precision therefore cannot be assessed from the registry record. The broader stated objective includes costs, resource use, and health-related quality of life, but numerical results for those outcomes are also not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry establishes the study’s design and the outcomes it intended to assess, but it does not report numerical primary-outcome results. There are no posted UPDRS means, standard deviations, changes from baseline, confidence intervals, or p-values in the registry record. Consequently, it is not possible to describe whether scores rose or fell, how large any change was, or how precisely an effect was estimated. This absence should not be mistaken for evidence of no change or for evidence of a particular treatment effect.
The design limits what a comparison over time could establish even if numerical changes were available. Participants were not randomly allocated, and there was no separate control arm. A score change within this cohort could reflect several influences, including the course of the condition, participant characteristics, concurrent care, changes in treatment, or differences in who remained available for assessment. Without a suitable comparison and adequate control of these factors, an observed time pattern would not by itself identify the causal effect of Duodopa.
The three exposure-history groups do not provide a randomized contrast. Duodopa-naïve participants and participants already treated for different durations could differ in ways that affect both their baseline status and later measurements. Their outcomes should therefore be described as group-specific observations, not as evidence that one exposure history is better or worse than another. The registry itself cautions against treating the groups as like-for-like controls.
The registry’s stated health-economic objective is to collect information about resource use, disease-related costs, and health-related quality of life over time. The objective is not itself a result. Numerical findings for these outcomes are not reported in the registry record, so conclusions about costs, resource utilization, or quality of life cannot be drawn from the listed study objective.
The adverse-event record lists counts of participants affected in each exposure-history group, as well as selected serious-event terms and percentages. These describe reported events in the study groups; without a randomized comparator, exposure-time information, and fuller event-level context, they do not establish comparative safety or causation. Death counts are not reported in the registry record.
Overall, the available record supports a description of the study’s setting, design, planned outcome measures, and recorded adverse-event counts. It does not support a quantitative statement about the primary endpoint’s observed change, the precision of that change, or a causal treatment effect. Those limitations should remain explicit when interpreting the study.
9. Statistical Methods Explained
The endpoint is continuous: the primary measure is a mean UPDRS score, with standard deviation specified as the measure of dispersion. In general, a mean describes the arithmetic center of observed scores, while a standard deviation describes how spread out individual scores are around that center. These are complementary summaries. A mean alone does not show whether scores are tightly clustered or highly variable. The registry does not report the primary endpoint’s numerical means or standard deviations.
What does a change over time describe?
In general, a repeated-measures study observes participants at more than one time point. A difference between a group’s baseline and follow-up summaries describes a time pattern in the measured cohort. It is not automatically the same as a treatment effect. Other explanations can include the natural course of disease, changes in care, participant-level differences, and selective availability of follow-up data. Random allocation and an appropriate comparison group can help separate treatment effects from other influences; neither is part of this study’s design as recorded.
The primary endpoint names baseline and Month 12, with the timeframe identifying baseline as Month -3. The registry says the outcome is summarized as a mean and standard deviation, but does not report the numerical summaries, an estimate of change, or an uncertainty interval. A confidence interval, in general, is a range of values compatible with the data and the statistical method used, and helps convey estimation uncertainty. No confidence interval for the primary outcome is reported in the registry record, so precision cannot be evaluated from that record.
Why does the study structure matter?
The study is non-randomized, unmasked, and classified as single-group. In general, randomization helps balance measured and unmeasured characteristics between assigned groups, while masking can limit some forms of expectation-related influence on measurement or reporting. Because this study lacks random allocation and masking, comparisons across time or exposure-history groups may be affected by differences in participants, treatment history, follow-up, or assessment. The registry does not report a statistical adjustment plan that would show how such differences were handled.
The three groups are defined by prior Duodopa exposure: naïve, non-naïve for less than 2 years, and non-naïve for at least 2 years. This categorization can describe outcomes by treatment history, but it does not create a controlled comparison. In general, prior exposure can be associated with differences in disease history, treatment selection, or eligibility. Without details of adjustment and the numerical outcomes, the extent of any such differences and their effect on comparisons cannot be evaluated.
How should the outcome scale be read?
The registry states that higher UPDRS scores are associated with more disability. Parts I to III use response scales from 0 to 4 per question; Part IV uses 0 or 1 for some questions and a 5-point scale for others. The listed component score ranges are 0 to 16 for Part I, 0 to 52 for Part II, 0 to 108 for Part III, and 0 to 23 for Part IV. The total score range is 0 to 176 and is described as the sum of responses in Parts I to III. These details define how the registry describes the measure; they do not reveal the cohort’s observed scores.
In general, score ranges help readers understand the scale, but they do not by themselves establish what constitutes an important change for an individual or group. A clinically meaningful-change threshold is not reported in the registry record. Nor are the numerical UPDRS outcomes reported, so no score movement can be compared with any threshold.
What can the planned sample-size illustration establish?
In general, a sample-size calculation describes how many participants a hypothetical design might require under specified assumptions. The registry’s stated planning assumptions refer to a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and detecting a stated fraction of an observed effect. The record describes these calculations as planning illustrations rather than the trial’s own design. It also states that such illustrations are not observed power. The trial itself was non-randomized and single-group, so the two-arm assumptions do not describe its allocation. Numerical illustration results and the trial’s sample-size justification are not reported in the registry record.
In general, observed power is not a substitute for reporting an effect estimate and its uncertainty. A study’s enrollment does not by itself show whether a particular effect was estimated precisely. Here, numerical primary results and their uncertainty are absent from the registry record, and the exact primary analysis population size is not reported.
What does the adverse-event summary represent?
In general, adverse-event counts describe recorded events or affected participants under the definitions and observation periods used in a study. The record lists participants at risk and participants affected by serious and other adverse events in each exposure-history group. It also lists selected serious-event terms with percentages. Those data can describe what was recorded, but do not alone establish that the study treatment caused an event or allow a fair comparison between groups. The registry does not provide enough information in the posted record to assess event timing, exposure duration, or comparative rates. Death counts are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 60 outcome measures and 43 analyses. The primary outcome itself includes a total UPDRS score and four subscores, and the secondary outcomes include several clinical scales and cognitive measures. When many outcomes or analyses are examined, the chance of at least one apparently notable result arising by chance can increase. In general, multiplicity procedures and a prespecified hierarchy can help define how evidence across multiple tests is interpreted.
A multiplicity adjustment, testing hierarchy, or distinction between confirmatory and exploratory analyses is not reported in the registry record. The record also does not report the analysis results or the p-values needed to assess how findings across outcomes were handled. It is therefore not possible to determine whether any reported inference accounted for multiple comparisons.
The primary population description requires at least one dose and specified assessment data, with different entry requirements for naïve and non-naïve participants. The exact number analyzed and the number missing at each time point are not reported in the registry record. The handling of missing observations, withdrawals, incomplete assessments, and any imputation method is also not reported in the registry record.
In general, missing data can affect an estimate when participants with unavailable follow-up differ from those who remain observed. The impact depends on why data are missing, how much is missing, and the analysis method. Without counts, reasons, or analysis details, the direction or size of any missing-data bias cannot be assessed. A detailed statistical analysis plan is not reported in the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Duodopa Naïve | 24 | 36 | 66.7% |
| Duodopa Non-naïve < 2 Years | 17 | 22 | 77.3% |
| Duodopa Non-naïve ≥ 2 Years | 14 | 18 | 77.8% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Duodopa Naïve | 29 of 36 |
| Duodopa Non-naïve < 2 Years | 22 of 22 |
| Duodopa Non-naïve ≥ 2 Years | 17 of 18 |
Most frequent serious adverse event terms
| Event term | Organ system | Duodopa Naïve | Duodopa Non-naïve < 2 Years | Duodopa Non-naïve ≥ 2 Years |
|---|---|---|---|---|
| Medical device change | Surgical and medical procedures | 9 of 36 | 9 of 22 | 3 of 18 |
| Pneumonia | Infections and infestations | 4 of 36 | 3 of 22 | 1 of 18 |
| Fall | Injury, poisoning and procedural complications | 1 of 36 | 3 of 22 | 2 of 18 |
| Hallucination | Psychiatric disorders | 4 of 36 | 1 of 22 | 1 of 18 |
| Device related infection | Infections and infestations | 3 of 36 | 1 of 22 | 1 of 18 |
| Device dislocation | Injury, poisoning and procedural complications | 3 of 36 | 1 of 22 | 1 of 18 |
| Dyskinesia | Nervous system disorders | 2 of 36 | 1 of 22 | 2 of 18 |
| Anaemia | Blood and lymphatic system disorders | 1 of 36 | 2 of 22 | 1 of 18 |
| Chest pain | General disorders | 1 of 36 | 1 of 22 | 1 of 18 |
| Urosepsis | Infections and infestations | 1 of 36 | 1 of 22 | 1 of 18 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Duodopa Naïve | Duodopa Non-naïve < 2 Years | Duodopa Non-naïve ≥ 2 Years |
|---|---|---|---|---|
| Device dislocation | Injury, poisoning and procedural complications | 7 of 36 | 8 of 22 | 5 of 18 |
| Constipation | Gastrointestinal disorders | 8 of 36 | 3 of 22 | 4 of 18 |
| Excessive granulation tissue | Skin and subcutaneous tissue disorders | 6 of 36 | 7 of 22 | 2 of 18 |
| Device related infection | Infections and infestations | 4 of 36 | 6 of 22 | 4 of 18 |
| Depression | Psychiatric disorders | 7 of 36 | 4 of 22 | 2 of 18 |
| Anaemia | Blood and lymphatic system disorders | 6 of 36 | 4 of 22 | 2 of 18 |
| Blood homocysteine increased | Investigations | 2 of 36 | 4 of 22 | 6 of 18 |
| Medical device change | Surgical and medical procedures | 6 of 36 | 5 of 22 | 1 of 18 |
| Hallucination | Psychiatric disorders | 7 of 36 | 2 of 22 | 2 of 18 |
| Urinary tract infection | Infections and infestations | 2 of 36 | 4 of 22 | 4 of 18 |
Serious events with the highest arm-level rate: medical device change (40.9%), pneumonia (13.6%), fall (13.6%), medical device removal (13.6%), medical device complication (11.1%).
The registry reports serious adverse events for three exposure-history groups. Among Duodopa-naïve participants, 24 of 36 at risk were affected by serious adverse events, and 29 of 36 were affected by other adverse events. Among non-naïve participants treated for less than 2 years, 17 of 22 at risk were affected by serious adverse events, and 22 of 22 were affected by other adverse events. Among non-naïve participants treated for at least 2 years, 14 of 18 at risk were affected by serious adverse events, and 17 of 18 were affected by other adverse events.
The record lists medical device change at 40.9% as a selected serious-event term, followed by pneumonia, fall, and medical device removal at 13.6% each, and medical device complication and dehydration at 11.1% each. These listed percentages should be read as registry entries for selected event terms, not as comparative estimates between randomized arms. The registry does not report a control group, and the groups differ by prior exposure history.
Counts of participants affected are not the same as counts of individual event episodes. The record does not report event timing, duration of exposure, or additional context needed to interpret comparative rates. Death counts are not reported in the registry record. These summaries describe recorded safety information; they do not establish that treatment caused an event or support a causal comparison between groups.
12. What the Result Does, and Does Not, Mean
The study record documents a long-term, routine-care cohort of people with advanced idiopathic Parkinson’s disease treated with Duodopa. It identifies the primary clinical measure, the secondary outcomes, the health-economic objective, and adverse-event counts across groups defined by prior treatment history. That information is useful for understanding what the registry intended to examine and how the cohort was organized.
The record does not report numerical primary UPDRS results, so it cannot show the observed mean scores, change over time, or precision of an estimate. It also does not report numerical results for the stated health-economic objectives or the listed secondary outcomes. The absence of results in the registry record is not evidence that outcomes remained unchanged, and it does not establish any particular benefit or lack of benefit.
The non-randomized, single-group design also limits causal interpretation. Comparisons across time or among exposure-history groups could be influenced by differences in participants and their prior care. The groups are not randomized treatment and control arms, and the registry explicitly cautions against treating them as a like-for-like comparison. Any observed association would need to be interpreted in that context.
The adverse-event counts and selected terms provide a description of recorded events, but do not establish causation or comparative safety. The available record does not give the information needed to account for exposure time or to determine whether event risks differed between comparable groups. Overall, the registry record supports a study-design description, not a quantitative conclusion about treatment effect, outcome precision, or causal safety differences.
13. Why This Trial Matters Statistically
This study is statistically notable because its stated objective is broader than its primary clinical endpoint. The study description focuses on health-economic data, resource use, Parkinson’s disease-related costs, and health-related quality of life, while the listed primary endpoint is the mean UPDRS total score and subscores at baseline and Month 12. Those are related areas of assessment, but they answer different questions. Numerical results for either the UPDRS endpoint or the health-economic objectives are not reported in the registry record.
The study also illustrates the distinction between a cohort and a controlled comparison. Its exposure-history groups may help organize descriptions of participants with different prior experience of Duodopa, but they are not randomized arms. This distinction matters when interpreting apparent differences: group membership can reflect treatment history and participant characteristics, not just the intervention contrast a randomized trial is designed to estimate.
The registry’s listing of many outcome measures and analyses raises a general issue of multiplicity. When many outcomes are assessed, readers need to know which analyses were prespecified and how multiple testing was handled. Those details are not reported in the registry record, so the strength and role of any potential findings cannot be assessed from the record.
Finally, the listed sample-size assumptions describe planning illustrations, not the study’s actual design or observed power. This is important because a planning calculation under equal allocation between two arms does not match a non-randomized, single-group study. Taken together, the record is a useful example of why design, outcome availability, analysis plans, and the distinction between descriptive and causal claims all matter in clinical biostatistics.
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 registry record does not report numerical results for the primary endpoint, secondary outcomes, health-economic objectives, or quality-of-life objectives. Without outcome estimates and their uncertainty, the magnitude, direction, and precision of any changes cannot be assessed. The record also does not report a detailed statistical analysis plan, the sample-size justification, or the methods used to handle multiple outcomes.
The study was non-randomized, unmasked, and single-group, with no separate control arm. The three groups are defined by prior Duodopa exposure and are not like-for-like randomized comparisons. This design limits causal interpretation of changes over time and differences between groups. The registry does not report an adjustment strategy that would clarify how participant differences were addressed.
The exact number in the primary analysis population, the number with missing assessments, and reasons for missing data are not reported in the registry record. The record also does not report how incomplete follow-up was handled. These omissions prevent assessment of whether the analyzed participants differed from those without follow-up data.
For safety, the registry lists affected-participant counts and selected serious-event terms, but does not report event timing, exposure duration, or death counts. These gaps limit assessment of event rates and comparisons across groups. The record’s planning assumptions are illustrative and do not supply a justification for the cohort’s enrollment. These are limitations of what can be concluded from the registry record, not findings about what occurred outside it.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Long-term Study of Duodopa (Levodopa/Carbidopa) in Advanced Parkinson's: Health Outcomes & Net Economic Impact — NCT00141518.
- Registry record last updated 2016-07-18; status last verified 2016-06.
- Results first posted 2016-07-18.
- 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.
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18. Record Summary
This completed Phase 4 study was a non-randomized, unmasked, single-group study of Duodopa in advanced idiopathic Parkinson’s disease, with an enrollment of 77. Its primary outcome was mean UPDRS total score and subscores at baseline and Month 12. Secondary measures included Parkinson’s disease staging, the Schwab and England scale, and MMSE scores, with outcomes listed through Month 36. The stated broader objective concerned resource use, disease-related costs, and health-related quality of life.
The registry distinguishes participants by prior Duodopa exposure, but these groups are not randomized control arms. Numerical outcome results, confidence intervals, the detailed analysis plan, and the exact primary analysis population size are not reported in the registry record. Adverse-event counts and selected serious-event terms are listed; death counts are not reported in the registry record. The available information supports description of the design and recorded safety summaries, but not a quantitative estimate of treatment effect or a causal comparison.