Anti-PF4/ Heparin Antibodies Early Seroconversion in Hip Fracture Patients Receiving Low Molecular Weight Heparin Prophylaxis: a Pilot Study of 100 Consecutive Patients

Abstract

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