الفهرس 
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Abstract
von Willebrand disease (vWD) is an autosomally inherited bleeding disorder caused by a deficiency or abnormality of von Willebrand factor (vWF). vWF is a multimeric adhesive protein which plays an important role in primary hemostasis. Defects in vWF can cause bleeding by impairing platelet adhesion or by reducing the concentration of FVIII.
vWD has a prevalence of about 1% in the general population, but the figure for clinically relevant cases is lower (about 100/million inhabitants). It affects both males and females and can be diagnosed at any age.
Clinical spectrum of the disease is characterized by an extreme heterogeneity of bleeding symp toms. Mucosal bleeding is typical of all vWD cases but hemarthrosis and hematomas may also be present when FVIII levels are low. Severe life threatening episodes are rarely reported.
vWD is classified into three primary categories. Type 1 vWD appear to have a partial quantitative deficiency of vWF with mild symptoms, type 2 vWD have qualitative variants and clinically more homogeneous. Type 3 vWD is rare. Type 2 vWD is divided into four subtypes (2A, 2B, 2M and 2N), and type 2A includes type 2C, type 2D, type 2E, and 2U vWD.
An array of tests is usually required to characterize the vWD types of the disorder and establish the best treatment modality.
Essential laboratory parameters for proper diagnosis and classification of vWD include BT, FVIII:C, vWF:Ag, vWF:Rco, vWF:CB, RIPA, and analysis of vWF multimers .In this study, the incidence of type 1 vWD was (40%), type 2 vWD was (46.6%) and type 3 was vWD (13.3%). The incidence of type 2 vWD was (46.6%) as type 2 M was (16.6%) and type 2 A or B was (30% ). The proper classification of type II was mediated by vWF:Ag, vWF:Rco and vWF:CB.
We succeeded to discriminate type IIA or B from each of type I type and IIM vWD by using vWF:CB% and vWF:CB/vWF:Ag .
vWF:CB should be included in the first choice tests as vWF:CB is superior to the vWF:RCo assay. The vWF:RCo and vWF:CB assays measures different functions of vWF protein and the use of these tests in combination allows for more evaluation for the presence of vWD to detect all forms of vWD.
In conclusion, vWF: CBA appears to improve the diagnosis of vWD at the phenotypic level and we suggest its inclusion in the group of the first choice tests, together with vWF:Ag, with or without vWF:RCo. When difficulties in the standardization procedures exist, we advise including vWF: RCo as a second choice tests, together with multimer analysis.