Alzheimer's PET Imaging in Racially/Ethnically Diverse Adults: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Alzheimer's PET Imaging in Racially/Ethnically Diverse Adults (NCT03706261), a na phase 1 study. The primary outcome is Regional SUVR Value for 18F-MK-6240.

2. Clinical Question

The central statistical question is whether variation in regional tau-tracer uptake is associated with the cognitive and cerebrovascular measures of interest, and whether patterns differ across racial and ethnic groups. Those are questions about relationships among measured characteristics in a diverse cohort. They are not estimates of the effect of assigning participants to a treatment: the design has one group, no allocation, and no masking. The registry record describes intended scientific questions, but does not report estimates, uncertainty intervals, or tests that would establish the strength or precision of any association.

3. Trial Design

The registry identifies this as a Phase 1, completed, single-group study with no allocation and no masking. Enrollment is recorded as 145. The study is titled Alzheimer’s PET Imaging in Racially/Ethnically Diverse Adults, and its stated focus is imaging in a multi-racial and multi-ethnic cohort. It is not described as a randomized comparison, and its single-group structure should guide how its findings are interpreted.

The cohort description says that participants with or without a positive family history of Alzheimer’s disease would have a tau PET scan using 18F-MK-6240 over a 30 to 60-minute scanning period, and an 18F-Florbetaben PET scan over a 20-minute period. The two tracers have different stated roles in the imaging study; neither is described as a treatment assignment or a control condition. The primary outcome is regional SUVR for 18F-MK-6240, with a listed timeframe of 1 day.

The recorded start date is 2019-03-22, the primary completion date is 2023-07-14, and the status is completed. The registry says 115 participants had complete PET scans with the primary tracer. It lists 2 outcome measures and 0 analyses. Those entries do not give numerical results or show what analyses may have been conducted outside the record. A protocol, detailed statistical analysis plan, recruitment flow, and explanation of the difference between enrollment and the number with complete scans are not reported in the registry record.

Because there is no randomized comparator, the design can describe imaging measurements and examine associations, but it cannot by itself separate those relationships from all other participant characteristics. The record does not specify whether or how analyses accounted for differences among participants, nor does it report the methods used to compare racial or ethnic groups. These omissions limit what can be concluded from the registry entry, even though the study objectives identify important questions about diversity, tau pathology, cognition, and cerebrovascular disease.

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

Analysis population for the primary outcome, as defined in the registry: 115 participants had complete PET scans with this tracer

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: Of the 145 participants who consented to be in the study, 3 participants withdrew prior to receiving any scan. No baseline data was collected from these 3 participants.

6. Primary Endpoint

The registry lists the primary outcome as Regional SUVR Value for 18F-MK-6240, measured over 1 day.

The primary endpoint is regional standardized uptake value ratio (SUVR) for 18F-MK-6240. It is a continuous imaging measure, and the registry specifies that the reported summary is a mean with standard deviation. SUVR expresses tracer uptake in a brain region relative to a reference, but the reference region and the image-processing details are not reported in the registry record. The endpoint timeframe is listed as 1 day.

The record states that this regional measure is intended to investigate associations with memory, olfactory function, and cerebrovascular disease. More broadly, the study examines the extent to which tau pathology is associated with cognition, differences in tau pathology across racial and ethnic groups, and relationships between MRI markers of small-vessel cerebrovascular disease and tau pathology. It also investigates amyloid-dependent tau spreading. These aims explain why a regional imaging measure is useful: it can be related to other measured characteristics and considered across brain regions or participant groups.

A mean describes the average SUVR in the analyzed group or region; a standard deviation describes how spread out individual measurements are around that mean. Neither statistic, on its own, quantifies an association with cognition or establishes a difference between groups. The registry record does not report the mean, standard deviation, association estimates, or their uncertainty. It therefore defines the intended endpoint but does not provide enough numerical information to judge its observed level, variability, or relationship to other measures.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a continuous imaging measure: regional SUVR for 18F-MK-6240, summarized as a mean and standard deviation. A continuous measure can take a range of values rather than representing an event count. The mean gives a central summary, while the standard deviation describes variation among measurements. The standard deviation is not a confidence interval and does not, by itself, show how precisely the mean has been estimated. The numerical mean and standard deviation are not reported in the registry record.

What does SUVR represent?

In general, a standardized uptake value ratio compares measured tracer uptake in a region with uptake in a reference region. It is used to make regional PET uptake easier to compare within an imaging analysis. The choice of reference region, scan processing, quality control, and regional definitions can influence interpretation. Those technical details are not reported in the registry record, so the meaning of any particular regional value cannot be reconstructed from the entry alone. The record names 18F-MK-6240 as the tracer for the primary outcome and identifies a 1-day timeframe.

How would an association be interpreted?

In general, an association describes how two measured characteristics vary together. An association between SUVR and a cognitive or cerebrovascular measure would not, on its own, show that one characteristic caused the other. Other participant characteristics could influence both measurements. Analyses can sometimes adjust for measured factors, but the registry record does not describe whether adjustment was used, which covariates were considered, or how the association was modeled. No numerical association estimate or uncertainty interval is reported.

The study aims include associations with cognition, memory, olfactory function, and cerebrovascular disease, as well as differences across racial and ethnic groups and investigation of amyloid-dependent tau spreading. These are related but distinct analyses. A result for one outcome or region would not automatically answer the other questions. The record lists 2 outcome measures but does not give a complete set of numerical outcome results or analysis details. It records 0 analyses, so analysis results are not reported in the registry record.

Why do uncertainty intervals matter?

In general, a confidence interval represents uncertainty around an estimate under the assumptions of the analysis. It helps readers judge which effect sizes are reasonably compatible with the data and method. A point estimate without an interval gives less information about precision; a significance test alone does not communicate the full range of plausible values. The registry record reports no confidence intervals, standard errors, p-values, or numerical association estimates for the primary outcome. Thus, precision and statistical compatibility cannot be assessed from the entry.

What can planning calculations say?

In general, a sample-size calculation asks how much information a future study might need to detect a chosen effect under specified assumptions. Planning illustrations associated with this study use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They define the effect of interest as a stated fraction of the observed effect. These are planning assumptions, not a description of the study’s design: this trial is recorded as a single-group study with no allocation, not as an equal-allocation trial with two randomized arms.

The illustrations are not observed power. Observed power is not a substitute for an effect estimate and its uncertainty, and a planning calculation cannot establish that a study detected an effect. The observed effect used as a basis for the illustrations is not reported in the registry record, so the assumptions cannot be independently assessed from the entry. For time-to-event outcomes, the stated illustration approach concerns total events; other sample-size illustrations are expressed as participants per arm. The primary outcome is continuous, not a time-to-event outcome.

What does over-dispersion mean in general?

Over-dispersion is a general issue for count data: it occurs when variation is greater than a model assumes, and can make conventional uncertainty estimates too small if the model is not suited to the data. The primary endpoint in this study is a continuous SUVR measure, so over-dispersion is not a description of that endpoint. The registry’s adverse-event counts are also not a substitute for the primary continuous outcome analysis. The record does not report a statistical model for either efficacy or safety outcomes.

In general, a sound analysis also depends on a clear analysis population, transparent handling of incomplete observations, and methods suited to the study question. The registry reports that 115 participants had complete PET scans with the primary tracer, but does not specify the analysis population, missing-data method, or whether participants with incomplete scans contributed to other analyses. These details are necessary to understand how observed measurements were selected and how far results might generalize beyond participants with complete scans.

10. Multiplicity, Missing Data and Analysis Populations

The study describes several scientific questions: associations between tau pathology and cognition, differences across racial and ethnic groups, relationships between MRI markers of small-vessel cerebrovascular disease and tau pathology, and amyloid-dependent tau spreading. The primary endpoint description additionally names memory, olfactory function, and cerebrovascular disease. When an investigation examines multiple outcomes, regions, groups, or associations, the chance of obtaining an apparently notable result among many tests can increase. In general, multiplicity methods may control that risk or identify a prespecified primary analysis. A multiplicity strategy, a hierarchy of outcomes, and prespecified analysis details are not reported in the registry record.

The record lists 2 outcome measures and 0 analyses, but provides no numerical analysis results. It identifies 115 participants with complete PET scans for the primary tracer and enrollment of 145. It does not explain the missing scans, define an analysis population, or state how incomplete observations were handled. It does not report whether scans that were incomplete for the primary tracer could be used for other outcomes, or whether any missingness assumptions were assessed.

In general, a complete-case analysis uses only participants with the required measurements, while imputation methods attempt to account for missing values under explicit assumptions. Neither approach can be attributed to this study based on the registry entry. The difference between the enrollment and complete-scan entries should not be converted into an assumed count of missing outcomes or a missing-data rate. The reasons for incomplete data and the analysis population are not reported in the registry record.

These omissions affect interpretation: without a stated multiplicity plan, readers cannot tell how the study handled multiple statistical questions; without a missing-data strategy, readers cannot assess how incomplete imaging may have influenced estimates. Neither issue demonstrates that the analyses were inappropriate. It means the registry record does not contain the information needed to evaluate them.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports safety information for an All Participants group. It records 142 participants at risk for serious adverse events and 0 serious adverse events. It also records 142 at risk for other adverse events and 19 affected by other adverse events. Deaths are recorded as 0. No top serious adverse-event terms are listed.

These counts describe the safety entries in the registry record; they are not efficacy outcomes and do not answer the study’s imaging questions. The record does not provide descriptions of the 19 other adverse events, their severity, timing, duration, or possible relationship to study procedures. It also does not explain why the at-risk group differs from the enrollment entry. These details are not reported in the registry record.

A zero count in the serious-adverse-event field means that no such events are recorded in this entry; it is not proof that no safety concerns could occur in other settings or populations. Likewise, the other-event count should not be read as a causal effect of either tracer. The registry describes imaging procedures, not randomized treatment exposure, and does not provide a comparison group for attributing events. Safety interpretation should therefore remain limited to the recorded counts and their reporting context.

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

The registry record establishes the broad scope of a completed imaging study: a racially and ethnically diverse cohort, tau PET using 18F-MK-6240, an additional 18F-Florbetaben PET scan, and a primary regional SUVR outcome. It also records intended investigation of cognition, memory, olfactory function, cerebrovascular disease, racial and ethnic group differences, and amyloid-dependent tau spreading. These details identify the questions the study set out to examine.

They do not establish what the study found. The registry record does not report the primary SUVR mean or standard deviation, association estimates, group comparisons, uncertainty intervals, or statistical tests. It is therefore not possible to judge the direction, magnitude, or precision of the scientific findings from this record. The completed status does not substitute for numerical results, and a stated research objective should not be mistaken for evidence that an association or difference was observed.

The design also limits what the study could establish about cause and effect. It is a single-group study without allocation or masking, and the two tracer scans are not a randomized comparator. Relationships among imaging, cognitive, and cerebrovascular measurements would be observational. Even if results were reported, an association would not by itself show that one characteristic caused another, and group differences would not explain why those differences occurred.

The record reports 115 participants with complete PET scans using the primary tracer and enrollment of 145, but does not describe the reason for incomplete scans or the analysis population. The safety entry records no serious adverse events or deaths, alongside 19 other adverse events among 142 at risk. These are limited registry entries, not comprehensive evidence about effects outside the recorded follow-up and reporting.

Accordingly, the strongest defensible reading is descriptive: the record documents a completed imaging study, its planned scientific questions, one primary continuous outcome, and selected enrollment and safety information. It does not provide the outcome results needed to assess the central research questions or their statistical precision.

13. Why This Trial Matters Statistically

This study is statistically notable for its focus on imaging within a racially and ethnically diverse cohort and for linking tau PET measures to cognitive and cerebrovascular questions. The scientific aims span several kinds of comparison and association: regional tau uptake with cognition and related measures, variation across racial and ethnic groups, and relationships with MRI markers of small-vessel cerebrovascular disease. That range makes clear why the choice of outcomes, regions, comparisons, and analysis populations matters.

It also illustrates the difference between a study objective and a reported statistical result. The registry identifies regional SUVR for 18F-MK-6240 as the primary outcome and describes it as a mean with standard deviation, yet it does not report the values or analyses. Without estimates and measures of uncertainty, readers cannot determine whether a pattern is substantial, precise, or compatible with a broad range of possibilities. Transparent reporting is essential for turning an imaging question into an interpretable quantitative finding.

The single-group design is another important statistical feature. It is suited to describing measurements and investigating associations, but it does not create a randomized contrast. Comparisons across participant characteristics require attention to possible confounding and to how groups and outcomes are defined. The registry record does not report the methods used for these comparisons, which restricts assessment of their validity and precision.

Finally, the entry’s enrollment and complete-scan information, along with its limited adverse-event counts, show why analysis populations and missing-data reporting matter. The record does not explain incomplete scans or specify how they were treated. Reporting those details, alongside effect estimates, uncertainty, and methods for handling multiple questions, would make the study’s evidence easier to evaluate and reproduce.

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.

A key limitation of interpretation is that the registry record does not report numerical results for the primary SUVR endpoint or the study’s stated association and group-comparison questions. The mean and standard deviation, effect estimates, uncertainty intervals, and p-values are not reported in the registry record. The record lists 2 outcome measures and 0 analyses, so it does not provide the statistical findings needed to assess the scientific aims.

The entry describes a single-group study with no allocation and no masking. It therefore does not supply a randomized control comparison. The separate 18F-Florbetaben scan is part of the imaging procedures, not a like-for-like comparator arm. Any reported relationships would need to be interpreted as observational, with potential influence from characteristics that the registry does not say were measured or adjusted for.

Several analysis details are also absent. The registry does not report the PET reference region, regional definitions, image-processing procedures, statistical models, covariate adjustment, or multiplicity strategy. It does not state the analysis population or how incomplete scans were handled. Although 115 participants had complete PET scans with the primary tracer and enrollment is recorded as 145, the reasons for that difference are not reported in the registry record.

The safety entry is limited as well. It records 0 serious adverse events, 19 other adverse events, and 0 deaths among the stated at-risk groups, but does not provide descriptions of the other events or their possible relationship to study procedures. These registry limitations do not establish that additional analyses or documentation do not exist elsewhere; they mean that such information is not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Alzheimer's PET Imaging in Racially/Ethnically Diverse Adults — NCT03706261.
• Registry record last updated 2025-08-01; status last verified 2025-07.
• Results first posted 2025-08-01.
• 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

NCT03706261 is a completed Phase 1, single-group PET imaging study in racially and ethnically diverse adults. The registry records enrollment of 145 and describes PET imaging with 18F-MK-6240 and 18F-Florbetaben. The primary endpoint is regional SUVR for 18F-MK-6240, summarized as a mean with standard deviation and listed with a 1-day timeframe. The record says 115 participants had complete PET scans with this tracer.

The study’s aims include investigating tau pathology in relation to cognition, memory, olfactory function, cerebrovascular disease, racial and ethnic group differences, MRI markers of small-vessel cerebrovascular disease, and amyloid-dependent tau spreading. Numerical results and analysis methods for those questions are not reported in the registry record. Safety entries record 0 serious adverse events, 19 other adverse events, and 0 deaths among 142 at risk.