Heparin/PF4 Antibodies Formation after Heparin Treatment: Temporal Aspects and Long-Term Follow-Up

Heparin-induced thrombocytopenia (HIT) is an immunologic drug reaction characterized by the presence of heparin-induced antibodies against heparin-platelets factor4(PF4) complex, thrombocytopenia, and paradoxical thrombosis. Little information is available on the persistence of heparin/PF4 antibody complexes in the plasma.The aim of this study was to evaluate the time course of heparin/PF4 antibodies in patients (pts) exposed to heparin. We enrolled 500 pts treated with i.v. heparin as part of perioperative management of CABG, 131 of them developed serologically confirmed heparin/PF4 antibodies, and were then selected and followed-up. Serum concentration of circulating heparin-induced antibodies was repeatedly assessed over a period of 3 years by an ELISA immunoassay; we also evaluated occurrence of thrombotic events during follow-up. 131 of 500 pts (26.2%) developed anti-PF4/heparin antibodies which persisted for 90 days (median time 95%CI 80 to 156). Baseline platelet count did not differ between the antibody-positive and -negative groups, in contrast the nadir platelet count was significantly lower in antibody-positive pts (85.000 \ub1 21.000 vs 141.000 \ub1 41.000, p < 0.001)