Optimizing the Diagnosis of Heparin Induced Thrombocytopenia

Ottawa Hospital Research Institute180 enrolled

Overview

Multicentre (Ottawa and Halifax) prospective cohort study using a diagnostic approach in patients clinically suspected to have HIT that combines pretest probability assessment with quantitative interpretation of anti-PF4 assay.

The proposed is a prospective cohort study exploring a novel diagnostic approach to Heparin Induced Thrombocytopenia (HIT) using a combination of pretest probability assessment and quantitative interpretation of the anti-platelet factor 4 Immunological assay (anti-PF4). Patient with a clinical suspicion of HIT will follow the study diagnostic algorithm (Figure 1). The study algorithm will be considered a safe approach to move forward into a larger RCT if the upper limit of the 95% confidence interval for 'false negative management failures' is ≤ 4% based on a Serotonin Release Assay (SRA) gold standard. The main objective of the pilot study is to inform feasibility and recruitment barriers for a larger randomized control trial.

Study Type

INTERVENTIONAL

Allocation

Purpose

DIAGNOSTIC

Masking

NONE

Enrollment

180

Conditions

Heparin-induced Thrombocytopenia (HIT)

Interventions

Diagnostic algorithmDIAGNOSTIC_TEST

The treating physician will complete an enrollment assessment including the 4T score pretest probability assessment14. All patients will have laboratory testing for HIT anti-PF4 as well as SRA testing. Results of the anti-PF4 assay (OD value) will be available to the treating physician who will be instructed to follow the study diagnostic algorithm

Eligibility

Sex: ALLMin age: 18 Years

Medical Language ↔ Plain English

Inclusion Criteria: * Patient with clinical suspicion of HIT by treating physician Exclusion Criteria: 1. Less than 18 years of age; 2. Prior diagnosis of HIT ever; 3. Patient enrolled within preceding 100 days; 4. Functional/ confirmatory platelet activation results available at the time of enrollment; 5. Requiring cardio-pulmonary bypass or percutaneous cardiac angioplasty or any other cardiac or vascular surgery/procedure requiring intra-operative/procedural heparin administration planned within 30 days; 6. Unable to complete study follow up; 7. Unable to obtain consent (or proxy consent from substitute decision maker where applicable); 8. Life expectancy less than 30 days; 9. Greater than 72 hours from clinical suspicion of HIT and/or request for HIT anti-PF4 ELISA testing.

Locations (1)

The Ottawa Hospital

Ottawa, Ontario, Canada

RECRUITING

Outcomes

Primary Outcomes

Recruitment

The pilot will be considered feasible if recruitment of at least 7.5 patients per month (total between the two sites) is achieved.

Time frame: 2 years

False negative management failures

The rate of false negative 'management failures' where the study protocol concludes HIT unlikely but SRA (reference standard laboratory test) is positive for HIT (≥50% Serotonin release).

Time frame: 2 years

Secondary Outcomes

Major arterial and venous thromboembolism events

Events will be ascertained from the date of study consent. However, venous or arterial thrombotic events detected on investigations ordered within 24 hours of study entry will be captured as baseline events and will be counted separately from thrombotic events which occur after the initial 24 hours of study enrolment.

Time frame: 24 hours of baseline and 24 of study enrolment

Proximal deep vein thrombosis

Testing performed because of symptoms in a patient with (new) non-compressibility of the common femoral vein, popliteal vein or calf trifurcation vein of the leg on ultrasound; or new non-compressibility or visualization of thrombus in the jugular vein, subclavian vein or axillary vein on ultrasound; or an intraluminal defect seen in one more than one view in proximal leg or arm veins on venography will be diagnostic for deep vein thrombosis.

Time frame: 2 years

Pulmonary embolism

Testing performed because of symptoms in a patient with a high probability lung scan (i.e. at least one segmental perfusion mismatch) or CT pulmonary angiography (i.e. intraluminal filling defect in the main, lobar or segmental pulmonary arteries) will be diagnostic for pulmonary embolism.

Time frame: 2 years

Central Contacts

Chantal Rockwell, BA

CONTACT

613-737-8899 crockwell@ohri.ca

Data from ClinicalTrials.gov

This platform is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional.