Haematologica 2004;89: supplement no. 8 - Supplements ...

106PostersVWF-LIA appears to be at least as sensitive as thetraditional ELISA test for the diagnosis of VWD type1. Although less sensitive than the ELISA test, theLIA assay appears to be useful for a rapid screeningof VWD in subjects with bleeding symptoms.PO-024A NEW APPROACH TO MEASURE VWF ACTIVITY AND ADAMTS13Preda l,* Lattuada A,* Rossi F,* Vaghi U,° Libera L,*Rossi E**S.I.M.T. Az. Ospedaliera L.Sacco, Milano;°Centro Trasfusionale Osp. S.Giuseppe, Milan, ItalyDeficiencies of Adamts 13, that cleaves von willebrandfactor (VWF) physiologically, reduce or abolishthe degradation of ultralarge VWF multimers thatcause the formation of intravascular thrombi inpatients with thrombotic microangiopathies (TMA).The measurements of functional VWF and Adamts13are important for the diagnosis of patients with TMA.To verify the sensitivity, accuracy of a new methodto quantify both VWF activity and Adamts13. Weanalysed a group of 60 normal controls, 10 pregnantwomen and two patients with TTP. Normal plasma (100% of Adamts13 ) was diluted with TTP patients(< 6% of Adamts13) to obtain 0, 10, 20, 40, 80 and100% of the Adamts13. A comparison was madebetween the results obtained with this method andtraditional methods. Method: one dilution in TRISbuffer and one dilution in UREA of the plasma samplesto be tested were incubated four hours at 37°C.The samples were then analysed to obtain basal andresidual VWF activity (after degradation ofAdamts13). The differences between the two valueswere directly proportional to ADAMTS13. Materials:HemosIL VWF act (IL) was used for the measurementsof VWF activity. VWF antigen ( IL) for the measurementsof VWF :Ag. Results. The coefficent ofvariation within- and between- assay was 4% and6% respectively. Normal range of Adamts13 was 75-125%. The values of Adamts13 in two patients withTTP were 3%, 5%,during normal pregnancy, themeans of Adamts13 were: 108% in the firsttrimester, 92% in the second and 89% in the thirdtrimester and in different dilution of normal plasmaand TTP plasma were 3%, 8%, 21%, 46%, 89%, 98%.Conclusion: This method is reproducible, accurate,rapid and easy to perform. This method in combinationwith automated VWF:Ag latex assay could beused for early diagnosis of VWD or TMA.PO-025AUTOMATED METHOD TO MEASURE ADAMTS13Preda L, Lattuada A, Rossi F, Crivelli S, Candolfi R,Rossi ES.I.M.T. Az.Ospedaliera L.Sacco, Milan, ItalyAdamts13 is a metalloprotease that cleaves vonWillebrand Factor (VWF) physiologically. In theabsence of this protease, ultralarge multimers ofVWF circulate in patients with thrombotic microangiopathies(TMA) and cause intravascular thrombi. Itsvalue is important for the diagnosis of patients withTTP. Aim of the study: to develop a fast and automatedmethod for measurement of Adamts13.Methods. All reagents used in this method are commercial:Von Willebrand Reagent (Dade Behringer)is reconstituted to obtain 340÷360 10⁄/microLiter ofplatelets. Ristocetin 50 mg/mL (Mascia Brunelli,Milan, Italy) is reconstituted with 0.5 mL of buffer(Diluent A ) supplied with the kit. The source of VWFused as substrate for protease was a commercial FVI-II concentrate. An automated VWF:RCo on ACL9000was used to determine Adamts13.The samples werediluted in buffer containing Urea and BaCl2 andincubated for 30 minutes a 37°C. The plasma werethen incubated over night at room temperature withsubstrate. Proteases were read automatically oncoagulometer. Patients: 60 normal controls, 10 pregnantwomen and two TTP patients. The accuracy ofthe test was determined by different dilutions ofplasma with 100% of Adamts13 and plasma with