Diagnosis of Von Willebrand's Disease

Diagnostic Criteria

Prolonged bleeding time indicates a defect in primary hemostasis, such as platelet function or von Willebrand factor, in patients with suspected bleeding disorders 1
Normal PT excludes deficiencies in the extrinsic pathway, including factors VII, X, V, II, and fibrinogen, in individuals with normal coagulation profiles 1
Prolonged PTT indicates a deficiency in the intrinsic pathway, including factors VIII, IX, XI, or XII, in patients with coagulopathy 1
Normal platelet count excludes thrombocytopenic disorders like ITP or TTP in patients with bleeding symptoms 1
The combination of prolonged bleeding time and prolonged PTT with a normal platelet count is consistent with Von Willebrand's disease, as recommended by the American Academy of Pediatrics 1

Hemophilia A and Christmas disease/Hemophilia B would show prolonged PTT due to factor VIII or IX deficiency, but bleeding time would be normal because platelet function and von Willebrand factor are intact, according to the American College of Medical Genetics 1
Idiopathic Thrombocytopenic Purpura would show thrombocytopenia, not a normal count, and PTT would be normal, as stated by the American Society of Hematology 1
Thrombotic Thrombocytopenic Purpura would show thrombocytopenia and is not an inherited bleeding disorder, as noted by the National Institute of Neurological Disorders and Stroke 1

PT and PTT are not reliable screening tests for VWD, and the prolonged bleeding time is the key distinguishing feature, as recommended by the American College of Medical Genetics 1
Confirmatory testing should include von Willebrand factor activity, such as ristocetin cofactor activity, as suggested by the American Academy of Pediatrics 1