The haemostatic process is characterized by a series of biochemical
reactions aiming at preventing blood loss through blood clot formation. This latter
process is mediated by the interaction of platelets on the surface of the injured vessel
wall which in turn induces the coagulative phase requiring the activation of inactive
zymogen into active proteases.
Haemophilia A and B are rare disorders in which the coagulation cascade is affected
due to the lack of blood clotting FVIII and FIX, respectively.
In order to provide the appropriate therapy for patients with these bleeding disorders,
several laboratory tests have to be performed. The initial screening is conducted by
screening global tests such as prothrombin time (PT) and activated partial
thromboplastin time (aPTT) but only this latter is prolonged in hemophilia. Next, the
measurement of factor activity is required for the diagnostic assessment and
classification of the disease severity. Three methods can be performed for evaluating
FVIII activity including one-stage, two-stage and chromogenic assays. Approximately 30% of severe Haemophilia patients develop FVIII inhibitors which
neutralize the clotting activity. The most common assay employed for the detection of
inhibitors is the Bethesda assay that combines plasma containing normal amount of
FVIII with same volume of patient plasma.
Problems in Haemophilia diagnosis or inhibitor detection can occur at any stage in the
clinical diagnosis/laboratory phase, from the pre-analytical to the analytical to postanalytical.
Therefore, the aim of this chapter is to summarize the diagnostic
approaches, pitfalls and interpretation of coagulation assay in Haemophilia.
Keywords: Clotting factor, Haemostasis, Haemophilia, Inhibitors assays,
Laboratory test.