Parallel determination of von Willebrand factor--Ristocetin and Botrocetin cofactors.

The quantitative determinations of von Willebrand Factor (vWF)-Ristocetin cofactor (vWF:RCof) and the Botrocetin cofactor (vWF:BCof) are important parameters for the diagnosis of von Willebrand's disease. These cofactors are usually determined in a platelet aggregometer using separate platelet reagents and assay protocols. We describe a method for the preparation of platelets made from outdated platelet concentrates and fixed with paraformaldehyde which agglutinate to ristocetin and to botrocetin. The platelet agglutination assay protocol has been simplified such that the same aggregometer instrument, platelet reagent, buffers and the reaction volumes can be used for parallel determination of vWF:RCof and vWF:BCof.

Lupus anticoagulant in women with multiple spontaneous miscarriage.

A link between the presence of the lupus anticoagulant (LA) and recurrent spontaneous miscarriage exists; however, the incidence of the LA in patients with unexplained recurrent miscarriage is unknown. We have therefore investigated the incidence of the LA in women with recurrent miscarriage but without evidence of systemic lupus erythematosus or other syndromes known to predispose towards spontaneous abortion. Plasma from 29 such women was obtained and tested in the activated partial thromboplastin time (APTT), testing for correction with normal plasma if prolonged and in the dilute simplastin time test (DSTT), again mixing with normal plasma if prolonged. Using a prolongation in either/or both tests which was not corrected by mixing with normal plasma as criteria for the presence of the LA, 14 (48%) patients showed evidence for the presence of the LA. Substitution of platelet-rich plasma for phospholipid and plasma in the APTT corrected the prolonged clotting time in every patient (9/29) in which it was prolonged, further substantiating the presence of the LA. We suggest that the presence of the LA should be investigated in any patient with unexplained recurrent miscarriage.