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 PET Fibrin Imaging of DVT and PE (NCT04022915), a na phase 1 study. The primary outcome is Location of the Thrombus Within the Lungs.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04022915 |
| Phase | Phase 1 |
| Condition | Pulmonary Embolism, Deep Vein Thrombosis, Venous Thromboembolism |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 6 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Peter Caravan |
| Results posted | Yes |
2. Clinical Question
Population
Participants with acute pulmonary embolism were the study population described in the arm record. The study also concerns pulmonary embolism and deep vein thrombosis, with venous thromboembolism listed as a condition. The registry record lists enrollment of 6 participants; additional eligibility details are not reported in the registry record.
Intervention
Participants were to receive 64Cu-FBP8 and undergo PET-CT imaging. The study's stated aim was to investigate a novel PET probe for imaging fresh intravascular blood clots in pulmonary embolism and deep vein thrombosis.
Comparator
This was a single-group study, not a randomized comparison. For the primary endpoint, the location of thrombus regions of interest on PET-CT was compared with regions of interest corresponding to filling defects on CT angiography. That imaging reference is not a separate randomized treatment arm.
Primary question
Within 72 hours, where were thrombus regions of interest located in the lungs on PET-CT, and how did those locations compare with filling-defect regions on CT angiography? The registry record describes this question but does not report the resulting participant counts or an analysis of agreement between the imaging assessments.
3. Trial Design
The registry record describes a phase 1, single-group study with enrollment of 6 participants. Its listed status is terminated. The study started on 2019-05-13, and the primary completion date is recorded as 2022-07-19. The reason for termination and details about recruitment or follow-up are not reported in the registry record.
The intervention included 64Cu-FBP8, listed as a drug, and PET-CT imaging, listed as a diagnostic test. The described arm is acute pulmonary embolism: participants were to receive 64Cu-FBP8 and undergo PET-CT. There is no parallel control arm described. Allocation is listed as not applicable, the model is single group, and masking is listed as none.
The study aim was imaging fresh intravascular clots in pulmonary embolism and deep vein thrombosis. Its primary outcome concerned the location of thrombus regions of interest within the lungs, assessed using PET-CT and compared with regions of filling defects on CT angiography. The timeframe is 72 hours. Secondary outcomes named in the record concern correlation between normalized 64Cu-FBP8 fibrin activity and plasma D-dimer, overall clot burden within the lungs, and overall clot burden within the thigh.
This design is primarily descriptive and imaging-focused. Since there is no randomized control group, it cannot estimate a randomized between-group treatment contrast. The registry record does not report a protocol-level statistical plan, eligibility criteria, or the reason the study was terminated.
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: Of 6 enrolled participants, 64Cu-FBP8 PET imaging studies were conducted in 5 participants; one participant withdrew before PET imaging.
Overall Study
| Stage | Acute Pulmonary Embolism |
|---|---|
| STARTED | 6 |
| COMPLETED | 5 |
| NOT COMPLETED | 1 |
Reasons for not completing this period:
| Reason | Acute Pulmonary Embolism |
|---|---|
| Withdrawal by Subject | 1 |
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: Including all recruited participants.
| Characteristic | Unit | Acute Pulmonary Embolism |
|---|---|---|
| Participants analysed | 6 | |
| Age, Continuous | years | 61.8 (42 to 81) |
| Sex: Female, Male: Female | Participants | 3 |
| Sex: Female, Male: Male | Participants | 3 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 1 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 2 |
| Race (NIH/OMB): White | Participants | 3 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 0 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 6 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| D-dimer | ng/ml | 2814 (290 to 10000) |
6. Primary Endpoint
The registry lists the primary outcome as Location of the Thrombus Within the Lungs, measured over 72 hours.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the location of thrombus regions of interest within the lungs, measured in participants during the stated 72-hour timeframe. PET-CT is used to identify the thrombus regions of interest, and their locations are compared with regions of filling defects on CT angiography. The outcome is specified as a count of participants, rather than a continuous measurement such as clot volume.
Comparing imaging locations can address whether the PET-CT-defined regions correspond spatially to findings on the CT angiogram. This is a question about imaging localization, not a direct comparison of clinical outcomes between treatment groups. The CT angiogram functions as the imaging reference in the endpoint description; it is not a control arm in the trial design.
The registry record does not report the number of participants with findings at each location, the criteria used to define a match, or a numerical measure of agreement. Without those results, the endpoint's observed distribution and the precision of any comparison cannot be assessed. The registry record also does not state how multiple regions within a participant, if present, were handled in the participant-level count.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes a small, single-group imaging study with enrollment of 6 participants. It states the primary question and its 72-hour timeframe, but does not report the primary endpoint results. In particular, there are no posted participant counts by thrombus location, no estimate of correspondence between PET-CT and CT angiography, and no confidence interval or p-value for that endpoint. The imaging question can therefore be described, but its observed answer cannot be inferred from this record.
The study's stated purpose was to investigate 64Cu-FBP8 PET imaging of fresh intravascular clots in pulmonary embolism and deep vein thrombosis. Secondary outcomes were listed for normalized fibrin activity in relation to plasma D-dimer and for clot burden in the lungs and thigh. The registry record reports six outcome measures but no analyses. It does not provide values for those secondary outcomes, their uncertainty, or results of any correlation analysis.
The design places limits on the kinds of conclusions it can support. With a single group and no randomized comparator, the study does not provide a randomized contrast between treatments. Its primary endpoint is an imaging-location comparison against CT angiography, not an estimate of clinical benefit or a comparison of patient outcomes. The registry record does not report whether the imaging findings changed management or were associated with later clinical outcomes.
Small enrollment also means that any participant-level estimates, if available, would be based on limited information and could be imprecise. However, no confidence intervals or other precision measures are reported, so the extent of uncertainty cannot be quantified from the registry record. The count of participants alone does not establish how consistently findings were observed.
The safety record lists 0 serious adverse events among 6 at risk and 0 other adverse events among 6 at risk in the acute pulmonary embolism group; it also lists 2 deaths. These are descriptive counts. The registry record does not report the timing, causes, or relationship of the deaths to study procedures or the imaging agent, so causal interpretations are not supported by the available information.
Overall, the record documents an imaging study's planned question, design, enrollment, and limited safety counts, but it does not report efficacy or imaging-performance results. No conclusion about diagnostic performance or treatment effect can be drawn from the registry record alone.
9. Statistical Methods Explained
The study is listed as a single-group design. In general, a single-group study describes outcomes among participants receiving the study procedure without a concurrent randomized comparison group. This can be appropriate for an early imaging investigation, but it does not separate effects of the study procedure from other influences in the way a randomized comparison is designed to do. In this study, the central comparison is between PET-CT locations and CT-angiogram filling-defect regions, as specified for the primary endpoint.
What does a participant count represent?
The primary endpoint is defined as a count of participants. In general, a count endpoint reports how many participants meet a stated criterion or fall into a specified category. The registry record names the outcome as the location of thrombus within the lungs, but does not report the location categories, participant-level results, or the rule for assigning a participant to a category. A count describes frequency; by itself, it does not quantify how precisely the underlying frequency is estimated.
The distinction between participants and imaging regions matters. A participant may have more than one region of interest, but the record does not explain whether multiple regions were combined, counted separately, or reduced to a participant-level classification. The endpoint is listed in participants, so the participant is the stated unit. Further handling details are not reported in the registry record.
How should an imaging comparison be understood?
In general, comparing the location of findings across imaging methods asks whether the methods identify corresponding anatomical regions. A transparent analysis needs an operational definition of correspondence and a plan for observations that do not match or cannot be assessed. The registry record gives the comparison target—PET-CT thrombus regions of interest versus CT-angiogram filling defects—but does not report the matching rule, image-reading procedures, reader masking, or a statistical measure of agreement.
An imaging reference is not automatically a perfect measure of the underlying condition. The endpoint description establishes CT angiography as the reference for this comparison, but the record does not describe how reference findings were adjudicated or whether uncertainty in either imaging method was evaluated. These missing details restrict interpretation of any potential agreement result, even if a result were available elsewhere.
What can confidence intervals and p-values tell readers?
In general, a confidence interval describes the uncertainty around an estimate under the assumptions of the analysis. A narrower interval indicates greater precision, while a wider interval indicates less precision. A p-value is a measure of how compatible the observed data are with a specified statistical null model; it is not a measure of clinical importance or proof that a finding is true. Neither type of statistic is reported for the primary outcome in the registry record.
For a small study, estimates can be unstable, and a lack of statistical significance would not by itself establish that there is no association or no imaging correspondence. Conversely, an apparently strong estimate from a small dataset can have substantial uncertainty. Since the endpoint results and precision estimates are not reported, these general considerations cannot be turned into a numerical assessment of this study.
What does over-dispersion mean in general?
For count data, over-dispersion means that the observed variation is greater than a model's assumed variation. If a model fails to account for this, standard errors may be too small and statistical evidence may appear more precise than it is. This is a general issue for some count analyses, not a reported feature of this study. The registry record does not report a count model, dispersion estimate, or analysis plan, so there is no basis to say whether over-dispersion was assessed or relevant to a particular analysis.
How should planning sample sizes be read?
Any sample-size illustrations associated with the record are planning calculations, not observed power. The stated assumptions use a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect expressed as a stated fraction of an observed effect. For time-to-event calculations, the stated quantity is the total number of events; other calculations are expressed as participants per arm. These are generic planning assumptions, and the equal-allocation, two-arm illustration does not describe this single-group trial's actual design.
A planning calculation estimates the sample size that would be needed under its assumptions; it does not show the probability that this completed study detected an effect. The record does not report a sample-size justification for the trial, the effect used to generate any illustration, or the trial's own statistical analysis plan. No recalculated treatment comparison is applicable from the registry entries, and no primary analysis is posted.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists six outcome measures, including the primary outcome and secondary outcomes concerning fibrin activity in relation to plasma D-dimer and overall clot burden in the lungs and thigh. When a study evaluates multiple outcomes or multiple statistical tests, the chance of at least one apparently notable result can increase. Statistical plans sometimes address this multiplicity by identifying a primary analysis, adjusting inference, or treating secondary findings as exploratory. These are general approaches; the registry record does not report a multiplicity strategy.
The record reports no analyses and does not provide outcome results, p-values, or confidence intervals. It is therefore not possible to determine whether multiple testing occurred, whether any adjustment was applied, or how findings across outcomes were interpreted. The primary outcome is identified, but the analysis hierarchy and any prespecified decision rules are not reported in the registry record.
Information about missing observations is also not reported in the registry record. There is no account of incomplete imaging, unavailable CT angiograms, withdrawals, or how missing outcome data would be handled. Analysis populations—such as which participants were included for each endpoint—are not described. The enrollment count alone does not establish how many participants contributed usable data to a particular outcome.
These omissions matter because missingness and analysis choices can affect which observations contribute to estimates. Without participant flow, endpoint-specific denominators, and a stated analysis population, readers cannot assess the completeness of the outcome data or judge whether an analysis used all enrolled participants. The registry record does not provide enough detail to evaluate these issues.
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 |
|---|---|---|---|
| Acute Pulmonary Embolism | 0 | 6 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Acute Pulmonary Embolism | 2 of 6 |
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 |
|---|---|
| Acute Pulmonary Embolism | 0 of 6 |
For the acute pulmonary embolism group, the registry record lists 0 serious adverse events among 6 participants at risk and 0 other adverse events among 6 participants at risk. It also lists 2 deaths. These figures are separate descriptive safety entries; they should not be combined into a single count or interpreted as showing that the deaths were adverse events of a particular type.
The record does not report when the deaths occurred, their causes, whether they were considered related to 64Cu-FBP8 or PET-CT, or how long participants were followed for safety. It also does not provide descriptions of individual events. Accordingly, the counts do not establish whether the study procedures caused or contributed to any event.
Zero recorded events in a small enrolled group does not rule out events that were not observed, not recorded, or that could occur in a broader population. The listed counts are useful as a description of what the registry record reports, but they are not a complete characterization of safety or a comparative estimate of risk.
12. What the Result Does, and Does Not, Mean
The record establishes that a phase 1, single-group study was conducted to investigate 64Cu-FBP8 PET-CT imaging of fresh intravascular clots. It identifies a primary imaging question: the location of thrombus regions of interest in the lungs, compared with filling-defect regions on CT angiography within 72 hours. It also names secondary questions involving fibrin activity, plasma D-dimer, and clot burden.
What the record does not establish is the answer to those questions. No primary or secondary outcome results are reported, and no statistical analyses are listed. There are no posted counts by location, correlation estimates, clot-burden results, confidence intervals, or p-values. Readers cannot determine from the registry record how often the imaging findings corresponded or how precise any estimate was.
The study was not a randomized treatment comparison. Its single-group design and imaging-reference comparison do not provide a direct estimate of treatment benefit, and the record does not report clinical outcome comparisons. It also does not report whether imaging changed care or predicted subsequent outcomes. The study's stated aim should not be mistaken for a demonstrated diagnostic or clinical effect.
Enrollment of 6 participants gives context for the scale of the investigation, but enrollment is not the same as the number with evaluable results for every outcome. Endpoint-specific denominators and missing-data information are not reported. The listed safety counts are similarly descriptive and lack information about timing, attribution, and follow-up.
Accordingly, the defensible interpretation is limited to the study's design, aims, outcome definitions, enrollment, status, and recorded safety counts. The absence of posted results does not establish that the imaging method succeeded or failed; it means the registry record does not allow that assessment.
13. Why This Trial Matters Statistically
This study illustrates the distinction between a study question and a reported result. The registry record identifies an imaging question that can be stated precisely: whether PET-CT locations of thrombus regions of interest correspond to filling-defect locations on CT angiography within the specified timeframe. But without participant-level counts or an analysis, the question remains unanswered in the posted record.
It also highlights how design determines the scope of inference. A single-group imaging investigation can describe what was observed in its participants and compare imaging locations with a reference method. It cannot, without a separate comparison design, estimate a randomized treatment contrast. Readers need to keep the endpoint's imaging focus distinct from questions about clinical benefit or comparative safety.
Early phase studies often address feasibility or measurement questions, but the registry record's stated phase alone does not establish what analyses were performed or what conclusions are justified. A clear statistical interpretation requires outcome results, denominators, uncertainty estimates, analysis methods, and information about missing observations. Those details are not reported in this record.
The safety entries also show why counts need context. Recording 0 serious adverse events and 0 other adverse events alongside 2 deaths is not enough to infer causes or relationships. Follow-up duration, event descriptions, and attribution would be needed to interpret the safety experience more fully.
Statistically, the record is informative about intended measurement and study structure, while limited as evidence about observed imaging performance. Recognizing that distinction prevents a study aim from being treated as a demonstrated result.
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 most consequential limitation for interpretation is that the registry record does not report primary or secondary outcome results. The study's imaging question is clearly described, but there are no participant counts by location, numerical agreement results, correlation estimates, or clot-burden findings to evaluate. No analyses are listed.
The design is single group, with allocation listed as not applicable and masking listed as none. There is no randomized control group. The primary comparison uses CT-angiogram filling-defect regions as an imaging reference, but the registry record does not specify how image correspondence was defined, how images were read, or whether readers were masked to other findings.
Enrollment was 6 participants, and endpoint-specific denominators are not reported. The record does not provide information about incomplete scans, missing outcome data, exclusions from analyses, or the analysis population. It also does not describe a statistical plan, multiplicity handling, sample-size justification, or the rationale for termination.
The safety record gives counts but not event timing, causes, duration of follow-up, or attribution to the study agent or procedure. Therefore, the deaths and adverse-event entries cannot be interpreted causally or as a comprehensive safety assessment. The stated primary timeframe is 72 hours, but the record does not clarify the follow-up period for safety outcomes.
These limitations arise from information not reported in the registry record; they do not establish that the study lacked procedures or analyses beyond what is recorded. They do mean that its imaging performance, precision, completeness of outcome ascertainment, and safety context cannot be assessed from the registry record alone.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: PET Fibrin Imaging of DVT and PE — NCT04022915.
- Registry record last updated 2026-03-18; status last verified 2026-02.
- Results first posted 2026-03-18.
- 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
NCT04022915 is a phase 1, single-group study titled PET Fibrin Imaging of DVT and PE. It investigated 64Cu-FBP8 with PET-CT imaging in the context of pulmonary embolism and deep vein thrombosis. The record lists enrollment of 6 participants, status as terminated, a start date of 2019-05-13, and a primary completion date of 2022-07-19.
The primary outcome concerns the location of thrombus regions of interest in the lungs compared with filling defects on CT angiography, with a 72-hour timeframe. Secondary outcomes address fibrin activity in relation to plasma D-dimer and clot burden. The registry record reports no analyses or outcome results. It lists 0 serious adverse events, 0 other adverse events, and 2 deaths in the acute pulmonary embolism group; event details and attribution are not reported in the registry record.