[Blind spots of the diagnostic hemostasis screen].

The most powerful instrument to establish the presence or absence of a coagulation disorder is the history of the patient. In addition, screening laboratory tests (consisting of the platelet count, bleeding time and global clotting assays, such as the prothrombin time and the activated partial thromboplastin time) may be helpful to support the diagnosis. In two patients, a 21-year-old man and a 10-year-old girl, with a marked history of enhanced bleeding normal screening laboratory tests were found. The male patient had a congenital alpha 2-antiplasmin deficiency and the girl had a homozygous deficiency of factor XIII. Some defects in the coagulation system (such as defects in fibrin network formation and fibrinolysis, but also mild Von Willebrand disease) are indeed not detected by screening laboratory tests. In patients with a strong suspicion of a coagulation disorder such defects should be specifically tested for.