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 Thromboembolic Risk Screening in Patients With Cancer and COVID-19 (NCT04616846), a non-randomized na study. The primary outcome is Rate of Venous Thromboembolism.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04616846 |
| Phase | NA |
| Condition | Neoplasms Malignant, Covid19, Thromboembolism |
| Allocation | Non-Randomized |
| Design model | Crossover |
| Masking | None (open label) |
| Enrollment | 88 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Centre Antoine Lacassagne |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns patients with cancer and COVID-19, with a COVID-19-negative cohort also named in the registry’s secondary outcome. The record lists 88 participants overall. For the primary endpoint, it specifies 20 COVID-19-positive participants, of whom only 12 underwent diagnostic procedures to detect thrombosis; data for the other 8 are missing because the examinations were not conducted.
Intervention
The listed intervention is peripheral venous ultrasound, a diagnostic test. The primary endpoint description refers more broadly to specific diagnostic procedures for detecting thrombosis. The registry does not report further details about the procedures, their timing beyond the endpoint timeframe, or how decisions to conduct them were made.
Comparator
The secondary outcome names a comparison of symptomatic venous thromboembolism between COVID-19-negative and COVID-19-positive patients. The registry labels the allocation non-randomized, and it does not provide arm descriptions or establish that the cohorts are otherwise comparable. The secondary comparison therefore should not be read as a randomized treatment comparison.
Primary question
The primary endpoint is the number of participants with deep venous thrombosis and/or pulmonary embolism from Day 9 to Day 42. In the endpoint description, the relevant group is the COVID-19-positive participants. The record does not report the number with either condition, so the primary event result cannot be summarized from this record. The secondary question concerns symptomatic events across COVID-19 status.
3. Trial Design
The registry record identifies NCT04616846 as a completed study titled Thromboembolic Risk Screening in Patients With Cancer and COVID-19. The sponsor is Centre Antoine Lacassagne. The recorded start date is 2020-08-04, and the primary completion date is 2022-01-25. The phase is listed as not applicable. Enrollment is 88.
The allocation is non-randomized, masking is none, and the model is labelled crossover. These labels do not, by themselves, explain how participants entered cohorts, whether or how they crossed over, or what sequence of assessments was used. Those details are not reported in the registry record. The control and infected cohort descriptions are blank, so the record does not set out the groups’ eligibility or assessment procedures in those fields.
The listed diagnostic intervention is peripheral venous ultrasound. The primary endpoint concerns deep venous thrombosis and/or pulmonary embolism from Day 9 to Day 42. Its population description focuses on 20 COVID-19-positive participants and notes that diagnostic procedures were performed for 12; the remaining 8 have missing data because the examinations were not conducted. A secondary outcome is the rate of symptomatic venous thromboembolism between COVID-19-negative and COVID-19-positive patients.
The record lists 2 outcome measures, but no analysis results are listed. It does not report the statistical analysis plan, the rationale for the enrollment target, or details of any interim analyses. The non-randomized design means that comparisons between COVID-19 status groups should be interpreted as observational, not as evidence from allocated treatment groups.
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: COVID-19 positivity was an eligibility requirement for analysis. Out of all registered patients, only 20 were COVID-19 positive. Due to this extremely small sample size and a lack of statistical power, the prospective and retrospective cohorts were combined into a single analytical pool. Subgroup analyses were impossible. Additionally, only 12 of these 20 participants underwent the specific diagnostic procedures required for full evaluation.
Overall Study
| Stage | Enrolled Study Cohort |
|---|---|
| STARTED | 88 |
| Included | 84 |
| Tested Positive for COVID-19 | 20 |
| COMPLETED | 12 |
| NOT COMPLETED | 76 |
Reasons for not completing this period:
| Reason | Enrolled Study Cohort |
|---|---|
| Tested Negative for COVID-19 | 68 |
| Specific diagnostic procedures not conducted | 8 |
Analysis population for the primary outcome, as defined in the registry: Out of the 20 COVID-19 positive participants, only 12 underwent specific diagnostic procedures to detect thrombosis. Data for the remaining 8 participants are missing as the exams were not conducted.
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 | Single Group |
|---|---|---|
| Participants analysed | 84 | |
| Age, Continuous | years | 61.73 (SD 11.92) |
| Sex: Female, Male: Female | Participants | 31 |
| Sex: Female, Male: Male | Participants | 53 |
| Race and Ethnicity Not Collected | Participants | — |
| COVID-19 Vaccination Status: Yes | Participants | 17 |
| COVID-19 Vaccination Status: No | Participants | 43 |
| COVID-19 Status: Positive | Participants | 20 |
| COVID-19 Status: Negative | Participants | 64 |
6. Primary Endpoint
The registry lists the primary outcome as Rate of Venous Thromboembolism, measured over From Day 9 to Day 42.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is titled Rate of Venous Thromboembolism, with the unit recorded as participants. It is defined as deep venous thrombosis and/or pulmonary embolism, assessed from Day 9 to Day 42. In practical terms, this is a participant-level event outcome: the endpoint concerns whether a participant was found to have either condition during the stated period. The record does not provide a count of participants with an event.
The endpoint is relevant to the study’s screening question because diagnostic procedures are used to look for thrombosis. A count of detected cases can describe events identified among participants who were assessed. However, it cannot establish the event frequency in a wider population unless the assessment process and missing examinations are accounted for. Here, the record says only 12 of 20 COVID-19-positive participants underwent specific diagnostic procedures, and it does not report the findings for those procedures.
The word rate in the endpoint title should not be taken to mean that a person-time rate is reported: the unit is participants, and no person-time measure is described. The record also does not explain whether every endpoint event required imaging confirmation, how symptomatic and asymptomatic findings were classified for the primary endpoint, or how events were adjudicated. Those endpoint details are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes an intended assessment of venous thromboembolism among patients with cancer and COVID-19, alongside a secondary comparison by COVID-19 status. It does not report the primary event count. Consequently, the record alone does not show how many assessed participants had deep venous thrombosis or pulmonary embolism, nor does it provide a numerical estimate of the primary endpoint or its precision.
Missing diagnostic assessments are central to interpretation. The endpoint description states that 12 of the 20 COVID-19-positive participants underwent specific diagnostic procedures, while data for the remaining 8 are missing because examinations were not conducted. The observed findings among those examined, even if displayed elsewhere, would describe the assessed participants unless the analysis accounted for those without examinations. The registry does not report the findings or a method for handling missing endpoint data.
The secondary outcome concerns symptomatic venous thromboembolism in COVID-19-negative and COVID-19-positive patients. Because allocation is non-randomized, any observed difference between these cohorts could reflect differences between the people included in each group, their clinical circumstances, or how they were assessed, as well as any relationship with COVID-19 status. The registry does not report adjustment methods or other analyses that would help distinguish these possibilities. The result should therefore not be interpreted as a causal effect.
The completed status and enrollment total describe the study record, but they do not establish that every participant contributed an observed primary endpoint. In particular, the endpoint population description identifies missing examinations in the COVID-19-positive group. The record also lists 2 outcome measures and no analysis results. It does not provide an estimate, confidence interval, or p-value for the primary outcome in the information.
Confidence intervals, as a general statistical concept, describe the uncertainty around an estimated quantity under the assumptions of the analysis. They cannot resolve unmeasured or systematically missing outcomes by themselves. A narrow interval, if one were reported, would not automatically address the fact that some participants were not examined; the missing-data process and analysis population would also matter. In this case, the registry does not report an interval or the analysis methods needed to evaluate such uncertainty.
Thus, the most defensible reading is descriptive and limited: the study set out to screen for thromboembolism, but the registry information does not include the primary event findings. The incomplete diagnostic ascertainment among COVID-19-positive participants further limits how broadly any assessed-case findings could be generalized. The posted record does not establish whether screening identified a particular frequency of events or whether that frequency differed between COVID-19 status groups.
9. Statistical Methods Explained
The registry labels the primary endpoint as a participant count for venous thromboembolism. For a binary endpoint, the basic descriptive information is the number of participants with the event and the number assessed. Such counts can be summarized as a proportion, but the narrative does not calculate one: the primary event count is not reported in the registry record. The endpoint title uses the word rate, while its unit is participants; the record does not describe a person-time analysis.
What an event count can tell us
As a general statistical explanation, a count makes the number of observed events visible, while a proportion relates that count to the number of participants assessed. A confidence interval can express the statistical uncertainty around an estimate. Its width depends in part on the amount of information available and the number of events. These summaries describe sampling uncertainty under their assumptions; they do not correct for selection into testing or for outcomes that were never measured.
That distinction matters because the endpoint description says diagnostic procedures were conducted for 12 of 20 COVID-19-positive participants. The other 8 are recorded as missing because the examinations were not conducted. A complete-case summary would use only participants with assessments, if that were the analysis used, but the registry does not report an analysis population or say how missing endpoint data were handled. It is therefore not possible to determine from this record whether any posted estimate uses all eligible participants, only those examined, or another approach.
How to read the cohort comparison
The listed secondary outcome compares symptomatic venous thromboembolism between COVID-19-negative and COVID-19-positive patients. Since allocation is non-randomized, this is an observational comparison. As a general principle, differences between groups in an observational study can be associated with factors other than the group label. Adjustment can address measured factors when appropriate data and methods are available, but the registry record does not report an adjustment plan or analysis results. The record also does not provide enough group detail to assess comparability.
The registry labels the model crossover, but gives no crossover sequence or period details. The label alone does not identify the statistical method used, and the analysis method is not reported in the registry record. The record also does not describe the statistical test, model, confidence-interval method, or assumptions used for the primary endpoint.
What the planning illustration represents
The sample-size section on the page is a planning illustration computed from the observed effect, not the trial’s own design. The stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. For this non-time-to-event endpoint, planning values are expressed as participants per arm. They are not observed power, and they do not mean that the study enrolled those numbers per arm. The registry record does not report the sample-size justification used for the trial itself.
As a general explanation, a planning calculation asks how much information would be needed to detect a specified effect under selected assumptions. Its output depends on those assumptions, including the target effect and the statistical procedure. It is not a retrospective measure of whether the study had adequate power, and it cannot replace reporting the actual event counts and their uncertainty. The illustration should therefore be read as a hypothetical planning aid, not as a result of the trial.
The registry lists 2 outcome measures and no analyses. It does not describe whether the primary and secondary outcomes were tested, whether there were prespecified subgroup analyses, or whether missingness and multiple outcomes were incorporated into a formal statistical plan. A statistical result cannot be reconstructed from the design labels or the sample-size assumptions alone. The analysis methods and primary numerical findings are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The record lists 2 outcome measures: the primary venous thromboembolism endpoint and a secondary outcome concerning symptomatic venous thromboembolism by COVID-19 status. It lists no analysis results. The registry does not report whether the outcomes were tested together, whether one was designated as confirmatory, or whether any adjustment for multiple comparisons was planned. Multiplicity procedures and their rationale are not reported in the registry record.
As a general statistical concept, examining multiple outcomes or comparisons can increase the chance of seeing an apparently notable result by chance if each is interpreted as a separate test. Whether and how to account for that depends on the analysis objectives and plan. Without a reported plan or analysis results, this record does not support conclusions about multiplicity-adjusted inference.
The most explicit missing-data issue concerns the primary endpoint: among 20 COVID-19-positive participants, only 12 underwent specific diagnostic procedures, and the examinations were not conducted for the other 8. The record does not say whether missing outcomes were excluded, imputed, treated as no event, or handled in another way. It also does not report a sensitivity analysis assessing how conclusions might change under different assumptions about the missing participants.
The analysis population is not reported in the registry record. It is therefore unclear which enrolled participants were included in each outcome analysis, whether participants were excluded for reasons other than missing examinations, or how the COVID-19-negative cohort contributed to the primary endpoint. The record does not report a participant flow or reasons for any difference between enrollment and the 84 participants listed as at risk in the adverse-event summary. These gaps limit assessment of both the completeness and the reproducibility of the posted analyses.
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 |
|---|---|---|---|
| Single Group | 0 | 84 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Single Group | 0 of 84 |
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 |
|---|---|
| Single Group | 0 of 84 |
The serious adverse event summary lists a single group with 84 participants at risk, 0 participants with serious events, 0 participants with other events, and 0 deaths. These are the figures recorded for the adverse-event summary. They should be read as reported counts, not as evidence that no adverse events occurred in every participant or across every possible observation period.
The registry information does not describe the adverse-event collection window, how events were defined or assessed, or whether the summary covers the full enrolled population. Enrollment is 88, while the adverse-event group lists 84 at risk; the reason for that difference is not reported in the registry record. No serious adverse event terms are listed among the top serious terms.
As a general statistical point, a count of zero is a description of the recorded observations, not proof that the underlying event risk is zero. Interpreting safety counts also depends on follow-up duration, ascertainment, and the number of people actually observed. Those details are not reported. These figures should not be treated as a comparison between COVID-19 status cohorts or as an estimate of the effect of ultrasound, because the record presents them for a single group and does not describe such a safety comparison.
12. What the Result Does, and Does Not, Mean
This record documents a completed, non-randomized study of thromboembolic risk screening in patients with cancer and COVID-19. It identifies peripheral venous ultrasound as a diagnostic intervention and defines the primary endpoint as participants with deep venous thrombosis and/or pulmonary embolism from Day 9 to Day 42. It also names a secondary comparison of symptomatic venous thromboembolism between COVID-19-negative and COVID-19-positive patients.
The record does not report the primary endpoint event count or a statistical estimate for it. It therefore does not establish how many participants had an event, how precise any estimate was, or whether event frequency differed by COVID-19 status. The missing diagnostic procedures for 8 of the 20 COVID-19-positive participants mean that ascertainment was incomplete in the group described for the primary endpoint. How that missing information was treated in the analysis is not reported.
The observational cohort comparison, if interpreted from any posted group summaries, cannot by itself establish that COVID-19 status caused a difference. Participants were not randomly allocated, and the registry does not report adjustment methods or sufficient cohort detail to evaluate other explanations for a group difference. Likewise, the crossover model label is not accompanied by a description of crossover procedures or analysis.
As a general statistical point, a study result describes the participants assessed and the methods used; the strength and scope of inference depend on the quality and completeness of those data. A diagnostic screening study can describe detected findings, but it cannot establish unobserved events among people who were not examined without additional assumptions. The registry record does not provide the primary findings or methods necessary to assess those assumptions.
The posted record should therefore be read as a record of the study question and its stated endpoint, rather than as a complete quantitative account of the endpoint result. It does not establish a treatment effect, nor does it show that screening does or does not benefit patients. Those conclusions are not supported by the results and methods.
13. Why This Trial Matters Statistically
This study raises a statistical issue that is especially important in diagnostic research: the outcome is only observable when an assessment is conducted. The primary endpoint description says that diagnostic procedures were performed in 12 of 20 COVID-19-positive participants, with the remaining 8 missing because examinations were not conducted. The number examined is therefore central to understanding the endpoint, not a minor reporting detail.
When testing is incomplete, the assessed participants may not represent everyone in the group. As a general principle, if the decision to test is related to symptoms, clinical concern, or other characteristics associated with an outcome, a count among those tested may differ from the frequency among the whole group. The registry does not report why some participants were not examined or how the missing outcomes were handled. That prevents evaluation of the direction or size of any potential selection effect.
The non-randomized comparison also matters. COVID-19-positive and COVID-19-negative cohorts may differ in ways that affect observed events or the chance of being tested. Without reported adjustment methods and cohort details, the comparison is descriptive rather than a clear causal contrast. The design labels alone cannot resolve those issues.
Finally, the registry record is limited as a results report: it names the endpoint and study groups but does not include the primary event count or analyses. Clear reporting of assessed denominators, missing outcomes, group definitions, and uncertainty would be necessary to interpret the findings. These issues make this study useful for illustrating why endpoint ascertainment and transparent analysis are part of the statistical evidence, not merely operational details.
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 major trial-specific limitation in the registry record is incomplete diagnostic ascertainment for the primary endpoint. The endpoint description states that only 12 of the 20 COVID-19-positive participants underwent specific diagnostic procedures, while examinations were not conducted for the other 8. The record does not give the reasons for not conducting those examinations or describe how the missing outcomes were handled.
The primary event findings are not reported in the registry information. Without the event count, an estimate, or an uncertainty interval, the frequency and precision of the primary endpoint cannot be evaluated. The record also does not report analysis methods, a statistical analysis plan, sample-size justification, or interim analyses. These details are not reported in the registry record.
The comparison by COVID-19 status is non-randomized. The cohort descriptions are blank, and the record does not describe adjustment for potential differences between groups. The crossover model label is not accompanied by information about sequence, periods, or analysis. These omissions make it difficult to understand the design implementation or the basis for any cohort comparison.
The adverse-event summary lists 84 participants at risk, compared with enrollment of 88, but the reason for the difference is not reported. The registry does not describe the safety observation window or provide further context for the single-group summary. More generally, the absence of these details limits evaluation of completeness, selection, and reproducibility. The limitations concern what is reported in the registry record and do not establish that unreported procedures or analyses were not conducted.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Thromboembolic Risk Screening in Patients With Cancer and COVID-19 — NCT04616846.
- Registry record last updated 2026-07-01; status last verified 2026-06.
- Results first posted 2026-07-01.
- 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.
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18. Record Summary
NCT04616846 is a completed, non-randomized study titled Thromboembolic Risk Screening in Patients With Cancer and COVID-19, sponsored by Centre Antoine Lacassagne. The recorded start date is 2020-08-04, the primary completion date is 2022-01-25, and enrollment is 88. The registry lists peripheral venous ultrasound as the diagnostic intervention.
The primary endpoint is participant-level deep venous thrombosis and/or pulmonary embolism from Day 9 to Day 42. The record describes 20 COVID-19-positive participants, of whom 12 underwent diagnostic procedures; data for the other 8 are missing because examinations were not conducted. The primary event count and analysis results are not reported in the registry record. A secondary outcome compares symptomatic venous thromboembolism by COVID-19 status.
The adverse-event summary lists 84 participants at risk, with 0 serious events, 0 other events, and 0 deaths. The registry lists 2 outcome measures and no analyses. Its non-randomized design, incomplete endpoint ascertainment, and limited reporting of analysis methods constrain interpretation of the posted results.