Cone and plate(let) analyzer as a diagnostic tool in various types of thrombotic thrombocytopenic purpura and haemolytic uremic syndrome

Abstract number: P1798

Shenkman^* B., Budde† U., Angerhaus‡ D., Lubetsky§ A., Savion¶ N., Seligsohn§ U., Varon†† D.

††Department Hematology, Hadassah, Hebrew University Medical Ctr., Israel ¶Eye Res. Institute, Tel Aviv University, Israel; §Institute Thromb. & Hemost., Sheba Medical Ctr., Israel; ‡Laboratory Prof. Dr Arndt & Partner, Hamburg, Germany; †Laboratory Prof. Dr Arndt & Partner,Hamburg, Germany; ^*Sheba Medical Center, Israel;

Defficiency of von Willebrand factor-cleaving protease (vWF-CP) has recently been identified as an important factor in pathogenesis of thrombotic thrombocytopenic purpura (TTP). Currently available tests, e.g. assay of vWF-CP or finding the ultra-large vWF multimers, can distinguish between TTP and hemolytic uremic syndrome (HUS). However, these tests are complicated and require highly specialized laboratory. Recently, using the Cone and Plate(let) Analyzer (CPA), we showed that platelets of normal whole blood (O group) were excessively deposited under flow condition (1800 s^-1) when mixed with plasma from TTP patients. In the present study, we used this method to distinguish between inherited TTP (ITTP, n = 7), spontaneously acquired TTP (ATTP, n = 12), TTP after bone marrow transplantation (BMT, n = 10), TTP in patients with metastasizing malignant tumors (MMT, n = 20), and hemolytic uremic syndrome (HUS, n = 8). Plasma samples from 22 healthy volunteers served as a control in the mixture procedure with normal whole blood. The values of platelet adhesion (% surface coverage, SC) measured by CPA, were as follows: 7.1 ± 1.6 in control, 9.9 ± 3.2 in ITTP, 11.6 ± 2.4 in ATTP, 10.4 ± 2.6 in BMT, 10.4 ± 3.3 in MMT, and 6.7 ± 0.9 in HUS. The values of platelet aggregation (mm² average size, AS) were as follows: 28.6 ± 3.3 in control, 43.9 ± 13.0 in ITTP, 46.3 ± 8.3 in ATTP, 38.6 ± 6.6 in BMT, 41.1.4 ± 10.1 in MMT, and 28.2 ± 2.2 in HUS. Both SC and AS were significantly higher in patients with ITTP, ATTP, BMT and MMT compared to control and HUS. In HUS, the platelet function parameters were not different from the control. The values of VWF-CP activity (%) were as follows: 72.2 ± 35.0 in control, 12.0 ± 12.4 in ITTP, 8.8 ± 10.8 in ATTP, 51.5 ± 10.8 in BMT, 39.4 ± 27.3 in MMT, and 46.4 ± 9.3 in HUS. Significantly lower vWF-CP activity compared to control, was found only in ITTP and ATTP. The presence of vWF-CP inhibitor was found only in ATTP. All patient groups show similarly high levels of vWF antigen in plasma. We conclude that the CPA method may be useful for differentiation between various types of TTP and HUS.