Serotonin Release Assay for HIT Confirmation

Diagnostic Approach to HIT

The diagnosis of HIT requires careful review of clinical history and laboratory assays, according to the American Society of Hematology 1
Pre-test clinical scores, such as the 4Ts score, should guide initial testing strategies, as recommended by the American College of Chest Physicians 1
Immunoassays should be used as the first-line screening test for HIT, with a negative result effectively ruling out HIT due to high sensitivity, as stated by the International Society on Thrombosis and Haemostasis 1
Functional assays, such as the serotonin release assay (SRA), can confirm the diagnosis in cases with positive immunoassay results, with the American College of Chest Physicians recommending SRA for confirmation 2

SRA is technically difficult, requires human platelets from known reactive donors, and involves working with radiation, limiting its real-time utility, as noted by the American College of Chest Physicians 2

Blood samples should be collected from all patients with clinical suspicion of HIT, with samples collected at least 4 hours after cessation of unfractionated heparin infusion and ≥12 hours after a dose of LMW heparin, as recommended by the International Society on Thrombosis and Haemostasis 1
A positive SRA result in a patient with clinical features of HIT strongly supports the diagnosis and justifies continued alternative anticoagulation, according to the American College of Chest Physicians 2

Heparin-induced multi-electrode aggregometry (HIMEA) is being developed as a more accessible functional assay, as reported by the International Society on Thrombosis and Haemostasis 1