anti-pf4/ heparin antibodies early seroconversion in hip fracture patients receiving low molecular weight heparin prophylaxis: a pilot study of 100 consecutive patients

Objectives: heparin-induced thrombocytopenia (hit) represents a serious adverse reaction triggered by antibodies (anti-pf4/h) in heparin regimens. it is not clear if different low-molecular weight heparins (lmwhs) prompt distinct immunogenic responses in anti-pf4/h production and if these antibodies correlate with thrombocytopenia, thrombotic events, and early postoperative mortality. this pilot prospective study investigates the early output of anti-pf4/ h in elderly patients undergoing proximal femoral nailing for an intertrochanteric hip fracture surgery.methods: a total of 100 consecutive patients (72 females) with surgically treated intertrochanteric hip fractures were prospectively included. ninety-four patients were available for the final follow-up. twenty-seven patients received bemiparin, 42 enoxaparin and 25 tinzaparin. the levels of anti-pf4/h using the semi-quantitative latex-enhanced immunoassay; hemosil® hit-ab(pf4-h) and platelets (plt) levels were measured on the admission day and on day 5 following lmwh administration. patients were followed up for at least 3 months for major thrombotic events and all-cause mortality.results: no patient developed clinically evident hit, while 6 (6.4%) experienced thrombotic complications, and 22 (23.4%) passed away within 3 months after surgery. none of the patients with thrombotic complications tested positive for anti-pf4/h. upon evaluating patients’ seroconversion by day 5, six out of 94 (6.4%) patients tested positive for anti-pf4/h. among them, three patients received bemiparin, two tinzaparin, and one enoxaparin. no statistically significant variance was observed in anti-pf4/h seroconversion between different types of lmwhs (p-value = 0.545) or in plt count deviations (p-value = 0.990).conclusion: this pilot prospective study investigated anti-pf4/h production in older patients with hip fractures receiving different lmwhs. preliminary results suggest that all tested anticoagulants have similar immunogenicity profiles in terms of pf4/h sensitization. these findings highlight the overall safety of lmwhs in elderly hip fracture patients. moreover, the presence of anti-pf4/h appears unrelated to plt fluctuations, subsequent vte events and early postoperative mortality.        level of evidence: ii