title: The incidence and implications of anti-heparin-platelet factor 4 antibody formation in a pediatric cardiac surgical population.
abstract: BACKGROUND
  The incidence and implications of anti-heparin-platelet factor 4 (PF4) antibody seroconversion in the pediatric cardiac surgical population remain largely unexplored. We sought to prospectively characterize the incidence of seroconversion in two populations: neonates undergoing primary cardiac surgery and children undergoing reoperative cardiac surgery with a history of unfractionated heparin (UFH) exposure.
  
  
  METHODS
  One hundred and thirty-five consecutive patients were studied: Neonatal = 60 neonates, first time cardiac surgery. Reoperative (ReOp) = 75 children, reoperative cardiac surgery. Preoperative and postoperative day (POD) 5 and 10 blood samples were used to determine the presence of PF4 immunoglobulin (Ig)G, IgA, and IgM antibodies with enzyme-linked immunosorbent assay.
  
  
  RESULTS
  No anti-heparin/PF4 antibodies were detected preoperatively in either group. On POD 5, antibodies were present in 1 of 60 (1.7%) Neonatal; and in 12 of 75 (16%) ReOp; P = 0.006. On POD 10, antibodies were present in 1 of 60 (1.7%) Neonatal; and in 39 of 75 (52%) ReOp; P < 0.001. Seroconversion in ReOp patients on POD 10 was significantly associated (P = 0.03) with previous UFH exposures. Heparin-induced thrombocytopenia (HIT) was not diagnosed in any Neonatal patients. One ReOp patient (1.3%) seroconverted and developed HIT without thrombosis or skin lesions.
  
  
  CONCLUSIONS
  HIT is a rare occurrence in pediatric cardiac surgical patients. The incidence of anti-heparin-PF4 antibody seroconversion in children undergoing reoperation is approximately 50% at 10 days postoperatively, a finding similar to that reported in adult cardiac surgical patients. Both age and previous UFH exposure correlate with this rate of seroconversion. In contrast, the rate of seroconversion in neonates undergoing first time surgery is substantially lower.
authors.affiliation: Children's Hospital Boston, Boston, MA 02115, USA.
authors.forename: Mary P
authors.initials: MP
authors.lastname: Mullen
authors.forename: David L
authors.initials: DL
authors.lastname: Wessel
authors.forename: Kristen C
authors.initials: KC
authors.lastname: Thomas
authors.forename: Kimberlee
authors.initials: K
authors.lastname: Gauvreau
authors.forename: Ellis J
authors.initials: EJ
authors.lastname: Neufeld
authors.forename: Francis X
authors.initials: FX
authors.lastname: McGowan
authors.forename: James A
authors.initials: JA
authors.lastname: Dinardo
mesh_terms: D000917:Antibody Formation; D000925:Anticoagulants / Q000009:adverse effects* / Q000276:immunology; D006328:Cardiac Catheterization; D006348:Cardiac Surgical Procedures; D005260:Female; D006493:Heparin / Q000009:adverse effects* / Q000276:immunology; D006801:Humans; D007136:Immunoglobulins / Q000097:blood; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D010978:Platelet Factor 4 / Q000276:immunology; D012086:Reoperation; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000276:immunology
chemical_list: D000925:Anticoagulants; D007136:Immunoglobulins; D010978:Platelet Factor 4; D006493:Heparin