Patients with a history of blood clots are at risk of developing additional clots in the future. Doctors use a tool called a clinical decision rule to tell them how likely it is that a patient has a blood clot and if they should have further testing to look for the clot. This tool may cause doctors to over-diagnosis a recurrent clot because the symptoms may be left over from the previous clot. Correctly diagnosing a recurrent blood clot is very important since there are risks associated with both over-diagnosis and under-diagnosis. If a recurrent blood clot is missed (under-diagnosis) the patient is at risk of death from a clot in the lungs. If blood thinners are prescribed when they are not needed (over-diagnosis), the patient may have to take blood thinners for their lifetime and risk having serious bleeding.
Several tools have been developed to standardize the diagnostic management of a suspected first blood clot. One of these tools is the use of a clinical decision rule. Clinical decision rules have been designed to help clinicians make diagnostic and therapeutic decisions at the bedside. A score is computed on the presence of some criteria from the patient's medical history, clinical signs and symptoms. The score provides the probability of a blood clot. The rules can be used in combinations with a simple blood test - called D-dimer - to identify patients at low risk who don't require diagnostic imaging testing. Benefits include reduced costs, length in hospital and radiation exposure. Patients with prior blood clots have been shown to be less likely to benefit from the non-invasive testing. Therefore, they often need to undergo imaging tests, which are frequently difficult to interpret in patients with prior blood clots since residual clots are often present and are difficult to distinguish from a recurrent clot. The objective of this study is to try to prospectively assess the role of existing clinical decision rules in patients with prior blood clots, and to attempt to improve them in order to increase the yield of non-invasive testing and to reduce the risk of over-diagnosis with imaging tests. With respect to this study, clots within the deep veins of the legs are called deep vein thrombosis (DVT), while clots in the lungs are called pulmonary embolism (PE).
Study Type
OBSERVATIONAL
Enrollment
744
Nova Scotia Health Authority
Halifax, Nova Scotia, Canada
Hamilton Health Sciences Centre
Hamilton, Ontario, Canada
Lawson Health Research Institute
London, Ontario, Canada
The Ottawa Hospital
Ottawa, Ontario, Canada
Hopital Montfort
Ottawa, Ontario, Canada
Humber River Hospital
Toronto, Ontario, Canada
Sir Mortimer B. Davis Jewish General Hospital
Montreal, Quebec, Canada
Leiden University Medical Centre
Leiden, Netherlands
Geneva University Hospital
Geneva, Switzerland
Validation of the Wells DVT Clinical Decision Rule
The Wells DVT Clinical Decision Rule (CDR) assigns a score from -2 to +9 based on clinical variables (e.g., active cancer, limb swelling, localized tenderness, prior history of DVT, alternative diagnosis as likely or more likely than DVT). In this study, the 3-level Wells DVT CDR was applied prospectively at presentation (Day 0) to participants with suspected recurrent DVT, using data collected from patient history and physical examination. Scores classify patients into low (≤0), moderate (1-2), or high (≥3) probability of DVT. Higher scores indicate greater probability of recurrent DVT. The outcome measure was the rate of confirmed recurrent DVT events within each Wells category, confirmed by objective imaging and adjudicated by an independent committee.
Time frame: Day 0 (at time of suspected recurrent DVT)
Validation of the Wells PE Clinical Decision Rule
The 3-level Wells PE score (range 0-12.5) was calculated from history and exam at the index visit. Scores ≤4 = PE unlikely, \>4 = PE likely. Higher scores indicate greater likelihood of PE. The outcome is the proportion with confirmed recurrent PE at the index diagnostic work-up, adjudicated by blinded review of imaging.
Time frame: Day 0 (at time of suspected recurrent PE)
Validation of the Geneva PE Clinical Decision Rule
The revised Geneva score (range 0-22) was calculated from history and exam at the index visit. Scores 0-3 = low, 4-10 = intermediate, ≥11 = high probability. Higher scores indicate greater likelihood of PE. The outcome is the proportion with confirmed recurrent PE at the index diagnostic work-up, adjudicated by blinded review of imaging.
Time frame: Day 0 (at time of suspected recurrent PE)
Accuracy of Current D-dimer Testing Methods
D-dimer testing at the index visit was performed using the institutional cut-off for positivity in place during the study period (2014-2019). Results were classified as positive or negative. The outcome is the proportion with confirmed recurrent VTE in each test category at the index diagnostic work-up, adjudicated by blinded review of imaging.
Time frame: Day 0 (at time of suspected recurrent VTE)
Rate of Confirmed Events Using Current Wells DVT/Wells PE/Geneva PE in Participants on Anticoagulant Therapy
The Wells DVT, Wells PE, and Geneva PE scores were calculated at the index visit in participants on anticoagulation. Score ranges and cut-offs as per respective rules. The outcome is the proportion with confirmed recurrent VTE in each risk category at the index diagnostic work-up, adjudicated by blinded review of imaging.
Time frame: Day 0 (at time of suspected recurrent VTE)
All-Cause Mortality Within 90 Days of Index Visit
Number of participants who died from any cause from enrollment (Day 0) through Day 90 follow-up for those without confirmed recurrent VTE at enrollment.
Time frame: From enrollment (Day 0) through Day 90 follow-up for those not diagnosed with a confirmed recurrent VTE at enrollment
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