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 Deep Brain Stimulation (DBS) for Early Stage Parkinson's Disease (PD) (NCT00282152), a randomized na study. The primary outcome is Safety: Time to Reach a 4 Point Increase (Worsening) in Unified Parkinson's Disease Rating Scale (UPDRS) Motor Score.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00282152 |
| Phase | NA |
| Condition | Parkinson's Disease |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 37 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Vanderbilt University Medical Center |
| Results posted | Yes |
2. Clinical Question
Population
People with early-stage Parkinson’s disease. The registry record reports enrollment of 37 and says the primary analysis included all 29 subjects who completed at least one follow-up visit, following an intent-to-treat principle. Further eligibility details are not reported in the registry record.
Intervention
Bilateral subthalamic nucleus deep brain stimulation (B-STN DBS) alongside optimal drug therapy. The DBS group continued optimal drug therapy as prescribed by the treating neurologist.
Comparator
Optimal drug therapy alone. The registry describes the drugs as standard-of-care Parkinson’s disease medicines and notes that the drug form, dosage, frequency, and duration could vary.
Primary question
For safety and tolerability, would the DBS-plus-drug-therapy group reach a 4-point increase in UPDRS motor score more quickly than the optimal-drug-therapy group over baseline to 24 months? The stated hypothesis was that the DBS group would not worsen more quickly.
The primary outcome concerns the timing of a specified worsening threshold, rather than simply the motor score at one follow-up visit. The registry reports mean times for the two groups and a log-rank analysis. It labels the analysis as non-inferiority, but the non-inferiority margin and the decision rule for concluding non-inferiority are not reported in the registry record.
The study also posted secondary outcomes concerning UPDRS mentation, behavior and mood; activities of daily living; motor examination excluding rigidity; complications of therapy; and total UPDRS. These outcomes broaden the domains under consideration, but they do not change the primary safety question. The registry does not report enough detail to establish how those outcomes influenced the trial’s primary conclusion.
3. Trial Design
The registry describes a randomized, single-masked, parallel-group trial. Participants were assigned to optimal drug therapy alone or to bilateral subthalamic nucleus deep brain stimulation alongside optimal drug therapy. The record lists enrollment of 37 and indicates that the study is completed. It gives a start date of 2006-03 and a primary completion date of 2012-01.
The comparison was designed as a feasibility study focused on safety and tolerability. Its stated primary hypothesis was that participants receiving DBS plus optimal drug therapy would not worsen more quickly than those receiving optimal drug therapy alone. The registry also describes the pilot as intended to provide information relevant to planning a larger, multicenter trial. It does not report a formal sample-size justification, the details of any such future design, or a protocol-level statistical analysis plan.
The treatment contrast is between the two assigned strategies, not between DBS and no treatment: both groups received optimal drug therapy. The drug regimen could vary in form, dosage, frequency, and duration. The DBS group continued medication while receiving stimulation of both the right and left subthalamic nucleus. The record identifies DBS as a device intervention and optimal drug therapy as a drug intervention.
For the primary analysis, the registry says that all 29 subjects who completed at least one follow-up visit were included following an intent-to-treat principle. That wording should be read as the registry’s description of the analyzed population; the record does not explain how participants without a follow-up visit were handled. Further information about allocation concealment, the identity of the masked party, or the masking procedure is 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: 7 participants excluded prior to treatment ( 1 withdrew consent and 6 failed screening)
Overall Study
| Stage | Optimal Drug Therapy (ODT) | Deep Brain Stimulation (DBS) Plus Optimal Drug Therapy (ODT) |
|---|---|---|
| STARTED | 15 | 15 |
| COMPLETED | 14 | 15 |
| NOT COMPLETED | 1 | 0 |
Reasons for not completing this period:
| Reason | Optimal Drug Therapy (ODT) | Deep Brain Stimulation (DBS) Plus Optimal Drug Therapy (ODT) |
|---|---|---|
| Withdrawal by Subject | 1 | 0 |
Analysis population for the primary outcome, as defined in the registry: all 29 subjects that completed at least one follow up visit were included in the primary analysis following intent to treat principle
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 | Optimal Drug Therapy (ODT) | Deep Brain Stimulation (DBS) Plus Optimal Drug Therapy (ODT) | Total |
|---|---|---|---|---|
| Participants analysed | 15 | 15 | 30 | |
| Age, Continuous | years | 60 (51 to 69) | 60 (52 to 74) | 60 (51 to 74) |
| Sex: Female, Male: Female | Participants | 2 | 1 | 3 |
| Sex: Female, Male: Male | Participants | 13 | 14 | 27 |
| Region of Enrollment: United States | participants | 15 | 15 | 30 |
6. Primary Endpoint
The registry lists the primary outcome as Safety: Time to Reach a 4 Point Increase (Worsening) in Unified Parkinson's Disease Rating Scale (UPDRS) Motor Score, measured over baseline to 24 months.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | months |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is titled “Safety: Time to Reach a 4 Point Increase (Worsening) in Unified Parkinson’s Disease Rating Scale (UPDRS) Motor Score.” It measures the time from baseline until a participant reaches the specified worsening threshold. The registry gives the timeframe as baseline to 24 months and reports the outcome in months.
A time-to-event outcome keeps information about when the threshold is reached, rather than reducing the follow-up to whether worsening occurred at a single endpoint visit. In general, this can be useful when participants reach an event at different times or when follow-up ends before an event is observed. The registry does not report the event counts, censoring details, or operational rules used to determine when the threshold was reached, so those aspects cannot be assessed from the posted record.
The group summaries are means with 95% confidence intervals. The optimal-drug-therapy group has a reported mean of 15.0 months, with a 95% confidence interval from 10.7 to 19.3. The DBS-plus-optimal-drug-therapy group has a reported mean of 14.1 months, with a 95% confidence interval from 10.3 to 18.0. The registry also reports a log-rank comparison. These summaries describe time to the defined worsening event; they are not direct measures of all aspects of safety or Parkinson’s disease progression.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted group summaries give a mean time to the 4-point UPDRS motor worsening threshold of 15.0 months for optimal drug therapy and 14.1 months for DBS plus optimal drug therapy. Their 95% confidence intervals are 10.7 to 19.3 months and 10.3 to 18.0 months, respectively. The intervals overlap substantially. A confidence interval describes uncertainty around an estimated quantity under the analysis used; it is not a range containing a fixed proportion of individual participants’ event times.
The registry reports a log-rank p-value of 0.968 and labels the analysis as non-inferiority. A p-value is a measure of how compatible the observed data are with a specified statistical null model; it is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of an effect. The p-value alone does not establish non-inferiority. A non-inferiority interpretation requires a prespecified margin and an appropriate decision rule, and those details are not reported in the registry record.
The primary hypothesis focused on whether the DBS-plus-drug-therapy group would not worsen more quickly. The reported analysis does not, by itself, show that the groups are equivalent or that clinically meaningful differences have been ruled out. The confidence intervals and reported p-value should be interpreted alongside the trial’s size, the analysis population, and the missing details about the time-to-event data and non-inferiority framework.
The registry describes the primary analysis population as all 29 subjects with at least one follow-up visit, included following an intent-to-treat principle. That population description does not provide the number or timing of events, the censoring pattern, or the handling of missing follow-up. Those details matter for evaluating a time-to-event analysis. The record also reports enrollment of 37, but does not explain the flow from enrollment to the primary analysis population.
This was a pilot feasibility trial, and its stated purpose included informing the design of a larger trial. The reported results therefore offer a limited statistical account of the primary safety endpoint. They do not resolve the broader question of whether DBS changes the course of Parkinson’s disease, and the registry’s result should not be read as a general claim about treatment efficacy or safety.
9. Statistical Methods Explained
The registry identifies the primary outcome as a continuous measure summarized by a mean and 95% confidence interval, while the outcome title and reported test concern time to a worsening event. These descriptions capture related but distinct statistical features: the mean summarizes the reported times, and the log-rank test compares event-time distributions. The record does not give enough detail to determine how the mean was estimated in the presence of censoring or to reproduce the analysis.
What does a time-to-event analysis compare?
In general, a time-to-event method uses both the timing of events and information from participants who have not had an event by the end of their observed follow-up. Such participants may be censored: their event time is not observed, but their follow-up contributes information up to the point observation ends. A log-rank test is a general method for comparing event-time patterns between groups. Its result depends on the event and censoring information, not merely on the reported group means and confidence intervals. Event counts, censoring details, and the analysis rules are not reported in the registry record.
The reported p-value is 0.968. In general, a p-value quantifies how unusual the observed test result would be under a specified null hypothesis and the assumptions of the test. It does not quantify the probability that a treatment is effective, nor does a large p-value establish that two strategies are the same. Interpretation also depends on the hypothesis and test framework. Here, the registry labels the log-rank result as non-inferiority, but does not report the non-inferiority margin or the full decision rule.
What does non-inferiority require?
In general, a non-inferiority analysis asks whether the intervention is not worse than the comparator by more than a prespecified, clinically acceptable margin. The margin defines how much difference could still be considered compatible with non-inferiority. A p-value or a failure to find evidence of a difference is not a substitute for that margin. The registry record does not report the margin, how it was selected, or the confidence-interval criterion used to reach a non-inferiority conclusion. Consequently, the label attached to the reported analysis cannot be independently evaluated from the available details.
The primary endpoint’s confidence intervals are reported as 95% intervals around group means. In general, a confidence interval conveys uncertainty about an estimated parameter under the analysis assumptions. It is not an interval containing most individual observations, and interval overlap is not itself a formal test of equivalence or non-inferiority. The group estimates and their intervals provide context for the result, but they do not supply the missing non-inferiority margin or event-time information.
Why are summary-statistic recalculations limited?
A recalculation based on posted summary statistics is a simple, unadjusted calculation and cannot necessarily reproduce a sponsor analysis that uses participant-level data, censoring, or a different model. For this outcome, the registry record indicates that a two-arm comparison for a continuous endpoint could not be calculated because values were missing or not estimable. The reported log-rank analysis is therefore the available inferential comparison for the primary endpoint. A mean and its confidence interval do not contain enough information to reconstruct a log-rank test.
The record describes the primary analysis population as all 29 subjects who completed at least one follow-up visit, following an intent-to-treat principle. In general, intent-to-treat analysis refers to analyzing participants according to their assigned groups, but implementation depends on how missing outcomes and participants without follow-up are handled. The registry does not explain these details, so the population label alone does not establish how all randomized participants contributed to the endpoint analysis.
What do the planning illustrations mean?
In general, a sample-size planning illustration translates an assumed effect and statistical design choices into an approximate requirement for a future study. The registry’s planning assumptions describe a two-sided significance level of 0.05, equal allocation, a normal approximation, and effects defined as fractions of the observed effect. For time-to-event illustrations, the stated quantity is the total number of events; for other outcomes, it is participants per arm. These are planning illustrations based on the observed effect, not evidence that the present trial had a particular power. The record does not report that these assumptions were the trial’s own original design assumptions.
More generally, statistical interpretation depends on whether the endpoint, analysis population, test, and decision criterion match the question being asked. The registry identifies the endpoint and reports a log-rank p-value, but does not report event counts, the non-inferiority margin, detailed missing-data methods, or a complete statistical plan. Those omissions limit reproducibility and make the result less informative than a fully specified analysis would be.
10. Analyses Reported by the Sponsor
| Method | Estimate | 95% CI | P-value |
|---|---|---|---|
| Log Rank | not reported | 0.968 |
The registry reports the trial’s log-rank analysis with p = 0.968 and labels it as a non-inferiority analysis. This is the posted inferential result for the primary time-to-event endpoint. The registry also indicates that values were missing or not estimable for a two-arm comparison treated as a continuous endpoint, so a simple recalculated continuous-endpoint comparison is not available.
A recalculation from summary means and confidence intervals would not recreate a log-rank analysis, which in general uses event timing and censoring information. The event counts and censoring details needed to reproduce that analysis are not reported in the registry record. The reported means and intervals can describe the posted group summaries, but they do not independently verify the log-rank result or establish non-inferiority without the margin and decision rule.
No discrepancy between a recalculation and the reported analysis is flagged in the registry record. The sponsor’s reported analysis remains the available formal comparison, while its non-inferiority interpretation cannot be fully assessed from the posted information.
11. Multiplicity, Missing Data and Analysis Populations
The registry lists five secondary outcomes: changes in UPDRS Part I, mentation, behavior and mood; Part II, activities of daily living; Part III, motor examination excluding rigidity; Part IV, complications of therapy; and total UPDRS. It reports seven outcome measures and two analyses. The record does not explain how the secondary outcomes relate to the primary hypothesis or identify a multiplicity adjustment.
Multiplicity arises when several outcomes or tests are considered. In general, examining multiple results can increase the chance of finding at least one apparently notable result even when no corresponding effect exists. Adjustments or a prespecified hierarchy can address that issue, but the statistical plan and any multiplicity strategy are not reported in the registry record. The five posted secondary outcomes should therefore be treated as additional outcome information rather than as confirmatory evidence under a known family-wise testing plan.
The primary analysis population is described as all 29 subjects who completed at least one follow-up visit, included following an intent-to-treat principle. Enrollment is reported as 37. The registry does not describe participant flow, explain how participants without a follow-up visit were handled, or specify the population used for each secondary analysis. No count of missing primary endpoint observations, missing-data method, imputation procedure, or sensitivity analysis is reported in the registry record.
For a time-to-event endpoint, censoring and the timing of follow-up are relevant to the analysis. The record does not report event counts or censoring details. It also does not explain whether other analyses were planned, which analyses were prespecified, or how the two listed analyses relate to the outcome measures. These omissions make it difficult to assess the full analysis strategy and the robustness of the reported result.
12. 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 |
|---|---|---|---|
| Optimal Drug Therapy (ODT) | 0 | 14 | 0.0% |
| Deep Brain Stimulation (DBS) Plus Optimal Drug Therapy (ODT) | 2 | 15 | 13.3% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Optimal Drug Therapy (ODT) | 0 of 14 |
| Deep Brain Stimulation (DBS) Plus Optimal Drug Therapy (ODT) | 0 of 15 |
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 |
|---|---|
| Optimal Drug Therapy (ODT) | 15 of 15 |
| Deep Brain Stimulation (DBS) Plus Optimal Drug Therapy (ODT) | 15 of 15 |
Most frequent serious adverse event terms
| Event term | Organ system | Optimal Drug Therapy (ODT) | Deep Brain Stimulation (DBS) Plus Optimal Drug Therapy (ODT) |
|---|---|---|---|
| Perioperative infarction in left basil ganglia | Nervous system disorders | 0 of 14 | 1 of 15 |
| Infection | Infections and infestations | 0 of 14 | 1 of 15 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Optimal Drug Therapy (ODT) | Deep Brain Stimulation (DBS) Plus Optimal Drug Therapy (ODT) |
|---|---|---|---|
| Insomnia | Nervous system disorders | 5 of 14 | 8 of 15 |
| Nausea | Gastrointestinal disorders | 6 of 14 | 3 of 15 |
| Weight decreased | General disorders | 6 of 14 | 3 of 15 |
| Nasopharyngitis | Immune system disorders | 2 of 14 | 5 of 15 |
| Dyspnoea | Respiratory, thoracic and mediastinal disorders | 3 of 14 | 4 of 15 |
| Weight increased | General disorders | 5 of 14 | 2 of 15 |
| Dizziness | Nervous system disorders | 5 of 14 | 1 of 15 |
| Dysphagia | Gastrointestinal disorders | 3 of 14 | 3 of 15 |
| Vomiting | Gastrointestinal disorders | 4 of 14 | 1 of 15 |
| Fatigue | General disorders | 2 of 14 | 3 of 15 |
Serious events with the highest arm-level rate: perioperative infarction in left basil ganglia (6.7%), infection (6.7%).
The registry reports serious adverse events among 0 of 14 participants at risk in the optimal-drug-therapy group and 2 of 15 at risk in the DBS-plus-optimal-drug-therapy group. It reports no deaths in either group. The listed top serious adverse-event terms are “Perioperative infarction in left basil ganglia” and “Infection,” each reported as 6.7%.
These are descriptive safety counts from the registry record. They do not, on their own, establish whether an event was caused by the assigned intervention, how severe or persistent it was, or whether all events were collected in the same way. The record does not report further details about event timing, adjudication, or attribution.
The registry also lists other adverse events among 15 of 15 participants at risk in each group. Serious and other adverse events are different categories in the record and should not be combined into a single count. Because the study is a pilot and the safety details are limited, these figures describe what was posted rather than providing a precise estimate of comparative safety.
13. What the Result Does, and Does Not, Mean
The posted results describe a randomized comparison of DBS plus optimal drug therapy with optimal drug therapy alone for the time to a 4-point worsening in UPDRS motor score. The reported mean times are 14.1 months for the DBS group and 15.0 months for the drug-therapy group, with 95% confidence intervals of 10.3 to 18.0 and 10.7 to 19.3 months, respectively. The log-rank analysis has a reported p-value of 0.968.
These figures do not establish that the strategies are equivalent. A large p-value is not proof of no difference, and the registry does not report the non-inferiority margin needed to evaluate the stated non-inferiority framework. The confidence intervals communicate uncertainty around the group means but do not answer whether a clinically relevant difference has been ruled out.
The findings also do not establish a broader effect on Parkinson’s disease progression. The registry’s primary endpoint concerns one specified motor-score threshold over baseline to 24 months. It is not a direct measure of every motor, non-motor, quality-of-life, or long-term disease outcome. The listed secondary outcomes cover several UPDRS domains, but the record does not report a multiplicity plan or a complete account of their analyses.
The posted serious adverse-event counts are limited descriptive observations. They should not be read as definitive comparative risk estimates. Further details about event attribution and follow-up are not reported in the registry record. More generally, the pilot’s stated purpose was focused on safety and tolerability and informing future trial design; the record does not support a broad claim that DBS either changes or does not change the course of disease.
14. Why This Trial Matters Statistically
This trial raises a useful statistical distinction between testing for a difference and testing for non-inferiority. A non-inferiority question is not answered simply by a non-significant difference test or by a large p-value. It needs a specified margin and a decision rule that relate the estimate and its uncertainty to that margin. Although the registry labels the primary analysis as non-inferiority, those key details are not reported in the registry record.
The endpoint also illustrates why summary means alone are insufficient for many time-to-event analyses. The outcome concerns when participants reach a worsening threshold, and the reported inferential method is a log-rank test. Event times and censoring contribute to that comparison, while group means and confidence intervals cannot reproduce it. Reporting event counts and follow-up details would help readers understand and assess the analysis.
The record identifies an intent-to-treat principle but describes the primary analysis population as participants who completed at least one follow-up visit. That makes transparent reporting of participant flow and missing-data handling especially relevant. The registry gives enrollment and the analyzed population counts, but does not explain the intervening flow or how participants without follow-up were handled.
Finally, a pilot trial can inform later research without settling an efficacy question. The record says the study was intended to provide safety and tolerability information and support design of a larger trial. Statistically, that context cautions against treating the single reported primary comparison as a definitive test of a broad clinical claim.
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 record does not report the non-inferiority margin or the full decision rule for the primary analysis. Without these, the label “non-inferiority” cannot be independently evaluated. The record also does not provide the event counts, censoring information, or detailed analysis rules needed to reproduce the log-rank comparison.
The primary analysis population is described as the 29 subjects who completed at least one follow-up visit, following an intent-to-treat principle, while enrollment is reported as 37. The record does not explain participant flow between enrollment and analysis, how participants without a follow-up visit were treated, or how missing endpoint data were handled. It does not provide sensitivity analyses for these choices.
The statistical plan is not reported in enough detail to determine which analyses were prespecified, how the two listed analyses relate to the seven outcome measures, or whether multiplicity was addressed. No formal sample-size justification for this trial is reported. Planning assumptions based on an observed effect are not evidence of the trial’s original design rationale or of observed power.
Further design details—including allocation concealment and the masking procedure—are not reported in the registry record. The record describes the trial as single-masked, but does not say who was masked. The primary endpoint timeframe ends at 24 months, so the posted endpoint does not describe outcomes beyond that period. The available serious adverse-event information also lacks event timing, attribution, and adjudication details. These limits constrain both reproducibility and the scope of conclusions that can be drawn from the posted results.
16. Related Tutorials
17. Related Statistical Calculators
18. Sources
- ClinicalTrials.gov: Deep Brain Stimulation (DBS) for Early Stage Parkinson's Disease (PD) — NCT00282152.
- Registry record last updated 2017-05-30; status last verified 2017-03.
- Results first posted 2017-05-30.
- 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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19. Record Summary
The registry describes a completed, randomized, single-masked, parallel-group pilot trial of bilateral subthalamic nucleus DBS plus optimal drug therapy versus optimal drug therapy alone in Parkinson’s disease. Enrollment was 37. The primary endpoint was time to a 4-point worsening in UPDRS motor score over baseline to 24 months.
The primary analysis included all 29 subjects who completed at least one follow-up visit, described as following an intent-to-treat principle. Mean times were 15.0 months for optimal drug therapy and 14.1 months for DBS plus optimal drug therapy. The reported log-rank p-value was 0.968; the registry labels the analysis as non-inferiority.
The non-inferiority margin, event counts, censoring details, and missing-data methods are not reported in the registry record. Serious adverse events were reported for 0 of 14 participants at risk in the drug-therapy group and 2 of 15 in the DBS group, with no deaths reported in either group.