Clinical Predictors for Venous Thromboembolism in Patients With a History of Thrombosis (PREDICTORS): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Clinical Predictors for Venous Thromboembolism in Patients With a History of Thrombosis (PREDICTORS) (NCT02297373), a registered phase not stated study. The primary outcome is Validation of the Wells DVT Clinical Decision Rule.

2. Clinical Question

3. Trial Design

The registry identifies this study as Clinical Predictors for Venous Thromboembolism in Patients With a History of Thrombosis (PREDICTORS), sponsored by Ottawa Hospital Research Institute. Its status is COMPLETED. The recorded study start date is 2014-11-19, and the primary completion date is 2019-01-03. Enrollment is listed as 744.

The study evaluated clinical decision rules in people with a history of thrombosis who presented with concern for another event. For the primary outcome, the Wells DVT rule was applied prospectively at presentation, designated Day 0. The description states that scores were based on patient history and physical examination, and that the outcome was confirmed recurrent DVT within each rule category. Confirmation was based on objective imaging and adjudication by an independent committee.

The primary outcome description reports that 723 participants were included in the study. Of these, 401 presented with suspected isolated DVT without signs or symptoms of PE; 108 of those 401 had a confirmed DVT diagnosis. These figures describe the study population and confirmed diagnoses, not the event rates within each Wells category.

The registry also names secondary outcomes concerning the accuracy of current D-dimer testing methods, confirmed events using current Wells DVT, Wells PE, and Geneva PE rules in participants receiving anticoagulant therapy, and all-cause mortality within 90 days of the index visit. The record does not provide further details about the allocation process, a control arm, or the statistical analysis plan. It is not a randomized treatment comparison, and the registry does not state an allocation method.

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: Between Nov 2014 and Jan 2019, 744 participants consented and had baseline data and blood samples collected. Verification of prior VTE history excluded 21 with non-qualifying events, leaving 723 who met eligibility and were included. Those with recurrent VTE diagnosed at enrolment completed participation at the initial visit; those who did not have recurrent VTE diagnosed at enrolment were followed up by phone at Day 90.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Of the 723 participants included in the study, 401 presented with suspicion of isolated DVT, without signs or symptoms of PE. Of the 401 presenting with suspicion of isolated DVT, 108 had a confirmed diagnosis of DVT.

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.

6. Primary Endpoint

The registry lists the primary outcome as Validation of the Wells DVT Clinical Decision Rule, measured over Day 0 (at time of suspected recurrent DVT).

The primary endpoint concerns the rate of confirmed recurrent DVT events within the Wells DVT clinical decision rule categories. The rule assigns a score from -2 to +9 using clinical variables, then groups participants into low, moderate, or high probability of DVT. The registry describes low scores as zero or less, moderate scores as one to two, and high scores as three or more. Confirmation of recurrent DVT was based on objective imaging and independent committee adjudication.

This endpoint is used to assess whether the categories correspond to observed confirmed events in the population being evaluated. In general, a validation study asks whether a rule’s classifications provide useful separation between people who do and do not have the target condition. Category-specific counts or rates are needed to assess that separation. The registry record does not report those category-specific results, nor does it report sensitivity, specificity, predictive values, or another summary of diagnostic performance.

The record does state that 108 participants with suspected isolated DVT had a confirmed diagnosis, among 401 who presented with that suspicion. Those figures provide context for the evaluated subgroup, but do not show how confirmed events were distributed across the Wells categories. The primary endpoint therefore cannot be fully interpreted from the reported aggregate figures alone.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a diagnostic validation measure rather than a treatment response. Participants were assessed with the Wells DVT clinical decision rule at presentation, and the registry describes grouping their scores into low, moderate, and high probability categories. The target condition was recurrent DVT confirmed by objective imaging and adjudicated by an independent committee.

What does prospective application mean?

In general, prospective application means that the rule is applied as part of the study assessment at the time participants present, rather than being reconstructed only after their outcome is known. This can help keep the classification tied to information available at the clinical encounter. The registry says the rule was applied prospectively at Day 0 using patient history and physical examination. It does not describe blinding, training procedures, or whether assessors were unaware of imaging results; those details are not reported in the registry record.

What do the risk categories tell us?

In general, a clinical decision rule combines clinical information to organize patients into categories intended to reflect different levels of probability. The Wells DVT rule described in this record uses factors such as active cancer, limb swelling, localized tenderness, prior DVT, and an alternative diagnosis judged at least as likely. Higher scores indicate greater probability of recurrent DVT according to the registry description. A category is a classification, not a confirmed diagnosis. Its meaning must be evaluated against the observed outcome.

For that evaluation, the important descriptive information is the number of participants assigned to each category and how many in each category had confirmed recurrent DVT. Those results would allow readers to see whether confirmed events were more common in higher probability categories and to assess the amount of data supporting each rate. The record does not report these counts or rates. It therefore does not support a numerical assessment of category separation or precision.

What would uncertainty estimates add?

In general, a confidence interval describes the range of values compatible with a statistical estimate under the assumptions of the analysis. For a category-specific event rate, an interval would show how much uncertainty remains around that estimated rate. A narrow interval generally indicates greater precision than a wide interval, although precision does not by itself establish whether a diagnostic rule is useful. No confidence intervals or other uncertainty estimates for the primary outcome are reported in the registry record.

General diagnostic performance measures answer related but distinct questions. Sensitivity describes the proportion of people with the target condition classified as positive under a specified rule threshold; specificity describes the proportion without the condition classified as negative. Predictive values describe the probability of the condition given a test classification in the studied population. These measures require clear definitions of the positive classification and complete outcome information. The record does not report such measures or define a binary threshold for this analysis, so none can be inferred from the overall confirmed diagnosis count.

How should the enrollment figures be read?

The registry lists enrollment of 744, while the primary outcome description states that 723 participants were included in the study and identifies 401 with suspected isolated DVT. These are reported figures with different descriptions. The record does not explain the relationship between enrollment and the population included in the primary outcome description, so no reason for the difference should be assumed. The 108 confirmed diagnoses apply to the described isolated DVT subgroup; they are not a count for every participant enrolled in the study.

What does the planning information represent?

In general, sample-size planning estimates the number of participants or events that may be needed to detect a specified effect under stated assumptions. The registry’s planning description identifies a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect defined as a stated fraction of an observed effect. It distinguishes participant-per-arm planning for most outcomes from total-event planning for time-to-event outcomes. These are planning assumptions, not observed results or evidence of the study’s actual design. The registry record does not report numerical sample-size illustrations or a sample-size justification for this study. The record also does not identify a randomized two-arm comparison, so the planning assumptions should not be mistaken for a description of the study allocation.

Finally, a statistical analysis plan specifies how outcome data will be summarized and analyzed, including choices such as thresholds, adjustment, and uncertainty estimation. Such choices can affect interpretation. The registry record lists no analyses and does not report a statistical analysis plan for the primary validation outcome. In general, absence of a reported plan makes it difficult to distinguish prespecified analyses from analyses selected after observing results. It is not evidence that a particular analysis was or was not carried out outside the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists six outcome measures and names secondary outcomes concerning D-dimer testing accuracy, event confirmation using Wells DVT, Wells PE, and Geneva PE rules among participants receiving anticoagulant therapy, and all-cause mortality within 90 days of the index visit. It does not report a multiplicity strategy, such as how interpretation would account for assessing several outcomes or comparisons. The statistical analysis plan is not reported in the registry record.

In general, multiplicity arises when several hypotheses or outcomes are assessed. If each is considered separately without an overall plan, the chance of at least one apparently unusual result can increase. A prespecified approach can clarify which results are primary, how secondary results will be interpreted, and whether adjustments are planned. The registry identifies a primary outcome but does not describe such procedures. It lists no analyses, so there are no posted analysis results from which to determine how multiplicity was handled.

The record identifies 723 participants included in the study and a subgroup of 401 with suspected isolated DVT, but it does not report missing-data counts, reasons for missing data, or methods for handling missing outcomes or rule assessments. It also does not describe imputation, complete-case analysis, or sensitivity analyses. These details are not reported in the registry record.

Analysis populations are not fully specified beyond the stated participant counts. The record does not explain the relationship between enrollment of 744 and the 723 participants included in the primary outcome description. The number of participants assessed in each Wells category is also not reported. Consequently, the completeness and composition of the analysis set for the primary validation outcome cannot be assessed from the registry information.

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 0% reporting threshold.

The registry’s adverse-event information lists an all-cause mortality group. It records 723 at risk in each of two displayed columns, zero affected in each, and 12 deaths. The record also names all-cause mortality within 90 days of the index visit as a secondary outcome. It does not state whether the 12 deaths correspond to that 90-day outcome, so the two pieces of information should not be assumed to refer to the same time window.

These fields should be read as separate reported entries, not combined into a rate or percentage. The registry does not provide a definition of the two at-risk or affected columns in the information available for this summary. The zero affected entries therefore should not be interpreted as meaning that there were no deaths, since the same adverse-event information separately records 12 deaths. The relationship between those entries is not explained in the registry record.

No serious adverse-event terms are listed. This means the registry record does not name specific serious adverse events in this entry; it does not establish that no events occurred. The study is a diagnostic validation study rather than a randomized treatment comparison, and the mortality figures do not describe a comparison between assigned treatments. They should be interpreted as registry-reported safety information, with the definitions and timing limitations kept in view.

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

The record establishes that the Wells DVT clinical decision rule was applied prospectively at presentation to participants with suspected recurrent DVT, and it describes how the rule classified scores into probability categories. It also reports that, among 401 participants with suspected isolated DVT, 108 had a confirmed diagnosis. The confirmation process is described as objective imaging with adjudication by an independent committee.

Those details do not reveal how many confirmed cases occurred in each Wells category. Without the category-specific results, readers cannot determine from the registry record whether the categories separated participants with confirmed DVT from those without it, or how precise any such separation might be. No estimates of diagnostic performance or confidence intervals are reported. The record therefore does not establish the rule’s accuracy or its clinical value in this study.

In general, a diagnostic rule is evaluated in relation to a defined population, assessment process, and reference standard. Results from one setting may not automatically apply to another, especially when the people assessed, clinical context, or diagnostic procedures differ. The registry describes a population with a history of thrombosis and suspected recurrence, but does not report enough detail to characterize all aspects of that population or assessment process.

This study should not be interpreted as a randomized comparison of treatments. It does not report that participants were assigned to a treatment group or provide evidence of a treatment effect. Nor do the aggregate counts establish whether using the Wells rule changes testing, treatment, or health outcomes. The record’s stated concern is the challenge of distinguishing a recurrent event from persistent symptoms after a prior clot; evidence addressing the rule’s performance would require the category-specific outcome results.

The completion status indicates that the registry lists the study as completed, but completion alone does not supply missing statistical results. Interpretation is limited to the information recorded: study population counts, the outcome definition, and the described confirmation process. Further claims about discrimination, clinical impact, harms avoided, or treatment decisions are not supported by the reported results.

13. Why This Trial Matters Statistically

Diagnostic studies matter statistically because a clinical classification is useful only insofar as it relates to the condition it is intended to assess. In suspected recurrent DVT, the registry describes a specific challenge: symptoms from an earlier clot may complicate assessment of a possible new event. A rule that organizes clinical findings into probability categories can be evaluated by comparing those categories with independently confirmed outcomes.

The PREDICTORS record is relevant because it describes prospective application of the Wells DVT rule in this recurrent-event setting and defines confirmation using objective imaging and independent adjudication. That design information clarifies what the primary validation question concerns. The record also distinguishes participants presenting with suspected isolated DVT from the broader study population, which is important when interpreting the reported counts.

Statistically, however, the central evidence for category validation is the distribution of confirmed events and non-events across categories. Without those data, it is not possible to assess whether higher probability classifications corresponded to more confirmed DVT, or how much uncertainty surrounds that pattern. This illustrates a general principle: a well-defined endpoint and study procedure are necessary, but readers also need outcome summaries and uncertainty estimates to judge the evidence.

The record also names other diagnostic and mortality outcomes, emphasizing that a study may address several related questions. Clear distinction between a primary outcome and secondary outcomes helps readers understand which question is central, while a reported analysis plan helps explain how multiple findings are handled. Those analytical details are not reported. The study therefore offers useful context about the intended validation task, while the registry’s lack of category-specific results limits what can be concluded statistically.

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 principal limitation for interpreting the primary outcome is that the registry record does not report confirmed event counts or rates within the Wells DVT categories. It also does not report the number of participants assigned to each category. As a result, the primary validation question cannot be answered from the available figures. Measures such as sensitivity, specificity, predictive values, and confidence intervals are also not reported.

The relationship between enrollment of 744 and the 723 participants described as included in the study is not explained. The record identifies 401 participants with suspected isolated DVT and 108 confirmed diagnoses in that subgroup, but does not provide a complete accounting of participants outside this subgroup or explain how they contribute to the primary outcome analysis. Reasons for any difference between enrollment and the included population are not reported in the registry record.

The record does not report the statistical analysis plan, missing-data procedures, analysis populations beyond the stated counts, or methods for handling multiple outcomes. It does not describe blinding of clinical-rule assessment or outcome adjudication, or whether all participants received the same verification procedures. These details cannot be assumed from the statement that events were objectively imaged and independently adjudicated.

The registry does not identify a randomized comparator or allocation method. The study therefore should not be read as a treatment comparison. Its findings, as reported, concern a diagnostic classification question in participants with suspected recurrent DVT; the extent to which they apply to other populations or settings cannot be determined from the registry record. The mortality entry also does not clarify whether its 12 deaths correspond to the named 90-day secondary outcome.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Clinical Predictors for Venous Thromboembolism in Patients With a History of Thrombosis (PREDICTORS) — NCT02297373.
• Registry record last updated 2025-09-05; status last verified 2025-09.
• Results first posted 2025-09-05.
• 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

Clinical Predictors for Venous Thromboembolism in Patients With a History of Thrombosis (PREDICTORS), NCT02297373, is listed as COMPLETED and sponsored by Ottawa Hospital Research Institute. The recorded start date is 2014-11-19, the primary completion date is 2019-01-03, and enrollment is 744.

The primary outcome concerns validation of the Wells DVT clinical decision rule among participants presenting with suspected recurrent DVT. The registry describes prospective application at Day 0 and confirmation of recurrent DVT through objective imaging and independent committee adjudication. It reports 723 participants included in the study; 401 had suspected isolated DVT, and 108 of those had a confirmed diagnosis.

The record does not report confirmed event counts within the Wells categories, diagnostic performance estimates, confidence intervals, a statistical analysis plan, or missing-data methods. It lists six outcome measures, no analyses, and an all-cause mortality entry recording 12 deaths. The relationship between that death count and the named 90-day mortality outcome is not reported.