<prompt> Which is not true regarding Bernard syndrome-Ristocetin aggregation is normalAggregation with collagen and ADP is normalLarge plateletsThrombocytopenia  <response>: Answer is option 1, The ristocetin-induced platelet aggregation is an ex vivo assay for live platelet function. It measures platelet aggregation with the help of von Willebrand factor and exogenous antibiotic ristocetin added in a graded fashion The ristocetin-induced platelet aggregation RIPA is an ex vivo assay for live platelet function. It measures platelet aggregation with the help of von Willebrand factor vWF and exogenous antibiotic ristocetinadded in a graded fashion. It is similar to the ristocetin cofactor assay but has the added benefit in that it helps in the diagnosis of type 2Bpseudo von Willebrand disease vWD and Bernard-Soulier syndrome because it uses patients live endogenous platelets, whereas ristocetin cofactor assay tests the function of only the vWF and not the platelets. Ristocetin cofactor assay uses the patients platelet poor plasma with vWF but no platelets and adds ristocetin and exogenous formalin-fixed platelets which can passively agglutinate but not actively aggregate, as they are dead. Formalin does not allow the extrinsic platelets to secrete the vWF of their a-granules, and thus only the activity of the intrinsic vWF is tested. Ref Robbins 9e pg 82 