ristocetin and Hemorrhagic-Disorders

Numerous laboratory tests are in use to detect congenital or acquired platelet function disorders. Platelet aggregometry, using ADP, collagen, arachidonic acid or ristocetin as inductor is the standard test system for diagnosis. It is also used to detect platelet non-response to antiplatelet therapy. Studies have demonstrated that laboratory assessment of platelet non response to aspirin or clopidogrel is associated with adverse outcomes, and they indicate the importance of adjusting antiplatelet therapy in patients with a low degree of platelet inhibition. Nevertheless, a standardized method for identifying these patients is still missing.

Topics: Adenosine Diphosphate; Arachidonic Acid; Aspirin; Blood Platelet Disorders; Clopidogrel; Collagen; Hemorrhagic Disorders; Humans; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Function Tests; Predictive Value of Tests; Prognosis; Ristocetin; Ticlopidine

Hemorrhagic tendency in patients with myelodysplastic syndrome (MDS) is mainly attributed to thrombocytopenia. However, platelet function in these patients has not been thoroughly investigated.. The aim of our study is to evaluate platelet function in patients with primary MDS.. Platelet function was studied with aggregometry in response to ristocetin, collagen, ADP and adrenaline in 26 MDS patients and 15 healthy individuals.. Aggregation was defective in 21 patients (80.7%). Adrenaline was the agonist with the most profound defect (45.9%), followed by ADP (58.7%), whereas aggregation with ristocetin and collagen was at the borderline. Abnormal aggregation to all four agonists was detected in 6 patients (23%). On the contrary, aggregation results were normal in only 5 patients (19.2%). RAEB-t (refractory anemia with excess blasts in transformation) patients were most seriously affected.. MDS patients have impaired platelet aggregation in response to one or more stimulants. Platelet aggregation was not statistically different between MDS patients at early stages of the disease (<12 months) and those at later stages (>12 months). Defective platelet aggregation is strongly related to MDS of worse prognosis. None of our patients was detected to have hyperfunctional platelets, defined as platelets aggregating spontaneously. Functional defects in MDS do not elicit hemorrhagic tendency.

Topics: Adenosine Diphosphate; Aged; Aged, 80 and over; Collagen; Epinephrine; Female; Hemorrhagic Disorders; Humans; Male; Middle Aged; Myelodysplastic Syndromes; Platelet Aggregation; Ristocetin; Time Factors

In a case of severe IgG kappa myeloma with cryoglobulinaemia usual concentrations of epinephrine, collagen, ADP, arachidonic acid, thrombin and ristocetin caused no aggregation of platelets in platelet rich plasma. However, in contrast to other agents ristocetin induced platelet aggregation in higher concentrations. The investigations showed, that the aggregating activity was inhibited by binding of ristocetin to the abnormal protein. Following saturation of the monoclonal protein, the surplus ristocetin caused normal aggregation. This indicates that platelets actually preserved their responsiveness to ristocetin. Possible causes of the phenomenon are discussed.

Topics: Aged; Cryoglobulinemia; Female; Hemorrhagic Disorders; Humans; Immunoglobulin G; Immunoglobulin kappa-Chains; Multiple Myeloma; Platelet Aggregation; Protein Binding; Ristocetin; von Willebrand Diseases

A 60-year-old Black female presented with a haemorrhagic diathesis and an acquired factor VIII/von Willebrand factor (VIII/vWf) inhibitor. This inhibitor was classified as an IgA immunoglobulin and was active not only against factor VIII coagulant (VIII:C) activity but also against plasma von Willebrand factor (vWf). The purified IgA also interacted with normal platelets to inhibit ristocetin-induced platelet aggregation (RIPA). In contrast, studies with haemophilia A plasma and platelets revealed that the inhibitor did not react significantly with these plasmas or platelets. The significant differences in the inhibition of vWf assay both of the plasma and the platelets of the haemophilia A patients suggests that part of the haemorrhagic diathesis may be related not only to the inhibition of VIII:C but also to interference with platelet function. In addition, these studies suggest that there may be significant differences in the factor VIII-related antigen (VIII R:Ag) on platelets in haemophilia A patients compared to normal.

Topics: Blood Coagulation Factors; Blood Coagulation Tests; Factor VIII; Female; Hemophilia A; Hemorrhagic Disorders; Humans; Immunoglobulin A; Middle Aged; Platelet Aggregation; Ristocetin; von Willebrand Factor

Topics: Adult; Albinism; Factor VIII; Female; Hemorrhage; Hemorrhagic Disorders; Humans; Platelet Aggregation; Postoperative Complications; Ristocetin; Syndrome

The authors have examined 8 cases with Hermansky-Pudlak syndrome in whom besides the usual abnormalities of abnormal aggregation with collagen, absence of second wave of aggregation, reduction of the 5-HT uptake, presence of 5-HIAA in the platelets, two new abnormalities are described: the presence of a large amount of an unidentified metabolite after 5-HT incorporation which differs from 5-HT and 5 hydroxytryptophol and an abnormal incorporation of labelled glycerol in the triglycerides. Correlation between abnormal lipid metabolism and defective 5-HT incorporation is discussed.

Topics: Adenosine Diphosphate; Albinism; Bone Marrow; Bone Marrow Cells; Clot Retraction; Collagen; Cytoplasmic Granules; Epinephrine; Glycerol; Hemorrhagic Disorders; Humans; Macrophages; Platelet Aggregation; Ristocetin; Serotonin; Syndrome; Triglycerides

Platelet aggregation by various inductors was studied in citrated and heparinized plasma of the following groups of subjects: Normal, hemophilia A, combined factor V and factor VIII deficiency, v. Willeprand's disease and congenital afibrinognemia. The results may be summarized as follows: A-platelet aggregation in citrated plasm 1) platelet aggregation by common inductors ADP, adrenalin and collagen was normal in all groups of subjects but for the patients with congential afibrinogenemia in whom adrenalin induced aggregation was absent or markedly refuced whereas ADP and collagen gave slightly reduced or near normal aggregation curves. 2) platelet aggregation by ristocetin was normal in all groups of subjects but for v. Willebrand's disease in which it was absent. B-platelet aggregation in heparized plasma. 1) platelet aggregation by common inductors resulted to be normal in all groups of subjects except in congenital afibrinogenemia. In this latter case the pattern was still mildly defective but here was an increased aggregation as compared to citrated plasma. These findings have been interpretemmon inductors. 2) platelet aggregation by ristocetin resulted to be absent in all groups of subjects investigated. The possible mechanism of action of the inhibitory effect exercised py heparin with regard to restocetin is discussed.

Topics: Adenosine Diphosphate; Afibrinogenemia; Collagen; Epinephrine; Factor V Deficiency; Hemophilia A; Hemorrhagic Disorders; Heparin; Humans; Platelet Adhesiveness; Ristocetin; von Willebrand Diseases

Topics: Adult; Azathioprine; Blood Coagulation Tests; Collagen Diseases; Factor VIII; Female; Hemorrhagic Disorders; Humans; Jaundice; Methylprednisolone; Platelet Adhesiveness; Platelet Aggregation; Ristocetin; Splenomegaly; von Willebrand Diseases