This section describes the diagnostic algorithms used to diagnose and monitor selected bleeding disorders.
Treatment of von Willebrand disease (VWD) is dependent on a differential diagnosis, which requires classification of VWD into one of six types. Thus, in addition to initial laboratory investigation for the diagnosis of VWD, specific assays are required for the diagnosis of VWD type.
The development of an inhibitor complicates the management of persons with haemophilia, limiting treatment options and resulting in poorer outcomes. Patients with haemophilia A (HA) or B (HB) who are exposed to products that contain coagulation factors should be screened for the presence of an inhibitor whenever a reduced treatment response or lower than expected factor recovery levels are observed.
Factor V congenital deficiency (FV CD) is characterised by prolonged activated partial thromboplastin and prothrombin times. Specific factor activity assays are required to differentiate FV CD from combined FV and FVIII deficiency.
As factor X (FX) plays a role in both the intrinsic and extrinsic coagulation pathways, prolonged activated partial thromboplastin time (aPTT) and prothrombin times (PT) can be an indicator of FX congenital deficiency (FX CD). Depending on the genetic variant, however, diagnostic tests can also vary. Thus, Russell’s viper venom tests and direct factor activity assays are necessary to confirm a FX CD diagnosis.
An isolated, prolonged activated partial thromboplastin time (aPTT), is suggestive of a FXI deficiency once other intrinsic pathway coagulation factors have been excluded.
Because factor XII congenital deficiency (FXII CD) does not manifest as a clinical phenotype, the finding of a prolonged activated partial thromboplastin time and diagnosis of FXII CD through a factor activity assay is often delayed.
The diagnosis of FXIII congenital deficiency (FXIII CD) must be based on results of appropriate laboratory tests. Standard coagulation screening tests, including prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen level, platelet count and bleeding time are normal, therefore a complete evaluation of the clotting system should include specific FXIII assays.
Large platelets, low platelet count and abnormal platelet function can indicate Bernard-Soulier syndrome (BSS). However, flow cytometry with antibodies directed against the glycoprotein (GP) subunits of the GPIb-IX-V complex ensures diagnosis.