PharmacoMRI of Parkinson Disease: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for PharmacoMRI of Parkinson Disease (NCT01528592), a na na study. The primary outcome is Correlation Coefficient Between UPDRS III Score and Independent Components Analysis Network Strength in Left Parietal Cortex..

2. Clinical Question

The clinical question is about brain-network measurements in different medication states, rather than a comparison between separately assigned treatment groups. The registry description says subjects underwent MRI scanning off medication and again 1 hour after receiving medication. It does not report how the medication-off state was established or how long it lasted.

The stated rationale is that motor symptoms may respond differently from cognitive symptoms to dopaminergic treatments. The investigators hypothesized that comparing resting-state networks in the on and off states would show greater effects on networks associated with motor control. That is a hypothesis, not a result: the registry record does not report whether the observed data supported it.

The primary measure is a correlation coefficient linking a motor score to a network-strength measure. The record does not specify in its outcome description which medication-state observations contribute to that coefficient. Nor does it provide the coefficient or an uncertainty estimate. Consequently, the clinical question can be described from the study aims, but its observed answer cannot be recovered from the posted record.

3. Trial Design

PharmacoMRI of Parkinson Disease is listed as a completed pilot study sponsored by Northwestern University. The record gives a study start of 2011-06 and a primary completion date of 2012-07. Its phase and allocation are listed as NA. Masking is listed as NONE, and the model is SINGLE GROUP.

The registry describes an On / Off medication group. Subjects undergo MRI scanning in the medication off state and 1 hour after receiving medications; the intervention is Carbidopa-Levodopa. This is a within-participant medication-state arrangement in the sense that the description refers to the same subjects being scanned in each state. The record does not describe a randomized treatment assignment or an independent concurrent control group. It therefore should not be read as a randomized comparison between separate groups.

Enrollment is listed as 18. That enrollment figure is not itself a report of how many participants completed both scans, had usable imaging, or contributed to the primary endpoint. Those details are not reported in the registry record. The record also does not state whether all participants received the same dose, how medication timing was standardized, or how adherence to the scanning schedule was assessed.

The pilot designation identifies the study as exploratory in its stated purpose, but the registry record does not report a sample-size justification or explain whether the study was designed to estimate a particular effect with a specified precision. Information about the imaging acquisition protocol, sequence of scans, and any washout or medication-withholding procedures is not reported in the registry record. The single-group structure and absent masking are important context when interpreting any possible on/off association: the design does not isolate medication state from other changes that may occur between scans.

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.

Population: Patients with Parkinson's disease on dopaminergic therapy.

6. Primary Endpoint

The registry lists the primary outcome as Correlation Coefficient Between UPDRS III Score and Independent Components Analysis Network Strength in Left Parietal Cortex., measured over 1 hour.

The primary endpoint is the correlation coefficient between UPDRS III score and independent components analysis network strength in the left parietal cortex. UPDRS III is identified in the registry as the Unified Parkinson's Disease Rating Scale composite motor score. The network-strength measure is derived from independent components analysis, and the specified brain location is the left parietal cortex. The endpoint is unitless and its timeframe is listed as 1 hour.

A correlation coefficient describes the direction and strength of association between two measured quantities. In this endpoint, those quantities are a motor score and a brain-network strength measure. It is not, by itself, a direct estimate of the effect of medication, and it does not establish that a change in one measure caused a change in the other. The coefficient also does not show whether the association is clinically important without further context and uncertainty information.

In general, linking a clinical measure to a brain-imaging measure can help researchers examine whether variation in a measured network corresponds with variation in motor symptoms. The study's rationale centers on motor control networks and medication state, which makes a motor score relevant to its question. However, the registry record does not report the coefficient, its direction, its precision, or the analysis population used to estimate it. It also does not clarify which medication-state observations were used for the stated correlation. The endpoint's planned meaning is therefore clearer than its observed result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a single-group study with no masking and allocation listed as NA. Its description places MRI scans in two medication states for the same subjects: off medication and 1 hour after receiving medication. The record does not describe a separate randomized control group. This design context matters because comparisons across states are not equivalent to comparisons between independently assigned treatment arms.

What does a correlation coefficient describe?

In general, a correlation coefficient summarizes how two measured variables vary together. Its sign indicates the direction of an association, while its magnitude indicates how closely the measurements follow a linear pattern. A correlation is not a treatment-effect estimate and does not establish causality. In this study, the named variables are UPDRS III score and independent components analysis network strength in the left parietal cortex. The registry does not post the coefficient, so its direction and magnitude cannot be interpreted.

The record identifies UPDRS III as a composite motor score and specifies a brain-network strength measurement. Those measures occupy different domains: one is a clinical motor measure and the other is an imaging-derived measure. In general, an association between measures from different domains can be scientifically informative, but interpretation depends on how each measure was collected, how the network was defined, and which observations entered the analysis. These details are not reported in the registry record.

Why does the repeated-state design matter?

In general, a within-participant design compares measurements from the same participant across conditions. It can account for stable participant characteristics in a way that a comparison of unrelated groups cannot. The study description is consistent with scans in both medication states, but the registry does not provide a participant-level analysis method. It does not state whether the primary analysis used paired observations, a model accounting for repeated measurements, or another approach.

Repeated measurements can also be affected by changes between sessions, including order, time, fatigue, scanner conditions, or other procedural factors. These are general design considerations, not reported events in this study. The registry does not state the scan order, whether it was standardized, or how possible time-related effects were addressed. With masking listed as NONE, the record does not describe a masked assessment process. It does not say whether image processing or endpoint assessment was conducted without knowledge of medication state.

What can be said about statistical precision?

In general, a confidence interval gives a range of values compatible with an estimate under the statistical model, and communicates uncertainty more directly than an estimate alone. The registry record does not report a confidence interval for the primary endpoint. It also does not post a standard error, test statistic, or p value. Therefore, neither the size of the estimated association nor its precision can be assessed from the posted results.

The record's planning assumptions describe illustrations using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; they specify that the effect to detect is a stated fraction of an observed effect. They are described as planning illustrations rather than the trial's own design. No numerical planning results are available in the registry record, and the record does not report the observed endpoint effect needed to judge such illustrations. These assumptions should not be read as evidence of the study's actual power or as a report of a prespecified sample-size plan.

How should an absent analysis be read?

The record lists zero analyses. That means no analysis results are posted in the registry entry; it does not establish why results are absent or whether analyses were conducted elsewhere. The record does not describe the statistical model, covariates, handling of repeated measures, missing-data strategy, or decision rules for selecting an analysis. Those elements are not reported in the registry record. Without them, a reader cannot reproduce the primary analysis or evaluate whether its method matched the data structure.

In general, a sound interpretation of an estimate depends on the estimator, the observations included, and the assumptions used. Here, the endpoint definition is available, but the estimate and key analysis details are not. The practical statistical conclusion is limited: the registry defines a motor-to-imaging association as the primary outcome, while leaving its analysis and numerical result unavailable.

10. Multiplicity, Missing Data and Analysis Populations

The registry identifies a primary outcome measure and lists zero analyses. It does not report a statistical analysis plan, secondary outcome results, or the number of statistical tests conducted outside the posted record. A multiplicity strategy, such as whether any adjustment was planned for testing several outcomes or network regions, is not reported in the registry record.

In general, testing multiple hypotheses can increase the chance that at least one result appears noteworthy by chance. How that concern should be addressed depends on the planned outcomes, model, and inferential goals. The record names the left parietal cortex for the primary endpoint, but does not explain whether other regions or network measures were explored. It is therefore not possible to determine the breadth of analyses or whether any multiplicity adjustment was used.

Missing-data procedures are also not reported in the registry record. Enrollment is listed as 18, but that does not indicate how many had usable MRI measurements, completed scans in both medication states, or contributed to the correlation analysis. The record does not describe exclusions, incomplete observations, or the handling of missing clinical or imaging measurements.

The analysis population is not reported in the registry record. It is unclear whether the endpoint was intended to include all enrolled participants, only those with both scans, or another defined subset. The population field for the endpoint is blank. In general, a clear account of the analysis population and missing-data approach helps readers understand which participants inform an estimate and whether exclusions could affect interpretation. Without those details, the reported endpoint cannot be tied to a defined set of analyzed observations.

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.

The registry lists an On / Off Medication group with 18 participants at risk for serious adverse events and 0 serious adverse events. It also lists 18 at risk for other adverse events and 0 other adverse events. These are the posted safety counts for the group; they should be read as registry entries, not as proof that no event of any kind occurred outside the recorded categories or reporting period.

The death count is not reported in the registry record. No serious adverse event terms are listed. The record does not give additional detail about how events were collected, the duration of safety follow-up, or whether all participants had the same period of observation. It also does not provide event definitions or an explanatory narrative about the safety entries.

In general, an observed count of zero does not establish that an event is impossible or that risk is absent. Interpretation depends on the number of people actually observed, the completeness and duration of follow-up, and the methods used to capture events. The registry's at-risk counts are not evidence about exposure time or completeness of follow-up. Given the pilot study context and the limited safety detail, the figures describe what the registry reports but do not support a broad safety conclusion.

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

The study addresses a focused research question: whether resting-state brain networks differ between medication states in people with Parkinson's Disease, with particular interest in networks associated with motor control. Its primary measure is a correlation between UPDRS III motor score and independent components analysis network strength in the left parietal cortex. The study description and hypothesis provide context for why those measurements were selected.

The registry record does not report the primary correlation coefficient or a numerical on/off comparison. It therefore does not show the direction, magnitude, or precision of an observed relationship. The record also does not report a p value, confidence interval, or analysis population. The listed completed status and enrollment do not fill those gaps. No claim that the hypothesis was supported or unsupported can be drawn from the posted information.

In general, a measured correlation can indicate that two variables vary together, but it cannot establish that medication caused a network change or that the network measure caused a change in motor status. A scan-based association is also not, by itself, a measure of clinical benefit. The registry's primary endpoint is an association between a clinical score and an imaging measure, not a reported clinical outcome comparing randomized treatment groups.

The design is a single-group on/off assessment, without masking listed in the record and without a separate like-for-like control group. That structure may be suitable for an exploratory within-participant question, but it does not remove all alternative explanations for differences between scan states. The record does not report how scan order, time-related changes, measurement reliability, or missing scans were addressed.

The responsible conclusion is narrow. The registry records a pilot study rationale, intervention, scanning arrangement, and primary endpoint, along with safety counts. It does not provide the result needed to judge the observed brain-network association. Any broader inference about treatment effects, symptom change, or clinical importance would go beyond what the registry record reports.

13. Why This Trial Matters Statistically

This study matters statistically because it links a clinical motor measure with a brain-imaging measure in a within-participant medication-state setting. Such a question involves more than comparing group averages: the primary endpoint is a correlation, and its interpretation depends on the relationship between two measurements, the participants contributing data, and the handling of repeated observations. The registry record defines the measures but does not provide the analysis needed to assess that relationship.

The design also illustrates an important distinction between a comparison of conditions and a randomized comparison of treatment groups. The same subjects are described as being scanned off medication and after receiving medication. This can make participant-level comparison relevant, while leaving possible differences between scan occasions to be considered. General statistical reasoning emphasizes matching the analysis to the repeated structure and making timing and measurement procedures transparent.

The pilot setting makes precision especially important to communicate. In general, an estimate without an uncertainty interval can be difficult to distinguish from a result that is unstable or imprecise. Here, neither the correlation estimate nor its confidence interval is posted. Enrollment is recorded, but the number included in the endpoint analysis and the extent of missing imaging data are not reported in the registry record.

The record also illustrates why a stated hypothesis and an endpoint definition should not be mistaken for evidence of an effect. The rationale concerns motor-control networks, while the registered primary outcome is a correlation between motor score and left parietal network strength. Without a numerical result and analysis details, the hypothesis remains a question rather than a demonstrated finding. Transparent reporting of the estimate, precision, analysis population, and handling of repeated measurements would be necessary to evaluate the statistical evidence.

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 specific to interpreting this study follow from the information absent in the registry record. The primary endpoint is defined, but the coefficient and its uncertainty are not posted. There is no reported p value or confidence interval. As a result, the observed association cannot be characterized in magnitude, direction, or precision.

The single-group on/off arrangement has no separately described control group, and masking is listed as NONE. The record does not state how the medication-off state was established, whether scan order was standardized, or how timing and other differences between scan occasions were handled. It does not describe the imaging protocol, network definition process, or whether measurement assessment was masked to medication state.

Enrollment is listed as 18, but the endpoint analysis population and the number with usable scans are not reported in the registry record. There is no account of missing observations, exclusions, or analysis of incomplete data. The primary outcome's population field is blank. These gaps make it impossible to tell precisely which observations would underpin the registered correlation.

The registry also does not report the statistical model or analysis plan, including how repeated observations were handled or whether other network measures were examined. The sample-size planning assumptions are identified as illustrations rather than the trial's own design, and no numerical planning results or observed effect are reported. Finally, the safety record lists zero serious and zero other adverse events, but does not describe the duration or completeness of safety follow-up. These limitations constrain interpretation of both efficacy-related measurements and safety entries.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: PharmacoMRI of Parkinson Disease — NCT01528592.
• Registry record last updated 2018-05-03; status last verified 2018-04.
• Results first posted 2013-12-24.
• 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

The registry record describes NCT01528592, PharmacoMRI of Parkinson Disease, as a completed pilot study sponsored by Northwestern University. The listed start is 2011-06 and primary completion is 2012-07. The condition is Parkinson's Disease; phase and allocation are listed as NA. The design is SINGLE GROUP, with masking listed as NONE and enrollment of 18.

The intervention is Carbidopa-Levodopa. The study description says subjects underwent MRI scanning in the medication off state and 1 hour after receiving medications. The primary outcome is the correlation coefficient between UPDRS III score and independent components analysis network strength in the left parietal cortex.

The registry does not report the primary estimate, its uncertainty, or an analysis population. Safety entries list 0 serious and 0 other adverse events, with deaths not reported in the registry record. The record defines an exploratory question and measurement strategy, but does not provide numerical primary results for statistical interpretation.