IMPACT Ristocetin High reagent is used to detect platelet dysfunction like von Willebrand Disease, Bernard-Soulier-Syndrome, or Glanzmann thrombasthenia in whole blood.

Ristocetin, which was introduced into clinical medicine as an antibiotic in the 1950’s, was subsequently withdrawn, in part, because it caused thrombocytopaenia. It was later demonstrated that this drug would aggregate (more strictly agglutinate) platelets in-vitro. In an unknown fashion, the antibiotic ristocetin causes von Willebrand factor to bind the platelet receptor Glycoprotein Ib (GpIb), so when ristocetin is added to normal blood, it causes agglutination. This effect is important for the IMPACT technology without a high sheer stress, which is needed to activate the von Willebrand factor.

In von Willebrand Disease, where von Willebrand factor is absent or defective, abnormal agglutination occurs.