HIT Antibodies Undetectable by ELISA Activate Platelets in Mice and Humans

Heparin-induced thrombocytopenia is a prothrombotic immune-mediated reaction caused by antibodies targeting platelet factor 4 and heparin complexes [1, 2]. Because the resulting platelet activation can lead to life-threatening arterial and venous thrombosis, rapid diagnosis is essential for transitioning patients to non-heparin anticoagulants [3, 2]. Current diagnostic algorithms rely heavily on the enzyme-linked immunosorbent assay (a laboratory technique used to detect and measure antibodies in the blood) to identify these complexes, often using negative results to exclude the condition [4, 5]. However, the clinical utility of these immunoassays depends on the assumption that all pathogenic antibodies bind to the specific complexes presented in the assay [5]. Recent evidence suggests that the diagnostic landscape is more complex than previously understood, particularly regarding antibodies that activate platelets through mechanisms that bypass standard detection.