Giancarlo Castaman

Platelet von Willebrand factor assay: results using two methods for platelet lysis

Two different methods (using Triton X-100 and glycerol) for lysing platelets to measure platelet vWF concentrations were compared directly. The platelet concentration of von Willebrand factor antigen (vWF:Ag) was similar for both methods, whereas ristocetin cofactor activity (Ricof) was higher with Triton than with glycerol. After storing platelet lysates for two months at -80 degrees C vWF:Ag and Ricof concentrations decreased with both methods of lysis. Larger than normal (supranormal) vWF multimeric forms could be visualized in platelet lysates obtained using both methods, with no change of the multimeric pattern during storage. Triton can be recommended as the agent of choice to lyse platelets for measurement of their vWF concentration, but the samples must be assayed within two weeks to avoid decay of Ricof activity.

Management of Spontaneous Bleeding and Prevention of Bleeding After Dental Extractions and Other Surgical Procedures in Mild Hemophilia a and Von Willebrand’s Disease: Ten Years of Experience at the Vicenza Hemophilia and Thrombosis Center

Desmopressin (DDAVP) is the treatment of first-choice for the management of patients with mild hemophilia A and von Willebrand disease1,2. This agent is cheap and safe and it is useful in about 80 % of cases. DDAVP has had a major impact in the therapeutic efforts for the prevention and treatment of bleeding in such patients. Since its introduction for clinical use3, the large majority of patients with these disorders can safely avoid the use of blood products (cryoprecipitate, commercial factor VIII concentrates), that, although rendered almost completely safe by virucidal methods, still have a potential risk of transmitting blood-borne viruses4,5.

Fall Off of Factor VIII Elicited by Desmopressin Administration in Hemophiliacs and von Willebrand’s Disease Patients

The decay of factor VIII: C elicited by Desmopressin (DDAVP) administration has been one of the first topics addressed by investigators1, 2 since the discovery of the effects of this new compound in normal subjects, hemophiliacs and patients with von Willebrand’s disease (vWD).

Multicenter Italian Study on Subcutaneous Concentrated Desmopressin (Emosint) for the in-Hospital and Home Treatment of Patients with von Willebrand Disease and Mild or Moderate Hemophilia A: Outline of the Project

In the last 15 years desmopressin has been increasingly used for the management of patients with von Willebrand disease (vWD) and mild or moderate hemophilia A1-3. More recently, this agent proved also successful in the management of patients with platelet function defects4 or for the correction of bleeding diathesis of uremia5. In most cases, this synthetic drug allows the avoidance of any blood products resulting in a safe and cheap treatment. Several hundred patients have already been treated all around the world, but due to the initial limitation posed by the unavailability of the concentrated form of this agent, most treatment was administered intravenously and for this reason was reserved to in-hospital patients.

Multicenter Evaluation of a New Concentrated Desmopressin Preparation (Emosint) Administered Intravenously or Subcutaneously: Analysis of Biological Responses and Side-Effects in 49 Patients with Hemophilia a and Von Willebrand’s Disease

After Kohler et al1 first administered desmopressin subcutaneously, Kohler’s2 and Mariani’s3,4groups proved that the subcutaneous (s.c.) and the intravenous (i.v.) route were pharmacologically and biologically equivalent. A minor difference was that the peak level of elicited factor VIII (VIII: C) was reached 60 minutes after s.c. injection compared to 30 minutes after the end of i.v. infusion. First clinical trials with s.c. administration were similarly successful4,5. With the availability of a more concentrated preparation of desmopressin the s.c. route was increasingly used for clinical reasons and this way of administration was confirmed as a simple, safe and effective alternative 5,6. Furthermore, Mannucci et al.7 provided experimental evidence suggesting that 0.3 μ/kg is a dose sufficient to elicit a maximal biological response, at least in terms of VIII/vWF increments and that the drug absorption after s.c. administration is less bound to intersubject variability. From the review of the above cited papers, more than one hundred cases are evaluable, including about 10 cases with von Willebrand disease, subcutaneously injected with desmopressin. Of them, at least 50 % received the concentrated formulation s.c, mostly for clinical reasons. In 30 cases the two routes of administration were examined in a cross-over design in the same subject3,4,7 and proved strictly comparable in terms of VIII: C increment.