title: Concurrent acquired inhibitors to factor VIII and IX, a laboratory artifact: a case report.
abstract: Acquired inhibitors to coagulation factors other than factor VIII are extremely rare. We describe a case of a 59-year-old woman with abnormal bleeding, diagnosed with concurrent inhibitor antibodies to factor VIII and IX by Bethesda testing. We demonstrate that anti-FVIII antibodies of a very high titre are capable of disturbing the aPTT-based Bethesda assay, resulting in falsely-positive antibodies to factor IX. The case also illustrates the usefulness of the immunological assay (ELISA) in complementing the inhibitor diagnosis.
authors.affiliation: Department of Hematology, University Medical Centre Ljubljana, Slovenia.
authors.forename: Saša Anžej
authors.initials: SA
authors.lastname: Doma
authors.affiliation: Department of Clinical Chemistry and Transfusion Medicine, Halland Hospital, Halmstad, Sweden ; at the time of the investigation working at the Coagulation laboratory of Malmö Centre for Thrombosis and Haemostasis, Skane University Hospital, Malmö, Sweden.
authors.forename: Andreas
authors.initials: A
authors.lastname: Hillarp
authors.affiliation: Department of Hematology, University Medical Centre Ljubljana, Slovenia.
authors.forename: Tadej
authors.initials: T
authors.lastname: Pajič
authors.affiliation: Department of Hematology, University Medical Centre Ljubljana, Slovenia.
authors.forename: Dušan
authors.initials: D
authors.lastname: Andoljšek
authors.affiliation: Department of Hematology, University Medical Centre Ljubljana, Slovenia.
authors.forename: Peter
authors.initials: P
authors.lastname: Černelč
authors.affiliation: Department of Hematology, University Medical Centre Ljubljana, Slovenia.
authors.forename: Irena
authors.initials: I
authors.lastname: Preldžnik Zupan
mesh_terms: D001323:Autoantibodies / Q000276:immunology; D001778:Blood Coagulation Disorders / Q000276:immunology* / Q000473:pathology; D001780:Blood Coagulation Tests; D004797:Enzyme-Linked Immunosorbent Assay; D005164:Factor IX / Q000037:antagonists & inhibitors / Q000276:immunology*; D005169:Factor VIII / Q000037:antagonists & inhibitors / Q000276:immunology*; D005260:Female; D006801:Humans; D008875:Middle Aged
chemical_list: D001323:Autoantibodies; D005169:Factor VIII; D005164:Factor IX
keywords: autoantibody; blood coagulation factor; enzyme-linked immunosorbent assay; inhibitor