3] Nonstandard abbreviations: FVIII, factor VIII; PT, prothrombin time; APTT, activated partial thromboplastin time; AT, antithrombin; VWF, von Willebrand factor; VWF:Ag, VWF antigen; VWF:CB, VWF collagen binding; VWF:RCo, VWF ristocetin cofactor
activity; FVIII:C, FVIII coagulant activity; FIX:C, FIX coagulant activity; PC-chrom, protein C chromogenic; PS-act, protein S activity; PS-total, protein S total; PS-free, protein S free; PC-clot, PC clotting; [CV.
Consequently, various alternative VWF activity assays have been developed over the last few years in an attempt to overcome the limitations and improve the performance or even to replace the VWF: RCo assay; including the VWF collagen binding assay, an automated ristocetin cofactor
activity assay using an automated coagulation analyser (64), a recombinant platelet GPIb-based ELISA assay (65,66), flow cytometric assays (67), the latex particle-enhanced immunoturbidimetric or chemiluminescence assay which utilises monoclonal antibody against VWF-GPIb binding site at domain A1 (2,46,68,69), and a gain-of-function GPIb ELISA assay (60).
7g/dL Platelets: elevated, 574K CDC hemostasis laboratory results * von Willebrand factor antigen Reduced, 64% Ristocetin cofactor
Borderline, 69% Factor VIII Normal, 94% ADO blood type B Home environmental Reported cigarette smoking Yes in the home Reported flooding in the home Yes Reported mold in the home Yes Home renovations during infant's Yes life Range of culturable fungal counts No sampling performed (cfu/[m.
Comparative study on collagen-binding enzyme-linked immunosorbent assay and ristocetin cofactor
activity assays for detection of functional activity of von Willebrand factor.
70) Additional laboratory studies show normal VWF antigen and ristocetin cofactor
activity to distinguish Bernard-Soulier syndrome from von Willebrand disease.
5 s, reference interval 24-35 s), mild thrombocytopenia (116 K/[micro]L, reference interval 150-450 K/[micro]L), typical von Willebrand factor antigen level (VWF:Ag) (108%, reference interval 52%-214%), typical factor VIII activity (98%, reference interval 56%-191%), decreased von Willebrand factor ristocetin cofactor
activity (VWF:RCo) (19%, reference interval 51%-215%), and decreased VWF:RCo/VWF:Ag ratio (0.
Results: Based on the von Willebrand factor antigen (vWF:Ag) and ristocetin cofactor
activity (vWF:RCo) levels and bleeding symptoms, vWD type-1 was diagnosed in 14 individuals (4 males, 10 females; prevalence: 1.
Other laboratory findings which aid in diagnosis of vWD type 2B are relative decrease in plasma high molecular weight vWFmultimers (6), disproportionately low ristocetin cofactor
activity compared to vWFlevels (7) and mildly reduced or normal vWF assay.
von Willebrand factor ristocetin cofactor
(VWF:RCo) assay: implementation on an automated coagulometer (ACL).
ABBREVIATIONS: ELISA = Enzyme Linked Immuno-sorbent Assay; EQA = external quality assurance; LIA = Latex Immuno-Assay; LLS = Lower limit of sensitivity; QAP = Quality Assurance Program; VWD = von Willebrand disease; VWF = von Willebrand Factor; VWF:Act = von Willebrand Factor Activity' (assay); VWF:Ag = von Willebrand Factor Antigen (assay); VWF:CB = von Willebrand Factor collagen binding (assay); VWF:RCo = von Willebrand Factor Ristocetin Cofactor
These variants are differentiated on the basis of a panel of lab tests that include the bleeding time, platelet count, partial thromboplastin time, yon Willebrand factor (vWF) activity and antigen, factor VIII levels, ristocetin cofactor
, and vWF multimeric composition.
The company also developed the first automated ristocetin cofactor
activity test that detects Von Willebrand disease, which is the most common inherited bleeding disorder.
In this case, the initial VWD testing panel identified significantly decreased plasma von Willebrand factor ristocetin cofactor
activity (VWF:RCo), with a discordantly low ratio of VWF:RCo to von Willebrand factor antigen level (VWF:Ag) and normal coagulation factor VIII activity, suggesting types 2A, 2B, or 2M VWD (or acquired von Willebrand syndrome).
Because of its varying penetration, the diagnosis of von Willebrand disease is elusive and requires repeated ristocetin-induced platelet aggregometry assays supplemented with additional assays such as ristocetin cofactor
and VWF immunoassay.
VWF:Ag, ristocetin cofactor
activity (VWF:RCo), collagen binding with type III VWF:CB, and multimer distribution were performed on all samples as previously described (11).