PRP was allowed to stand at room temperature for 30 minutes Platelet aggregation was performed by turbidometric technique on Chronolog aggregometer by adding 10 um/ml Adenosine diphosphate (ADP) and 1.25 mg/ml Ristocetin
and collagen 2 ug/ml, Epinephrine 10 um/ml in 250uL PRP in separate cuvettes.
Supply of reagents and consumables for the determination of villebrand ristocetin
cofactor-dependent activity with the provision of plc (including delivery, commissioning, training and maintenance).
Platelet aggregation is highly specific for GT, as platelet aggregation fails to occur with any agonist, except ristocetin
, where the reaction is preserved.
The most widely used method is turbidimetry, which measures the average platelet aggregation from the difference in optical density between platelet-rich plasma (PRP) and platelet-poor plasma (PPP), when an agonist is added as ADP, epinephrine, collagen, and ristocetin
, to name a few; as the platelets are added, they allow a greater passage of light, decreasing the optical density, yielding the result through the aggregation curves as a function of time.
PRP at 1 : 10 dilution and ristocetin
, used to induce the initial VWF-platelet binding under static conditions , are then added to the labeled VWF solution.
Laboratory evaluation confirmed type 1 VWD with ristocetin
cofactor activity of 38%, von Willebrand antigen level of 41%, factor VIII level of 60%, and a normal von Willebrand factor multimer distribution.
Von Willebrand studies were normal (Von Willebrand factor [VWF] antigen, 112 IU/dL; ristocetin
cofactor, 120 IU/dL; factor VIII [FVIII] activity, 98 IU/mL).
Further workup with coagulation studies showed decreased factor VIII, vWF antigen, and vWF: ristocetin
cofactor assay, and negative Bethesda assay, indicating acquired von Willebrand disease.
Review of her baseline laboratory studies revealed that her von Willebrand factor antigen (VWF:Ag) was 18% (normal: 41-153%), ristocetin
cofactor activity (VWF:RCo) was <20% (normal: 42-200%), and factor VIII activity was 34% (normal: 50-200%).
 ([lambda] = 1060 nm and energy 10-50 J) observed similar results--the authors showed a reduction in aggregation response to collagen, ADP, and ristocetin
All the agonists used in the platelet aggregation assays (collagen from equine tendon, adenosine diphosphate (ADP), and ristocetin
) were purchased from Helena Laboratories (Beaumont, Texas, USA).
Von Willebrand factor ristocetin
cofactor (VWF: RCo) activity was measured with an in-house assay in a aggregometer (Chronolog Aggregometer 490) that measures the rate of aggregation of platelets in the presence of VWF and ristocetin