▁of ▁or ▁reduction ▁of ▁v WF , ▁as ▁seen ▁in ▁von ▁Wille brand ▁disease ▁( v WD ), ▁or ▁absence ▁or ▁reduction ▁in ▁numbers ▁of ▁GP 1 b ▁re cept ors , ▁as ▁in ▁Bernard – S ou lier ▁synd rome ▁( B SS ). ▁R IST O test ▁can ▁be ▁performed ▁in ▁two ▁concentr ations ; ▁R IST Oh igh ▁and ▁R IST O low . ▁In ▁R IST Oh igh , ▁a ▁r ist oc et in ▁concentration ▁of ▁ 0 , 7 7   m g / ml ▁is ▁applied . ▁This ▁normally ▁indu ces ▁a ▁strong ▁plate let ▁aggreg ation , ▁and ▁low ▁or ▁absent ▁aggreg ation ▁can ▁be ▁caused ▁by ▁the ▁earlier ▁mentioned ▁conditions ▁v WD ▁and ▁B SS . ▁In ▁R IST O low , ▁the ▁r ist oc et in ▁concentration ▁is ▁just ▁ 0 , 2   m g / ml , ▁and ▁at ▁a ▁level ▁that ▁does ▁not ▁normally ▁indu ce ▁a ▁strong ▁aggreg ation ▁response . ▁This ▁test ▁can ▁detect ▁if ▁v WF ▁shows ▁a ▁stronger ▁than ▁normal ▁t endency ▁to ▁aggregate ▁plate lets , ▁which ▁can ▁be ▁seen ▁in ▁a ▁sub type ▁of ▁v WD ▁called ▁v WD II b . ▁ ▁TR AP test ▁Th rom bin ▁re ceptor ▁activ ating ▁pe pt ide - 6 ▁( TR AP - 6 ) ▁activ ates ▁plate lets ▁through ▁the ▁th rom bin ▁re ceptor ▁prote ase ▁activ ated ▁re ceptor - 1 ▁( PAR - 1 ). ▁Binding ▁of ▁TR AP -