Platelet factor V supports hemostasis in a patient with an acquired factor V inhibitor, as shown by prothrombinase and tenase assays.
A woman with gross hematuria was shown to have a severe isolated factor V deficiency due to a factor V inhibitor of 200 U/ml titer. Hematuria persisted despite multiple infusions of plasma but, after one transfusion with 1 U platelets, urine red blood cells decreased by more than 98%. To evaluate the patient's platelet function we performed prothrombinase and tenase assays with platelets from the patient and from normal donors. By prothrombinase assay, ionophore-activated patient platelets showed 42% of the activity of normal platelets in their ability to support prothrombin activation by activated factor X; whereas in a 'tenase' assay, which measures the platelets' ability to support factor X activation by activated factor IX + activated factor VIII, their activity was 117% of normal. The addition of excess bovine activated factor V to the prothrombinase assay fully corrected the defect. The results demonstrate the benefit of platelet transfusion and indicate that in this case the platelets are the primary source of factor V for hemostasis.
Perdekamp
Maria T Grosse
MT
Division of Hematology, Department of Medicine, Decatur, IL, USA.
Rubenstein
David A
DA
Jesty
Jolyon
J
Hultin
Mae B
MB
D003546:Cysteine Endopeptidases / Q000737:chemistry*; D005165:Factor V / Q000037:antagonists & inhibitors* / Q000627:therapeutic use*; D005166:Factor V Deficiency / Q000097:blood / Q000175:diagnosis* / Q000188:drug therapy; D005260:Female; D006417:Hematuria / Q000209:etiology / Q000628:therapy; D006487:Hemostasis; D006801:Humans; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000737:chemistry*; D017713:Platelet Transfusion / Q000379:methods*; D013925:Thromboplastin / Q000737:chemistry*; D016896:Treatment Outcome
D009363:Neoplasm Proteins; D005165:Factor V; D013925:Thromboplastin; D003546:Cysteine Endopeptidases; C030910:cancer procoagulant