▁a ▁conform ational ▁change ▁in ▁the ▁g ly cop rote in ▁II b / III a ▁( G PI I b / III a ) ▁re ceptor , ▁giving ▁it ▁high ▁aff inity ▁for ▁f ibr in ogen . ▁Binding ▁of ▁f ibr in ogen ▁to ▁G PI I b / III a ▁re cept ors ▁leads ▁to ▁plate let - to - plate let ▁brid ges ▁and ▁results ▁in ▁plate let ▁aggreg ation . ▁Anti plate let ▁dru gs ▁like ▁c lop id og rel ▁and ▁pr as ug rel ▁irre vers ibly ▁in hib it ▁the ▁AD P ▁re ceptor ▁P 2 Y 1 2 , ▁leading ▁to ▁a ▁decre ased ▁AD P - indu ced ▁plate let ▁aggreg ation . ▁Dru gs ▁that ▁in hib it ▁the ▁G PI I b / III a ▁re ceptor , ▁e . g . ▁e pt if ib at ide , ▁can ▁also ▁reduce ▁or ▁eliminate ▁the ▁AD P - indu ced ▁plate let ▁response . ▁ ▁AS PI test ▁In ▁the ▁AS PI test ▁a rach id onic ▁acid ▁is ▁added ▁to ▁the ▁sal ine - d il uted ▁blood ▁sample . ▁A rach id onic ▁acid ▁is ▁converted ▁to ▁prost ag land in ▁H 2 ▁( PG H 2 ) ▁by ▁cy clo ox y gen ase - 1 ▁( CO X 1 ), ▁and ▁P G H 2 ▁is ▁then ▁converted ▁to ▁th rom box ane ▁A 2 ▁( TX A 2 ) ▁by ▁th rom box ane ▁synth ase