The Thrombostat 4000 A Sensitive Screening Test for von Willebrand's Disease

Abstract

The determination of the bleeding time (HT) is an essential diagnoslic tool for von Willebrand's disease (vWD). However, the slandardized Simplate® BT still displays many variables and disadvanlages. The present study reports on the sensitivity of the in vitro bleeding test (lVBT) in SI vWD cases of different types and severity in comparison to the Simplate BT, and the correlation of both to each other as well as to von Willebrand factor (vWF:RCo) aclivity. The IVBT was performed in two modifica· tions (2 mmol/L CaCl z and 4 mmol/L ADP) on the Thl"omboslat 4oo().The IVBT, particularly wilh CaCl z , showed clearly higher sensilivity than the BT (CaCl z : 84.3%, ADP: 61.7%, CaCl z + ADP: 86.3, BT: 52.9%). The BT even failed in one patient wilh severe (type 2B) and in three with moderate vWD. The IVBT only failed in very mild forms of the disease (vW-F:RCo> 25%). In addition, the IVBT with ADP showed a close correlation to the vWF:RCo aclivity (r 2 = 0.73). The significantly lowel" cOl"relation of the BT with vWF:RCo (.-l = 0.49) was particularly due to the poor l"esults in vWD of type 2 (type 2:r 2 = 0.29; types I and 3:.-:z = 0.61). Finally, BT and IVBT-ADP correlated with each other (.-l = 0.53), a rather good correlation considering that both are complex functionaltests. It can be concluded from our study Ihat From Ih~D~porlmMI ofTransfusion M~dicine and H~moslauol 0ffY. UnN~r$ily Clinics, Marburg. *81txXJ Transfusion Sen'ic:e and General Hospiwl. Hamburg-Harburg. mid tDeporlmenl ofIongiology. Cenler a/

Influence of ABO blood groups on primary hemostasis

“…In contrast to previous investigations of vWD 23 , a significant correlation between vWF levels and IVBT values could not be proved. However, this can easily be explained by the fact that only healthy donors without bleeding history and with normal IVBT results, with most showing normal levels of vWF, were investigated.…”

“…In 1995, we were able to show that the IVBT is a suitable and very sensitive screening test for vWD and that it can replace the measurement of in vivo bleeding time 23 . The sensitivity was 84.3 percent for the TST‐CaCl 2, as compared to 52.9 percent of the bleeding time.…”

“…The RIPA was measured with an aggregometer (PAP‐4, Bio/Data Corp., Hatboro, PA) using platelet‐rich plasma and ristocetin in concentrations of 1.5, 1.0, and 0.5 mg pr mL 40 . For further details of the method, readers should see Weippert‐Kretschmer et al 23 …”

“…The determination of the vWF ristocetin cofactor (vWF:RCo) was carried out according to the method of Weiss et al 43 Measuring was also done with the aggregometer (PAP‐4) and performed in duplicate by using lyophilized platelets (Dade Behring). For further details of the method, readers shoujld see Weippert‐Kretschmer et al 23 …”

Laboratory Diagnosis of Congenital von Willebrand Disease

“…Recently, ex vivo BT models have been developed that should overcome the limitations of the in vivo BT (Thrombostat 400 with its advanced version PFA 100) [30][31][32] and the filter method of O'Brien. 33 Both methods use a high-flow system with shear forces that resemble those in arterioles.…”